contrib/wpa_supplicant-0.5.8/rsa.c

   1 /*
   2  * RSA
   3  * Copyright (c) 2006, 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 "crypto.h"
  19 #include "asn1.h"
  20 #include "bignum.h"
  21 #include "rsa.h"
  22
  23
  24 struct crypto_rsa_key {
  25         int private_key; /* whether private key is set */
  26         struct bignum *n; /* modulus (p * q) */
  27         struct bignum *e; /* public exponent */
  28         /* The following parameters are available only if private_key is set */
  29         struct bignum *d; /* private exponent */
  30         struct bignum *p; /* prime p (factor of n) */
  31         struct bignum *q; /* prime q (factor of n) */
  32         struct bignum *dmp1; /* d mod (p - 1); CRT exponent */
  33         struct bignum *dmq1; /* d mod (q - 1); CRT exponent */
  34         struct bignum *iqmp; /* 1 / q mod p; CRT coefficient */
  35 };
  36
  37
  38 static const u8 * crypto_rsa_parse_integer(const u8 *pos, const u8 *end,
  39                                            struct bignum *num)
  40 {
  41         struct asn1_hdr hdr;
  42
  43         if (pos == NULL)
  44                 return NULL;
  45
  46         if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
  47             hdr.class != ASN1_CLASS_UNIVERSAL || hdr.tag != ASN1_TAG_INTEGER) {
  48                 wpa_printf(MSG_DEBUG, "RSA: Expected INTEGER - found class %d "
  49                            "tag 0x%x", hdr.class, hdr.tag);
  50                 return NULL;
  51         }
  52
  53         if (bignum_set_unsigned_bin(num, hdr.payload, hdr.length) < 0) {
  54                 wpa_printf(MSG_DEBUG, "RSA: Failed to parse INTEGER");
  55                 return NULL;
  56         }
  57
  58         return hdr.payload + hdr.length;
  59 }
  60
  61
  62 /**
  63  * crypto_rsa_import_public_key - Import an RSA public key
  64  * @buf: Key buffer (DER encoded RSA public key)
  65  * @len: Key buffer length in bytes
  66  * Returns: Pointer to the public key or %NULL on failure
  67  */
  68 struct crypto_rsa_key *
  69 crypto_rsa_import_public_key(const u8 *buf, size_t len)
  70 {
  71         struct crypto_rsa_key *key;
  72         struct asn1_hdr hdr;
  73         const u8 *pos, *end;
  74
  75         key = os_zalloc(sizeof(*key));
  76         if (key == NULL)
  77                 return NULL;
  78
  79         key->n = bignum_init();
  80         key->e = bignum_init();
  81         if (key->n == NULL || key->e == NULL) {
  82                 crypto_rsa_free(key);
  83                 return NULL;
  84         }
  85
  86         /*
  87          * PKCS #1, 7.1:
  88          * RSAPublicKey ::= SEQUENCE {
  89          *     modulus INTEGER, -- n
  90          *     publicExponent INTEGER -- e
  91          * }
  92          */
  93
  94         if (asn1_get_next(buf, len, &hdr) < 0 ||
  95             hdr.class != ASN1_CLASS_UNIVERSAL ||
  96             hdr.tag != ASN1_TAG_SEQUENCE) {
  97                 wpa_printf(MSG_DEBUG, "RSA: Expected SEQUENCE "
  98                            "(public key) - found class %d tag 0x%x",
  99                            hdr.class, hdr.tag);
 100                 goto error;
 101         }
 102         pos = hdr.payload;
 103         end = pos + hdr.length;
 104
 105         pos = crypto_rsa_parse_integer(pos, end, key->n);
 106         pos = crypto_rsa_parse_integer(pos, end, key->e);
 107
 108         if (pos == NULL)
 109                 goto error;
 110
 111         if (pos != end) {
 112                 wpa_hexdump(MSG_DEBUG,
 113                             "RSA: Extra data in public key SEQUENCE",
 114                             pos, end - pos);
 115                 goto error;
 116         }
 117
 118         return key;
 119
 120 error:
 121         crypto_rsa_free(key);
 122         return NULL;
 123 }
 124
 125
 126 /**
 127  * crypto_rsa_import_private_key - Import an RSA private key
 128  * @buf: Key buffer (DER encoded RSA private key)
 129  * @len: Key buffer length in bytes
 130  * Returns: Pointer to the private key or %NULL on failure
 131  */
 132 struct crypto_rsa_key *
 133 crypto_rsa_import_private_key(const u8 *buf, size_t len)
 134 {
 135         struct crypto_rsa_key *key;
 136         struct bignum *zero;
 137         struct asn1_hdr hdr;
 138         const u8 *pos, *end;
 139
 140         key = os_zalloc(sizeof(*key));
 141         if (key == NULL)
 142                 return NULL;
 143
 144         key->private_key = 1;
 145
 146         key->n = bignum_init();
 147         key->e = bignum_init();
 148         key->d = bignum_init();
 149         key->p = bignum_init();
 150         key->q = bignum_init();
 151         key->dmp1 = bignum_init();
