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openssl/crypto/evp/e_rc4_hmac_md5.c
Andy Polyakov 8e20499629 crypto/evp: harden RC4_MD5 cipher. 
Originally a crash in 32-bit build was reported CHACHA20-POLY1305
cipher. The crash is triggered by truncated packet and is result
of excessive hashing to the edge of accessible memory (or bogus
MAC value is produced if x86 MD5 assembly module is involved). Since
hash operation is read-only it is not considered to be exploitable
beyond a DoS condition.

Thanks to Robert Święcki for report.

CVE-2017-3731

Reviewed-by: Rich Salz <rsalz@openssl.org>
2017-01-26 10:54:01 +00:00

262 lines
7.7 KiB
C
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/*
* Copyright 2011-2016 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include <openssl/opensslconf.h>
#include <stdio.h>
#include <string.h>
#if !defined(OPENSSL_NO_RC4) && !defined(OPENSSL_NO_MD5)
# include <openssl/crypto.h>
# include <openssl/evp.h>
# include <openssl/objects.h>
# include <openssl/rc4.h>
# include <openssl/md5.h>
# include "internal/evp_int.h"
typedef struct {
RC4_KEY ks;
MD5_CTX head, tail, md;
size_t payload_length;
} EVP_RC4_HMAC_MD5;
# define NO_PAYLOAD_LENGTH ((size_t)-1)
void rc4_md5_enc(RC4_KEY *key, const void *in0, void *out,
MD5_CTX *ctx, const void *inp, size_t blocks);
# define data(ctx) ((EVP_RC4_HMAC_MD5 *)EVP_CIPHER_CTX_get_cipher_data(ctx))
static int rc4_hmac_md5_init_key(EVP_CIPHER_CTX *ctx,
const unsigned char *inkey,
const unsigned char *iv, int enc)
{
EVP_RC4_HMAC_MD5 *key = data(ctx);
RC4_set_key(&key->ks, EVP_CIPHER_CTX_key_length(ctx), inkey);
MD5_Init(&key->head); /* handy when benchmarking */
key->tail = key->head;
key->md = key->head;
key->payload_length = NO_PAYLOAD_LENGTH;
return 1;
}
# if defined(RC4_ASM) && defined(MD5_ASM) && ( \
defined(__x86_64) || defined(__x86_64__) || \
defined(_M_AMD64) || defined(_M_X64) )
# define STITCHED_CALL
# endif
# if !defined(STITCHED_CALL)
# define rc4_off 0
# define md5_off 0
# endif
static int rc4_hmac_md5_cipher(EVP_CIPHER_CTX *ctx, unsigned char *out,
const unsigned char *in, size_t len)
{
EVP_RC4_HMAC_MD5 *key = data(ctx);
# if defined(STITCHED_CALL)
size_t rc4_off = 32 - 1 - (key->ks.x & (32 - 1)), /* 32 is $MOD from
* rc4_md5-x86_64.pl */
md5_off = MD5_CBLOCK - key->md.num, blocks;
unsigned int l;
extern unsigned int OPENSSL_ia32cap_P[];
# endif
size_t plen = key->payload_length;
if (plen != NO_PAYLOAD_LENGTH && len != (plen + MD5_DIGEST_LENGTH))
return 0;
if (EVP_CIPHER_CTX_encrypting(ctx)) {
if (plen == NO_PAYLOAD_LENGTH)
plen = len;
# if defined(STITCHED_CALL)
/* cipher has to "fall behind" */
if (rc4_off > md5_off)
md5_off += MD5_CBLOCK;
if (plen > md5_off && (blocks = (plen - md5_off) / MD5_CBLOCK) &&
(OPENSSL_ia32cap_P[0] & (1 << 20)) == 0) {
MD5_Update(&key->md, in, md5_off);
RC4(&key->ks, rc4_off, in, out);
rc4_md5_enc(&key->ks, in + rc4_off, out + rc4_off,
&key->md, in + md5_off, blocks);
blocks *= MD5_CBLOCK;
rc4_off += blocks;
md5_off += blocks;
key->md.Nh += blocks >> 29;
key->md.Nl += blocks <<= 3;
if (key->md.Nl < (unsigned int)blocks)
key->md.Nh++;
} else {
rc4_off = 0;
md5_off = 0;
}
# endif
MD5_Update(&key->md, in + md5_off, plen - md5_off);
if (plen != len) { /* "TLS" mode of operation */
if (in != out)
