2 * Copyright (C) 2005-2011 Andre Noll <maan@systemlinux.org>
4 * Licensed under the GPL v2. For licencing details see COPYING.
7 /** \file crypt.c Openssl-based encryption/decryption routines. */
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>
25 struct asymmetric_key {
30 * Fill a buffer with random content.
32 * \param buf The buffer to fill.
33 * \param num The size of \a buf in bytes.
35 * This function puts \a num cryptographically strong pseudo-random bytes into
36 * buf. If libssl can not guarantee an unpredictable byte sequence (for example
37 * because the PRNG has not been seeded with enough randomness) the function
38 * logs an error message and calls exit().
40 void get_random_bytes_or_die(unsigned char *buf, int num)
44 /* RAND_bytes() returns 1 on success, 0 otherwise. */
45 if (RAND_bytes(buf, num) == 1)
47 err = ERR_get_error();
48 PARA_EMERG_LOG("%s\n", ERR_reason_error_string(err));
53 * Seed pseudo random number generators.
55 * This function reads 64 bytes from /dev/urandom and adds them to the SSL
56 * PRNG. It also seeds the PRNG used by random() with a random seed obtained
57 * from SSL. If /dev/random could not be read, an error message is logged and
58 * the function calls exit().
60 * \sa RAND_load_file(3), \ref get_random_bytes_or_die(), srandom(3),
61 * random(3), \ref para_random().
63 void init_random_seed_or_die(void)
65 int seed, ret = RAND_load_file("/dev/urandom", 64);
68 PARA_EMERG_LOG("could not seed PRNG (ret = %d)\n", ret);
71 get_random_bytes_or_die((unsigned char *)&seed, sizeof(seed));
75 static int check_key_file(const char *file, int private)
79 if (stat(file, &st) != 0)
80 return -ERRNO_TO_PARA_ERROR(errno);
81 if (private != LOAD_PRIVATE_KEY)
83 if ((st.st_uid == getuid()) && (st.st_mode & 077) != 0)
88 static EVP_PKEY *load_key(const char *file, int private)
91 EVP_PKEY *pkey = NULL;
92 int ret = check_key_file(file, private);
95 PARA_ERROR_LOG("%s\n", para_strerror(-ret));
98 key = BIO_new(BIO_s_file());
101 if (BIO_read_filename(key, file) > 0) {
102 if (private == LOAD_PRIVATE_KEY)
103 pkey = PEM_read_bio_PrivateKey(key, NULL, NULL, NULL);
105 pkey = PEM_read_bio_PUBKEY(key, NULL, NULL, NULL);
111 static int get_openssl_key(const char *key_file, RSA **rsa, int private)
113 EVP_PKEY *key = load_key(key_file, private);
116 return (private == LOAD_PRIVATE_KEY)? -E_PRIVATE_KEY
118 *rsa = EVP_PKEY_get1_RSA(key);
122 return RSA_size(*rsa);
125 #define KEY_TYPE_TXT "ssh-rsa"
127 /* check if it is an ssh rsa key */
128 static size_t is_ssh_rsa_key(char *data, size_t size)
132 if (size < strlen(KEY_TYPE_TXT) + 2)
134 cp = memchr(data, ' ', size);
137 if (strncmp(KEY_TYPE_TXT, data, strlen(KEY_TYPE_TXT)))
140 if (cp >= data + size)
148 * This base64/uudecode stuff below is taken from openssh-5.2p1, Copyright (c)
149 * 1996 by Internet Software Consortium. Portions Copyright (c) 1995 by
150 * International Business Machines, Inc.
