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/*
* PKCS #1 (RSA Encryption)
* Copyright (c) 2006-2014, Jouni Malinen <j@w1.fi>
*
* This software may be distributed under the terms of the BSD license.
* See README for more details.
*/
#include "includes.h"
#include "common.h"
#include "crypto/crypto.h"
#include "rsa.h"
#include "asn1.h"
#include "pkcs1.h"
static int pkcs1_generate_encryption_block(u8 block_type, size_t modlen,
const u8 *in, size_t inlen,
u8 *out, size_t *outlen)
{
size_t ps_len;
u8 *pos;
/*
* PKCS #1 v1.5, 8.1:
*
* EB = 00 || BT || PS || 00 || D
* BT = 00 or 01 for private-key operation; 02 for public-key operation
* PS = k-3-||D||; at least eight octets
* (BT=0: PS=0x00, BT=1: PS=0xff, BT=2: PS=pseudorandom non-zero)
* k = length of modulus in octets (modlen)
*/
if (modlen < 12 || modlen > *outlen || inlen > modlen - 11) {
wpa_printf(MSG_DEBUG, "PKCS #1: %s - Invalid buffer "
"lengths (modlen=%lu outlen=%lu inlen=%lu)",
__func__, (unsigned long) modlen,
(unsigned long) *outlen,
(unsigned long) inlen);
return -1;
}
pos = out;
*pos++ = 0x00;
*pos++ = block_type; /* BT */
ps_len = modlen - inlen - 3;
switch (block_type) {
case 0:
os_memset(pos, 0x00, ps_len);
pos += ps_len;
break;
case 1:
os_memset(pos, 0xff, ps_len);
pos += ps_len;
break;
case 2:
if (os_get_random(pos, ps_len) < 0) {
wpa_printf(MSG_DEBUG, "PKCS #1: %s - Failed to get "
"random data for PS", __func__);
return -1;
}
while (ps_len--) {
if (*pos == 0x00)
*pos = 0x01;
pos++;
}
break;
default:
wpa_printf(MSG_DEBUG, "PKCS #1: %s - Unsupported block type "
"%d", __func__, block_type);
return -1;
}
*pos++ = 0x00;
os_memcpy(pos, in, inlen); /* D */
return 0;
}
int pkcs1_encrypt(int block_type, struct crypto_rsa_key *key,
int use_private, const u8 *in, size_t inlen,
u8 *out, size_t *outlen)
{
size_t modlen;
modlen = crypto_rsa_get_modulus_len(key);
if (pkcs1_generate_encryption_block(block_type, modlen, in, inlen,
out, outlen) < 0)
return -1;
return crypto_rsa_exptmod(out, modlen, out, outlen, key, use_private);
}
int pkcs1_v15_private_key_decrypt(struct crypto_rsa_key *key,
const u8 *in, size_t inlen,
u8 *out, size_t *outlen)
{
int res;
u8 *pos, *end;
res = crypto_rsa_exptmod(in, inlen, out, outlen, key, 1);
if (res)
return res;
if (*outlen < 2 || out[0] != 0 || out[1] != 2)
return -1;
/* Skip PS (pseudorandom non-zero octets) */
pos = out + 2;
end = out + *outlen;
while (*pos && pos < end)
pos++;
if (pos == end)
return -1;
if (pos - out - 2 < 8) {
/* PKCS #1 v1.5, 8.1: At least eight octets long PS */
wpa_printf(MSG_INFO, "LibTomCrypt: Too short padding");
return -1;
}
pos++;
*outlen -= pos - out;
/* Strip PKCS #1 header */
os_memmove(out, pos, *outlen);
return 0;
}
int pkcs1_decrypt_public_key(struct crypto_rsa_key *key,
const u8 *crypt, size_t crypt_len,
u8 *plain, size_t *plain_len)
{
size_t len;
u8 *pos;
len = *plain_len;
if (crypto_rsa_exptmod(crypt, crypt_len, plain, &len, key, 0) < 0)
return -1;
/*
* PKCS #1 v1.5, 8.1:
*
* EB = 00 || BT || PS || 00 || D
* BT = 00 or 01
* PS = k-3-||D|| times (00 if BT=00) or (FF if BT=01)
* k = length of modulus in octets
*
* Based on 10.1.3, "The block type shall be 01" for a signature.
