Reformatting of s3_{cbc|clnt}.c
Change-Id: Ie873bdf0dd5a66e76e6ebf909b1f1fe29b6fa611
This commit is contained in:
Adam Langley
+408
-429
@@ -76,27 +76,25 @@
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* 0: (in non-constant time) if the record is publicly invalid.
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* 1: if the padding was valid
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* -1: otherwise. */
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int ssl3_cbc_remove_padding(const SSL* s,
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SSL3_RECORD *rec,
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unsigned block_size,
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unsigned mac_size)
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{
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unsigned padding_length, good;
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const unsigned overhead = 1 /* padding length byte */ + mac_size;
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int ssl3_cbc_remove_padding(const SSL *s, SSL3_RECORD *rec, unsigned block_size,
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unsigned mac_size) {
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unsigned padding_length, good;
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const unsigned overhead = 1 /* padding length byte */ + mac_size;
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/* These lengths are all public so we can test them in non-constant
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* time. */
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if (overhead > rec->length)
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return 0;
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/* These lengths are all public so we can test them in non-constant
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* time. */
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if (overhead > rec->length) {
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return 0;
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}
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padding_length = rec->data[rec->length-1];
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good = constant_time_ge(rec->length, padding_length+overhead);
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/* SSLv3 requires that the padding is minimal. */
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good &= constant_time_ge(block_size, padding_length+1);
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padding_length = good & (padding_length+1);
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rec->length -= padding_length;
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rec->type |= padding_length<<8; /* kludge: pass padding length */
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return constant_time_select_int(good, 1, -1);
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padding_length = rec->data[rec->length - 1];
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good = constant_time_ge(rec->length, padding_length + overhead);
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/* SSLv3 requires that the padding is minimal. */
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good &= constant_time_ge(block_size, padding_length + 1);
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padding_length = good & (padding_length + 1);
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rec->length -= padding_length;
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rec->type |= padding_length << 8; /* kludge: pass padding length */
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return constant_time_select_int(good, 1, -1);
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}
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/* tls1_cbc_remove_padding removes the CBC padding from the decrypted, TLS, CBC
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@@ -110,64 +108,61 @@ int ssl3_cbc_remove_padding(const SSL* s,
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* 0: (in non-constant time) if the record is publicly invalid.
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* 1: if the padding was valid
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* -1: otherwise. */
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int tls1_cbc_remove_padding(const SSL* s,
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SSL3_RECORD *rec,
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unsigned block_size,
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unsigned mac_size)
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{
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unsigned padding_length, good, to_check, i;
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const unsigned overhead = 1 /* padding length byte */ + mac_size;
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/* Check if version requires explicit IV */
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if (SSL_USE_EXPLICIT_IV(s))
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{
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/* These lengths are all public so we can test them in
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* non-constant time.
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*/
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if (overhead + block_size > rec->length)
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return 0;
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/* We can now safely skip explicit IV */
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rec->data += block_size;
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rec->input += block_size;
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rec->length -= block_size;
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}
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else if (overhead > rec->length)
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return 0;
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int tls1_cbc_remove_padding(const SSL *s, SSL3_RECORD *rec, unsigned block_size,
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unsigned mac_size) {
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unsigned padding_length, good, to_check, i;
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const unsigned overhead = 1 /* padding length byte */ + mac_size;
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padding_length = rec->data[rec->length-1];
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/* Check if version requires explicit IV */
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if (SSL_USE_EXPLICIT_IV(s)) {
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/* These lengths are all public so we can test them in
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* non-constant time. */
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if (overhead + block_size > rec->length) {
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return 0;
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}
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/* We can now safely skip explicit IV */
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rec->data += block_size;
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rec->input += block_size;
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rec->length -= block_size;
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} else if (overhead > rec->length) {
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return 0;
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}
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good = constant_time_ge(rec->length, overhead+padding_length);
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/* The padding consists of a length byte at the end of the record and
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* then that many bytes of padding, all with the same value as the
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* length byte. Thus, with the length byte included, there are i+1
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* bytes of padding.
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*
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* We can't check just |padding_length+1| bytes because that leaks
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* decrypted information. Therefore we always have to check the maximum
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* amount of padding possible. (Again, the length of the record is
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* public information so we can use it.) */
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to_check = 256; /* maximum amount of padding, inc length byte. */
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if (to_check > rec->length)
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to_check = rec->length;
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padding_length = rec->data[rec->length - 1];
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for (i = 0; i < to_check; i++)
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{
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unsigned char mask = constant_time_ge_8(padding_length, i);
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unsigned char b = rec->data[rec->length-1-i];
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/* The final |padding_length+1| bytes should all have the value
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* |padding_length|. Therefore the XOR should be zero. */
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good &= ~(mask&(padding_length ^ b));
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}
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good = constant_time_ge(rec->length, overhead + padding_length);
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/* The padding consists of a length byte at the end of the record and
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* then that many bytes of padding, all with the same value as the
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* length byte. Thus, with the length byte included, there are i+1
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* bytes of padding.
