aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorDemi Marie Obenour <demiobenour@gmail.com>2022-12-09 17:19:08 -0500
committerSandrine Bailleux <sandrine.bailleux@arm.com>2023-01-10 14:52:45 +0100
commitf5c51855d36e399e6e22cc1eb94f6b58e51b3b6d (patch)
treef311d3f772b581c52038521afa792ca04c4e2121
parentabb8f936fd0ad085b1966bdc2cddf040ba3865e3 (diff)
downloadtrusted-firmware-a-f5c51855d36e399e.tar.gz
fix(auth): properly validate X.509 extensions
get_ext() does not check the return value of the various mbedtls_* functions, as cert_parse() is assumed to have guaranteed that they will always succeed. However, it passes the end of an extension as the end pointer to these functions, whereas cert_parse() passes the end of the TBSCertificate. Furthermore, cert_parse() does *not* check that the contents of the extension have the same length as the extension itself. Before fd37982a19a4a291 ("fix(auth): forbid junk after extensions"), cert_parse() also does not check that the extension block extends to the end of the TBSCertificate. This is a problem, as mbedtls_asn1_get_tag() leaves *p and *len undefined on failure. In practice, this results in get_ext() continuing to parse at different offsets than were used (and validated) by cert_parse(), which means that the in-bounds guarantee provided by cert_parse() no longer holds. This patch fixes the remaining flaw by enforcing that the contents of an extension are the same length as the extension itself. Change-Id: Id4570f911402e34d5d6c799ae01a01f184c68d7c Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com> Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
-rw-r--r--drivers/auth/mbedtls/mbedtls_x509_parser.c18
1 files changed, 12 insertions, 6 deletions
diff --git a/drivers/auth/mbedtls/mbedtls_x509_parser.c b/drivers/auth/mbedtls/mbedtls_x509_parser.c
index 44b25ba72b..bef2f3d0a6 100644
--- a/drivers/auth/mbedtls/mbedtls_x509_parser.c
+++ b/drivers/auth/mbedtls/mbedtls_x509_parser.c
@@ -355,33 +355,39 @@ static int cert_parse(void *img, unsigned int img_len)
* in the boot chain.
*/
do {
+ unsigned char *end_ext_data;
+
ret = mbedtls_asn1_get_tag(&p, end, &len,
MBEDTLS_ASN1_CONSTRUCTED |
MBEDTLS_ASN1_SEQUENCE);
if (ret != 0) {
return IMG_PARSER_ERR_FORMAT;
}
+ end_ext_data = p + len;
/* Get extension ID */
- ret = mbedtls_asn1_get_tag(&p, end, &len, MBEDTLS_ASN1_OID);
+ ret = mbedtls_asn1_get_tag(&p, end_ext_data, &len, MBEDTLS_ASN1_OID);
if (ret != 0) {
return IMG_PARSER_ERR_FORMAT;
}
p += len;
/* Get optional critical */
- ret = mbedtls_asn1_get_bool(&p, end, &is_critical);
+ ret = mbedtls_asn1_get_bool(&p, end_ext_data, &is_critical);
if ((ret != 0) && (ret != MBEDTLS_ERR_ASN1_UNEXPECTED_TAG)) {
return IMG_PARSER_ERR_FORMAT;
}
- /* Data should be octet string type */
- ret = mbedtls_asn1_get_tag(&p, end, &len,
+ /*
+ * Data should be octet string type and must use all bytes in
+ * the Extension.
+ */
+ ret = mbedtls_asn1_get_tag(&p, end_ext_data, &len,
MBEDTLS_ASN1_OCTET_STRING);
- if (ret != 0) {
+ if ((ret != 0) || ((p + len) != end_ext_data)) {
return IMG_PARSER_ERR_FORMAT;
}
- p += len;
+ p = end_ext_data;
} while (p < end);
if (p != end) {