memcpy(out + rc4_off, in + rc4_off, plen - rc4_off);
/* calculate HMAC and append it to payload */
MD5_Final(out + plen, &key->md);
key->md = key->tail;
MD5_Update(&key->md, out + plen, MD5_DIGEST_LENGTH);
MD5_Final(out + plen, &key->md);
/* encrypt HMAC at once */
RC4(&key->ks, len - rc4_off, out + rc4_off, out + rc4_off);
} else {
RC4(&key->ks, len - rc4_off, in + rc4_off, out + rc4_off);
}
} else {
unsigned char mac[MD5_DIGEST_LENGTH];
# if defined(STITCHED_CALL)
/* digest has to "fall behind" */
if (md5_off > rc4_off)
rc4_off += 2 * MD5_CBLOCK;
else
rc4_off += MD5_CBLOCK;
if (len > rc4_off && (blocks = (len - rc4_off) / MD5_CBLOCK) &&
(OPENSSL_ia32cap_P[0] & (1 << 20)) == 0) {
RC4(&key->ks, rc4_off, in, out);
MD5_Update(&key->md, out, md5_off);
rc4_md5_enc(&key->ks, in + rc4_off, out + rc4_off,
&key->md, out + md5_off, blocks);
blocks *= MD5_CBLOCK;
rc4_off += blocks;
md5_off += blocks;
l = (key->md.Nl + (blocks << 3)) & 0xffffffffU;
if (l < key->md.Nl)
key->md.Nh++;
key->md.Nl = l;
key->md.Nh += blocks >> 29;
} else {
md5_off = 0;
rc4_off = 0;
}
# endif
/* decrypt HMAC at once */
RC4(&key->ks, len - rc4_off, in + rc4_off, out + rc4_off);
if (plen != NO_PAYLOAD_LENGTH) { /* "TLS" mode of operation */
MD5_Update(&key->md, out + md5_off, plen - md5_off);
/* calculate HMAC and verify it */
MD5_Final(mac, &key->md);
key->md = key->tail;
MD5_Update(&key->md, mac, MD5_DIGEST_LENGTH);
MD5_Final(mac, &key->md);
if (CRYPTO_memcmp(out + plen, mac, MD5_DIGEST_LENGTH))
return 0;
} else {
MD5_Update(&key->md, out + md5_off, len - md5_off);
}
}
key->payload_length = NO_PAYLOAD_LENGTH;
return 1;
}
static int rc4_hmac_md5_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg,
void *ptr)
{
EVP_RC4_HMAC_MD5 *key = data(ctx);
switch (type) {
case EVP_CTRL_AEAD_SET_MAC_KEY:
{
unsigned int i;
unsigned char hmac_key[64];
memset(hmac_key, 0, sizeof(hmac_key));
if (arg > (int)sizeof(hmac_key)) {
MD5_Init(&key->head);
MD5_Update(&key->head, ptr, arg);
MD5_Final(hmac_key, &key->head);
} else {
memcpy(hmac_key, ptr, arg);
}
for (i = 0; i < sizeof(hmac_key); i++)
hmac_key[i] ^= 0x36; /* ipad */
MD5_Init(&key->head);
MD5_Update(&key->head, hmac_key, sizeof(hmac_key));
for (i = 0; i < sizeof(hmac_key); i++)
hmac_key[i] ^= 0x36 ^ 0x5c; /* opad */
MD5_Init(&key->tail);
MD5_Update(&key->tail, hmac_key, sizeof(hmac_key));
OPENSSL_cleanse(hmac_key, sizeof(hmac_key));
return 1;
}
case EVP_CTRL_AEAD_TLS1_AAD:
{
unsigned char *p = ptr;
unsigned int len;
if (arg != EVP_AEAD_TLS1_AAD_LEN)
return -1;
len = p[arg - 2] << 8 | p[arg - 1];
if (!EVP_CIPHER_CTX_encrypting(ctx)) {
if (len < MD5_DIGEST_LENGTH)
return -1;
len -= MD5_DIGEST_LENGTH;
p[arg - 2] = len >> 8;
p[arg - 1] = len;
}
key->payload_length = len;
key->md = key->head;
MD5_Update(&key->md, p, arg);
return MD5_DIGEST_LENGTH;
}
default:
return -1;
}
}
static EVP_CIPHER r4_hmac_md5_cipher = {
# ifdef NID_rc4_hmac_md5
NID_rc4_hmac_md5,
# else
NID_undef,
# endif
1, EVP_RC4_KEY_SIZE, 0,
EVP_CIPH_STREAM_CIPHER | EVP_CIPH_VARIABLE_LENGTH |
EVP_CIPH_FLAG_AEAD_CIPHER,
rc4_hmac_md5_init_key,
rc4_hmac_md5_cipher,
NULL,
sizeof(EVP_RC4_HMAC_MD5),
NULL,
NULL,
rc4_hmac_md5_ctrl,
NULL
};
const EVP_CIPHER *EVP_rc4_hmac_md5(void)
{
return (&r4_hmac_md5_cipher);
}
#endif
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