From e5420be6cd09af2550b128575a675490cfba0483 Mon Sep 17 00:00:00 2001
From: Ben Laurie <ben@links.org>
Date: Mon, 28 Jan 2013 17:31:49 +0000
Subject: [PATCH] Make CBC decoding constant time.
This patch makes the decoding of SSLv3 and TLS CBC records constant
time. Without this, a timing side-channel can be used to build a padding
oracle and mount Vaudenay's attack.
This patch also disables the stitched AESNI+SHA mode pending a similar
fix to that code.
In order to be easy to backport, this change is implemented in ssl/,
rather than as a generic AEAD mode. In the future this should be changed
around so that HMAC isn't in ssl/, but crypto/ as FIPS expects.
(cherry picked from commit e130841bccfc0bb9da254dc84e23bc6a1c78a64e)
Conflicts:
crypto/evp/c_allc.c
ssl/ssl_algs.c
ssl/ssl_locl.h
ssl/t1_enc.c
---
crypto/evp/c_allc.c | 1 +
ssl/Makefile | 4 +-
ssl/d1_enc.c | 49 +++--------------
ssl/s3_enc.c | 108 ++++++++++++++++++++++++--------------
ssl/s3_pkt.c | 76 +++++++++++++--------------
ssl/ssl3.h | 4 ++
ssl/ssl_algs.c | 2 +
ssl/ssl_locl.h | 34 ++++++++++++
ssl/t1_enc.c | 124 ++++++++++++++++++++------------------------
9 files changed, 214 insertions(+), 188 deletions(-)
diff --git a/crypto/evp/c_allc.c b/crypto/evp/c_allc.c
index c5f9268378..e67022fc6f 100644
--- a/crypto/evp/c_allc.c
+++ b/crypto/evp/c_allc.c
@@ -194,6 +194,7 @@ void OpenSSL_add_all_ciphers(void)
EVP_add_cipher_alias(SN_aes_256_cbc,"AES256");
EVP_add_cipher_alias(SN_aes_256_cbc,"aes256");
#endif
+#endif
#ifndef OPENSSL_NO_CAMELLIA
EVP_add_cipher(EVP_camellia_128_ecb());
diff --git a/ssl/Makefile b/ssl/Makefile
index 2b275faf6a..79581e4410 100644
--- a/ssl/Makefile
+++ b/ssl/Makefile
@@ -22,7 +22,7 @@ LIB=$(TOP)/libssl.a
SHARED_LIB= libssl$(SHLIB_EXT)
LIBSRC= \
s2_meth.c s2_srvr.c s2_clnt.c s2_lib.c s2_enc.c s2_pkt.c \
- s3_meth.c s3_srvr.c s3_clnt.c s3_lib.c s3_enc.c s3_pkt.c s3_both.c \
+ s3_meth.c s3_srvr.c s3_clnt.c s3_lib.c s3_enc.c s3_pkt.c s3_both.c s3_cbc.c \
s23_meth.c s23_srvr.c s23_clnt.c s23_lib.c s23_pkt.c \
t1_meth.c t1_srvr.c t1_clnt.c t1_lib.c t1_enc.c \
d1_meth.c d1_srvr.c d1_clnt.c d1_lib.c d1_pkt.c \
@@ -33,7 +33,7 @@ LIBSRC= \
bio_ssl.c ssl_err.c kssl.c t1_reneg.c
LIBOBJ= \
s2_meth.o s2_srvr.o s2_clnt.o s2_lib.o s2_enc.o s2_pkt.o \
- s3_meth.o s3_srvr.o s3_clnt.o s3_lib.o s3_enc.o s3_pkt.o s3_both.o \
+ s3_meth.o s3_srvr.o s3_clnt.o s3_lib.o s3_enc.o s3_pkt.o s3_both.o s3_cbc.o \
s23_meth.o s23_srvr.o s23_clnt.o s23_lib.o s23_pkt.o \
t1_meth.o t1_srvr.o t1_clnt.o t1_lib.o t1_enc.o \
d1_meth.o d1_srvr.o d1_clnt.o d1_lib.o d1_pkt.o \
diff --git a/ssl/d1_enc.c b/ssl/d1_enc.c
index 07a5e97ce5..c13b495a08 100644
--- a/ssl/d1_enc.c
+++ b/ssl/d1_enc.c
@@ -131,15 +131,15 @@ int dtls1_enc(SSL *s, int send)
SSL3_RECORD *rec;
