*
*/
-#include "../crypto/constant_time_locl.h"
+#include "internal/constant_time_locl.h"
#include "ssl_locl.h"
#include <openssl/md5.h>
*/
#define MAX_HASH_BLOCK_SIZE 128
-/*-
- * ssl3_cbc_remove_padding removes padding from the decrypted, SSLv3, CBC
- * record in |rec| by updating |rec->length| in constant time.
- *
- * block_size: the block size of the cipher used to encrypt the record.
- * returns:
- * 0: (in non-constant time) if the record is publicly invalid.
- * 1: if the padding was valid
- * -1: otherwise.
- */
-int ssl3_cbc_remove_padding(const SSL *s,
- SSL3_RECORD *rec,
- unsigned block_size, unsigned mac_size)
-{
- unsigned padding_length, good;
- const unsigned overhead = 1 /* padding length byte */ + mac_size;
-
- /*
- * These lengths are all public so we can test them in non-constant time.
- */
- if (overhead > rec->length)
- return 0;
-
- padding_length = rec->data[rec->length - 1];
- good = constant_time_ge(rec->length, padding_length + overhead);
- /* SSLv3 requires that the padding is minimal. */
- good &= constant_time_ge(block_size, padding_length + 1);
- rec->length -= good & (padding_length + 1);
- return constant_time_select_int(good, 1, -1);
-}
-
-/*-
- * tls1_cbc_remove_padding removes the CBC padding from the decrypted, TLS, CBC
- * record in |rec| in constant time and returns 1 if the padding is valid and
- * -1 otherwise. It also removes any explicit IV from the start of the record
- * without leaking any timing about whether there was enough space after the
- * padding was removed.
- *
- * block_size: the block size of the cipher used to encrypt the record.
- * returns:
- * 0: (in non-constant time) if the record is publicly invalid.
- * 1: if the padding was valid
- * -1: otherwise.
- */
-int tls1_cbc_remove_padding(const SSL *s,
- SSL3_RECORD *rec,
- unsigned block_size, unsigned mac_size)
-{
- unsigned padding_length, good, to_check, i;
- const unsigned overhead = 1 /* padding length byte */ + mac_size;
- /* Check if version requires explicit IV */
- if (SSL_USE_EXPLICIT_IV(s)) {
- /*
- * These lengths are all public so we can test them in non-constant
- * time.
- */
- if (overhead + block_size > rec->length)
- return 0;
- /* We can now safely skip explicit IV */
- rec->data += block_size;
- rec->input += block_size;
- rec->length -= block_size;
- rec->orig_len -= block_size;
- } else if (overhead > rec->length)
- return 0;
-
- padding_length = rec->data[rec->length - 1];
-
- /*
- * 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) &&
- !(padding_length & 1)) {
- s->s3->flags |= TLS1_FLAGS_TLS_PADDING_BUG;
- }
- if ((s->s3->flags & TLS1_FLAGS_TLS_PADDING_BUG) && padding_length > 0) {
- padding_length--;
- }
- }
-
- if (EVP_CIPHER_flags(s->enc_read_ctx->cipher) & EVP_CIPH_FLAG_AEAD_CIPHER) {
- /* padding is already verified */
- rec->length -= padding_length + 1;
- return 1;
- }
-
- good = constant_time_ge(rec->length, overhead + padding_length);
- /*
- * The padding consists of a length byte at the end of the record and
- * then that many bytes of padding, all with the same value as the length
- * byte. Thus, with the length byte included, there are i+1 bytes of
- * padding. We can't check just |padding_length+1| bytes because that
- * leaks decrypted information. Therefore we always have to check the
- * maximum amount of padding possible. (Again, the length of the record
- * is public information so we can use it.)
- */
- to_check = 255; /* maximum amount of padding. */
- if (to_check > rec->length - 1)
- to_check = rec->length - 1;
-
- for (i = 0; i < to_check; i++) {
- unsigned char mask = constant_time_ge_8(padding_length, i);
- unsigned char b = rec->data[rec->length - 1 - i];
- /*
- * The final |padding_length+1| bytes should all have the value
- * |padding_length|. Therefore the XOR should be zero.
- */
- good &= ~(mask & (padding_length ^ b));
- }
-
- /*
- * If any of the final |padding_length+1| bytes had the wrong value, one
- * or more of the lower eight bits of |good| will be cleared.
- */
- good = constant_time_eq(0xff, good & 0xff);
- rec->length -= good & (padding_length + 1);
-
- return constant_time_select_int(good, 1, -1);
-}
-
-/*-
- * ssl3_cbc_copy_mac copies |md_size| bytes from the end of |rec| to |out| in
- * constant time (independent of the concrete value of rec->length, which may
- * vary within a 256-byte window).
- *
- * ssl3_cbc_remove_padding or tls1_cbc_remove_padding must be called prior to
- * this function.
- *
- * On entry:
- * rec->orig_len >= md_size
- * md_size <= EVP_MAX_MD_SIZE
- *
- * If CBC_MAC_ROTATE_IN_PLACE is defined then the rotation is performed with
- * variable accesses in a 64-byte-aligned buffer. Assuming that this fits into
- * a single or pair of cache-lines, then the variable memory accesses don't
- * actually affect the timing. CPUs with smaller cache-lines [if any] are
- * not multi-core and are not considered vulnerable to cache-timing attacks.
- */
-#define CBC_MAC_ROTATE_IN_PLACE
-
-void ssl3_cbc_copy_mac(unsigned char *out,
- const SSL3_RECORD *rec, unsigned md_size)
-{
-#if defined(CBC_MAC_ROTATE_IN_PLACE)
- unsigned char rotated_mac_buf[64 + EVP_MAX_MD_SIZE];
- unsigned char *rotated_mac;
-#else
- unsigned char rotated_mac[EVP_MAX_MD_SIZE];
-#endif
-
- /*
- * mac_end is the index of |rec->data| just after the end of the MAC.
