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