Experimental encrypt-then-mac support.
Experimental support for encrypt then mac from
draft-gutmann-tls-encrypt-then-mac-02.txt
To enable it set the appropriate extension number (0x10 for the test server)
using e.g. -DTLSEXT_TYPE_encrypt_then_mac=0x10
For non-compliant peers (i.e. just about everything) this should have no
effect.
diff --git a/ssl/s3_pkt.c b/ssl/s3_pkt.c
index 65b742c..3f936c0 100644
--- a/ssl/s3_pkt.c
+++ b/ssl/s3_pkt.c
@@ -408,6 +408,30 @@
/* decrypt in place in 'rr->input' */
rr->data=rr->input;
rr->orig_len=rr->length;
+ /* If in encrypt-then-mac mode calculate mac from encrypted record.
+ * All the details below are public so no timing details can leak.
+ */
+ if (SSL_USE_ETM(s) && s->read_hash)
+ {
+ unsigned char *mac;
+ mac_size=EVP_MD_CTX_size(s->read_hash);
+ OPENSSL_assert(mac_size <= EVP_MAX_MD_SIZE);
+ if (rr->length < mac_size)
+ {
+ al=SSL_AD_DECODE_ERROR;
+ SSLerr(SSL_F_SSL3_GET_RECORD,SSL_R_LENGTH_TOO_SHORT);
+ goto f_err;
+ }
+ rr->length -= mac_size;
+ mac = rr->data + rr->length;
+ i=s->method->ssl3_enc->mac(s,md,0 /* not send */);
+ if (i < 0 || CRYPTO_memcmp(md, mac, (size_t)mac_size) != 0)
+ {
+ al=SSL_AD_BAD_RECORD_MAC;
+ SSLerr(SSL_F_SSL3_GET_RECORD,SSL_R_DECRYPTION_FAILED_OR_BAD_RECORD_MAC);
+ goto f_err;
+ }
+ }
enc_err = s->method->ssl3_enc->enc(s,0);
/* enc_err is:
@@ -430,7 +454,7 @@
/* r->length is now the compressed data plus mac */
if ((sess != NULL) &&
(s->enc_read_ctx != NULL) &&
- (EVP_MD_CTX_md(s->read_hash) != NULL))
+ (EVP_MD_CTX_md(s->read_hash) != NULL) && !SSL_USE_ETM(s))
{
/* s->read_hash != NULL => mac_size != -1 */
unsigned char *mac = NULL;
@@ -820,7 +844,7 @@
* from wr->input. Length should be wr->length.
* wr->data still points in the wb->buf */
- if (mac_size != 0)
+ if (!SSL_USE_ETM(s) && mac_size != 0)
{
if (s->method->ssl3_enc->mac(s,&(p[wr->length + eivlen]),1) < 0)
goto err;
@@ -840,6 +864,13 @@
/* ssl3_enc can only have an error on read */
s->method->ssl3_enc->enc(s,1);
+ if (SSL_USE_ETM(s) && mac_size != 0)
+ {
+ if (s->method->ssl3_enc->mac(s,p + wr->length,1) < 0)
+ goto err;
+ wr->length+=mac_size;
+ }
+
/* record length after mac and block padding */
s2n(wr->length,plen);
