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tls13: srv: Fix potential stack buffer overread

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Fix potential stack buffer overread when
checking PSK binders.

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
This commit is contained in:
Ronald Cron 2024-03-19 13:54:15 +01:00
parent 720c72b6ba
commit a5c5c58107
2 changed files with 11 additions and 1 deletions
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4
ChangeLog.d/binder-overread.txt Normal file
View File

@ -0,0 +1,4 @@
Security
* Fix a stack buffer overread (less than 256 bytes) when parsing a TLS 1.3
ClientHello in a TLS 1.3 server supporting some PSK key exchange mode. A
malicious client could cause information disclosure or a denial of service.

8
library/ssl_tls13_server.c
View File

@ -414,6 +414,10 @@ static int ssl_tls13_offered_psks_check_binder_match(
size_t psk_len;
unsigned char server_computed_binder[PSA_HASH_MAX_SIZE];
if (binder_len != PSA_HASH_LENGTH(psk_hash_alg)) {
return SSL_TLS1_3_BINDER_DOES_NOT_MATCH;
}
/* Get current state of handshake transcript. */
ret = mbedtls_ssl_get_handshake_transcript(
ssl, mbedtls_md_type_from_psa_alg(psk_hash_alg),
@ -443,7 +447,9 @@ static int ssl_tls13_offered_psks_check_binder_match(
server_computed_binder, transcript_len);
MBEDTLS_SSL_DEBUG_BUF(3, "psk binder ( received ): ", binder, binder_len);
if (mbedtls_ct_memcmp(server_computed_binder, binder, binder_len) == 0) {
if (mbedtls_ct_memcmp(server_computed_binder,
binder,
PSA_HASH_LENGTH(psk_hash_alg)) == 0) {
return SSL_TLS1_3_BINDER_MATCH;
}