EVP_CIPHER_CTX *ds;
unsigned long l;
- int bs,i,ii,j,k,n=0;
+ int bs,i,j,k,mac_size=0;
const EVP_CIPHER *enc;
if (send)
{
if (EVP_MD_CTX_md(s->write_hash))
{
- n=EVP_MD_CTX_size(s->write_hash);
- if (n < 0)
+ mac_size=EVP_MD_CTX_size(s->write_hash);
+ if (mac_size < 0)
return -1;
}
ds=s->enc_write_ctx;
@@ -164,8 +164,8 @@ int dtls1_enc(SSL *s, int send)
{
if (EVP_MD_CTX_md(s->read_hash))
{
- n=EVP_MD_CTX_size(s->read_hash);
- if (n < 0)
+ mac_size=EVP_MD_CTX_size(s->read_hash);
+ if (mac_size < 0)
return -1;
}
ds=s->enc_read_ctx;
@@ -245,44 +245,9 @@ int dtls1_enc(SSL *s, int send)
}
#endif /* KSSL_DEBUG */
+ rec->orig_len = rec->length;
if ((bs != 1) && !send)
- {
- ii=i=rec->data[l-1]; /* padding_length */
- i++;
- if (s->options&SSL_OP_TLS_BLOCK_PADDING_BUG)
- {
- /* First packet is even in size, so check */
- if ((memcmp(s->s3->read_sequence,
- "\0\0\0\0\0\0\0\0",8) == 0) && !(ii & 1))
- s->s3->flags|=TLS1_FLAGS_TLS_PADDING_BUG;
- if (s->s3->flags & TLS1_FLAGS_TLS_PADDING_BUG)
- i--;
- }
- /* TLS 1.0 does not bound the number of padding bytes by the block size.
- * All of them must have value 'padding_length'. */
- if (i + bs > (int)rec->length)
- {
- /* Incorrect padding. SSLerr() and ssl3_alert are done
- * by caller: we don't want to reveal whether this is
- * a decryption error or a MAC verification failure
- * (see http://www.openssl.org/~bodo/tls-cbc.txt)
- */
- return -1;
- }
- for (j=(int)(l-i); j<(int)l; j++)
- {
- if (rec->data[j] != ii)
- {
- /* Incorrect padding */
- return -1;
- }
- }
- rec->length-=i;
-
- rec->data += bs; /* skip the implicit IV */
- rec->input += bs;
- rec->length -= bs;
- }
+ return tls1_cbc_remove_padding(s, rec, bs, mac_size);
}
return(1);
}
diff --git a/ssl/s3_enc.c b/ssl/s3_enc.c
index b14597076d..de5354aefd 100644
--- a/ssl/s3_enc.c
+++ b/ssl/s3_enc.c
@@ -470,7 +470,7 @@ int ssl3_enc(SSL *s, int send)
SSL3_RECORD *rec;
EVP_CIPHER_CTX *ds;
unsigned long l;
- int bs,i;
+ int bs,i,mac_size=0;
const EVP_CIPHER *enc;
if (send)
@@ -531,22 +531,12 @@ int ssl3_enc(SSL *s, int send)
EVP_Cipher(ds,rec->data,rec->input,l);
+ rec->orig_len = rec->length;
+
+ if (EVP_MD_CTX_md(s->read_hash) != NULL)
+ mac_size = EVP_MD_CTX_size(s->read_hash);
if ((bs != 1) && !send)
- {
- i=rec->data[l-1]+1;
- /* SSL 3.0 bounds the number of padding bytes by the block size;
- * padding bytes (except the last one) are arbitrary */
- if (i > bs)
- {
- /* Incorrect padding. SSLerr() and ssl3_alert are done
- * by caller: we don't want to reveal whether this is
- * a decryption error or a MAC verification failure
- * (see http://www.openssl.org/~bodo/tls-cbc.txt) */
- return -1;
- }
- /* now i <= bs <= rec->length */
- rec->length-=i;
- }
+ return ssl3_cbc_remove_padding(s, rec, bs, mac_size);
