Clarify CMS_decrypt behaviour.
[openssl.git] / ssl / s3_cbc.c
index e9b112c..73e12b6 100644 (file)
@@ -53,8 +53,6 @@
  *
  */
 
-#include <stdint.h>
-
 #include "ssl_locl.h"
 
 #include <openssl/md5.h>
 #define DUPLICATE_MSB_TO_ALL(x) ( (unsigned)( (int)(x) >> (sizeof(int)*8-1) ) )
 #define DUPLICATE_MSB_TO_ALL_8(x) ((unsigned char)(DUPLICATE_MSB_TO_ALL(x)))
 
+/* constant_time_lt returns 0xff if a<b and 0x00 otherwise. */
+static unsigned constant_time_lt(unsigned a, unsigned b)
+       {
+       a -= b;
+       return DUPLICATE_MSB_TO_ALL(a);
+       }
+
 /* constant_time_ge returns 0xff if a>=b and 0x00 otherwise. */
 static unsigned constant_time_ge(unsigned a, unsigned b)
        {
@@ -86,7 +91,7 @@ static unsigned constant_time_ge(unsigned a, unsigned b)
        }
 
 /* constant_time_eq_8 returns 0xff if a==b and 0x00 otherwise. */
-static unsigned char constant_time_eq_8(unsigned char a, unsigned char b)
+static unsigned char constant_time_eq_8(unsigned a, unsigned b)
        {
        unsigned c = a ^ b;
        c--;
@@ -139,15 +144,22 @@ int tls1_cbc_remove_padding(const SSL* s,
                            unsigned mac_size)
        {
        unsigned padding_length, good, to_check, i;
-       const char has_explicit_iv =
-               s->version >= TLS1_1_VERSION || s->version == DTLS1_VERSION;
-       const unsigned overhead = 1 /* padding length byte */ +
-                                 mac_size +
-                                 (has_explicit_iv ? block_size : 0);
-
-       /* These lengths are all public so we can test them in non-constant
-        * time. */
-       if (overhead > rec->length)
+       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];
@@ -172,6 +184,13 @@ int tls1_cbc_remove_padding(const SSL* s,
                        }
                }
 
+       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
@@ -207,29 +226,9 @@ int tls1_cbc_remove_padding(const SSL* s,
 
        rec->length -= good & (padding_length+1);
 
-       /* We can always safely skip the explicit IV. We check at the beginning
-        * of this function that the record has at least enough space for the
-        * IV, MAC and padding length byte. (These can be checked in
-        * non-constant time because it's all public information.) So, if the
-        * padding was invalid, then we didn't change |rec->length| and this is
-        * safe. If the padding was valid then we know that we have at least
-        * overhead+padding_length bytes of space and so this is still safe
-        * because overhead accounts for the explicit IV. */
-       if (has_explicit_iv)
-               {
-               rec->data += block_size;
-               rec->input += block_size;
-               rec->length -= block_size;
-               rec->orig_len -= block_size;
-               }
-
        return (int)((good & 1) | (~good & -1));
        }
 
-#if defined(_M_AMD64) || defined(__x86_64__)
-#define CBC_MAC_ROTATE_IN_PLACE
-#endif
-
 /* 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).
@@ -243,15 +242,18 @@ int tls1_cbc_remove_padding(const SSL* s,
  *
  * 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 cache-line, then the variable memory accesses don't actually affect
- * the timing. This has been tested to be true on Intel amd64 chips.
+ * 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[EVP_MAX_MD_SIZE*2];
+       unsigned char rotated_mac_buf[64+EVP_MAX_MD_SIZE];
        unsigned char *rotated_mac;
 #else
        unsigned char rotated_mac[EVP_MAX_MD_SIZE];
@@ -271,7 +273,7 @@ void ssl3_cbc_copy_mac(unsigned char* out,
        OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
 
 #if defined(CBC_MAC_ROTATE_IN_PLACE)
-       rotated_mac = (unsigned char*) (((intptr_t)(rotated_mac_buf + 64)) & ~63);
+       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. */
@@ -289,16 +291,13 @@ void ssl3_cbc_copy_mac(unsigned char* out,
        rotate_offset = (div_spoiler + mac_start - scan_start) % md_size;
 