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*
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* We can't check just |padding_length+1| bytes because that leaks
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* decrypted information. Therefore we always have to check the maximum
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* amount of padding possible. (Again, the length of the record is
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* public information so we can use it.) */
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to_check = 256; /* maximum amount of padding, inc length byte. */
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if (to_check > rec->length) {
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to_check = rec->length;
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}
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/* If any of the final |padding_length+1| bytes had the wrong value,
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* one or more of the lower eight bits of |good| will be cleared. */
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good = constant_time_eq(0xff, good & 0xff);
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for (i = 0; i < to_check; i++) {
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unsigned char mask = constant_time_ge_8(padding_length, i);
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unsigned char b = rec->data[rec->length - 1 - i];
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/* The final |padding_length+1| bytes should all have the value
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* |padding_length|. Therefore the XOR should be zero. */
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good &= ~(mask & (padding_length ^ b));
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}
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padding_length = good & (padding_length+1);
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rec->length -= padding_length;
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rec->type |= padding_length<<8; /* kludge: pass padding length */
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/* If any of the final |padding_length+1| bytes had the wrong value,
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* one or more of the lower eight bits of |good| will be cleared. */
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good = constant_time_eq(0xff, good & 0xff);
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return constant_time_select_int(good, 1, -1);
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}
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padding_length = good & (padding_length + 1);
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rec->length -= padding_length;
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rec->type |= padding_length << 8; /* kludge: pass padding length */
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return constant_time_select_int(good, 1, -1);
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}
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/* ssl3_cbc_copy_mac copies |md_size| bytes from the end of |rec| to |out| in
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* constant time (independent of the concrete value of rec->length, which may
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@@ -188,144 +183,135 @@ int tls1_cbc_remove_padding(const SSL* s,
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*/
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#define CBC_MAC_ROTATE_IN_PLACE
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void ssl3_cbc_copy_mac(unsigned char* out,
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const SSL3_RECORD *rec,
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unsigned md_size,unsigned orig_len)
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{
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void ssl3_cbc_copy_mac(unsigned char *out, const SSL3_RECORD *rec,
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unsigned md_size, unsigned orig_len) {
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#if defined(CBC_MAC_ROTATE_IN_PLACE)
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unsigned char rotated_mac_buf[64+EVP_MAX_MD_SIZE];
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unsigned char *rotated_mac;
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unsigned char rotated_mac_buf[64 + EVP_MAX_MD_SIZE];
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unsigned char *rotated_mac;
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#else
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unsigned char rotated_mac[EVP_MAX_MD_SIZE];
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unsigned char rotated_mac[EVP_MAX_MD_SIZE];
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#endif
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/* mac_end is the index of |rec->data| just after the end of the MAC. */
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unsigned mac_end = rec->length;
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unsigned mac_start = mac_end - md_size;
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/* scan_start contains the number of bytes that we can ignore because
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* the MAC's position can only vary by 255 bytes. */
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unsigned scan_start = 0;
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unsigned i, j;
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unsigned div_spoiler;
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unsigned rotate_offset;
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/* mac_end is the index of |rec->data| just after the end of the MAC. */
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unsigned mac_end = rec->length;
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unsigned mac_start = mac_end - md_size;
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/* scan_start contains the number of bytes that we can ignore because
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* the MAC's position can only vary by 255 bytes. */
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unsigned scan_start = 0;
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unsigned i, j;
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unsigned div_spoiler;
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unsigned rotate_offset;
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assert(orig_len >= md_size);
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assert(md_size <= EVP_MAX_MD_SIZE);
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assert(orig_len >= md_size);
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assert(md_size <= EVP_MAX_MD_SIZE);
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#if defined(CBC_MAC_ROTATE_IN_PLACE)
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rotated_mac = rotated_mac_buf + ((0-(size_t)rotated_mac_buf)&63);
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rotated_mac = rotated_mac_buf + ((0 - (size_t)rotated_mac_buf) & 63);
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#endif
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/* This information is public so it's safe to branch based on it. */
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if (orig_len > md_size + 255 + 1)
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scan_start = orig_len - (md_size + 255 + 1);
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/* div_spoiler contains a multiple of md_size that is used to cause the
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* modulo operation to be constant time. Without this, the time varies
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* based on the amount of padding when running on Intel chips at least.
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*
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* The aim of right-shifting md_size is so that the compiler doesn't
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* figure out that it can remove div_spoiler as that would require it
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* to prove that md_size is always even, which I hope is beyond it. */
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div_spoiler = md_size >> 1;
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div_spoiler <<= (sizeof(div_spoiler)-1)*8;
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rotate_offset = (div_spoiler + mac_start - scan_start) % md_size;
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/* This information is public so it's safe to branch based on it. */
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if (orig_len > md_size + 255 + 1) {
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scan_start = orig_len - (md_size + 255 + 1);
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}
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/* div_spoiler contains a multiple of md_size that is used to cause the
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* modulo operation to be constant time. Without this, the time varies
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* based on the amount of padding when running on Intel chips at least.
