pkcs1.c revision 8d520ff1dc2da35cdca849e982051b86468016d8 
1/*
2 * PKCS #1 (RSA Encryption)
3 * Copyright (c) 2006-2009, Jouni Malinen <j@w1.fi>
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License version 2 as
7 * published by the Free Software Foundation.
8 *
9 * Alternatively, this software may be distributed under the terms of BSD
10 * license.
11 *
12 * See README and COPYING for more details.
13 */
14
15#include "includes.h"
16
17#include "common.h"
18#include "rsa.h"
19#include "pkcs1.h"
20
21
22static int pkcs1_generate_encryption_block(u8 block_type, size_t modlen,
23					   const u8 *in, size_t inlen,
24					   u8 *out, size_t *outlen)
25{
26	size_t ps_len;
27	u8 *pos;
28
29	/*
30	 * PKCS #1 v1.5, 8.1:
31	 *
32	 * EB = 00 || BT || PS || 00 || D
33	 * BT = 00 or 01 for private-key operation; 02 for public-key operation
34	 * PS = k-3-||D||; at least eight octets
35	 * (BT=0: PS=0x00, BT=1: PS=0xff, BT=2: PS=pseudorandom non-zero)
36	 * k = length of modulus in octets (modlen)
37	 */
38
39	if (modlen < 12 || modlen > *outlen || inlen > modlen - 11) {
40		wpa_printf(MSG_DEBUG, "PKCS #1: %s - Invalid buffer "
41			   "lengths (modlen=%lu outlen=%lu inlen=%lu)",
42			   __func__, (unsigned long) modlen,
43			   (unsigned long) *outlen,
44			   (unsigned long) inlen);
45		return -1;
46	}
47
48	pos = out;
49	*pos++ = 0x00;
50	*pos++ = block_type; /* BT */
51	ps_len = modlen - inlen - 3;
52	switch (block_type) {
53	case 0:
54		os_memset(pos, 0x00, ps_len);
55		pos += ps_len;
56		break;
57	case 1:
58		os_memset(pos, 0xff, ps_len);
59		pos += ps_len;
60		break;
61	case 2:
62		if (os_get_random(pos, ps_len) < 0) {
63			wpa_printf(MSG_DEBUG, "PKCS #1: %s - Failed to get "
64				   "random data for PS", __func__);
65			return -1;
66		}
67		while (ps_len--) {
68			if (*pos == 0x00)
69				*pos = 0x01;
70			pos++;
71		}
72		break;
73	default:
74		wpa_printf(MSG_DEBUG, "PKCS #1: %s - Unsupported block type "
75			   "%d", __func__, block_type);
76		return -1;
77	}
78	*pos++ = 0x00;
79	os_memcpy(pos, in, inlen); /* D */
80
81	return 0;
82}
83
84
85int pkcs1_encrypt(int block_type, struct crypto_rsa_key *key,
86		  int use_private, const u8 *in, size_t inlen,
87		  u8 *out, size_t *outlen)
88{
89	size_t modlen;
90
91	modlen = crypto_rsa_get_modulus_len(key);
92
93	if (pkcs1_generate_encryption_block(block_type, modlen, in, inlen,
94					    out, outlen) < 0)
95		return -1;
96
97	return crypto_rsa_exptmod(out, modlen, out, outlen, key, use_private);
98}
99
100
101int pkcs1_v15_private_key_decrypt(struct crypto_rsa_key *key,
102				  const u8 *in, size_t inlen,
103				  u8 *out, size_t *outlen)
104{
105	int res;
106	u8 *pos, *end;
107
108	res = crypto_rsa_exptmod(in, inlen, out, outlen, key, 1);
109	if (res)
110		return res;
111
112	if (*outlen < 2 || out[0] != 0 || out[1] != 2)
113		return -1;
114
115	/* Skip PS (pseudorandom non-zero octets) */
116	pos = out + 2;
117	end = out + *outlen;
118	while (*pos && pos < end)
119		pos++;
120	if (pos == end)
121		return -1;
122	pos++;
123
124	*outlen -= pos - out;
125
126	/* Strip PKCS #1 header */
127	os_memmove(out, pos, *outlen);
128
129	return 0;
130}
131
132
133int pkcs1_decrypt_public_key(struct crypto_rsa_key *key,
134			     const u8 *crypt, size_t crypt_len,
135			     u8 *plain, size_t *plain_len)
136{
137	size_t len;
138	u8 *pos;
139
140	len = *plain_len;
141	if (crypto_rsa_exptmod(crypt, crypt_len, plain, &len, key, 0) < 0)
142		return -1;
143
144	/*
145	 * PKCS #1 v1.5, 8.1:
146	 *
147	 * EB = 00 || BT || PS || 00 || D
148	 * BT = 00 or 01
149	 * PS = k-3-||D|| times (00 if BT=00) or (FF if BT=01)
150	 * k = length of modulus in octets
151	 */
152
153	if (len < 3 + 8 + 16 /* min hash len */ ||
154	    plain[0] != 0x00 || (plain[1] != 0x00 && plain[1] != 0x01)) {
155		wpa_printf(MSG_INFO, "LibTomCrypt: Invalid signature EB "
156			   "structure");
157		return -1;
158	}
159
160	pos = plain + 3;
161	if (plain[1] == 0x00) {
162		/* BT = 00 */
163		if (plain[2] != 0x00) {
164			wpa_printf(MSG_INFO, "LibTomCrypt: Invalid signature "
165				   "PS (BT=00)");
166			return -1;
167		}
168		while (pos + 1 < plain + len && *pos == 0x00 && pos[1] == 0x00)
169			pos++;
170	} else {
171		/* BT = 01 */
172		if (plain[2] != 0xff) {
173			wpa_printf(MSG_INFO, "LibTomCrypt: Invalid signature "
174				   "PS (BT=01)");
175			return -1;
176		}
177		while (pos < plain + len && *pos == 0xff)
178			pos++;
179	}
180
181	if (pos - plain - 2 < 8) {
182		/* PKCS #1 v1.5, 8.1: At least eight octets long PS */
183		wpa_printf(MSG_INFO, "LibTomCrypt: Too short signature "
184			   "padding");
185		return -1;
186	}
187
188	if (pos + 16 /* min hash len */ >= plain + len || *pos != 0x00) {
189		wpa_printf(MSG_INFO, "LibTomCrypt: Invalid signature EB "
190			   "structure (2)");
191		return -1;
192	}
193	pos++;
194	len -= pos - plain;
195
196	/* Strip PKCS #1 header */
197	os_memmove(plain, pos, len);
198	*plain_len = len;
199
200	return 0;
201}
202