crypt.c

   1 /*
   2  * Copyright (C) 2005 Andre Noll <maan@tuebingen.mpg.de>
   3  *
   4  * Licensed under the GPL v2. For licencing details see COPYING.
   5  */
   6
   7 /** \file crypt.c Openssl-based encryption/decryption routines. */
   8
   9 #include <regex.h>
  10 #include <sys/types.h>
  11 #include <sys/socket.h>
  12 #include <openssl/rand.h>
  13 #include <openssl/err.h>
  14 #include <openssl/rc4.h>
  15 #include <openssl/pem.h>
  16 #include <openssl/sha.h>
  17 #include <openssl/bn.h>
  18 #include <openssl/aes.h>
  19
  20 #include "para.h"
  21 #include "error.h"
  22 #include "string.h"
  23 #include "crypt.h"
  24 #include "fd.h"
  25 #include "crypt_backend.h"
  26
  27 struct asymmetric_key {
  28         RSA *rsa;
  29 };
  30
  31 void get_random_bytes_or_die(unsigned char *buf, int num)
  32 {
  33         unsigned long err;
  34
  35         /* RAND_bytes() returns 1 on success, 0 otherwise. */
  36         if (RAND_bytes(buf, num) == 1)
  37                 return;
  38         err = ERR_get_error();
  39         PARA_EMERG_LOG("%s\n", ERR_reason_error_string(err));
  40         exit(EXIT_FAILURE);
  41 }
  42
  43 /*
  44  * Read 64 bytes from /dev/urandom and adds them to the SSL PRNG. Seed the PRNG
  45  * used by random() with a random seed obtained from SSL. If /dev/random is not
  46  * readable the function calls exit().
  47  *
  48  * \sa RAND_load_file(3), \ref get_random_bytes_or_die(), srandom(3),
  49  * random(3), \ref para_random().
  50  */
  51 void init_random_seed_or_die(void)
  52 {
  53         int seed, ret = RAND_load_file("/dev/urandom", 64);
  54
  55         if (ret != 64) {
  56                 PARA_EMERG_LOG("could not seed PRNG (ret = %d)\n", ret);
  57                 exit(EXIT_FAILURE);
  58         }
  59         get_random_bytes_or_die((unsigned char *)&seed, sizeof(seed));
  60         srandom(seed);
  61 }
  62
  63 static EVP_PKEY *load_key(const char *file, int private)
  64 {
  65         BIO *key;
  66         EVP_PKEY *pkey = NULL;
  67         int ret = check_key_file(file, private);
  68
  69         if (ret < 0) {
  70                 PARA_ERROR_LOG("%s\n", para_strerror(-ret));
  71                 return NULL;
  72         }
  73         key = BIO_new(BIO_s_file());
  74         if (!key)
  75                 return NULL;
  76         if (BIO_read_filename(key, file) > 0) {
  77                 if (private == LOAD_PRIVATE_KEY)
  78                         pkey = PEM_read_bio_PrivateKey(key, NULL, NULL, NULL);
  79                 else
  80                         pkey = PEM_read_bio_PUBKEY(key, NULL, NULL, NULL);
  81         }
  82         BIO_free(key);
  83         return pkey;
  84 }
  85
  86 static int get_openssl_key(const char *key_file, RSA **rsa, int private)
  87 {
  88         EVP_PKEY *key = load_key(key_file, private);
  89
  90         if (!key)
  91                 return (private == LOAD_PRIVATE_KEY)? -E_PRIVATE_KEY
  92                         : -E_PUBLIC_KEY;
  93         *rsa = EVP_PKEY_get1_RSA(key);
  94         EVP_PKEY_free(key);
  95         if (!*rsa)
  96                 return -E_RSA;
  97         return RSA_size(*rsa);
  98 }
  99
 100 /*
 101  * The public key loading functions below were inspired by corresponding code
 102  * of openssh-5.2p1, Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo,
 103  * Finland. However, not much of the original code remains.
