/* $OpenBSD: s3_cbc.c,v 1.16 2017/01/23 08:08:06 beck Exp $ */

/* ====================================================================

 * 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 "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

/* Some utility functions are needed:

 *

 * These macros return the given value with the MSB copied to all the other

 * bits. They use the fact that arithmetic shift shifts-in the sign bit.

 * However, this is not ensured by the C standard so you may need to replace

 * them with something else on odd CPUs. */

#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)

{

}

/* constant_time_ge returns 0xff if a>=b and 0x00 otherwise. */

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 a, unsigned b)

{

}

/* 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;

	/* Check if version requires explicit IV */

		/* These lengths are all public so we can test them in

		 * non-constant time.

		 */

		/* We can now safely skip explicit IV */

		/* padding is already verified */

	}

	/* 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. */

		/* The final |padding_length+1| bytes should all have the value

		 * |padding_length|. Therefore the XOR should be zero. */

	}

	/* 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. We

	 * AND the bottom 8 bits together and duplicate the result to all the

	 * bits. */

/* 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;

#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. */

	/* 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;

#if defined(CBC_MAC_ROTATE_IN_PLACE)

#endif

	/* This information is public so it's safe to branch based on it. */

	/* 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. */

	}

	/* Now rotate the MAC */

#if defined(CBC_MAC_ROTATE_IN_PLACE)

	j = 0;

		/* in case cache-line is 32 bytes, touch second line */

	}

#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)

{

}

static void

tls1_sha1_final_raw(void* ctx, unsigned char *md_out)

{

static void

tls1_sha256_final_raw(void* ctx, unsigned char *md_out)

{

	unsigned i;

	}

static void

tls1_sha512_final_raw(void* ctx, unsigned char *md_out)

{

	unsigned i;

	}

/* Largest hash context ever used by the functions above. */

#define LARGEST_DIGEST_CTX SHA512_CTX

/* Type giving the alignment needed by the above */

#define LARGEST_DIGEST_CTX_ALIGNMENT SHA_LONG64

/* 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)

{

	case NID_md5:

	case NID_sha1:

	case NID_sha224:

	case NID_sha256:

	case NID_sha384:

	case NID_sha512:

	default:

	}

/* ssl3_cbc_digest_record computes the MAC of a decrypted, padded 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.

 *

 * 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. )

 */

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)

{

		/*

		 * Alignment here is to allow this to be cast as SHA512_CTX

		 * without losing alignment required by the 64-bit SHA_LONG64

		 * integer it contains.

		 */

		LARGEST_DIGEST_CTX_ALIGNMENT 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 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 */

	/* hmac_pad is the masked HMAC key. */

	/* 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. */

	case NID_md5:

		md_final_raw = tls1_md5_final_raw;

		md_transform = (void(*)(void *ctx, const unsigned char *block)) MD5_Transform;

		md_size = 16;

		length_is_big_endian = 0;

	case NID_sha1:

		md_final_raw = tls1_sha1_final_raw;

		md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA1_Transform;

		md_size = 20;

	case NID_sha224:

		md_final_raw = tls1_sha256_final_raw;

		md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA256_Transform;

		md_size = 224/8;

	case NID_sha256:

		md_final_raw = tls1_sha256_final_raw;

		md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA256_Transform;

		md_size = 32;

	case NID_sha384:

		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;

	case NID_sha512:

		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;

	default:

		/* ssl3_cbc_record_digest_supported should have been

		 * called first to check that the hash function is

		 * supported. */

	}

	header_length = 13;

	/* 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.

	 *

	 * 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 = 6;

	/* From now on we're dealing with the MAC, which conceptually has 13

	 * bytes of `header' before the start of the data (TLS) */

	/* max_mac_bytes contains the maximum bytes of bytes in the MAC, including

	* |header|, assuming that there's no padding. */

	/* num_blocks is the maximum number of hash blocks. */

	/* 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. */

	/* c is the index of the 0x80 byte in the final hash block that

	 * contains application data. */

	/* index_a is the hash block number that contains the 0x80 terminating

	 * value. */

	/* index_b is the hash block number that contains the 64-bit hash

	 * length, in bits. */

	/* bits is the hash-length in bits. It includes the additional hash

	 * block for the masked HMAC key. */

	}

	/* Compute the initial HMAC block. */

	}

		/* k is a multiple of md_block_size. */

	}

	/* 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|. */

			unsigned char b = 0, is_past_c, is_past_cp1;

			/* 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. */

			/* If this is the block containing the end of the

			 * application data and we're past the 0x80 value then

			 * just write zero. */

			/* 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. */

			/* The final bytes of one of the blocks contains the

			 * length. */

				/* If this is index_b, write a length byte. */

		}

		/* If this is index_b, copy the hash value to |mac_out|. */

	}

	/* Complete the HMAC in the standard manner. */