openssl: Move to a module and split thirdparty lib

Same rationale as the previous commits.

1 files changed, 820 insertions, 0 deletions

diff --git a/thirdparty/openssl/ssl/s3_cbc.c b/thirdparty/openssl/ssl/s3_cbc.c
new file mode 100644
index 0000000000..557622f513
--- /dev/null
+++ b/thirdparty/openssl/ssl/s3_cbc.c
@@ -0,0 +1,820 @@
+/* ssl/s3_cbc.c */
+/* ====================================================================
+ * Copyright (c) 2012 The OpenSSL Project.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. All advertising materials mentioning features or use of this
+ *    software must display the following acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
+ *
+ * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
+ *    endorse or promote products derived from this software without
+ *    prior written permission. For written permission, please contact
+ *    openssl-core@openssl.org.
+ *
+ * 5. Products derived from this software may not be called "OpenSSL"
+ *    nor may "OpenSSL" appear in their names without prior written
+ *    permission of the OpenSSL Project.
+ *
+ * 6. Redistributions of any form whatsoever must retain the following
+ *    acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
+ * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ * ====================================================================
+ *
+ * This product includes cryptographic software written by Eric Young
+ * (eay@cryptsoft.com).  This product includes software written by Tim
+ * Hudson (tjh@cryptsoft.com).
+ *
+ */
+
+#include "../crypto/constant_time_locl.h"
+#include "ssl_locl.h"
+
+#include <openssl/md5.h>
+#include <openssl/sha.h>
+
+/*
+ * MAX_HASH_BIT_COUNT_BYTES is the maximum number of bytes in the hash's
+ * length field. (SHA-384/512 have 128-bit length.)
+ */
+#define MAX_HASH_BIT_COUNT_BYTES 16
+
+/*
+ * MAX_HASH_BLOCK_SIZE is the maximum hash block size that we'll support.
+ * Currently SHA-384/512 has a 128-byte block size and that's the largest
+ * supported by TLS.)
+ */
+#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);
+    padding_length = good & (padding_length + 1);
+    rec->length -= padding_length;
+    rec->type |= padding_length << 8; /* kludge: pass padding length */
+    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;
+    } 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 ((CRYPTO_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);
+    padding_length = good & (padding_length + 1);
+    rec->length -= padding_length;
+    rec->type |= padding_length << 8; /* kludge: pass padding length */
+
+    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, unsigned orig_len)
+{
+#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(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 (orig_len > md_size + 255 + 1)
+        scan_start = 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 < 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
+ * 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;
+    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)
+{
+    SHA_CTX *sha1 = ctx;
+    l2n(sha1->h0, md_out);
+    l2n(sha1->h1, md_out);
+    l2n(sha1->h2, 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;
+    unsigned i;
+
+    for (i = 0; i < 8; i++) {
+        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;
+    unsigned i;
+
+    for (i = 0; i < 8; i++) {
+        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)
+{
+#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;
+    }
+}
+
+/*-
+ * ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS
+ * record.
+ *
+ *   ctx: the EVP_MD_CTX from which we take the hash function.
+ *     ssl3_cbc_record_digest_supported must return true for this EVP_MD_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_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
+ *     record, including padding.
+ *   is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS.
+ *
+ * On entry: by virtue of having been through one of the remove_padding
+ * functions, above, we know that data_plus_mac_size is large enough to contain
+ * a padding byte and MAC. (If the padding was invalid, it might contain the
+ * padding too. )
+ * Returns 1 on success or 0 on error
+ */
+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;
+    char length_is_big_endian = 1;
+
+    /*
+     * 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 (EVP_MD_CTX_type(ctx)) {
+    case NID_md5:
+        if (MD5_Init((MD5_CTX *)md_state.c) <= 0)
+            return 0;
+        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:
+        if (SHA1_Init((SHA_CTX *)md_state.c) <= 0)
+            return 0;
+        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:
+        if (SHA224_Init((SHA256_CTX *)md_state.c) <= 0)
+            return 0;
+        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:
+        if (SHA256_Init((SHA256_CTX *)md_state.c) <= 0)
+            return 0;
+        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:
+        if (SHA384_Init((SHA512_CTX *)md_state.c) <= 0)
+            return 0;
+        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;
+    case NID_sha512:
+        if (SHA512_Init((SHA512_CTX *)md_state.c) <= 0)
+            return 0;
+        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 supported.
+         */
+        OPENSSL_assert(0);
+        if (md_out_size)
+            *md_out_size = 0;
+        return 0;
+    }
+
+    OPENSSL_assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES);
+    OPENSSL_assert(md_block_size <= MAX_HASH_BLOCK_SIZE);
+    OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
+
+    header_length = 13;
+    if (is_sslv3) {
+        header_length = mac_secret_length + sslv3_pad_length + 8 /* sequence
+                                                                  * number */  +
+            1 /* record type */  +
+            2 /* record length */ ;
+    }
+
+    /*
+     * 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.
+     */
+
+    /*
+     * 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;
+    }
+
+    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);
+        OPENSSL_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;
+
+        md_transform(md_state.c, hmac_pad);
+    }
+
+    if (length_is_big_endian) {
+        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;
+    }
+
+    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). 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
+             */
+            if (header_length <= md_block_size) {
+                /* Should never happen */
+                return 0;
+            }
+            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);
+        }
+    }
+
+    memset(mac_out, 0, sizeof(mac_out));
+
+    /*
+     * 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++;
+
+            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;
+
+            /*
+             * 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;
+        }
+
+        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_MD_CTX_init(&md_ctx);
+    if (EVP_DigestInit_ex(&md_ctx, ctx->digest, NULL /* engine */ ) <= 0)
+        goto err;
+    if (is_sslv3) {
+        /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */
+        memset(hmac_pad, 0x5c, sslv3_pad_length);
+
+        if (EVP_DigestUpdate(&md_ctx, mac_secret, mac_secret_length) <= 0
+                || EVP_DigestUpdate(&md_ctx, hmac_pad, sslv3_pad_length) <= 0
+                || EVP_DigestUpdate(&md_ctx, mac_out, md_size) <= 0)
+            goto err;
+    } else {
+        /* Complete the HMAC in the standard manner. */
+        for (i = 0; i < md_block_size; i++)
+            hmac_pad[i] ^= 0x6a;
+
+        if (EVP_DigestUpdate(&md_ctx, hmac_pad, md_block_size) <= 0
+                || EVP_DigestUpdate(&md_ctx, mac_out, md_size) <= 0)
+            goto err;
+    }
+    EVP_DigestFinal(&md_ctx, md_out, &md_out_size_u);
+    if (md_out_size)
+        *md_out_size = md_out_size_u;
+    EVP_MD_CTX_cleanup(&md_ctx);
+
+    return 1;
+err:
+    EVP_MD_CTX_cleanup(&md_ctx);
+    return 0;
+}
+
+#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