 104  */
 105
 106 static int read_bignum(const unsigned char *buf, size_t len, BIGNUM **result)
 107 {
 108         const unsigned char *p = buf, *end = buf + len;
 109         uint32_t bnsize;
 110         BIGNUM *bn;
 111
 112         if (p + 4 < p)
 113                 return -E_BIGNUM;
 114         if (p + 4 > end)
 115                 return -E_BIGNUM;
 116         bnsize = read_ssh_u32(p);
 117         PARA_DEBUG_LOG("bnsize: %u\n", bnsize);
 118         p += 4;
 119         if (p + bnsize < p)
 120                 return -E_BIGNUM;
 121         if (p + bnsize > end)
 122                 return -E_BIGNUM;
 123         if (bnsize > 8192)
 124                 return -E_BIGNUM;
 125         bn = BN_bin2bn(p, bnsize, NULL);
 126         if (!bn)
 127                 return -E_BIGNUM;
 128         *result = bn;
 129         return bnsize + 4;
 130 }
 131
 132 static int read_rsa_bignums(const unsigned char *blob, int blen, RSA **result)
 133 {
 134         int ret;
 135         RSA *rsa;
 136         const unsigned char *p = blob, *end = blob + blen;
 137
 138         rsa = RSA_new();
 139         if (!rsa)
 140                 return -E_BIGNUM;
 141         ret = read_bignum(p, end - p, &rsa->e);
 142         if (ret < 0)
 143                 goto fail;
 144         p += ret;
 145         ret = read_bignum(p, end - p, &rsa->n);
 146         if (ret < 0)
 147                 goto fail;
 148         *result = rsa;
 149         return 1;
 150 fail:
 151         RSA_free(rsa);
 152         return ret;
 153 }
 154
 155 int get_asymmetric_key(const char *key_file, int private,
 156                 struct asymmetric_key **result)
 157 {
 158         struct asymmetric_key *key = NULL;
 159         void *map = NULL;
 160         unsigned char *blob = NULL;
 161         size_t map_size, blob_size, decoded_size;
 162         int ret, ret2;
 163         char *cp;
 164
 165         key = para_malloc(sizeof(*key));
 166         if (private) {
 167                 ret = get_openssl_key(key_file, &key->rsa, LOAD_PRIVATE_KEY);
 168                 goto out;
 169         }
 170         ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
 171         if (ret < 0)
 172                 goto out;
 173         ret = is_ssh_rsa_key(map, map_size);
 174         if (!ret) {
 175                 ret = para_munmap(map, map_size);
 176                 map = NULL;
 177                 if (ret < 0)
 178                         goto out;
 179                 ret = get_openssl_key(key_file, &key->rsa, LOAD_PUBLIC_KEY);
 180                 goto out;
 181         }
 182         cp = map + ret;
 183         PARA_INFO_LOG("decoding public rsa-ssh key %s\n", key_file);
 184         ret = -ERRNO_TO_PARA_ERROR(EOVERFLOW);
 185         if (map_size > INT_MAX / 4)
 186                 goto out_unmap;
 187         blob_size = 2 * map_size;
 188         blob = para_malloc(blob_size);
 189         ret = uudecode(cp, blob, blob_size);
 190         if (ret < 0)
 191                 goto out_unmap;
 192         decoded_size = ret;
 193         ret = check_ssh_key_header(blob, decoded_size);
 194         if (ret < 0)
 195                 goto out_unmap;
 196         ret = read_rsa_bignums(blob + ret, decoded_size - ret, &key->rsa);
 197         if (ret < 0)
 198                 goto out_unmap;
 199         ret = RSA_size(key->rsa);
 200 out_unmap:
 201         ret2 = para_munmap(map, map_size);
 202         if (ret >= 0 && ret2 < 0)
 203                 ret = ret2;
 204 out:
 205         if (ret < 0) {
 206                 free(key);
 207                 *result = NULL;
 208                 PARA_ERROR_LOG("key %s: %s\n", key_file, para_strerror(-ret));
 209         } else
 210                 *result = key;
 211         free(blob);
 212         return ret;
 213 }
 214
 215 void free_asymmetric_key(struct asymmetric_key *key)
 216 {
 217         if (!key)
 218                 return;
 219         RSA_free(key->rsa);
 220         free(key);
 221 }
 222
 223 int priv_decrypt(const char *key_file, unsigned char *outbuf,
 224                 unsigned char *inbuf, int inlen)
 225 {
 226         struct asymmetric_key *priv;
 227         int ret;
 228
 229         if (inlen < 0)
 230                 return -E_RSA;
 231         ret = get_asymmetric_key(key_file, LOAD_PRIVATE_KEY, &priv);
 232         if (ret < 0)
 233                 return ret;
 234         /*
 235          * RSA is vulnerable to timing attacks. Generate a random blinding
 236          * factor to protect against this kind of attack.