- */
- unsigned mac_end = rec->length;
- unsigned mac_start = mac_end - md_size;
- /*
- * scan_start contains the number of bytes that we can ignore because the
- * MAC's position can only vary by 255 bytes.
- */
- unsigned scan_start = 0;
- unsigned i, j;
- unsigned div_spoiler;
- unsigned rotate_offset;
- OPENSSL_assert(rec->orig_len >= md_size);
- OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
-
-#if defined(CBC_MAC_ROTATE_IN_PLACE)
- rotated_mac = rotated_mac_buf + ((0 - (size_t)rotated_mac_buf) & 63);
-#endif
-
- /* This information is public so it's safe to branch based on it. */
- if (rec->orig_len > md_size + 255 + 1)
- scan_start = rec->orig_len - (md_size + 255 + 1);
- /*
- * div_spoiler contains a multiple of md_size that is used to cause the
- * modulo operation to be constant time. Without this, the time varies
- * based on the amount of padding when running on Intel chips at least.
- * The aim of right-shifting md_size is so that the compiler doesn't
- * figure out that it can remove div_spoiler as that would require it to
- * prove that md_size is always even, which I hope is beyond it.
- */
- div_spoiler = md_size >> 1;
- div_spoiler <<= (sizeof(div_spoiler) - 1) * 8;
- rotate_offset = (div_spoiler + mac_start - scan_start) % md_size;
-
- memset(rotated_mac, 0, md_size);
- for (i = scan_start, j = 0; i < rec->orig_len; i++) {
- unsigned char mac_started = constant_time_ge_8(i, mac_start);
- unsigned char mac_ended = constant_time_ge_8(i, mac_end);
- unsigned char b = rec->data[i];
- rotated_mac[j++] |= b & mac_started & ~mac_ended;
- j &= constant_time_lt(j, md_size);
- }
-
- /* Now rotate the MAC */
-#if defined(CBC_MAC_ROTATE_IN_PLACE)
- j = 0;
- for (i = 0; i < md_size; i++) {
- /* in case cache-line is 32 bytes, touch second line */
- ((volatile unsigned char *)rotated_mac)[rotate_offset ^ 32];
- out[j++] = rotated_mac[rotate_offset++];
- rotate_offset &= constant_time_lt(rotate_offset, md_size);
- }
-#else
- memset(out, 0, md_size);
- rotate_offset = md_size - rotate_offset;
- rotate_offset &= constant_time_lt(rotate_offset, md_size);
- for (i = 0; i < md_size; i++) {
- for (j = 0; j < md_size; j++)
- out[j] |= rotated_mac[i] & constant_time_eq_8(j, rotate_offset);
- rotate_offset++;
- rotate_offset &= constant_time_lt(rotate_offset, md_size);
- }
-#endif
-}
/*
* u32toLE serialises an unsigned, 32-bit number (n) as four bytes at (p) in
l2n(sha1->h4, md_out);
}
-#define LARGEST_DIGEST_CTX SHA_CTX
-
-#ifndef OPENSSL_NO_SHA256
static void tls1_sha256_final_raw(void *ctx, unsigned char *md_out)
{
SHA256_CTX *sha256 = ctx;
}
}
-# undef LARGEST_DIGEST_CTX
-# define LARGEST_DIGEST_CTX SHA256_CTX
-#endif
-
-#ifndef OPENSSL_NO_SHA512
static void tls1_sha512_final_raw(void *ctx, unsigned char *md_out)
{
SHA512_CTX *sha512 = ctx;
}
}
-# undef LARGEST_DIGEST_CTX
-# define LARGEST_DIGEST_CTX SHA512_CTX
-#endif
+#undef LARGEST_DIGEST_CTX
+#define LARGEST_DIGEST_CTX SHA512_CTX
/*
* ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function
switch (EVP_MD_CTX_type(ctx)) {
case NID_md5:
case NID_sha1:
-#ifndef OPENSSL_NO_SHA256
case NID_sha224:
case NID_sha256:
-#endif
-#ifndef OPENSSL_NO_SHA512
case NID_sha384:
case NID_sha512:
-#endif
return 1;
default:
return 0;
(void (*)(void *ctx, const unsigned char *block))SHA1_Transform;
md_size = 20;
break;
-#ifndef OPENSSL_NO_SHA256
case NID_sha224:
SHA224_Init((SHA256_CTX *)md_state.c);
md_final_raw = tls1_sha256_final_raw;
(void (*)(void *ctx, const unsigned char *block))SHA256_Transform;
md_size = 32;
break;
-#endif
-#ifndef OPENSSL_NO_SHA512
case NID_sha384:
SHA384_Init((SHA512_CTX *)md_state.c);
md_final_raw = tls1_sha512_final_raw;
md_block_size = 128;
md_length_size = 16;
break;
-#endif
default:
/*
* ssl3_cbc_record_digest_supported should have been called first to
if (k > 0) {
if (is_sslv3) {
+ unsigned overhang;
+
/*
* The SSLv3 header is larger than a single block. overhang is
* the number of bytes beyond a single block that the header
- * consumes: either 7 bytes (SHA1) or 11 bytes (MD5).
+ * consumes: either 7 bytes (SHA1) or 11 bytes (MD5). There are no
+ * ciphersuites in SSLv3 that are not SHA1 or MD5 based and
+ * therefore we can be confident that the header_length will be
+ * greater than |md_block_size|. However we add a sanity check just
+ * in case
*/
- unsigned overhang = header_length - md_block_size;
+ if (header_length <= md_block_size) {
+ /* Should never happen */
+ return;
+ }
+ 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);
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