 152         key->dmq1 = bignum_init();
 153         key->iqmp = bignum_init();
 154
 155         if (key->n == NULL || key->e == NULL || key->d == NULL ||
 156             key->p == NULL || key->q == NULL || key->dmp1 == NULL ||
 157             key->dmq1 == NULL || key->iqmp == NULL) {
 158                 crypto_rsa_free(key);
 159                 return NULL;
 160         }
 161
 162         /*
 163          * PKCS #1, 7.2:
 164          * RSAPrivateKey ::= SEQUENCE {
 165          *    version Version,
 166          *    modulus INTEGER, -- n
 167          *    publicExponent INTEGER, -- e
 168          *    privateExponent INTEGER, -- d
 169          *    prime1 INTEGER, -- p
 170          *    prime2 INTEGER, -- q
 171          *    exponent1 INTEGER, -- d mod (p-1)
 172          *    exponent2 INTEGER, -- d mod (q-1)
 173          *    coefficient INTEGER -- (inverse of q) mod p
 174          * }
 175          *
 176          * Version ::= INTEGER -- shall be 0 for this version of the standard
 177          */
 178         if (asn1_get_next(buf, len, &hdr) < 0 ||
 179             hdr.class != ASN1_CLASS_UNIVERSAL ||
 180             hdr.tag != ASN1_TAG_SEQUENCE) {
 181                 wpa_printf(MSG_DEBUG, "RSA: Expected SEQUENCE "
 182                            "(public key) - found class %d tag 0x%x",
 183                            hdr.class, hdr.tag);
 184                 goto error;
 185         }
 186         pos = hdr.payload;
 187         end = pos + hdr.length;
 188
 189         zero = bignum_init();
 190         if (zero == NULL)
 191                 goto error;
 192         pos = crypto_rsa_parse_integer(pos, end, zero);
 193         if (pos == NULL || bignum_cmp_d(zero, 0) != 0) {
 194                 wpa_printf(MSG_DEBUG, "RSA: Expected zero INTEGER in the "
 195                            "beginning of private key; not found");
 196                 bignum_deinit(zero);
 197                 goto error;
 198         }
 199         bignum_deinit(zero);
 200
 201         pos = crypto_rsa_parse_integer(pos, end, key->n);
 202         pos = crypto_rsa_parse_integer(pos, end, key->e);
 203         pos = crypto_rsa_parse_integer(pos, end, key->d);
 204         pos = crypto_rsa_parse_integer(pos, end, key->p);
 205         pos = crypto_rsa_parse_integer(pos, end, key->q);
 206         pos = crypto_rsa_parse_integer(pos, end, key->dmp1);
 207         pos = crypto_rsa_parse_integer(pos, end, key->dmq1);
 208         pos = crypto_rsa_parse_integer(pos, end, key->iqmp);
 209
 210         if (pos == NULL)
 211                 goto error;
 212
 213         if (pos != end) {
 214                 wpa_hexdump(MSG_DEBUG,
 215                             "RSA: Extra data in public key SEQUENCE",
 216                             pos, end - pos);
 217                 goto error;
 218         }
 219
 220         return key;
 221
 222 error:
 223         crypto_rsa_free(key);
 224         return NULL;
 225 }
 226
 227
 228 /**
 229  * crypto_rsa_get_modulus_len - Get the modulus length of the RSA key
 230  * @key: RSA key
 231  * Returns: Modulus length of the key
 232  */
 233 size_t crypto_rsa_get_modulus_len(struct crypto_rsa_key *key)
 234 {
 235         return bignum_get_unsigned_bin_len(key->n);
 236 }
 237
 238
 239 /**
 240  * crypto_rsa_exptmod - RSA modular exponentiation
 241  * @in: Input data
 242  * @inlen: Input data length
 243  * @out: Buffer for output data
 244  * @outlen: Maximum size of the output buffer and used size on success
 245  * @key: RSA key
 246  * @use_private: 1 = Use RSA private key, 0 = Use RSA public key
 247  * Returns: 0 on success, -1 on failure
 248  */
 249 int crypto_rsa_exptmod(const u8 *in, size_t inlen, u8 *out, size_t *outlen,
 250                        struct crypto_rsa_key *key, int use_private)
 251 {
 252         struct bignum *tmp, *a = NULL, *b = NULL;
 253         int ret = -1;
 254         size_t modlen;
 255
 256         if (use_private && !key->private_key)
 257                 return -1;
 258
 259         tmp = bignum_init();
 260         if (tmp == NULL)
 261                 return -1;
 262
 263         if (bignum_set_unsigned_bin(tmp, in, inlen) < 0)
 264                 goto error;
 265         if (bignum_cmp(key->n, tmp) < 0) {
 266                 /* Too large input value for the RSA key modulus */
 267                 goto error;
 268         }
 269
 270         if (use_private) {
 271                 /*
 272                  * Decrypt (or sign) using Chinese remainer theorem to speed
 273                  * up calculation. This is equivalent to tmp = tmp^d mod n
 274                  * (which would require more CPU to calculate directly).
