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Fix miscalculation of maximum TLS 1.3 HKDF label length

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Signed-off-by: Hanno Becker <hanno.becker@arm.com>
This commit is contained in:
Hanno Becker 2020-09-10 09:23:12 +01:00
parent 29ea84e906
commit 2dfe1327e5
1 changed files with 7 additions and 4 deletions
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11
library/ssl_tls13_keys.c
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@ -75,6 +75,8 @@ struct mbedtls_ssl_tls1_3_labels_struct const mbedtls_ssl_tls1_3_labels =
* the HkdfLabel structure on success. * the HkdfLabel structure on success.
*/ */
static const char tls1_3_label_prefix[6] = "tls13 ";
#define SSL_TLS1_3_KEY_SCHEDULE_HKDF_LABEL_LEN( label_len, context_len ) \ #define SSL_TLS1_3_KEY_SCHEDULE_HKDF_LABEL_LEN( label_len, context_len ) \
( 2 /* expansion length */ \ ( 2 /* expansion length */ \
+ 1 /* label length */ \ + 1 /* label length */ \
@ -84,6 +86,7 @@ struct mbedtls_ssl_tls1_3_labels_struct const mbedtls_ssl_tls1_3_labels =
#define SSL_TLS1_3_KEY_SCHEDULE_MAX_HKDF_LABEL_LEN \ #define SSL_TLS1_3_KEY_SCHEDULE_MAX_HKDF_LABEL_LEN \
SSL_TLS1_3_KEY_SCHEDULE_HKDF_LABEL_LEN( \ SSL_TLS1_3_KEY_SCHEDULE_HKDF_LABEL_LEN( \
sizeof(tls1_3_label_prefix) + \
MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_LABEL_LEN, \ MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_LABEL_LEN, \
MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_CONTEXT_LEN ) MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_CONTEXT_LEN )
@ -93,8 +96,8 @@ static void ssl_tls1_3_hkdf_encode_label(
const unsigned char *ctx, size_t clen, const unsigned char *ctx, size_t clen,
unsigned char *dst, size_t *dlen ) unsigned char *dst, size_t *dlen )
{ {
const char label_prefix[6] = "tls13 "; size_t total_label_len =
size_t total_label_len = sizeof( label_prefix ) + llen; sizeof(tls1_3_label_prefix) + llen;
size_t total_hkdf_lbl_len = size_t total_hkdf_lbl_len =
SSL_TLS1_3_KEY_SCHEDULE_HKDF_LABEL_LEN( total_label_len, clen ); SSL_TLS1_3_KEY_SCHEDULE_HKDF_LABEL_LEN( total_label_len, clen );
@ -106,8 +109,8 @@ static void ssl_tls1_3_hkdf_encode_label(
/* Add label incl. prefix */ /* Add label incl. prefix */
*p++ = (unsigned char)( total_label_len & 0xFF ); *p++ = (unsigned char)( total_label_len & 0xFF );
memcpy( p, label_prefix, sizeof(label_prefix) ); memcpy( p, tls1_3_label_prefix, sizeof(tls1_3_label_prefix) );
p += sizeof(label_prefix); p += sizeof(tls1_3_label_prefix);
memcpy( p, label, llen ); memcpy( p, label, llen );
p += llen; p += llen;