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Add ALPN validation in the client

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The ALPN protocol selected by the server must be one that we originally
advertised. We should verify that it is.

Follow on from CVE-2024-5535

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Neil Horman <nhorman@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/24716)
This commit is contained in:
Matt Caswell 2024-06-21 11:51:54 +01:00
parent e10a3a84bf
commit 238fa464d6
1 changed files with 24 additions and 0 deletions
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24
ssl/statem/extensions_clnt.c
View file

@ -1628,6 +1628,8 @@ int tls_parse_stoc_alpn(SSL_CONNECTION *s, PACKET *pkt, unsigned int context,
X509 *x, size_t chainidx)
{
size_t len;
PACKET confpkt, protpkt;
int valid = 0;
/* We must have requested it. */
if (!s->s3.alpn_sent) {
@ -1646,6 +1648,28 @@ int tls_parse_stoc_alpn(SSL_CONNECTION *s, PACKET *pkt, unsigned int context,
SSLfatal(s, SSL_AD_DECODE_ERROR, SSL_R_BAD_EXTENSION);
return 0;
}
/* It must be a protocol that we sent */
if (!PACKET_buf_init(&confpkt, s->ext.alpn, s->ext.alpn_len)) {
SSLfatal(s, SSL_AD_INTERNAL_ERROR, ERR_R_INTERNAL_ERROR);
return 0;
}
while (PACKET_get_length_prefixed_1(&confpkt, &protpkt)) {
if (PACKET_remaining(&protpkt) != len)
continue;
if (memcmp(PACKET_data(pkt), PACKET_data(&protpkt), len) == 0) {
/* Valid protocol found */
valid = 1;
break;
}
}
if (!valid) {
/* The protocol sent from the server does not match one we advertised */
SSLfatal(s, SSL_AD_DECODE_ERROR, SSL_R_BAD_EXTENSION);
return 0;
}
OPENSSL_free(s->s3.alpn_selected);
s->s3.alpn_selected = OPENSSL_malloc(len);
if (s->s3.alpn_selected == NULL) {