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-rw-r--r--crypto/evp/evp_enc.c58
1 files changed, 28 insertions, 30 deletions
diff --git a/crypto/evp/evp_enc.c b/crypto/evp/evp_enc.c
index 7b1842a52a6d..2e863ac54204 100644
--- a/crypto/evp/evp_enc.c
+++ b/crypto/evp/evp_enc.c
@@ -67,7 +67,6 @@
#ifdef OPENSSL_FIPS
#include <openssl/fips.h>
#endif
-#include "constant_time_locl.h"
#include "evp_locl.h"
#ifdef OPENSSL_FIPS
@@ -501,21 +500,21 @@ 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)
@@ -534,34 +533,33 @@ 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)
- {
- 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);
- }
/*
- * 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.
+ * The following assumes that the ciphertext has been authenticated.
+ * Otherwise it provides a padding oracle.
*/
- 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;
+ n=ctx->final[b-1];
+ if (n == 0 || n > (int)b)
+ {
+ EVPerr(EVP_F_EVP_DECRYPTFINAL_EX,EVP_R_BAD_DECRYPT);
+ return(0);
+ }
+ 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)