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 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 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 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 } 125 126 127 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