一、 RSA填充方式
1, RSA_padding_add_PKCS1_type_1 : 私钥加密填充. 标志: 0x01. 填充:0xFF
2, RSA_padding_add_PKCS1_type_2 : 公钥加密填充. 标志: 0x02. 填充:非零随机数
3, RSA_padding_add_none : 无填充其实就是在高位填充 0x00.
二、Openssl 中关于RSA填充部分的代码(路径 : openssl/crypto/rsa/rsa_pkl.c).
// RSA 加密算法填充方式.
// memcpy(目的地址,原地址,长度);
// 私钥加密的填充 01 ,使用oxFF 填充.
int RSA_padding_add_PKCS1_type_1(unsigned char *to, int tlen,
const unsigned char *from, int flen)
{
int j;
unsigned char *p;
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 = (unsigned char *)to;
*(p++) = 0;
*(p++) = 1; /* Private Key BT (Block Type) */
/* pad out with 0xff data */
j = tlen - 3 - flen;
memset(p, 0xff, j);
p += j;
*(p++) = '\0';
memcpy(p, from, (unsigned int)flen);
return (1);
}
int RSA_padding_check_PKCS1_type_1(unsigned char *to, int tlen,
const unsigned char *from, int flen,
int num)
{
int i, j;
const unsigned char *p;
p = from;
if ((num != (flen + 1)) || (*(p++) != 01)) {
RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,
RSA_R_BLOCK_TYPE_IS_NOT_01);
return (-1);
}
/* scan over padding data */
j = flen - 1; /* one for type. */
for (i = 0; i < j; i++) {
if (*p != 0xff) { /* should decrypt to 0xff */
if (*p == 0) {
p++;
break;
} else {
RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,
RSA_R_BAD_FIXED_HEADER_DECRYPT);
return (-1);
}
}
p++;
}
if (i == j) {
RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,
RSA_R_NULL_BEFORE_BLOCK_MISSING);
return (-1);
}
if (i < 8) {
RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,
RSA_R_BAD_PAD_BYTE_COUNT);
return (-1);
}
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);
}
// 公钥加密的填充, 使用非零随机数填充 . 02
int RSA_padding_add_PKCS1_type_2(unsigned char *to, int tlen,
const unsigned char *from, int flen)
{
int i, j;
unsigned char *p;
// 填充条件 : 数据长度必须小于Modulus长度 - 11 字节.
if (flen > (tlen - 11)) {
RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_TYPE_2,
RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
return (0);
}
p = (unsigned char *)to;
*(p++) = 0;
*(p++) = 2; /* Public Key BT (Block Type) */
/* pad out with non-zero random data */
j = tlen - 3 - flen;
if (RAND_bytes(p, j) <= 0)
return (0);
for (i = 0; i < j; i++) {
if (*p == '\0')
do {
if (RAND_bytes(p, 1) <= 0)
return (0);
} while (*p == '\0');
p++;
}
*(p++) = '\0';
memcpy(p, from, (unsigned int)flen);
return (1);
}
int RSA_padding_check_PKCS1_type_2(unsigned char *to, int tlen,
const unsigned char *from, int flen,
int num)
{
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;
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, ERR_R_MALLOC_FAILURE);
return -1;
}
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);
good = constant_time_is_zero(em[0]);
good &= constant_time_eq(em[1], 2);
found_zero_byte = 0;
for (i = 2; i < num; i++) {
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;
}
/*
* 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) {
mlen = -1;
goto err;
}
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;
}
// 无填充
int RSA_padding_add_none(unsigned char *to, int tlen,
const unsigned char *from, int flen)
{
if (flen > tlen) {
RSAerr(RSA_F_RSA_PADDING_ADD_NONE, RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
return (0);
}
if (flen < tlen) {
RSAerr(RSA_F_RSA_PADDING_ADD_NONE, RSA_R_DATA_TOO_SMALL_FOR_KEY_SIZE);
return (0);
}
memcpy(to, from, (unsigned int)flen);
return (1);
}
int RSA_padding_check_none(unsigned char *to, int tlen,
const unsigned char *from, int flen, int num)
{
if (flen > tlen) {
RSAerr(RSA_F_RSA_PADDING_CHECK_NONE, RSA_R_DATA_TOO_LARGE);
return (-1);
}
memset(to, 0, tlen - flen);
memcpy(to + tlen - flen, from, flen);
return (tlen);
}
