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 "utils/includes.h"
10
11 #include "utils/common.h"
12 #include "tls/rsa.h"
13 #include "tls/pkcs1.h"
14
15
pkcs1_generate_encryption_block(u8 block_type,size_t modlen,const u8 * in,size_t inlen,u8 * out,size_t * outlen)16 static 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
pkcs1_encrypt(int block_type,struct crypto_rsa_key * key,int use_private,const u8 * in,size_t inlen,u8 * out,size_t * outlen)79 int 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
pkcs1_v15_private_key_decrypt(struct crypto_rsa_key * key,const u8 * in,size_t inlen,u8 * out,size_t * outlen)95 int 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
pkcs1_decrypt_public_key(struct crypto_rsa_key * key,const u8 * crypt,size_t crypt_len,u8 * plain,size_t * plain_len)127 int 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