}
return(1);
}
@@ -704,7 +694,7 @@ int n_ssl3_mac(SSL *ssl, unsigned char *md, int send)
EVP_MD_CTX md_ctx;
const EVP_MD_CTX *hash;
unsigned char *p,rec_char;
- unsigned int md_size;
+ size_t md_size;
int npad;
int t;
@@ -729,28 +719,68 @@ int n_ssl3_mac(SSL *ssl, unsigned char *md, int send)
md_size=t;
npad=(48/md_size)*md_size;
- /* Chop the digest off the end :-) */
- EVP_MD_CTX_init(&md_ctx);
-
- EVP_MD_CTX_copy_ex( &md_ctx,hash);
- EVP_DigestUpdate(&md_ctx,mac_sec,md_size);
- EVP_DigestUpdate(&md_ctx,ssl3_pad_1,npad);
- EVP_DigestUpdate(&md_ctx,seq,8);
- rec_char=rec->type;
- EVP_DigestUpdate(&md_ctx,&rec_char,1);
- p=md;
- s2n(rec->length,p);
- EVP_DigestUpdate(&md_ctx,md,2);
- EVP_DigestUpdate(&md_ctx,rec->input,rec->length);
- EVP_DigestFinal_ex( &md_ctx,md,NULL);
-
- EVP_MD_CTX_copy_ex( &md_ctx,hash);
- EVP_DigestUpdate(&md_ctx,mac_sec,md_size);
- EVP_DigestUpdate(&md_ctx,ssl3_pad_2,npad);
- EVP_DigestUpdate(&md_ctx,md,md_size);
- EVP_DigestFinal_ex( &md_ctx,md,&md_size);
-
- EVP_MD_CTX_cleanup(&md_ctx);
+ if (!send &&
+ EVP_CIPHER_CTX_mode(ssl->enc_read_ctx) == EVP_CIPH_CBC_MODE &&
+ ssl3_cbc_record_digest_supported(hash))
+ {
+ /* This is a CBC-encrypted record. We must avoid leaking any
+ * timing-side channel information about how many blocks of
+ * data we are hashing because that gives an attacker a
+ * timing-oracle. */
+
+ /* npad is, at most, 48 bytes and that's with MD5:
+ * 16 + 48 + 8 (sequence bytes) + 1 + 2 = 75.
+ *
+ * With SHA-1 (the largest hash speced for SSLv3) the hash size
+ * goes up 4, but npad goes down by 8, resulting in a smaller
+ * total size. */
+ unsigned char header[75];
+ unsigned j = 0;
+ memcpy(header+j, mac_sec, md_size);
+ j += md_size;
+ memcpy(header+j, ssl3_pad_1, npad);
+ j += npad;
+ memcpy(header+j, seq, 8);
+ j += 8;
+ header[j++] = rec->type;
+ header[j++] = rec->length >> 8;
+ header[j++] = rec->length & 0xff;
+
+ ssl3_cbc_digest_record(
+ hash,
+ md, &md_size,
+ header, rec->input,
+ rec->length + md_size, rec->orig_len,
+ mac_sec, md_size,
+ 1 /* is SSLv3 */);
+ }
+ else
+ {
+ unsigned int md_size_u;
+ /* Chop the digest off the end :-) */
+ EVP_MD_CTX_init(&md_ctx);
+
+ EVP_MD_CTX_copy_ex( &md_ctx,hash);
+ EVP_DigestUpdate(&md_ctx,mac_sec,md_size);
+ EVP_DigestUpdate(&md_ctx,ssl3_pad_1,npad);
+ EVP_DigestUpdate(&md_ctx,seq,8);
+ rec_char=rec->type;
+ EVP_DigestUpdate(&md_ctx,&rec_char,1);
+ p=md;
+ s2n(rec->length,p);
+ EVP_DigestUpdate(&md_ctx,md,2);
+ EVP_DigestUpdate(&md_ctx,rec->input,rec->length);
+ EVP_DigestFinal_ex( &md_ctx,md,NULL);
+
+ EVP_MD_CTX_copy_ex( &md_ctx,hash);
+ EVP_DigestUpdate(&md_ctx,mac_sec,md_size);
+ EVP_DigestUpdate(&md_ctx,ssl3_pad_2,npad);
+ EVP_DigestUpdate(&md_ctx,md,md_size);