*/
if (len < 3 + 8 + 16 /* min hash len */ ||
plain[0] != 0x00 || plain[1] != 0x01) {
wpa_printf(MSG_INFO, "LibTomCrypt: Invalid signature EB "
"structure");
wpa_hexdump_key(MSG_DEBUG, "Signature EB", plain, len);
return -1;
}
pos = plain + 3;
/* BT = 01 */
if (plain[2] != 0xff) {
wpa_printf(MSG_INFO, "LibTomCrypt: Invalid signature "
"PS (BT=01)");
wpa_hexdump_key(MSG_DEBUG, "Signature EB", plain, len);
return -1;
}
while (pos < plain + len && *pos == 0xff)
pos++;
if (pos - plain - 2 < 8) {
/* PKCS #1 v1.5, 8.1: At least eight octets long PS */
wpa_printf(MSG_INFO, "LibTomCrypt: Too short signature "
"padding");
wpa_hexdump_key(MSG_DEBUG, "Signature EB", plain, len);
return -1;
}
if (pos + 16 /* min hash len */ >= plain + len || *pos != 0x00) {
wpa_printf(MSG_INFO, "LibTomCrypt: Invalid signature EB "
"structure (2)");
wpa_hexdump_key(MSG_DEBUG, "Signature EB", plain, len);
return -1;
}
pos++;
len -= pos - plain;
/* Strip PKCS #1 header */
os_memmove(plain, pos, len);
*plain_len = len;
return 0;
}
int pkcs1_v15_sig_ver(struct crypto_public_key *pk,
const u8 *s, size_t s_len,
const struct asn1_oid *hash_alg,
const u8 *hash, size_t hash_len)
{
int res;
u8 *decrypted;
size_t decrypted_len;
const u8 *pos, *end, *next, *da_end;
struct asn1_hdr hdr;
struct asn1_oid oid;
decrypted = os_malloc(s_len);
if (decrypted == NULL)
return -1;
decrypted_len = s_len;
res = crypto_public_key_decrypt_pkcs1(pk, s, s_len, decrypted,
&decrypted_len);
if (res < 0) {
wpa_printf(MSG_INFO, "PKCS #1: RSA decrypt failed");
os_free(decrypted);
return -1;
}
wpa_hexdump(MSG_DEBUG, "Decrypted(S)", decrypted, decrypted_len);
/*
* PKCS #1 v1.5, 10.1.2:
*
* DigestInfo ::= SEQUENCE {
* digestAlgorithm DigestAlgorithmIdentifier,
* digest Digest
* }
*
* DigestAlgorithmIdentifier ::= AlgorithmIdentifier
*
* Digest ::= OCTET STRING
*
*/
if (asn1_get_next(decrypted, decrypted_len, &hdr) < 0 ||
!asn1_is_sequence(&hdr)) {
asn1_unexpected(&hdr,
"PKCS #1: Expected SEQUENCE (DigestInfo)");
os_free(decrypted);
return -1;
}
wpa_hexdump(MSG_MSGDUMP, "PKCS #1: DigestInfo",
hdr.payload, hdr.length);
pos = hdr.payload;
end = pos + hdr.length;
/*
* X.509:
* AlgorithmIdentifier ::= SEQUENCE {
* algorithm OBJECT IDENTIFIER,
* parameters ANY DEFINED BY algorithm OPTIONAL
* }
*/
if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
!asn1_is_sequence(&hdr)) {
asn1_unexpected(&hdr,
"PKCS #1: Expected SEQUENCE (AlgorithmIdentifier)");
os_free(decrypted);
return -1;
}
wpa_hexdump(MSG_MSGDUMP, "PKCS #1: DigestAlgorithmIdentifier",
hdr.payload, hdr.length);
da_end = hdr.payload + hdr.length;
if (asn1_get_oid(hdr.payload, hdr.length, &oid, &next)) {
wpa_printf(MSG_DEBUG,
"PKCS #1: Failed to parse digestAlgorithm");
os_free(decrypted);
return -1;
}
wpa_hexdump(MSG_MSGDUMP, "PKCS #1: Digest algorithm parameters",
next, da_end - next);
/*
* RFC 5754: The correct encoding for the SHA2 algorithms would be to
* omit the parameters, but there are implementation that encode these
* as a NULL element. Allow these two cases and reject anything else.
*/
if (da_end > next &&
(asn1_get_next(next, da_end - next, &hdr) < 0 ||
!asn1_is_null(&hdr) ||
hdr.payload + hdr.length != da_end)) {
wpa_printf(MSG_DEBUG,
"PKCS #1: Unexpected digest algorithm parameters");
os_free(decrypted);
return -1;
}
if (!asn1_oid_equal(&oid, hash_alg)) {
char txt[100], txt2[100];
asn1_oid_to_str(&oid, txt, sizeof(txt));
asn1_oid_to_str(hash_alg, txt2, sizeof(txt2));
wpa_printf(MSG_DEBUG,
"PKCS #1: Hash alg OID mismatch: was %s, expected %s",
txt, txt2);
os_free(decrypted);
return -1;
}
/* Digest ::= OCTET STRING */
pos = da_end;
if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
!asn1_is_octetstring(&hdr)) {
asn1_unexpected(&hdr,
"PKCS #1: Expected OCTETSTRING (Digest)");
os_free(decrypted);
return -1;
}
wpa_hexdump(MSG_MSGDUMP, "PKCS #1: Decrypted Digest",
hdr.payload, hdr.length);
if (hdr.length != hash_len ||
os_memcmp_const(hdr.payload, hash, hdr.length) != 0) {
wpa_printf(MSG_INFO, "PKCS #1: Digest value does not match calculated hash");
os_free(decrypted);
return -1;
}
if (hdr.payload + hdr.length != decrypted + decrypted_len) {
wpa_printf(MSG_INFO,
"PKCS #1: Extra data after signature - reject");
wpa_hexdump(MSG_DEBUG, "PKCS #1: Extra data",
hdr.payload + hdr.length,
decrypted + decrypted_len - hdr.payload -
hdr.length);
os_free(decrypted);
return -1;
}
os_free(decrypted);
return 0;
}
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