From 125093b59f3c2a2d33785b5563d929d0472f1721 Mon Sep 17 00:00:00 2001 From: Andy Polyakov Date: Sat, 2 Feb 2013 19:29:59 +0100 Subject: [PATCH] e_aes_cbc_hmac_sha1.c: address the CBC decrypt timing issues. Address CBC decrypt timing issues and reenable the AESNI+SHA1 stitch. --- crypto/evp/c_allc.c | 2 - crypto/evp/e_aes_cbc_hmac_sha1.c | 207 +++++++++++++++++++++++++++---- ssl/s3_cbc.c | 37 +++--- ssl/ssl_algs.c | 2 - 4 files changed, 208 insertions(+), 40 deletions(-) diff --git a/crypto/evp/c_allc.c b/crypto/evp/c_allc.c index e230e6081e..2a45d435e5 100644 --- a/crypto/evp/c_allc.c +++ b/crypto/evp/c_allc.c @@ -195,13 +195,11 @@ void OpenSSL_add_all_ciphers(void) EVP_add_cipher(EVP_aes_256_xts()); EVP_add_cipher_alias(SN_aes_256_cbc,"AES256"); EVP_add_cipher_alias(SN_aes_256_cbc,"aes256"); -#if 0 /* Disabled because of timing side-channel leaks. */ #if !defined(OPENSSL_NO_SHA) && !defined(OPENSSL_NO_SHA1) EVP_add_cipher(EVP_aes_128_cbc_hmac_sha1()); EVP_add_cipher(EVP_aes_256_cbc_hmac_sha1()); #endif #endif -#endif #ifndef OPENSSL_NO_CAMELLIA EVP_add_cipher(EVP_camellia_128_ecb()); diff --git a/crypto/evp/e_aes_cbc_hmac_sha1.c b/crypto/evp/e_aes_cbc_hmac_sha1.c index 710fb79baf..18fc921010 100644 --- a/crypto/evp/e_aes_cbc_hmac_sha1.c +++ b/crypto/evp/e_aes_cbc_hmac_sha1.c @@ -1,5 +1,5 @@ /* ==================================================================== - * Copyright (c) 2011 The OpenSSL Project. All rights reserved. + * Copyright (c) 2011-2013 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 @@ -90,6 +90,10 @@ typedef struct defined(_M_AMD64) || defined(_M_X64) || \ defined(__INTEL__) ) +#if defined(__GNUC__) && __GNUC__>=2 && !defined(PEDANTIC) +# define BSWAP(x) ({ unsigned int r=(x); asm ("bswapl %0":"=r"(r):"0"(r)); r; }) +#endif + extern unsigned int OPENSSL_ia32cap_P[2]; #define AESNI_CAPABLE (1<<(57-32)) @@ -167,6 +171,9 @@ static void sha1_update(SHA_CTX *c,const void *data,size_t len) SHA1_Update(c,ptr,res); } +#ifdef SHA1_Update +#undef SHA1_Update +#endif #define SHA1_Update sha1_update static int aesni_cbc_hmac_sha1_cipher(EVP_CIPHER_CTX *ctx, unsigned char *out, @@ -184,6 +191,8 @@ static int aesni_cbc_hmac_sha1_cipher(EVP_CIPHER_CTX *ctx, unsigned char *out, sha_off = SHA_CBLOCK-key->md.num; #endif + key->payload_length = NO_PAYLOAD_LENGTH; + if (len%AES_BLOCK_SIZE) return 0; if (ctx->encrypt) { @@ -234,47 +243,203 @@ static int aesni_cbc_hmac_sha1_cipher(EVP_CIPHER_CTX *ctx, unsigned char *out, &key->ks,ctx->iv,1); } } else { - unsigned char mac[SHA_DIGEST_LENGTH]; + union { unsigned int u[SHA_DIGEST_LENGTH/sizeof(unsigned int)]; + unsigned char c[SHA_DIGEST_LENGTH]; } mac; /* decrypt HMAC|padding at once */ aesni_cbc_encrypt(in,out,len, &key->ks,ctx->iv,0); if (plen) { /* "TLS" mode of operation */ - /* figure out payload length */ - if (len<(size_t)(out[len-1]+1+SHA_DIGEST_LENGTH)) - return 0; - - len -= (out[len-1]+1+SHA_DIGEST_LENGTH); + size_t inp_len, mask, j, i; + unsigned int res, maxpad, pad, bitlen; + int ret = 1; + union { unsigned