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*
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* The aim of right-shifting md_size is so that the compiler doesn't
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* figure out that it can remove div_spoiler as that would require it
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* to prove that md_size is always even, which I hope is beyond it. */
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div_spoiler = md_size >> 1;
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div_spoiler <<= (sizeof(div_spoiler) - 1) * 8;
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rotate_offset = (div_spoiler + mac_start - scan_start) % md_size;
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memset(rotated_mac, 0, md_size);
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for (i = scan_start, j = 0; i < orig_len; i++)
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{
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unsigned char mac_started = constant_time_ge_8(i, mac_start);
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unsigned char mac_ended = constant_time_ge_8(i, mac_end);
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unsigned char b = rec->data[i];
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rotated_mac[j++] |= b & mac_started & ~mac_ended;
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j &= constant_time_lt(j,md_size);
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}
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memset(rotated_mac, 0, md_size);
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for (i = scan_start, j = 0; i < orig_len; i++) {
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unsigned char mac_started = constant_time_ge_8(i, mac_start);
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unsigned char mac_ended = constant_time_ge_8(i, mac_end);
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unsigned char b = rec->data[i];
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rotated_mac[j++] |= b & mac_started & ~mac_ended;
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j &= constant_time_lt(j, md_size);
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}
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/* Now rotate the MAC */
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/* Now rotate the MAC */
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#if defined(CBC_MAC_ROTATE_IN_PLACE)
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j = 0;
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for (i = 0; i < md_size; i++)
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{
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/* in case cache-line is 32 bytes, touch second line */
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((volatile unsigned char *)rotated_mac)[rotate_offset^32];
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out[j++] = rotated_mac[rotate_offset++];
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rotate_offset &= constant_time_lt(rotate_offset,md_size);
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}
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j = 0;
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for (i = 0; i < md_size; i++) {
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/* in case cache-line is 32 bytes, touch second line */
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((volatile unsigned char *)rotated_mac)[rotate_offset ^ 32];
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out[j++] = rotated_mac[rotate_offset++];
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rotate_offset &= constant_time_lt(rotate_offset, md_size);
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}
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#else
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memset(out, 0, md_size);
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rotate_offset = md_size - rotate_offset;
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rotate_offset &= constant_time_lt(rotate_offset,md_size);
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for (i = 0; i < md_size; i++)
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{
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for (j = 0; j < md_size; j++)
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out[j] |= rotated_mac[i] & constant_time_eq_8(j, rotate_offset);
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rotate_offset++;
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rotate_offset &= constant_time_lt(rotate_offset,md_size);
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}
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memset(out, 0, md_size);
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rotate_offset = md_size - rotate_offset;
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rotate_offset &= constant_time_lt(rotate_offset, md_size);
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for (i = 0; i < md_size; i++) {
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for (j = 0; j < md_size; j++) {
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out[j] |= rotated_mac[i] & constant_time_eq_8(j, rotate_offset);
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}
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rotate_offset++;
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rotate_offset &= constant_time_lt(rotate_offset, md_size);
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}
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#endif
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}
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}
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/* u32toLE serialises an unsigned, 32-bit number (n) as four bytes at (p) in
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* little-endian order. The value of p is advanced by four. */
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#define u32toLE(n, p) \
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(*((p)++)=(unsigned char)(n), \
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*((p)++)=(unsigned char)(n>>8), \
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*((p)++)=(unsigned char)(n>>16), \
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*((p)++)=(unsigned char)(n>>24))
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(*((p)++)=(unsigned char)(n), \
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*((p)++)=(unsigned char)(n>>8), \
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*((p)++)=(unsigned char)(n>>16), \
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*((p)++)=(unsigned char)(n>>24))
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/* These functions serialize the state of a hash and thus perform the standard
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* "final" operation without adding the padding and length that such a function
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* typically does. */
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static void tls1_sha1_final_raw(void* ctx, unsigned char *md_out)
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{
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SHA_CTX *sha1 = ctx;
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l2n(sha1->h0, md_out);
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l2n(sha1->h1, md_out);
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l2n(sha1->h2, md_out);
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l2n(sha1->h3, md_out);
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l2n(sha1->h4, md_out);
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}
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static void tls1_sha1_final_raw(void *ctx, unsigned char *md_out) {
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SHA_CTX *sha1 = ctx;
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l2n(sha1->h0, md_out);
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l2n(sha1->h1, md_out);
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l2n(sha1->h2, md_out);
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l2n(sha1->h3, md_out);
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l2n(sha1->h4, md_out);
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}
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#define LARGEST_DIGEST_CTX SHA_CTX
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static void tls1_sha256_final_raw(void* ctx, unsigned char *md_out)
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{
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SHA256_CTX *sha256 = ctx;
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unsigned i;
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static void tls1_sha256_final_raw(void *ctx, unsigned char *md_out) {
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SHA256_CTX *sha256 = ctx;
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unsigned i;
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for (i = 0; i < 8; i++)
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{
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l2n(sha256->h[i], md_out);
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}
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}
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for (i = 0; i < 8; i++) {
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l2n(sha256->h[i], md_out);
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}
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}
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#undef LARGEST_DIGEST_CTX
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#define LARGEST_DIGEST_CTX SHA256_CTX
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static void tls1_sha512_final_raw(void* ctx, unsigned char *md_out)
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{
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SHA512_CTX *sha512 = ctx;
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unsigned i;
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static void tls1_sha512_final_raw(void *ctx, unsigned char *md_out) {
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SHA512_CTX *sha512 = ctx;
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unsigned i;
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for (i = 0; i < 8; i++)
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{
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l2n8(sha512->h[i], md_out);
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}
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}
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for (i = 0; i < 8; i++) {
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l2n8(sha512->h[i], md_out);
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}
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}
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#undef LARGEST_DIGEST_CTX
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#define LARGEST_DIGEST_CTX SHA512_CTX
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/* ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function
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* which ssl3_cbc_digest_record supports. */
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char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx)
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{
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switch (EVP_MD_CTX_type(ctx))
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{
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case NID_sha1:
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case NID_sha256:
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case NID_sha384:
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return 1;
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default:
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return 0;
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}
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}
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char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx) {
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switch (EVP_MD_CTX_type(ctx)) {
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case NID_sha1:
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case NID_sha256:
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case NID_sha384:
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return 1;
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default:
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return 0;
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}
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}
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/* ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS
|
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* record.
