* [including the GNU Public Licence.]
*/
+#include "constant_time_locl.h"
+
#include <stdio.h>
#include "cryptlib.h"
#include <openssl/bn.h>
#include <openssl/rand.h>
int RSA_padding_add_PKCS1_type_1(unsigned char *to, int tlen,
- unsigned char *from, int flen)
+ const unsigned char *from, int flen)
{
int j;
unsigned char *p;
- if (flen > (tlen-11))
+ if (flen > (tlen-RSA_PKCS1_PADDING_SIZE))
{
RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_TYPE_1,RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
return(0);
*(p++)=0;
*(p++)=1; /* Private Key BT (Block Type) */
- /* padd out with 0xff data */
+ /* pad out with 0xff data */
j=tlen-3-flen;
memset(p,0xff,j);
p+=j;
}
int RSA_padding_check_PKCS1_type_1(unsigned char *to, int tlen,
- unsigned char *from, int flen, int num)
+ const unsigned char *from, int flen, int num)
{
int i,j;
- unsigned char *p;
+ const unsigned char *p;
p=from;
if ((num != (flen+1)) || (*(p++) != 01))
}
i++; /* Skip over the '\0' */
j-=i;
+ if (j > tlen)
+ {
+ RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,RSA_R_DATA_TOO_LARGE);
+ return(-1);
+ }
memcpy(to,p,(unsigned int)j);
return(j);
}
int RSA_padding_add_PKCS1_type_2(unsigned char *to, int tlen,
- unsigned char *from, int flen)
+ const unsigned char *from, int flen)
{
int i,j;
unsigned char *p;
}
int RSA_padding_check_PKCS1_type_2(unsigned char *to, int tlen,
- unsigned char *from, int flen, int num)
+ const unsigned char *from, int flen, int num)
{
- int i,j;
- unsigned char *p;
+ int i;
+ /* |em| is the encoded message, zero-padded to exactly |num| bytes */
+ unsigned char *em = NULL;
+ unsigned int good, found_zero_byte;
+ int zero_index = 0, msg_index, mlen = -1;
- p=from;
- if ((num != (flen+1)) || (*(p++) != 02))
+ if (tlen < 0 || flen < 0)
+ return -1;
+
+ /* PKCS#1 v1.5 decryption. See "PKCS #1 v2.2: RSA Cryptography
+ * Standard", section 7.2.2. */
+
+ if (flen > num)
+ goto err;
+
+ if (num < 11)
+ goto err;
+
+ em = OPENSSL_malloc(num);
+ if (em == NULL)
{
- RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2,RSA_R_BLOCK_TYPE_IS_NOT_02);
- return(-1);
+ RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2, ERR_R_MALLOC_FAILURE);
+ return -1;
}
-#ifdef PKCS1_CHECK
- return(num-11);
-#endif
+ memset(em, 0, num);
+ /*
+ * Always do this zero-padding copy (even when num == flen) to avoid
+ * leaking that information. The copy still leaks some side-channel
+ * information, but it's impossible to have a fixed memory access
+ * pattern since we can't read out of the bounds of |from|.
+ *
+ * TODO(emilia): Consider porting BN_bn2bin_padded from BoringSSL.
+ */
+ memcpy(em + num - flen, from, flen);
- /* scan over padding data */
- j=flen-1; /* one for type. */
- for (i=0; i<j; i++)
- if (*(p++) == 0) break;
+ good = constant_time_is_zero(em[0]);
+ good &= constant_time_eq(em[1], 2);
- if (i == j)
+ found_zero_byte = 0;
+ for (i = 2; i < num; i++)
{
- RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2,RSA_R_NULL_BEFORE_BLOCK_MISSING);
- return(-1);
+ unsigned int equals0 = constant_time_is_zero(em[i]);
+ zero_index = constant_time_select_int(~found_zero_byte & equals0, i, zero_index);
+ found_zero_byte |= equals0;
}
- if (i < 8)
+ /*
+ * PS must be at least 8 bytes long, and it starts two bytes into |em|.
+ * If we never found a 0-byte, then |zero_index| is 0 and the check
+ * also fails.
+ */
+ good &= constant_time_ge((unsigned int)(zero_index), 2 + 8);
+
+ /* Skip the zero byte. This is incorrect if we never found a zero-byte
+ * but in this case we also do not copy the message out. */
+ msg_index = zero_index + 1;
+ mlen = num - msg_index;
+
+ /* For good measure, do this check in constant time as well; it could
+ * leak something if |tlen| was assuming valid padding. */
+ good &= constant_time_ge((unsigned int)(tlen), (unsigned int)(mlen));
+
+ /*
+ * We can't continue in constant-time because we need to copy the result
+ * and we cannot fake its length. This unavoidably leaks timing
+ * information at the API boundary.
+ * TODO(emilia): this could be addressed at the call site,
+ * see BoringSSL commit 0aa0767340baf925bda4804882aab0cb974b2d26.
+ */
+ if (!good)
{
- RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2,RSA_R_BAD_PAD_BYTE_COUNT);
- return(-1);
+ mlen = -1;
+ goto err;
}
- i++; /* Skip over the '\0' */
- j-=i;
- memcpy(to,p,(unsigned int)j);
- return(j);
- }
+ memcpy(to, em + msg_index, mlen);
+err:
+ if (em != NULL)
+ OPENSSL_free(em);
+ if (mlen == -1)
+ RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2, RSA_R_PKCS_DECODING_ERROR);
+ return mlen;
+ }
projects / openssl.git / blobdiff