 275                  *
 276                  * dmp1 = (1/e) mod (p-1)
 277                  * dmq1 = (1/e) mod (q-1)
 278                  * iqmp = (1/q) mod p, where p > q
 279                  * m1 = c^dmp1 mod p
 280                  * m2 = c^dmq1 mod q
 281                  * h = q^-1 (m1 - m2) mod p
 282                  * m = m2 + hq
 283                  */
 284                 a = bignum_init();
 285                 b = bignum_init();
 286                 if (a == NULL || b == NULL)
 287                         goto error;
 288
 289                 /* a = tmp^dmp1 mod p */
 290                 if (bignum_exptmod(tmp, key->dmp1, key->p, a) < 0)
 291                         goto error;
 292
 293                 /* b = tmp^dmq1 mod q */
 294                 if (bignum_exptmod(tmp, key->dmq1, key->q, b) < 0)
 295                         goto error;
 296
 297                 /* tmp = (a - b) * (1/q mod p) (mod p) */
 298                 if (bignum_sub(a, b, tmp) < 0 ||
 299                     bignum_mulmod(tmp, key->iqmp, key->p, tmp) < 0)
 300                         goto error;
 301
 302                 /* tmp = b + q * tmp */
 303                 if (bignum_mul(tmp, key->q, tmp) < 0 ||
 304                     bignum_add(tmp, b, tmp) < 0)
 305                         goto error;
 306         } else {
 307                 /* Encrypt (or verify signature) */
 308                 /* tmp = tmp^e mod N */
 309                 if (bignum_exptmod(tmp, key->e, key->n, tmp) < 0)
 310                         goto error;
 311         }
 312
 313         modlen = crypto_rsa_get_modulus_len(key);
 314         if (modlen > *outlen) {
 315                 *outlen = modlen;
 316                 goto error;
 317         }
 318
 319         if (bignum_get_unsigned_bin_len(tmp) > modlen)
 320                 goto error; /* should never happen */
 321
 322         *outlen = modlen;
 323         os_memset(out, 0, modlen);
 324         if (bignum_get_unsigned_bin(
 325                     tmp, out +
 326                     (modlen - bignum_get_unsigned_bin_len(tmp)), NULL) < 0)
 327                 goto error;
 328
 329         ret = 0;
 330
 331 error:
 332         bignum_deinit(tmp);
 333         bignum_deinit(a);
 334         bignum_deinit(b);
 335         return ret;
 336 }
 337
 338
 339 /**
 340  * crypto_rsa_free - Free RSA key
 341  * @key: RSA key to be freed
 342  *
 343  * This function frees an RSA key imported with either
 344  * crypto_rsa_import_public_key() or crypto_rsa_import_private_key().
 345  */
 346 void crypto_rsa_free(struct crypto_rsa_key *key)
 347 {
 348         if (key) {
 349                 bignum_deinit(key->n);
 350                 bignum_deinit(key->e);
 351                 bignum_deinit(key->d);
 352                 bignum_deinit(key->p);
 353                 bignum_deinit(key->q);
 354                 bignum_deinit(key->dmp1);
 355                 bignum_deinit(key->dmq1);
 356                 bignum_deinit(key->iqmp);
 357                 os_free(key);
 358         }
 359 }