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@@ -346,277 +332,270 @@ char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx)
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* functions, above, we know that data_plus_mac_size is large enough to contain
|
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* a padding byte and MAC. (If the padding was invalid, it might contain the
|
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* padding too. ) */
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int ssl3_cbc_digest_record(
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const EVP_MD_CTX *ctx,
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unsigned char* md_out,
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size_t* md_out_size,
|
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const unsigned char header[13],
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const unsigned char *data,
|
||||
size_t data_plus_mac_size,
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size_t data_plus_mac_plus_padding_size,
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const unsigned char *mac_secret,
|
||||
unsigned mac_secret_length,
|
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char is_sslv3)
|
||||
{
|
||||
union { double align;
|
||||
unsigned char c[sizeof(LARGEST_DIGEST_CTX)]; } md_state;
|
||||
void (*md_final_raw)(void *ctx, unsigned char *md_out);
|
||||
void (*md_transform)(void *ctx, const unsigned char *block);
|
||||
unsigned md_size, md_block_size = 64;
|
||||
unsigned sslv3_pad_length = 40, header_length, variance_blocks,
|
||||
len, max_mac_bytes, num_blocks,
|
||||
num_starting_blocks, k, mac_end_offset, c, index_a, index_b;
|
||||
unsigned int bits; /* at most 18 bits */
|
||||
unsigned char length_bytes[MAX_HASH_BIT_COUNT_BYTES];
|
||||
/* hmac_pad is the masked HMAC key. */
|
||||
unsigned char hmac_pad[MAX_HASH_BLOCK_SIZE];
|
||||
unsigned char first_block[MAX_HASH_BLOCK_SIZE];
|
||||
unsigned char mac_out[EVP_MAX_MD_SIZE];
|
||||
unsigned i, j, md_out_size_u;
|
||||
EVP_MD_CTX md_ctx;
|
||||
/* mdLengthSize is the number of bytes in the length field that terminates
|
||||
* the hash. */
|
||||
unsigned md_length_size = 8;
|
||||
int 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) {
|
||||
union {
|
||||
double align;
|
||||
unsigned char c[sizeof(LARGEST_DIGEST_CTX)];
|
||||
} md_state;
|
||||
void (*md_final_raw)(void *ctx, unsigned char *md_out);
|
||||
void (*md_transform)(void *ctx, const unsigned char *block);
|
||||
unsigned md_size, md_block_size = 64;
|
||||
unsigned sslv3_pad_length = 40, header_length, variance_blocks, len,
|
||||
max_mac_bytes, num_blocks, num_starting_blocks, k, mac_end_offset, c,
|
||||
index_a, index_b;
|
||||
unsigned int bits; /* at most 18 bits */
|
||||
unsigned char length_bytes[MAX_HASH_BIT_COUNT_BYTES];
|
||||
/* hmac_pad is the masked HMAC key. */
|
||||
unsigned char hmac_pad[MAX_HASH_BLOCK_SIZE];
|
||||
unsigned char first_block[MAX_HASH_BLOCK_SIZE];
|
||||
unsigned char mac_out[EVP_MAX_MD_SIZE];
|
||||
unsigned i, j, md_out_size_u;
|
||||
EVP_MD_CTX md_ctx;
|
||||
/* mdLengthSize is the number of bytes in the length field that terminates
|
||||
* the hash. */
|
||||
unsigned md_length_size = 8;
|
||||
|
||||
/* This is a, hopefully redundant, check that allows us to forget about
|
||||
* many possible overflows later in this function. */
|
||||
assert(data_plus_mac_plus_padding_size < 1024*1024);
|
||||
/* This is a, hopefully redundant, check that allows us to forget about
|
||||
* many possible overflows later in this function. */
|
||||
assert(data_plus_mac_plus_padding_size < 1024 * 1024);
|
||||
|
||||
switch (EVP_MD_CTX_type(ctx))
|
||||
{
|
||||
case NID_sha1:
|
||||
SHA1_Init((SHA_CTX*)md_state.c);
|
||||
md_final_raw = tls1_sha1_final_raw;
|
||||
md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA1_Transform;
|
||||
md_size = 20;
|
||||
break;
|
||||
case NID_sha256:
|
||||
SHA256_Init((SHA256_CTX*)md_state.c);
|
||||
md_final_raw = tls1_sha256_final_raw;
|
||||
md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA256_Transform;
|
||||
md_size = 32;
|
||||
break;
|
||||
case NID_sha384:
|
||||
SHA384_Init((SHA512_CTX*)md_state.c);
|
||||
md_final_raw = tls1_sha512_final_raw;
|
||||
md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA512_Transform;
|
||||
md_size = 384/8;
|
||||
md_block_size = 128;
|
||||
md_length_size = 16;
|
||||
break;
|
||||
default:
|
||||
/* ssl3_cbc_record_digest_supported should have been
|
||||
* called first to check that the hash function is
|
||||
* supported. */
|
||||
assert(0);
|
||||
*md_out_size = 0;
|
||||
return 0;
|
||||
}
|
||||
switch (EVP_MD_CTX_type(ctx)) {
|
||||
case NID_sha1:
|
||||
SHA1_Init((SHA_CTX *)md_state.c);
|
||||
md_final_raw = tls1_sha1_final_raw;
|
||||
md_transform =
|
||||
(void (*)(void *ctx, const unsigned char *block))SHA1_Transform;
|
||||
md_size = 20;
|
||||
break;
|
||||
|
||||
assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES);
|
||||
assert(md_block_size <= MAX_HASH_BLOCK_SIZE);
|
||||
assert(md_size <= EVP_MAX_MD_SIZE);
|
||||
case NID_sha256:
|
||||
SHA256_Init((SHA256_CTX *)md_state.c);
|
||||
md_final_raw = tls1_sha256_final_raw;
|
||||
md_transform =
|
||||
(void (*)(void *ctx, const unsigned char *block))SHA256_Transform;
|
||||
md_size = 32;
|
||||
break;
|
||||
|
||||
header_length = 13;
|
||||
if (is_sslv3)
|
||||
{
|
||||
header_length =
|
||||
mac_secret_length +
|
||||
sslv3_pad_length +
|
||||
8 /* sequence number */ +
|
||||
1 /* record type */ +
|
||||
2 /* record length */;
|
||||
}
|
||||
case NID_sha384:
|
||||
SHA384_Init((SHA512_CTX *)md_state.c);
|
||||
md_final_raw = tls1_sha512_final_raw;
|
||||
md_transform =
|
||||
(void (*)(void *ctx, const unsigned char *block))SHA512_Transform;
|
||||
md_size = 384 / 8;
|
||||
md_block_size = 128;
|
||||
md_length_size = 16;
|
||||
break;
|
||||
|
||||
/* variance_blocks is the number of blocks of the hash that we have to
|
||||
* calculate in constant time because they could be altered by the
|
||||
* padding value.