+ EVP_DigestFinal_ex( &md_ctx,md,&md_size_u);
+ md_size = md_size_u;
+
+ EVP_MD_CTX_cleanup(&md_ctx);
+ }
ssl3_record_sequence_update(seq);
return(md_size);
diff --git a/ssl/s3_pkt.c b/ssl/s3_pkt.c
index 85ff7022de..2e0c173ecd 100644
--- a/ssl/s3_pkt.c
+++ b/ssl/s3_pkt.c
@@ -289,11 +289,9 @@ static int ssl3_get_record(SSL *s)
unsigned char *p;
unsigned char md[EVP_MAX_MD_SIZE];
short version;
- int mac_size;
+ unsigned mac_size;
int clear=0;
size_t extra;
- int decryption_failed_or_bad_record_mac = 0;
- unsigned char *mac = NULL;
rr= &(s->s3->rrec);
sess=s->session;
@@ -402,17 +400,10 @@ fprintf(stderr, "Record type=%d, Length=%d\n", rr->type, rr->length);
rr->data=rr->input;
enc_err = s->method->ssl3_enc->enc(s,0);
- if (enc_err <= 0)
+ if (enc_err == 0)
{
- if (enc_err == 0)
- /* SSLerr() and ssl3_send_alert() have been called */
- goto err;
-
- /* Otherwise enc_err == -1, which indicates bad padding
- * (rec->length has not been changed in this case).
- * To minimize information leaked via timing, we will perform
- * the MAC computation anyway. */
- decryption_failed_or_bad_record_mac = 1;
+ /* SSLerr() and ssl3_send_alert() have been called */
+ goto err;
}
#ifdef TLS_DEBUG
@@ -430,45 +421,54 @@ printf("\n");
if (!clear)
{
/* !clear => s->read_hash != NULL => mac_size != -1 */
+ unsigned char *mac = NULL;
+ unsigned char mac_tmp[EVP_MAX_MD_SIZE];
mac_size=EVP_MD_CTX_size(s->read_hash);
- OPENSSL_assert(mac_size >= 0);
+ OPENSSL_assert(mac_size <= EVP_MAX_MD_SIZE);
- if (rr->length > SSL3_RT_MAX_COMPRESSED_LENGTH+extra+mac_size)
+ /* orig_len is the length of the record before any padding was
+ * removed. This is public information, as is the MAC in use,
+ * therefore we can safely process the record in a different
+ * amount of time if it's too short to possibly contain a MAC.
+ */
+ if (rr->orig_len < mac_size ||
+ /* CBC records must have a padding length byte too. */
+ (EVP_CIPHER_CTX_mode(s->enc_read_ctx) == EVP_CIPH_CBC_MODE &&
+ rr->orig_len < mac_size+1))
{
-#if 0 /* OK only for stream ciphers (then rr->length is visible from ciphertext anyway) */
- al=SSL_AD_RECORD_OVERFLOW;
- SSLerr(SSL_F_SSL3_GET_RECORD,SSL_R_PRE_MAC_LENGTH_TOO_LONG);
+ al=SSL_AD_DECODE_ERROR;
+ SSLerr(SSL_F_SSL3_GET_RECORD,SSL_R_LENGTH_TOO_SHORT);
goto f_err;
-#else
- decryption_failed_or_bad_record_mac = 1;
-#endif
}
- /* check the MAC for rr->input (it's in mac_size bytes at the tail) */
- if (rr->length >= (unsigned int)mac_size)
+
+ if (EVP_CIPHER_CTX_mode(s->enc_read_ctx) == EVP_CIPH_CBC_MODE)
{
+ /* We update the length so that the TLS header bytes
+ * can be constructed correctly but we need to extract
+ * the MAC in constant time from within the record,
+ * without leaking the contents of the padding bytes.