        memset(rotated_mac, 0, md_size);
-       for (i = scan_start; i < rec->orig_len;)
+       for (i = scan_start, j = 0; i < rec->orig_len; i++)
                {
-               for (j = 0; j < md_size && i < rec->orig_len; i++, j++)
-                       {
-                       unsigned char mac_started = constant_time_ge(i, mac_start);
-                       unsigned char mac_ended = constant_time_ge(i, mac_end);
-                       unsigned char b = 0;
-                       b = rec->data[i];
-                       rotated_mac[j] |= b & mac_started & ~mac_ended;
-                       }
+               unsigned char mac_started = constant_time_ge(i, mac_start);
+               unsigned char mac_ended = constant_time_ge(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 */
@@ -306,30 +305,43 @@ void ssl3_cbc_copy_mac(unsigned char* out,
        j = 0;
        for (i = 0; i < md_size; i++)
                {
-               unsigned char offset = (div_spoiler + rotate_offset + i) % md_size;
-               out[j++] = rotated_mac[offset];
+               /* 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++)
                {
-               unsigned char offset = (div_spoiler + md_size - rotate_offset + i) % md_size;
                for (j = 0; j < md_size; j++)
-                       out[j] |= rotated_mac[i] & constant_time_eq_8(j, offset);
+                       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
+ * little-endian order. The value of p is advanced by four. */
+#define u32toLE(n, p) \
+       (*((p)++)=(unsigned char)(n), \
+        *((p)++)=(unsigned char)(n>>8), \
+        *((p)++)=(unsigned char)(n>>16), \
+        *((p)++)=(unsigned char)(n>>24))
+
 /* These functions serialize the state of a hash and thus perform the standard
  * "final" operation without adding the padding and length that such a function
  * typically does. */
 static void tls1_md5_final_raw(void* ctx, unsigned char *md_out)
        {
        MD5_CTX *md5 = ctx;
-       l2n(md5->A, md_out);
-       l2n(md5->B, md_out);
-       l2n(md5->C, md_out);
-       l2n(md5->D, md_out);
+       u32toLE(md5->A, md_out);
+       u32toLE(md5->B, md_out);
+       u32toLE(md5->C, md_out);
+       u32toLE(md5->D, md_out);
        }
 
 static void tls1_sha1_final_raw(void* ctx, unsigned char *md_out)
@@ -341,7 +353,9 @@ static void tls1_sha1_final_raw(void* ctx, unsigned char *md_out)
        l2n(sha1->h3, md_out);
        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;
@@ -352,7 +366,11 @@ static void tls1_sha256_final_raw(void* ctx, unsigned char *md_out)
                l2n(sha256->h[i], md_out);
                }
        }
+#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;
@@ -363,19 +381,30 @@ static void tls1_sha512_final_raw(void* ctx, unsigned char *md_out)
                l2n8(sha512->h[i], md_out);
                }
        }
+#undef  LARGEST_DIGEST_CTX
+#define LARGEST_DIGEST_CTX SHA512_CTX
+#endif
 
 /* ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function
  * which ssl3_cbc_digest_record supports. */
 char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx)
        {
-       switch (ctx->digest->type)
+#ifdef OPENSSL_FIPS
+       if (FIPS_mode())
+               return 0;
+#endif
+       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;
@@ -390,7 +419,7 @@ char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx)
  *   md_out: the digest output. At most EVP_MAX_MD_SIZE bytes will be written.
  *   md_out_size: if non-NULL, the number of output bytes is written here.
  *   header: the 13-byte, TLS record header.
- *   data: the record data itself, less any preceeding explicit IV.
+ *   data: the record data itself, less any preceding explicit IV.
  *   data_plus_mac_size: the secret, reported length of the data and MAC
  *     once the padding has been removed.
  *   data_plus_mac_plus_padding_size: the public length of the whole
@@ -413,14 +442,15 @@ void ssl3_cbc_digest_record(
        unsigned mac_secret_length,
        char is_sslv3)
        {
-       unsigned char md_state[sizeof(SHA512_CTX)];
+       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;
-       uint64_t bits;
+       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];
@@ -431,40 +461,46 @@ void ssl3_cbc_digest_record(
        /* mdLengthSize is the number of bytes in the length field that terminates
        * the hash. */
        unsigned md_length_size = 8;
+       char length_is_big_endian = 1;
+       int ret;
 
        /* This is a, hopefully redundant, check that allows us to forget about
         * many possible overflows later in this function. */
        OPENSSL_assert(data_plus_mac_plus_padding_size < 1024*1024);
 
-       switch (ctx->digest->type)
+       switch (EVP_MD_CTX_type(ctx))
                {
                case NID_md5:
-                       MD5_Init((MD5_CTX*)md_state);
+                       MD5_Init((MD5_CTX*)md_state.c);
                        md_final_raw = tls1_md5_final_raw;
                        md_transform = (void(*)(void *ctx, const unsigned char *block)) MD5_Transform;
                        md_size = 16;
                        sslv3_pad_length = 48;
+                       length_is_big_endian = 0;
                        break;
                case NID_sha1:
-                       SHA1_Init((SHA_CTX*)md_state);
+                       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;
+#ifndef OPENSSL_NO_SHA256
                case NID_sha224:
-                       SHA224_Init((SHA256_CTX*)md_state);
+                       SHA224_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 = 224/8;
                        break;
                case NID_sha256:
-                       SHA256_Init((SHA256_CTX*)md_state);
+                       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;
+#endif
+#ifndef OPENSSL_NO_SHA512
                case NID_sha384:
-                       SHA384_Init((SHA512_CTX*)md_state);
+                       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;
@@ -472,13 +508,14 @@ void ssl3_cbc_digest_record(
                        md_length_size = 16;
                        break;
                case NID_sha512:
-                       SHA512_Init((SHA512_CTX*)md_state);
+                       SHA512_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 = 64;
                        md_block_size = 128;
                        md_length_size = 16;
                        break;
+#endif
                default:
                        /* ssl3_cbc_record_digest_supported should have been
                         * called first to check that the hash function is
@@ -577,17 +614,25 @@ void ssl3_cbc_digest_record(
                for (i = 0; i < md_block_size; i++)
                        hmac_pad[i] ^= 0x36;
 