 237          */
 238         ret = -E_BLINDING;
 239         if (RSA_blinding_on(priv->rsa, NULL) == 0)
 240                 goto out;
 241         ret = RSA_private_decrypt(inlen, inbuf, outbuf, priv->rsa,
 242                 RSA_PKCS1_OAEP_PADDING);
 243         RSA_blinding_off(priv->rsa);
 244         if (ret <= 0)
 245                 ret = -E_DECRYPT;
 246 out:
 247         free_asymmetric_key(priv);
 248         return ret;
 249 }
 250
 251 int pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf,
 252                 unsigned len, unsigned char *outbuf)
 253 {
 254         int ret, flen = len; /* RSA_public_encrypt expects a signed int */
 255
 256         if (flen < 0)
 257                 return -E_ENCRYPT;
 258         ret = RSA_public_encrypt(flen, inbuf, outbuf, pub->rsa,
 259                 RSA_PKCS1_OAEP_PADDING);
 260         return ret < 0? -E_ENCRYPT : ret;
 261 }
 262
 263 struct aes_ctr_128_context {
 264         AES_KEY key;
 265         unsigned char ivec[AES_CRT128_BLOCK_SIZE];
 266         unsigned char ecount[AES_CRT128_BLOCK_SIZE];
 267         unsigned int num;
 268 };
 269
 270 struct stream_cipher {
 271         bool use_aes;
 272         union {
 273                 RC4_KEY rc4_key;
 274                 struct aes_ctr_128_context aes;
 275         } context;
 276 };
 277
 278 struct stream_cipher *sc_new(const unsigned char *data, int len,
 279                 bool use_aes)
 280 {
 281         int ret;
 282         struct stream_cipher *sc = para_malloc(sizeof(*sc));
 283         struct aes_ctr_128_context *aes;
 284
 285         sc->use_aes = use_aes;
 286         if (!use_aes) {
 287                 RC4_set_key(&sc->context.rc4_key, len, data);
 288                 return sc;
 289         }
 290         assert(len >= 2 * AES_CRT128_BLOCK_SIZE);
 291         aes = &sc->context.aes;
 292         ret = AES_set_encrypt_key(data, AES_CRT128_BLOCK_SIZE * 8 /* bits */,
 293                 &aes->key);
 294         assert(ret == 0);
 295         memcpy(aes->ivec, data + AES_CRT128_BLOCK_SIZE, AES_CRT128_BLOCK_SIZE);
 296         aes->num = 0;
 297         return sc;
 298 }
 299
 300 void sc_free(struct stream_cipher *sc)
 301 {
 302         free(sc);
 303 }
 304
 305 /**
 306  * The RC4() implementation of openssl apparently reads and writes data in
 307  * blocks of 8 bytes. So we have to make sure our buffer sizes are a multiple
 308  * of this.
 309  */
 310 #define RC4_ALIGN 8
 311
 312 static void rc4_crypt(RC4_KEY *key, struct iovec *src, struct iovec *dst)
 313 {
 314         size_t len = src->iov_len, l1, l2;
 315
 316         assert(len > 0);
 317         assert(len < ((typeof(src->iov_len))-1) / 2);
 318         l1 = ROUND_DOWN(len, RC4_ALIGN);
 319         l2 = ROUND_UP(len, RC4_ALIGN);
 320
 321         *dst = (typeof(*dst)) {
 322                 /* Add one for the terminating zero byte. */
 323                 .iov_base = para_malloc(l2 + 1),
 324                 .iov_len = len
 325         };
 326         RC4(key, l1, src->iov_base, dst->iov_base);
 327         if (len > l1) {
 328                 unsigned char remainder[RC4_ALIGN] = "";
 329                 memcpy(remainder, src->iov_base + l1, len - l1);
 330                 RC4(key, len - l1, remainder, dst->iov_base + l1);
 331         }
 332         ((char *)dst->iov_base)[len] = '\0';
 333 }
 334
 335 static void aes_ctr128_crypt(struct aes_ctr_128_context *aes, struct iovec *src,
 336                 struct iovec *dst)
 337 {
 338         size_t len = src->iov_len;
 339
 340         *dst = (typeof(*dst)) {
 341                 /* Add one for the terminating zero byte. */
 342                 .iov_base = para_malloc(len + 1),
 343                 .iov_len = len
 344         };
 345         AES_ctr128_encrypt(src->iov_base, dst->iov_base, len,
 346                 &aes->key, aes->ivec, aes->ecount, &aes->num);
 347         ((char *)dst->iov_base)[len] = '\0';
 348 }
 349
 350 void sc_crypt(struct stream_cipher *sc, struct iovec *src, struct iovec *dst)
 351 {
 352         if (sc->use_aes)
 353                 return aes_ctr128_crypt(&sc->context.aes, src, dst);
 354         return rc4_crypt(&sc->context.rc4_key, src, dst);
 355 }
 356
 357 void hash_function(const char *data, unsigned long len, unsigned char *hash)
 358 {
 359         SHA_CTX c;
 360         SHA1_Init(&c);
 361         SHA1_Update(&c, data, len);
 362         SHA1_Final(hash, &c);
 363 }