|
||||
*
|
||||
* In SSLv3, the padding must be minimal so the end of the plaintext
|
||||
* varies by, at most, 15+20 = 35 bytes. (We conservatively assume that
|
||||
* the MAC size varies from 0..20 bytes.) In case the 9 bytes of hash
|
||||
* termination (0x80 + 64-bit length) don't fit in the final block, we
|
||||
* say that the final two blocks can vary based on the padding.
|
||||
*
|
||||
* TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not
|
||||
* required to be minimal. Therefore we say that the final six blocks
|
||||
* can vary based on the padding.
|
||||
*
|
||||
* Later in the function, if the message is short and there obviously
|
||||
* cannot be this many blocks then variance_blocks can be reduced. */
|
||||
variance_blocks = is_sslv3 ? 2 : 6;
|
||||
/* From now on we're dealing with the MAC, which conceptually has 13
|
||||
* bytes of `header' before the start of the data (TLS) or 71/75 bytes
|
||||
* (SSLv3) */
|
||||
len = data_plus_mac_plus_padding_size + header_length;
|
||||
/* max_mac_bytes contains the maximum bytes of bytes in the MAC, including
|
||||
* |header|, assuming that there's no padding. */
|
||||
max_mac_bytes = len - md_size - 1;
|
||||
/* num_blocks is the maximum number of hash blocks. */
|
||||
num_blocks = (max_mac_bytes + 1 + md_length_size + md_block_size - 1) / md_block_size;
|
||||
/* In order to calculate the MAC in constant time we have to handle
|
||||
* the final blocks specially because the padding value could cause the
|
||||
* end to appear somewhere in the final |variance_blocks| blocks and we
|
||||
* can't leak where. However, |num_starting_blocks| worth of data can
|
||||
* be hashed right away because no padding value can affect whether
|
||||
* they are plaintext. */
|
||||
num_starting_blocks = 0;
|
||||
/* k is the starting byte offset into the conceptual header||data where
|
||||
* we start processing. */
|
||||
k = 0;
|
||||
/* mac_end_offset is the index just past the end of the data to be
|
||||
* MACed. */
|
||||
mac_end_offset = data_plus_mac_size + header_length - md_size;
|
||||
/* c is the index of the 0x80 byte in the final hash block that
|
||||
* contains application data. */
|
||||
c = mac_end_offset % md_block_size;
|
||||
/* index_a is the hash block number that contains the 0x80 terminating
|
||||
* value. */
|
||||
index_a = mac_end_offset / md_block_size;
|
||||
/* index_b is the hash block number that contains the 64-bit hash
|
||||
* length, in bits. */
|
||||
index_b = (mac_end_offset + md_length_size) / md_block_size;
|
||||
/* bits is the hash-length in bits. It includes the additional hash
|
||||
* block for the masked HMAC key, or whole of |header| in the case of
|
||||
* SSLv3. */
|
||||
default:
|
||||
/* ssl3_cbc_record_digest_supported should have been
|
||||
* called first to check that the hash function is
|
||||
* supported. */
|
||||
assert(0);
|
||||
*md_out_size = 0;
|
||||
return 0;
|
||||
}
|
||||
|
||||
/* For SSLv3, if we're going to have any starting blocks then we need
|
||||
* at least two because the header is larger than a single block. */
|
||||
if (num_blocks > variance_blocks + (is_sslv3 ? 1 : 0))
|
||||
{
|
||||
num_starting_blocks = num_blocks - variance_blocks;
|
||||
k = md_block_size*num_starting_blocks;
|
||||
}
|
||||
assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES);
|
||||
assert(md_block_size <= MAX_HASH_BLOCK_SIZE);
|
||||
assert(md_size <= EVP_MAX_MD_SIZE);
|
||||
|
||||
bits = 8*mac_end_offset;
|
||||
if (!is_sslv3)
|
||||
{
|
||||
/* Compute the initial HMAC block. For SSLv3, the padding and
|
||||
* secret bytes are included in |header| because they take more
|
||||
* than a single block. */
|
||||
bits += 8*md_block_size;
|
||||
memset(hmac_pad, 0, md_block_size);
|
||||
assert(mac_secret_length <= sizeof(hmac_pad));
|
||||
memcpy(hmac_pad, mac_secret, mac_secret_length);
|
||||
for (i = 0; i < md_block_size; i++)
|
||||
hmac_pad[i] ^= 0x36;
|
||||
header_length = 13;
|
||||
if (is_sslv3) {
|
||||
header_length = mac_secret_length + sslv3_pad_length +
|
||||
8 /* sequence number */ + 1 /* record type */ +
|
||||
2 /* record length */;
|
||||
}
|
||||
|
||||
md_transform(md_state.c, hmac_pad);
|
||||
}
|
||||
/* variance_blocks is the number of blocks of the hash that we have to
|
||||
* calculate in constant time because they could be altered by the
|
||||
* padding value.