+ * */
+ mac = mac_tmp;
+ ssl3_cbc_copy_mac(mac_tmp, rr, mac_size);
rr->length -= mac_size;
- mac = &rr->data[rr->length];
}
else
{
- /* record (minus padding) is too short to contain a MAC */
-#if 0 /* OK only for stream ciphers */
- al=SSL_AD_DECODE_ERROR;
- SSLerr(SSL_F_SSL3_GET_RECORD,SSL_R_LENGTH_TOO_SHORT);
- goto f_err;
-#else
- decryption_failed_or_bad_record_mac = 1;
- rr->length = 0;
-#endif
+ /* In this case there's no padding, so |rec->orig_len|
+ * equals |rec->length| and we checked that there's
+ * enough bytes for |mac_size| above. */
+ rr->length -= mac_size;
+ mac = &rr->data[rr->length];
}
- i=s->method->ssl3_enc->mac(s,md,0);
+
+ i=s->method->ssl3_enc->mac(s,md,0 /* not send */);
if (i < 0 || mac == NULL || CRYPTO_memcmp(md, mac, (size_t)mac_size) != 0)
- {
- decryption_failed_or_bad_record_mac = 1;
- }
+ enc_err = -1;
+ if (rr->length > SSL3_RT_MAX_COMPRESSED_LENGTH+extra+mac_size)
+ enc_err = -1;
}
- if (decryption_failed_or_bad_record_mac)
+ if (enc_err < 0)
{
/* A separate 'decryption_failed' alert was introduced with TLS 1.0,
* SSL 3.0 only has 'bad_record_mac'. But unless a decryption
diff --git a/ssl/ssl3.h b/ssl/ssl3.h
index 9c2c41287a..d3bd768c0e 100644
--- a/ssl/ssl3.h
+++ b/ssl/ssl3.h
@@ -349,6 +349,10 @@ typedef struct ssl3_record_st
/*r */ unsigned char *comp; /* only used with decompression - malloc()ed */
/*r */ unsigned long epoch; /* epoch number, needed by DTLS1 */
/*r */ unsigned char seq_num[8]; /* sequence number, needed by DTLS1 */
+/*rw*/ unsigned int orig_len; /* How many bytes were available before padding
+ was removed? This is used to implement the
+ MAC check in constant time for CBC records.
+ */
} SSL3_RECORD;
typedef struct ssl3_buffer_st
diff --git a/ssl/ssl_algs.c b/ssl/ssl_algs.c
index 0967b2dfe4..7f1a042b3d 100644
--- a/ssl/ssl_algs.c
+++ b/ssl/ssl_algs.c
@@ -86,6 +86,8 @@ int SSL_library_init(void)
EVP_add_cipher(EVP_aes_192_cbc());
EVP_add_cipher(EVP_aes_256_cbc());
#endif
+
+#endif
#ifndef OPENSSL_NO_CAMELLIA
EVP_add_cipher(EVP_camellia_128_cbc());
EVP_add_cipher(EVP_camellia_256_cbc());
diff --git a/ssl/ssl_locl.h b/ssl/ssl_locl.h
index 7cf1d19dde..6a4f62af7c 100644
--- a/ssl/ssl_locl.h
+++ b/ssl/ssl_locl.h
@@ -215,6 +215,15 @@
*((c)++)=(unsigned char)(((l)>> 8)&0xff), \
*((c)++)=(unsigned char)(((l) )&0xff))
+#define l2n8(l,c) (*((c)++)=(unsigned char)(((l)>>56)&0xff), \
+ *((c)++)=(unsigned char)(((l)>>48)&0xff), \
+ *((c)++)=(unsigned char)(((l)>>40)&0xff), \
+ *((c)++)=(unsigned char)(((l)>>32)&0xff), \
+ *((c)++)=(unsigned char)(((l)>>24)&0xff), \
+ *((c)++)=(unsigned char)(((l)>>16)&0xff), \
+ *((c)++)=(unsigned char)(((l)>> 8)&0xff), \
+ *((c)++)=(unsigned char)(((l) )&0xff))
+
#define n2l6(c,l) (l =((BN_ULLONG)(*((c)++)))<<40, \
l|=((BN_ULLONG)(*((c)++)))<<32, \
l|=((BN_ULLONG)(*((c)++)))<<24, \
@@ -1079,4 +1088,29 @@ int ssl_add_clienthello_renegotiate_ext(SSL *s, unsigned char *p, int *len,
int maxlen);
int ssl_parse_clienthello_renegotiate_ext(SSL *s, unsigned char *d, int len,
int *al);
+/* s3_cbc.c */
+void ssl3_cbc_copy_mac(unsigned char* out,
