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[tls] Use SHA-1 for TLS version 1.1 ECDSA signatures

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We currently use the MD5+SHA1 algorithm for all signatures when using
TLS version 1.1.  This is incorrect for ECDSA (or for any non-RSA
public-key algorithm): these should instead use SHA-1.

Fix by using SHA-1 for any non-RSA public-key algorithm for TLS
version 1.1.

Provide a weak rsa_algorithm symbol to use in the comparison, to avoid
unconditionally dragging in RSA support.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2026-09-18 16:38:24 +01:00
parent 6deb51d66c
commit f095adbed2
1 changed files with 36 additions and 20 deletions
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src/net/tls.c
+36 -20
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@@ -191,6 +191,9 @@ FILE_SECBOOT ( PERMITTED );
__einfo_uniqify ( EINFO_EPROTO, 0x04, \
"Certificate validation already in progress" )
/* Avoid dragging in RSA support unconditionally */
struct pubkey_algorithm rsa_algorithm __attribute__ (( weak ));
/** List of TLS session */
static LIST_HEAD ( tls_sessions );
@@ -2197,14 +2200,12 @@ static int tls_send_client_key_exchange ( struct tls_connection *tls ) {
* @ret rc Return status code
*/
static int tls_send_certificate_verify ( struct tls_connection *tls ) {
struct digest_algorithm *digest = tls->key.digest;
struct asn1_cursor *key = privkey_cursor ( tls->client.key );
struct tls_signature_hash_algorithm *sig_hash = NULL;
struct asn1_builder builder = { NULL, 0 };
struct x509_certificate *cert;
struct pubkey_algorithm *pubkey;
size_t digestsize = digest->digestsize;
uint8_t tbshash[digestsize];
struct digest_algorithm *digest;
int rc;
/* Sanity checks */
@@ -2221,8 +2222,11 @@ static int tls_send_certificate_verify ( struct tls_connection *tls ) {
}
pubkey = cert->signature_algorithm->pubkey;
/* TLSv1.2 and later use explicit algorithm identifiers */
/* Identify signature and hash algorithm */
if ( tls_version ( tls, TLS_VERSION_TLS_1_2 ) ) {
/* TLSv1.2 and above use explicit algorithm identifiers */
digest = tls->key.digest;
sig_hash = tls_signature_hash_algorithm ( pubkey, digest );
if ( ! sig_hash ) {
DBGC ( tls, "TLS %p could not identify (%s,%s) "
@@ -2231,27 +2235,18 @@ static int tls_send_certificate_verify ( struct tls_connection *tls ) {
rc = -ENOTSUP_SIG_HASH;
goto err_sig_hash;
}
}
/* Generate digest */
if ( ( rc = tlskey_tbshash ( &tls->key, &tls_client, digest, NULL, 0,
tbshash ) ) != 0 ) {
DBGC ( tls, "TLS %p could not generate CertificateVerify "
"digest: %s\n", tls, strerror ( rc ) );
goto err_tbshash;
}
} else {
/* Sign digest */
if ( ( rc = pubkey_sign ( pubkey, key, digest, tbshash,
&builder ) ) != 0 ) {
DBGC ( tls, "TLS %p could not sign %s digest using %s client "
"private key: %s\n", tls, digest->name, pubkey->name,
strerror ( rc ) );
goto err_pubkey_sign;
/* TLSv1.1 and below use fixed algorithms */
digest = ( ( pubkey == &rsa_algorithm ) ?
&md5_sha1_algorithm : &sha1_algorithm );
}
/* Construct Certificate Verify record */
{
size_t digestsize = digest->digestsize;
uint8_t tbshash[digestsize];
int use_sig_hash = ( ( sig_hash == NULL ) ? 0 : 1 );
struct {
uint32_t type_length;
@@ -2259,6 +2254,25 @@ static int tls_send_certificate_verify ( struct tls_connection *tls ) {
uint16_t signature_len;
} __attribute__ (( packed )) header;
/* Generate digest */
if ( ( rc = tlskey_tbshash ( &tls->key, &tls_client, digest,
NULL, 0, tbshash ) ) != 0 ) {
DBGC ( tls, "TLS %p could not generate "
"CertificateVerify digest: %s\n",
tls, strerror ( rc ) );
goto err_tbshash;
}
/* Sign digest */
if ( ( rc = pubkey_sign ( pubkey, key, digest, tbshash,
&builder ) ) != 0 ) {
DBGC ( tls, "TLS %p could not sign %s digest using "
"%s client private key: %s\n", tls,
digest->name, pubkey->name, strerror ( rc ) );
goto err_pubkey_sign;
}
/* Construct header */
header.type_length = ( cpu_to_le32 ( TLS_CERTIFICATE_VERIFY ) |
htonl ( builder.len +
sizeof ( header ) -
@@ -2269,6 +2283,7 @@ static int tls_send_certificate_verify ( struct tls_connection *tls ) {
}
header.signature_len = htons ( builder.len );
/* Prepend header */
if ( ( rc = asn1_prepend_raw ( &builder, &header,
sizeof ( header ) ) ) != 0 ) {
DBGC ( tls, "TLS %p could not construct Certificate "
@@ -2870,7 +2885,8 @@ static int tls_verify_signature ( struct tls_connection *tls,
sig_hash = &tmp;
memset ( sig_hash, 0, sizeof ( *sig_hash ) );
sig_hash->pubkey = suite->pubkey;
sig_hash->digest = &md5_sha1_algorithm;
sig_hash->digest = ( ( suite->pubkey == &rsa_algorithm ) ?
&md5_sha1_algorithm : &sha1_algorithm );
}
/* Verify signature */