|
||||
*
|
||||
* In SSLv3, the padding must be minimal so the end of the plaintext
|
||||
* varies by, at most, 15+20 = 35 bytes. (We conservatively assume that
|
||||
* the MAC size varies from 0..20 bytes.) In case the 9 bytes of hash
|
||||
* termination (0x80 + 64-bit length) don't fit in the final block, we
|
||||
* say that the final two blocks can vary based on the padding.
|
||||
*
|
||||
* TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not
|
||||
* required to be minimal. Therefore we say that the final six blocks
|
||||
* can vary based on the padding.
|
||||
*
|
||||
* Later in the function, if the message is short and there obviously
|
||||
* cannot be this many blocks then variance_blocks can be reduced. */
|
||||
variance_blocks = is_sslv3 ? 2 : 6;
|
||||
/* From now on we're dealing with the MAC, which conceptually has 13
|
||||
* bytes of `header' before the start of the data (TLS) or 71/75 bytes
|
||||
* (SSLv3) */
|
||||
len = data_plus_mac_plus_padding_size + header_length;
|
||||
/* max_mac_bytes contains the maximum bytes of bytes in the MAC, including
|
||||
* |header|, assuming that there's no padding. */
|
||||
max_mac_bytes = len - md_size - 1;
|
||||
/* num_blocks is the maximum number of hash blocks. */
|
||||
num_blocks =
|
||||
(max_mac_bytes + 1 + md_length_size + md_block_size - 1) / md_block_size;
|
||||
/* In order to calculate the MAC in constant time we have to handle
|
||||
* the final blocks specially because the padding value could cause the
|
||||
* end to appear somewhere in the final |variance_blocks| blocks and we
|
||||
* can't leak where. However, |num_starting_blocks| worth of data can
|
||||
* be hashed right away because no padding value can affect whether
|
||||
* they are plaintext. */
|
||||
num_starting_blocks = 0;
|
||||
/* k is the starting byte offset into the conceptual header||data where
|
||||
* we start processing. */
|
||||
k = 0;
|
||||
/* mac_end_offset is the index just past the end of the data to be
|
||||
* MACed. */
|
||||
mac_end_offset = data_plus_mac_size + header_length - md_size;
|
||||
/* c is the index of the 0x80 byte in the final hash block that
|
||||
* contains application data. */
|
||||
c = mac_end_offset % md_block_size;
|
||||
/* index_a is the hash block number that contains the 0x80 terminating
|
||||
* value. */
|
||||
index_a = mac_end_offset / md_block_size;
|
||||
/* index_b is the hash block number that contains the 64-bit hash
|
||||
* length, in bits. */
|
||||
index_b = (mac_end_offset + md_length_size) / md_block_size;
|
||||
/* bits is the hash-length in bits. It includes the additional hash
|
||||
* block for the masked HMAC key, or whole of |header| in the case of
|
||||
* SSLv3. */
|
||||
|
||||
memset(length_bytes,0,md_length_size-4);
|
||||
length_bytes[md_length_size-4] = (unsigned char)(bits>>24);
|
||||
length_bytes[md_length_size-3] = (unsigned char)(bits>>16);
|
||||
length_bytes[md_length_size-2] = (unsigned char)(bits>>8);
|
||||
length_bytes[md_length_size-1] = (unsigned char)bits;
|
||||
/* For SSLv3, if we're going to have any starting blocks then we need
|
||||
* at least two because the header is larger than a single block. */
|
||||
if (num_blocks > variance_blocks + (is_sslv3 ? 1 : 0)) {
|
||||
num_starting_blocks = num_blocks - variance_blocks;
|
||||
k = md_block_size * num_starting_blocks;
|
||||
}
|
||||
|
||||
if (k > 0)
|
||||
{
|
||||
if (is_sslv3)
|
||||
{
|
||||
/* The SSLv3 header is larger than a single block.