-               md_transform(md_state, hmac_pad);
+               md_transform(md_state.c, hmac_pad);
                }
 
-       j = 0;
-       if (md_length_size == 16)
+       if (length_is_big_endian)
                {
-               memset(length_bytes, 0, 8);
-               j = 8;
+               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;
+               }
+       else
+               {
+               memset(length_bytes,0,md_length_size);
+               length_bytes[md_length_size-5] = (unsigned char)(bits>>24);
+               length_bytes[md_length_size-6] = (unsigned char)(bits>>16);
+               length_bytes[md_length_size-7] = (unsigned char)(bits>>8);
+               length_bytes[md_length_size-8] = (unsigned char)bits;
                }
-       for (i = 0; i < 8; i++)
-               length_bytes[i+j] = bits >> (8*(7-i));
 
        if (k > 0)
                {
@@ -598,21 +643,21 @@ void ssl3_cbc_digest_record(
                         * block that the header consumes: either 7 bytes
                         * (SHA1) or 11 bytes (MD5). */
                        unsigned overhang = header_length-md_block_size;
-                       md_transform(md_state, header);
+                       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, first_block);
+                       md_transform(md_state.c, first_block);
                        for (i = 1; i < k/md_block_size - 1; i++)
-                               md_transform(md_state, data + md_block_size*i - overhang);
+                               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, first_block);
+                       md_transform(md_state.c, first_block);
                        for (i = 1; i < k/md_block_size; i++)
-                               md_transform(md_state, data + md_block_size*i - 13);
+                               md_transform(md_state.c, data + md_block_size*i - 13);
                        }
                }
 
@@ -662,8 +707,8 @@ void ssl3_cbc_digest_record(
                        block[j] = b;
                        }
 
-               md_transform(md_state, block);
-               md_final_raw(md_state, block);
+               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;
@@ -689,8 +734,55 @@ void ssl3_cbc_digest_record(
                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);
-       if (md_out_size)
+       ret = EVP_DigestFinal(&md_ctx, md_out, &md_out_size_u);
+       if (ret && md_out_size)
                *md_out_size = md_out_size_u;
        EVP_MD_CTX_cleanup(&md_ctx);
        }
+
+#ifdef OPENSSL_FIPS
+
+/* Due to the need to use EVP in FIPS mode we can't reimplement digests but
+ * we can ensure the number of blocks processed is equal for all cases
+ * by digesting additional data.
+ */
+
+void tls_fips_digest_extra(
+       const EVP_CIPHER_CTX *cipher_ctx, EVP_MD_CTX *mac_ctx,
+       const unsigned char *data, size_t data_len, size_t orig_len)
+       {
+       size_t block_size, digest_pad, blocks_data, blocks_orig;
+       if (EVP_CIPHER_CTX_mode(cipher_ctx) != EVP_CIPH_CBC_MODE)
+               return;
+       block_size = EVP_MD_CTX_block_size(mac_ctx);
+       /* We are in FIPS mode if we get this far so we know we have only SHA*
+        * digests and TLS to deal with.
+        * Minimum digest padding length is 17 for SHA384/SHA512 and 9
+        * otherwise.
+        * Additional header is 13 bytes. To get the number of digest blocks
+        * processed round up the amount of data plus padding to the nearest
+        * block length. Block length is 128 for SHA384/SHA512 and 64 otherwise.
+        * So we have:
+        * blocks = (payload_len + digest_pad + 13 + block_size - 1)/block_size
+        * equivalently:
+        * blocks = (payload_len + digest_pad + 12)/block_size + 1
+        * HMAC adds a constant overhead.
+        * We're ultimately only interested in differences so this becomes
+        * blocks = (payload_len + 29)/128
+        * for SHA384/SHA512 and
+        * blocks = (payload_len + 21)/64
+        * otherwise.
+        */
+       digest_pad = block_size == 64 ? 21 : 29;
+       blocks_orig = (orig_len + digest_pad)/block_size;
+       blocks_data = (data_len + digest_pad)/block_size;
+       /* MAC enough blocks to make up the difference between the original
+        * and actual lengths plus one extra block to ensure this is never a
+        * no op. The "data" pointer should always have enough space to
+        * perform this operation as it is large enough for a maximum
+        * length TLS buffer. 
+        */
+       EVP_DigestSignUpdate(mac_ctx, data,
+                               (blocks_orig - blocks_data + 1) * block_size);
+       }
+#endif