Check that we have enough padding characters.

Reviewed-by: Emilia Käsper <emilia@openssl.org> CVE-2016-2107 MR: #2572
openssl · May 3, 2016 · 68595c0 · 68595c0
1 parent 643e8e9
commit 68595c0
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diff --git a/crypto/evp/e_aes_cbc_hmac_sha1.c b/crypto/evp/e_aes_cbc_hmac_sha1.c
@@ -60,6 +60,7 @@
 # include <openssl/sha.h>
 # include <openssl/rand.h>
 # include "modes_lcl.h"
+# include "constant_time_locl.h"
 
 # ifndef EVP_CIPH_FLAG_AEAD_CIPHER
 #  define EVP_CIPH_FLAG_AEAD_CIPHER       0x200000
@@ -578,6 +579,8 @@ static int aesni_cbc_hmac_sha1_cipher(EVP_CIPHER_CTX *ctx, unsigned char *out,
             maxpad |= (255 - maxpad) >> (sizeof(maxpad) * 8 - 8);
             maxpad &= 255;
 
+            ret &= constant_time_ge(maxpad, pad);
+
             inp_len = len - (SHA_DIGEST_LENGTH + pad + 1);
             mask = (0 - ((inp_len - len) >> (sizeof(inp_len) * 8 - 1)));
             inp_len &= mask;

diff --git a/crypto/evp/e_aes_cbc_hmac_sha256.c b/crypto/evp/e_aes_cbc_hmac_sha256.c
@@ -60,6 +60,7 @@
 # include <openssl/sha.h>
 # include <openssl/rand.h>
 # include "modes_lcl.h"
+# include "constant_time_locl.h"
 
 # ifndef EVP_CIPH_FLAG_AEAD_CIPHER
 #  define EVP_CIPH_FLAG_AEAD_CIPHER       0x200000
@@ -589,6 +590,8 @@ static int aesni_cbc_hmac_sha256_cipher(EVP_CIPHER_CTX *ctx,
             maxpad |= (255 - maxpad) >> (sizeof(maxpad) * 8 - 8);
             maxpad &= 255;
 
+            ret &= constant_time_ge(maxpad, pad);
+
             inp_len = len - (SHA256_DIGEST_LENGTH + pad + 1);
             mask = (0 - ((inp_len - len) >> (sizeof(inp_len) * 8 - 1)));
             inp_len &= mask;