CVE-2023-2977: Possible buffer overrun vulnerability in pkcs15 `cardos_have_verifyrc_package` · Issue #2785 · OpenSC/OpenSC

Problem Description

On reviewing historical CVE vulnerabilities, I found a possible recurring vulnerability as CVE-2021-42782, which was reported by oss-fuzz and fixed in commit 1252aca.

The newly found issue exists in pkcs15-init module. Like the original bug in libopensc, cardos_have_verifyrc_package in pkcs15-cardos.c scans an ans1 buffer for 2 tags. The pointer p is moved after each sc_asn1_find_tag invocation, which results in the miscalculation of the length of left bytes in buffer and hence reading beyond the end of the buffer.

Proposed Resolution

Almost the same patch like 1252aca will do:

diff --git a/src/pkcs15init/pkcs15-cardos.c b/src/pkcs15init/pkcs15-cardos.c index 9715cf39…f41f73c3 100644 — a/src/pkcs15init/pkcs15-cardos.c +++ b/src/pkcs15init/pkcs15-cardos.c @@ -872,7 +872,7 @@ static int cardos_have_verifyrc_package(sc_card_t *card) sc_apdu_t apdu; u8 rbuf[SC_MAX_APDU_BUFFER_SIZE]; int r; - const u8 *p = rbuf, *q;

•   const u8  \*p = rbuf, \*q, \*pp;
    size\_t    len, tlen = 0, ilen = 0;
  
    sc\_format\_apdu(card, &apdu, SC\_APDU\_CASE\_2\_SHORT, 0xca, 0x01, 0x88);
  

@@ -888,13 +888,13 @@ static int cardos_have_verifyrc_package(sc_card_t *card) return 0;

    while (len != 0) {

- p = sc_asn1_find_tag(card->ctx, p, len, 0xe1, &tlen); - if (p == NULL)

•           pp = sc\_asn1\_find\_tag(card->ctx, p, len, 0xe1, &tlen);
  

•           if (pp == NULL)
                    return 0;
            if (card->type == SC\_CARD\_TYPE\_CARDOS\_M4\_3)     {
                    /\* the verifyRC package on CardOS 4.3B use Manufacturer ID 0x01 \*/
                    /\* and Package Number 0x07                                      \*/
  

- q = sc_asn1_find_tag(card->ctx, p, tlen, 0x01, &ilen);

•                   q = sc\_asn1\_find\_tag(card->ctx, pp, tlen, 0x01, &ilen);
                    if (q == NULL || ilen != 4)
                            return 0;
                    if (q\[0\] == 0x07)
  

@@ -902,7 +902,7 @@ static int cardos_have_verifyrc_package(sc_card_t *card) } else if (card->type == SC_CARD_TYPE_CARDOS_M4_4) { /* the verifyRC package on CardOS 4.4 use Manufacturer ID 0x03 */ /* and Package Number 0x02 */ - q = sc_asn1_find_tag(card->ctx, p, tlen, 0x03, &ilen);

•                   q = sc\_asn1\_find\_tag(card->ctx, pp, tlen, 0x03, &ilen);
                    if (q == NULL || ilen != 4)
                            return 0;
                    if (q\[0\] == 0x02)
  

Reference

https://www.opencve.io/cve/CVE-2021-42782
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=29912