+ const SSL3_RECORD *rec,
+ unsigned md_size);
+int ssl3_cbc_remove_padding(const SSL* s,
+ SSL3_RECORD *rec,
+ unsigned block_size,
+ unsigned mac_size);
+int tls1_cbc_remove_padding(const SSL* s,
+ SSL3_RECORD *rec,
+ unsigned block_size,
+ unsigned mac_size);
+char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx);
+void ssl3_cbc_digest_record(
+ const EVP_MD_CTX *ctx,
+ unsigned char* md_out,
+ size_t* md_out_size,
+ const unsigned char header[13],
+ const unsigned char *data,
+ size_t data_plus_mac_size,
+ size_t data_plus_mac_plus_padding_size,
+ const unsigned char *mac_secret,
+ unsigned mac_secret_length,
+ char is_sslv3);
+
#endif
diff --git a/ssl/t1_enc.c b/ssl/t1_enc.c
index 5a0bd66e4b..3fcb77b4dc 100644
--- a/ssl/t1_enc.c
+++ b/ssl/t1_enc.c
@@ -640,7 +640,7 @@ int tls1_enc(SSL *s, int send)
SSL3_RECORD *rec;
EVP_CIPHER_CTX *ds;
unsigned long l;
- int bs,i,ii,j,k,n=0;
+ int bs,i,j,k,pad=0,ret,mac_size=0;
const EVP_CIPHER *enc;
if (send)
@@ -676,11 +676,11 @@ int tls1_enc(SSL *s, int send)
printf("tls1_enc(%d)\n", send);
#endif /* KSSL_DEBUG */
- if ((s->session == NULL) || (ds == NULL) ||
- (enc == NULL))
+ if ((s->session == NULL) || (ds == NULL) || (enc == NULL))
{
memmove(rec->data,rec->input,rec->length);
rec->input=rec->data;
+ ret = 1;
}
else
{
@@ -708,13 +708,13 @@ int tls1_enc(SSL *s, int send)
#ifdef KSSL_DEBUG
{
- unsigned long ui;
+ unsigned long ui;
printf("EVP_Cipher(ds=%p,rec->data=%p,rec->input=%p,l=%ld) ==>\n",
- ds,rec->data,rec->input,l);
+ ds,rec->data,rec->input,l);
printf("\tEVP_CIPHER_CTX: %d buf_len, %d key_len [%d %d], %d iv_len\n",
- ds->buf_len, ds->cipher->key_len,
- DES_KEY_SZ, DES_SCHEDULE_SZ,
- ds->cipher->iv_len);
+ ds->buf_len, ds->cipher->key_len,
+ DES_KEY_SZ, DES_SCHEDULE_SZ,
+ ds->cipher->iv_len);
printf("\t\tIV: ");
for (i=0; i<ds->cipher->iv_len; i++) printf("%02X", ds->iv[i]);
printf("\n");
@@ -738,57 +738,26 @@ int tls1_enc(SSL *s, int send)
#ifdef KSSL_DEBUG
{
- unsigned long i;
- printf("\trec->data=");
+ unsigned long i;
+ printf("\trec->data=");
for (i=0; i<l; i++)
- printf(" %02x", rec->data[i]); printf("\n");
- }
+ printf(" %02x", rec->data[i]); printf("\n");
+ }
#endif /* KSSL_DEBUG */
+ rec->orig_len = rec->length;
+
+ ret = 1;
+ if (EVP_MD_CTX_md(s->read_hash) != NULL)
+ mac_size = EVP_MD_CTX_size(s->read_hash);
if ((bs != 1) && !send)
- {
- ii=i=rec->data[l-1]; /* padding_length */
- i++;
- /* NB: if compression is in operation the first packet
- * may not be of even length so the padding bug check
- * cannot be performed. This bug workaround has been
- * around since SSLeay so hopefully it is either fixed
- * now or no buggy implementation supports compression
- * [steve]
- */
- if ( (s->options&SSL_OP_TLS_BLOCK_PADDING_BUG)
- && !s->expand)
- {
- /* First packet is even in size, so check */
- if ((memcmp(s->s3->read_sequence,
- "\0\0\0\0\0\0\0\0",8) == 0) && !(ii & 1))
- s->s3->flags|=TLS1_FLAGS_TLS_PADDING_BUG;
- if (s->s3->flags & TLS1_FLAGS_TLS_PADDING_BUG)
- i--;
- }
- /* TLS 1.0 does not bound the number of padding bytes by the block size.