|
||||
* overhang is the number of bytes beyond a single
|
||||
* block that the header consumes: 7 bytes (SHA1). */
|
||||
unsigned overhang = header_length-md_block_size;
|
||||
md_transform(md_state.c, header);
|
||||
memcpy(first_block, header + md_block_size, overhang);
|
||||
memcpy(first_block + overhang, data, md_block_size-overhang);
|
||||
md_transform(md_state.c, first_block);
|
||||
for (i = 1; i < k/md_block_size - 1; i++)
|
||||
md_transform(md_state.c, data + md_block_size*i - overhang);
|
||||
}
|
||||
else
|
||||
{
|
||||
/* k is a multiple of md_block_size. */
|
||||
memcpy(first_block, header, 13);
|
||||
memcpy(first_block+13, data, md_block_size-13);
|
||||
md_transform(md_state.c, first_block);
|
||||
for (i = 1; i < k/md_block_size; i++)
|
||||
md_transform(md_state.c, data + md_block_size*i - 13);
|
||||
}
|
||||
}
|
||||
bits = 8 * mac_end_offset;
|
||||
if (!is_sslv3) {
|
||||
/* Compute the initial HMAC block. For SSLv3, the padding and
|
||||
* secret bytes are included in |header| because they take more
|
||||
* than a single block. */
|
||||
bits += 8 * md_block_size;
|
||||
memset(hmac_pad, 0, md_block_size);
|
||||
assert(mac_secret_length <= sizeof(hmac_pad));
|
||||
memcpy(hmac_pad, mac_secret, mac_secret_length);
|
||||
for (i = 0; i < md_block_size; i++) {
|
||||
hmac_pad[i] ^= 0x36;
|
||||
}
|
||||
|
||||
memset(mac_out, 0, sizeof(mac_out));
|
||||
md_transform(md_state.c, hmac_pad);
|
||||
}
|
||||
|
||||
/* We now process the final hash blocks. For each block, we construct
|
||||
* it in constant time. If the |i==index_a| then we'll include the 0x80
|
||||
* bytes and zero pad etc. For each block we selectively copy it, in
|
||||
* constant time, to |mac_out|. */
|
||||
for (i = num_starting_blocks; i <= num_starting_blocks+variance_blocks; i++)
|
||||
{
|
||||
unsigned char block[MAX_HASH_BLOCK_SIZE];
|
||||
unsigned char is_block_a = constant_time_eq_8(i, index_a);
|
||||
unsigned char is_block_b = constant_time_eq_8(i, index_b);
|
||||
for (j = 0; j < md_block_size; j++)
|
||||
{
|
||||
unsigned char b = 0, is_past_c, is_past_cp1;
|
||||
if (k < header_length)
|
||||
b = header[k];
|
||||
else if (k < data_plus_mac_plus_padding_size + header_length)
|
||||
b = data[k-header_length];
|
||||
k++;
|
||||
memset(length_bytes, 0, md_length_size - 4);
|
||||
length_bytes[md_length_size - 4] = (unsigned char)(bits >> 24);
|
||||
length_bytes[md_length_size - 3] = (unsigned char)(bits >> 16);
|
||||
length_bytes[md_length_size - 2] = (unsigned char)(bits >> 8);
|
||||
length_bytes[md_length_size - 1] = (unsigned char)bits;
|
||||
|
||||
is_past_c = is_block_a & constant_time_ge_8(j, c);
|
||||
is_past_cp1 = is_block_a & constant_time_ge_8(j, c+1);
|
||||
/* If this is the block containing the end of the
|
||||
* application data, and we are at the offset for the
|
||||
* 0x80 value, then overwrite b with 0x80. */
|
||||
b = constant_time_select_8(is_past_c, 0x80, b);
|
||||
/* If this the the block containing the end of the
|
||||
* application data and we're past the 0x80 value then
|
||||
* just write zero. */
|
||||
b = b&~is_past_cp1;
|
||||
/* If this is index_b (the final block), but not
|
||||
* index_a (the end of the data), then the 64-bit
|
||||
* length didn't fit into index_a and we're having to
|
||||
* add an extra block of zeros. */
|
||||
b &= ~is_block_b | is_block_a;
|
||||
if (k > 0) {
|
||||
if (is_sslv3) {
|
||||
/* The SSLv3 header is larger than a single block.
|
||||
* overhang is the number of bytes beyond a single
|
||||
* block that the header consumes: 7 bytes (SHA1). */
|
||||
unsigned overhang = header_length - md_block_size;
|
||||
md_transform(md_state.c, header);
|
||||
memcpy(first_block, header + md_block_size, overhang);
|
||||
memcpy(first_block + overhang, data, md_block_size - overhang);
|
||||
md_transform(md_state.c, first_block);
|
||||
for (i = 1; i < k / md_block_size - 1; i++) {
|
||||
md_transform(md_state.c, data + md_block_size * i - overhang);
|
||||
}
|
||||
} else {
|
||||
/* k is a multiple of md_block_size. */
|
||||
memcpy(first_block, header, 13);
|
||||
memcpy(first_block + 13, data, md_block_size - 13);
|
||||
md_transform(md_state.c, first_block);
|
||||
for (i = 1; i < k / md_block_size; i++) {
|
||||
md_transform(md_state.c, data + md_block_size * i - 13);
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
/* The final bytes of one of the blocks contains the
|
||||
* length. */
|
||||
if (j >= md_block_size - md_length_size)
|
||||
{
|
||||
/* If this is index_b, write a length byte. */
|
||||