int u[SHA_LBLOCK]; + unsigned char c[SHA_CBLOCK]; } + *data = (void *)key->md.data; if ((key->aux.tls_aad[plen-4]<<8|key->aux.tls_aad[plen-3]) - >= TLS1_1_VERSION) { - len -= AES_BLOCK_SIZE; + >= TLS1_1_VERSION) iv = AES_BLOCK_SIZE; - } - key->aux.tls_aad[plen-2] = len>>8; - key->aux.tls_aad[plen-1] = len; + if (len<(iv+SHA_DIGEST_LENGTH+1)) + return 0; + + /* omit explicit iv */ + out += iv; + len -= iv; + + /* figure out payload length */ + pad = out[len-1]; + maxpad = len-(SHA_DIGEST_LENGTH+1); + maxpad |= (255-maxpad)>>(sizeof(maxpad)*8-8); + maxpad &= 255; + + inp_len = len - (SHA_DIGEST_LENGTH+pad+1); + mask = (0-((inp_len-len)>>(sizeof(inp_len)*8-1))); + inp_len &= mask; + ret &= (int)mask; - /* calculate HMAC and verify it */ + key->aux.tls_aad[plen-2] = inp_len>>8; + key->aux.tls_aad[plen-1] = inp_len; + + /* calculate HMAC */ key->md = key->head; SHA1_Update(&key->md,key->aux.tls_aad,plen); - SHA1_Update(&key->md,out+iv,len); - SHA1_Final(mac,&key->md); +#if 1 + len -= SHA_DIGEST_LENGTH; /* amend mac */ + if (len>=(256+SHA_CBLOCK)) { + j = (len-(256+SHA_CBLOCK))&(0-SHA_CBLOCK); + j += SHA_CBLOCK-key->md.num; + SHA1_Update(&key->md,out,j); + out += j; + len -= j; + inp_len -= j; + } + + /* but pretend as if we hashed padded payload */ + bitlen = key->md.Nl+(inp_len<<3); /* at most 18 bits */ + mac.c[0] = 0; + mac.c[1] = (unsigned char)(bitlen>>16); + mac.c[2] = (unsigned char)(bitlen>>8); + mac.c[3] = (unsigned char)bitlen; + bitlen = mac.u[0]; + + mac.u[0]=0; + mac.u[1]=0; + mac.u[2]=0; + mac.u[3]=0; + mac.u[4]=0; + + for (res=key->md.num, j=0;j>(sizeof(j)*8-8); + c &= mask; + c |= 0x80&~mask&~((inp_len-j)>>(sizeof(j)*8-8)); + data->c[res++]=(unsigned char)c; + + if (res!=SHA_CBLOCK) continue; + + mask = 0-((inp_len+8-j)>>(sizeof(j)*8-1)); + data->u[SHA_LBLOCK-1] |= bitlen&mask; + sha1_block_data_order(&key->md,data,1); + mask &= 0-((j-inp_len-73)>>(sizeof(j)*8-1)); + mac.u[0] |= key->md.h0 & mask; + mac.u[1] |= key->md.h1 & mask; + mac.u[2] |= key->md.h2 & mask; + mac.u[3] |= key->md.h3 & mask; + mac.u[4] |= key->md.h4 & mask; + res=0; + } + + for(i=res;ic[i]=0; + + if (res>SHA_CBLOCK-8) { + mask = 0-((inp_len+8-j)>>(sizeof(j)*8-1)); + data->u[SHA_LBLOCK-1] |= bitlen&mask; + sha1_block_data_order(&key->md,data,1); + mask &= 0-((j-inp_len-73)>>(sizeof(j)*8-1)); + mac.u[0] |= key->md.h0 & mask; + mac.u[1] |= key->md.h1 & mask; + mac.u[2] |= key->md.h2 & mask; + mac.u[3] |= key->md.h3 & mask; + mac.u[4] |= key->md.h4 & mask; + + memset(data,0,SHA_CBLOCK); + j+=64; + } + data->u[SHA_LBLOCK-1] = bitlen; + sha1_block_data_order(&key->md,data,1); + mask = 0-((j-inp_len-73)>>(sizeof(j)*8-1)); + mac.u[0] |= key->md.h0 & mask; + mac.u[1] |= key->md.h1 & mask; + mac.u[2] |= key->md.h2 & mask; + mac.u[3] |= key->md.h3 & mask; + mac.u[4] |= key->md.h4 & mask; + +#ifdef BSWAP + mac.u[0] = BSWAP(mac.u[0]); + mac.u[1] = BSWAP(mac.u[1]); + mac.u[2] = BSWAP(mac.u[2]); + mac.u[3] = BSWAP(mac.u[3]); + mac.u[4] = BSWAP(mac.u[4]); +#else + for (i=0;i<5;i++) { + res = mac.u[i]; + mac.c[4*i+0]=(unsigned char)(res>>24); + mac.c[4*i+1]=(unsigned char)(res>>16); + mac.c[4*i+2]=(unsigned char)(res>>8); + mac.c[4*i+3]=(unsigned char)res; + } +#endif + len += SHA_DIGEST_LENGTH; +#else + SHA1_Update(&key->md,out,inp_len); + res = key->md.num; + SHA1_Final(mac.c,&key->md); + + { + unsigned int inp_blocks, pad_blocks; + + /* but pretend as if we hashed padded payload */ + inp_blocks = 1+((SHA_CBLOCK-9-res)>>(sizeof(res)*8-1)); + res += (unsigned int)(len-inp_len); + pad_blocks = res / SHA_CBLOCK; + res %= SHA_CBLOCK; + pad_blocks += 1+((SHA_CBLOCK-9-res)>>(sizeof(res)*8-1)); + for (;inp_blocksmd,data,1); + } +#endif key->md = key->tail; - SHA1_Update(&key->md,mac,SHA_DIGEST_LENGTH); - SHA1_Final(mac,&key->md); + SHA1_Update(&key->md,mac.c,SHA_DIGEST_LENGTH); + SHA1_Final(mac.c,&key->md); - if (memcmp(out+iv+len,mac,SHA_DIGEST_LENGTH)) - return 0; + /* verify HMAC */ + out += inp_len; + len -= inp_len; +#if 1 + { + unsigned char *p = out+len-1-maxpad-SHA_DIGEST_LENGTH; + size_t off = out-p; + unsigned int c, cmask; + + maxpad += SHA_DIGEST_LENGTH; + for (res=0,i=0,j=0;j>(sizeof(int)*8-1); + res |= (c^pad)&~cmask; /* ... and padding */ + cmask &= ((int)(off-1-j))>>(sizeof(int)*8-1); + res |= (c^mac.c[i])&cmask; + i += 1&cmask; + } + maxpad -= SHA_DIGEST_LENGTH; + + res = 0-((0-res)>>(sizeof(res)*8-1)); + ret &= (int)~res; + } +#else + for (res=0,i=0;i>(sizeof(res)*8-1)); + ret &= (int)~res; + + /* verify padding */ + pad = (pad&~res) | (maxpad&res); + out = out+len-1-pad; + for (res=0,i=0;i>(sizeof(res)*8-1); + ret &= (int)~res; +#endif + return ret; } else { SHA1_Update(&key->md,out,len); } } - key->payload_length = NO_PAYLOAD_LENGTH; - return 1; } diff --git a/ssl/s3_cbc.c b/ssl/s3_cbc.c index b91d84098d..3c2c16539d 100644 --- a/ssl/s3_cbc.c +++ b/ssl/s3_cbc.c @@ -150,6 +150,21 @@ int tls1_cbc_remove_padding(const SSL* s, if (overhead > rec->length) return 0; + /* 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; + } + padding_length = rec->data[rec->length-1]; /* NB: if compression is in operation the first packet may not be of @@ -172,6 +187,13 @@ 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; + 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 @@ -209,21 +231,6 @@ int tls1_cbc_remove_padding(const SSL* s, rec->length -= padding_length; rec->type |= padding_length<<8; /* kludge: pass padding length */ - /* 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; - } - return (int)((good & 1) | (~good & -1)); } diff --git a/ssl/ssl_algs.c b/ssl/ssl_algs.c index 41ccbaac30..9c34d19725 100644 --- a/ssl/ssl_algs.c +++ b/ssl/ssl_algs.c @@ -90,12 +90,10 @@ int SSL_library_init(void) EVP_add_cipher(EVP_aes_256_cbc()); EVP_add_cipher(EVP_aes_128_gcm()); EVP_add_cipher(EVP_aes_256_gcm()); -#if 0 /* Disabled because of timing side-channel leaks. */ #if !defined(OPENSSL_NO_SHA) && !defined(OPENSSL_NO_SHA1) EVP_add_cipher(EVP_aes_128_cbc_hmac_sha1()); EVP_add_cipher(EVP_aes_256_cbc_hmac_sha1()); #endif -#endif #endif #ifndef OPENSSL_NO_CAMELLIA -- 2.34.1