- * All of them must have value 'padding_length'. */
- if (i > (int)rec->length)
- {
- /* Incorrect padding. SSLerr() and ssl3_alert are done
- * by caller: we don't want to reveal whether this is
- * a decryption error or a MAC verification failure
- * (see http://www.openssl.org/~bodo/tls-cbc.txt) */
- return -1;
- }
- for (j=(int)(l-i); j<(int)l; j++)
- {
- if (rec->data[j] != ii)
- {
- /* Incorrect padding */
- return -1;
- }
- }
- rec->length-=i;
- }
+ ret = tls1_cbc_remove_padding(s, rec, bs, mac_size);
+ if (pad && !send)
+ rec->length -= pad;
}
- return(1);
+ return ret;
}
+
int tls1_cert_verify_mac(SSL *s, int md_nid, unsigned char *out)
{
unsigned int ret;
@@ -881,7 +850,7 @@ int tls1_mac(SSL *ssl, unsigned char *md, int send)
size_t md_size;
int i;
EVP_MD_CTX hmac, *mac_ctx;
- unsigned char buf[5];
+ unsigned char header[13];
int stream_mac = (send?(ssl->mac_flags & SSL_MAC_FLAG_WRITE_MAC_STREAM):(ssl->mac_flags&SSL_MAC_FLAG_READ_MAC_STREAM));
int t;
@@ -902,12 +871,6 @@ int tls1_mac(SSL *ssl, unsigned char *md, int send)
OPENSSL_assert(t >= 0);
md_size=t;
- buf[0]=rec->type;
- buf[1]=(unsigned char)(ssl->version>>8);
- buf[2]=(unsigned char)(ssl->version);
- buf[3]=rec->length>>8;
- buf[4]=rec->length&0xff;
-
/* I should fix this up TLS TLS TLS TLS TLS XXXXXXXX */
if (stream_mac)
{
@@ -926,17 +889,44 @@ int tls1_mac(SSL *ssl, unsigned char *md, int send)
s2n(send?ssl->d1->w_epoch:ssl->d1->r_epoch, p);
memcpy (p,&seq[2],6);
- EVP_DigestSignUpdate(mac_ctx,dtlsseq,8);
+ memcpy(header, dtlsseq, 8);
}
else
- EVP_DigestSignUpdate(mac_ctx,seq,8);
+ memcpy(header, seq, 8);
+
+ header[8]=rec->type;
+ header[9]=(unsigned char)(ssl->version>>8);
+ header[10]=(unsigned char)(ssl->version);
+ header[11]=(rec->length)>>8;
+ header[12]=(rec->length)&0xff;
- EVP_DigestSignUpdate(mac_ctx,buf,5);
- EVP_DigestSignUpdate(mac_ctx,rec->input,rec->length);
- t=EVP_DigestSignFinal(mac_ctx,md,&md_size);
- OPENSSL_assert(t > 0);
+ if (!send &&
+ EVP_CIPHER_CTX_mode(ssl->enc_read_ctx) == EVP_CIPH_CBC_MODE &&
+ ssl3_cbc_record_digest_supported(mac_ctx))
+ {
+ /* This is a CBC-encrypted record. We must avoid leaking any
+ * timing-side channel information about how many blocks of
+ * data we are hashing because that gives an attacker a
+ * timing-oracle. */
+ ssl3_cbc_digest_record(
+ mac_ctx,
+ md, &md_size,
+ header, rec->input,
+ rec->length + md_size, rec->orig_len,
+ ssl->s3->read_mac_secret,
+ ssl->s3->read_mac_secret_size,
+ 0 /* not SSLv3 */);
+ }
+ else
+ {
+ EVP_DigestSignUpdate(mac_ctx,header,sizeof(header));
+ EVP_DigestSignUpdate(mac_ctx,rec->input,rec->length);
+ t=EVP_DigestSignFinal(mac_ctx,md,&md_size);
+ OPENSSL_assert(t > 0);
+ }
- if (!stream_mac) EVP_MD_CTX_cleanup(&hmac);
+ if (!stream_mac)
+ EVP_MD_CTX_cleanup(&hmac);
#ifdef TLS_DEBUG
printf("sec=");
{unsigned int z; for (z=0; z<md_size; z++) printf("%02X ",mac_sec[z]); printf("\n"); }
--
2.25.1