b = constant_time_select_8(is_block_b, length_bytes[j-(md_block_size-md_length_size)], b);
|
||||
}
|
||||
block[j] = b;
|
||||
}
|
||||
memset(mac_out, 0, sizeof(mac_out));
|
||||
|
||||
md_transform(md_state.c, block);
|
||||
md_final_raw(md_state.c, block);
|
||||
/* If this is index_b, copy the hash value to |mac_out|. */
|
||||
for (j = 0; j < md_size; j++)
|
||||
mac_out[j] |= block[j]&is_block_b;
|
||||
}
|
||||
/* We now process the final hash blocks. For each block, we construct
|
||||
* it in constant time. If the |i==index_a| then we'll include the 0x80
|
||||
* bytes and zero pad etc. For each block we selectively copy it, in
|
||||
* constant time, to |mac_out|. */
|
||||
for (i = num_starting_blocks; i <= num_starting_blocks + variance_blocks;
|
||||
i++) {
|
||||
unsigned char block[MAX_HASH_BLOCK_SIZE];
|
||||
unsigned char is_block_a = constant_time_eq_8(i, index_a);
|
||||
unsigned char is_block_b = constant_time_eq_8(i, index_b);
|
||||
for (j = 0; j < md_block_size; j++) {
|
||||
unsigned char b = 0, is_past_c, is_past_cp1;
|
||||
if (k < header_length) {
|
||||
b = header[k];
|
||||
} else if (k < data_plus_mac_plus_padding_size + header_length) {
|
||||
b = data[k - header_length];
|
||||
}
|
||||
k++;
|
||||
|
||||
EVP_MD_CTX_init(&md_ctx);
|
||||
if (!EVP_DigestInit_ex(&md_ctx, ctx->digest, NULL /* engine */))
|
||||
{
|
||||
EVP_MD_CTX_cleanup(&md_ctx);
|
||||
return 0;
|
||||
}
|
||||
is_past_c = is_block_a & constant_time_ge_8(j, c);
|
||||
is_past_cp1 = is_block_a & constant_time_ge_8(j, c + 1);
|
||||
/* If this is the block containing the end of the
|
||||
* application data, and we are at the offset for the
|
||||
* 0x80 value, then overwrite b with 0x80. */
|
||||
b = constant_time_select_8(is_past_c, 0x80, b);
|
||||
/* If this the the block containing the end of the
|
||||
* application data and we're past the 0x80 value then
|
||||
* just write zero. */
|
||||
b = b & ~is_past_cp1;
|
||||
/* If this is index_b (the final block), but not
|
||||
* index_a (the end of the data), then the 64-bit
|
||||
* length didn't fit into index_a and we're having to
|
||||
* add an extra block of zeros. */
|
||||
b &= ~is_block_b | is_block_a;
|
||||
|
||||
if (is_sslv3)
|
||||
{
|
||||
/* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */
|
||||
memset(hmac_pad, 0x5c, sslv3_pad_length);
|
||||
/* The final bytes of one of the blocks contains the
|
||||
* length. */
|
||||
if (j >= md_block_size - md_length_size) {
|
||||
/* If this is index_b, write a length byte. */
|
||||
b = constant_time_select_8(
|
||||
is_block_b, length_bytes[j - (md_block_size - md_length_size)], b);
|
||||
}
|
||||
block[j] = b;
|
||||
}
|
||||
|
||||
EVP_DigestUpdate(&md_ctx, mac_secret, mac_secret_length);
|
||||
EVP_DigestUpdate(&md_ctx, hmac_pad, sslv3_pad_length);
|
||||
EVP_DigestUpdate(&md_ctx, mac_out, md_size);
|
||||
}
|
||||
else
|
||||
{
|
||||
/* Complete the HMAC in the standard manner. */
|
||||
for (i = 0; i < md_block_size; i++)
|
||||
hmac_pad[i] ^= 0x6a;
|
||||
md_transform(md_state.c, block);
|
||||
md_final_raw(md_state.c, block);
|
||||
/* If this is index_b, copy the hash value to |mac_out|. */
|
||||
for (j = 0; j < md_size; j++) {
|
||||
mac_out[j] |= block[j] & is_block_b;
|
||||
}
|
||||
}
|
||||
|
||||
EVP_DigestUpdate(&md_ctx, hmac_pad, md_block_size);
|
||||
EVP_DigestUpdate(&md_ctx, mac_out, md_size);
|
||||
}
|
||||
EVP_DigestFinal(&md_ctx, md_out, &md_out_size_u);
|
||||
*md_out_size = md_out_size_u;
|
||||
EVP_MD_CTX_cleanup(&md_ctx);
|
||||
EVP_MD_CTX_init(&md_ctx);
|
||||
if (!EVP_DigestInit_ex(&md_ctx, ctx->digest, NULL /* engine */)) {
|
||||
EVP_MD_CTX_cleanup(&md_ctx);
|
||||
return 0;
|
||||
}
|
||||
|
||||
return 1;
|
||||
}
|
||||
if (is_sslv3) {
|
||||
/* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */
|
||||
memset(hmac_pad, 0x5c, sslv3_pad_length);
|
||||
|
||||
EVP_DigestUpdate(&md_ctx, mac_secret, mac_secret_length);
|
||||
EVP_DigestUpdate(&md_ctx, hmac_pad, sslv3_pad_length);
|
||||
EVP_DigestUpdate(&md_ctx, mac_out, md_size);
|
||||
} else {
|
||||
/* Complete the HMAC in the standard manner. */
|
||||
for (i = 0; i < md_block_size; i++) {
|
||||
hmac_pad[i] ^= 0x6a;
|
||||
}
|
||||
|
||||
EVP_DigestUpdate(&md_ctx, hmac_pad, md_block_size);
|
||||
EVP_DigestUpdate(&md_ctx, mac_out, md_size);
|
||||
}
|
||||
EVP_DigestFinal(&md_ctx, md_out, &md_out_size_u);
|
||||
*md_out_size = md_out_size_u;
|
||||
EVP_MD_CTX_cleanup(&md_ctx);
|
||||
|
||||
return 1;
|
||||
}
|
||||
|
||||
+2072
-2194
File diff suppressed because it is too large
Load Diff
Reference in New Issue
Block a user