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Revert "RT3425: constant-time evp_enc"

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Causes more problems than it fixes: even though error codes
are not part of the stable API, several users rely on the
specific error code, and the change breaks them. Conversely,
we don't have any concrete use-cases for constant-time behaviour here.

This reverts commit 738911cde68b2b3706e502cf8daf5b14738f2f42.

Reviewed-by: Andy Polyakov <appro@openssl.org>
This commit is contained in:
Emilia Kasper 2014-12-17 14:47:33 +01:00
parent 0e1c318ece
commit 0cf552230e
2 changed files with 25 additions and 32 deletions
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2
crypto/evp/Makefile
View File

@ -406,7 +406,7 @@ evp_enc.o: ../../include/openssl/pkcs7.h ../../include/openssl/rand.h
evp_enc.o: ../../include/openssl/safestack.h ../../include/openssl/sha.h
evp_enc.o: ../../include/openssl/stack.h ../../include/openssl/symhacks.h
evp_enc.o: ../../include/openssl/x509.h ../../include/openssl/x509_vfy.h
evp_enc.o: ../constant_time_locl.h ../cryptlib.h evp_enc.c evp_locl.h
evp_enc.o: ../cryptlib.h evp_enc.c evp_locl.h
evp_err.o: ../../include/openssl/asn1.h ../../include/openssl/bio.h
evp_err.o: ../../include/openssl/crypto.h ../../include/openssl/e_os2.h
evp_err.o: ../../include/openssl/err.h ../../include/openssl/evp.h

55
crypto/evp/evp_enc.c
View File

@ -67,7 +67,6 @@
#ifdef OPENSSL_FIPS
#include <openssl/fips.h>
#endif
#include "constant_time_locl.h"
#include "evp_locl.h"
#ifdef OPENSSL_FIPS
@ -517,21 +516,21 @@ int EVP_DecryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl)
int EVP_DecryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl)
{
unsigned int i, b;
unsigned char pad, padding_good;
int i,n;
unsigned int b;
*outl=0;
if (ctx->cipher->flags & EVP_CIPH_FLAG_CUSTOM_CIPHER)
{
int ret = M_do_cipher(ctx, out, NULL, 0);
if (ret < 0)
i = M_do_cipher(ctx, out, NULL, 0);
if (i < 0)
return 0;
else
*outl = ret;
*outl = i;
return 1;
}
b=(unsigned int)(ctx->cipher->block_size);
b=ctx->cipher->block_size;
if (ctx->flags & EVP_CIPH_NO_PADDING)
{
if(ctx->buf_len)
@ -550,34 +549,28 @@ int EVP_DecryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl)
return(0);
}
OPENSSL_assert(b <= sizeof ctx->final);
pad=ctx->final[b-1];
padding_good = (unsigned char)(~constant_time_is_zero_8(pad));
padding_good &= constant_time_ge_8(b, pad);
for (i = 1; i < b; ++i)
n=ctx->final[b-1];
if (n == 0 || n > (int)b)
{
unsigned char is_pad_index = constant_time_lt_8(i, pad);
unsigned char pad_byte_good = constant_time_eq_8(ctx->final[b-i-1], pad);
padding_good &= constant_time_select_8(is_pad_index, pad_byte_good, 0xff);
EVPerr(EVP_F_EVP_DECRYPTFINAL_EX,EVP_R_BAD_DECRYPT);
return(0);
}
/*
* At least 1 byte is always padding, so we always write b - 1
* bytes to avoid a timing leak. The caller is required to have |b|
* bytes space in |out| by the API contract.
*/
for (i = 0; i < b - 1; ++i)
out[i] = ctx->final[i] & padding_good;
/* Safe cast: for a good padding, EVP_MAX_IV_LENGTH >= b >= pad */
*outl = padding_good & ((unsigned char)(b - pad));
return padding_good & 1;
for (i=0; i<n; i++)
{
if (ctx->final[--b] != n)
{
EVPerr(EVP_F_EVP_DECRYPTFINAL_EX,EVP_R_BAD_DECRYPT);
return(0);
}
}
n=ctx->cipher->block_size-n;
for (i=0; i<n; i++)
out[i]=ctx->final[i];
*outl=n;
}
else
{
*outl = 0;
return 1;
}
*outl=0;
return(1);
}
void EVP_CIPHER_CTX_free(EVP_CIPHER_CTX *ctx)