153 static const char Base64[] =
154 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
155 static const char Pad64 = '=';
157 * Skips all whitespace anywhere. Converts characters, four at a time, starting
158 * at (or after) src from base - 64 numbers into three 8 bit bytes in the
159 * target area. it returns the number of data bytes stored at the target, or -1
162 static int base64_decode(char const *src, unsigned char *target, size_t targsize)
164 unsigned int tarindex, state;
171 while ((ch = *src++) != '\0') {
172 if (para_isspace(ch)) /* Skip whitespace anywhere. */
178 pos = strchr(Base64, ch);
179 if (pos == 0) /* A non-base64 character. */
185 if (tarindex >= targsize)
187 target[tarindex] = (pos - Base64) << 2;
193 if (tarindex + 1 >= targsize)
195 target[tarindex] |= (pos - Base64) >> 4;
196 target[tarindex+1] = ((pos - Base64) & 0x0f)
204 if (tarindex + 1 >= targsize)
206 target[tarindex] |= (pos - Base64) >> 2;
207 target[tarindex+1] = ((pos - Base64) & 0x03)
215 if (tarindex >= targsize)
217 target[tarindex] |= (pos - Base64);
226 * We are done decoding Base-64 chars. Let's see if we ended
227 * on a byte boundary, and/or with erroneous trailing characters.
230 if (ch == Pad64) { /* We got a pad char. */
231 ch = *src++; /* Skip it, get next. */
233 case 0: /* Invalid = in first position */
234 case 1: /* Invalid = in second position */
237 case 2: /* Valid, means one byte of info */
238 /* Skip any number of spaces. */
239 for (; ch != '\0'; ch = *src++)
242 /* Make sure there is another trailing = sign. */
245 ch = *src++; /* Skip the = */
246 /* Fall through to "single trailing =" case. */
249 case 3: /* Valid, means two bytes of info */
251 * We know this char is an =. Is there anything but
252 * whitespace after it?
254 for (; ch != '\0'; ch = *src++)
259 * Now make sure for cases 2 and 3 that the "extra"
260 * bits that slopped past the last full byte were
261 * zeros. If we don't check them, they become a
262 * subliminal channel.
264 if (target && target[tarindex] != 0)
269 * We ended by seeing the end of the string. Make sure we
270 * have no partial bytes lying around.
279 static int uudecode(const char *src, unsigned char *target, size_t targsize)
284 /* copy the 'readonly' source */
285 encoded = para_strdup(src);
286 /* skip whitespace and data */
287 for (p = encoded; *p == ' ' || *p == '\t'; p++)
289 for (; *p != '\0' && *p != ' ' && *p != '\t'; p++)
291 /* and remove trailing whitespace because base64_decode needs this */
293 len = base64_decode(encoded, target, targsize);
295 return len >= 0? len : -E_BASE64;
299 * The public key loading functions below were inspired by corresponding code
300 * of openssh-5.2p1, Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo,
301 * Finland. However, not much of the original code remains.
306 * Can not use the inline functions of portable_io.h here because the byte
307 * order is different.
309 static uint32_t read_ssh_u32(const void *vp)
311 const unsigned char *p = (const unsigned char *)vp;
314 v = (uint32_t)p[0] << 24;
315 v |= (uint32_t)p[1] << 16;
316 v |= (uint32_t)p[2] << 8;
322 static int read_bignum(const unsigned char *buf, size_t len, BIGNUM **result)
324 const unsigned char *p = buf, *end = buf + len;
332 bnsize = read_ssh_u32(p);
333 PARA_DEBUG_LOG("bnsize: %u\n", bnsize);
337 if (p + bnsize > end)
341 bn = BN_bin2bn(p, bnsize, NULL);
348 static int read_rsa_bignums(const unsigned char *blob, int blen, RSA **result)
352 const unsigned char *p = blob, *end = blob + blen;
358 rlen = read_ssh_u32(p);
364 if (rlen < strlen(KEY_TYPE_TXT))
366 PARA_DEBUG_LOG("type: %s, rlen: %d\n", p, rlen);
367 if (strncmp((char *)p, KEY_TYPE_TXT, strlen(KEY_TYPE_TXT)))
374 ret = read_bignum(p, end - p, &rsa->e);
378 ret = read_bignum(p, end - p, &rsa->n);
390 * Read an asymmetric key from a file.
392 * \param key_file The file containing the key.
393 * \param private if non-zero, read the private key, otherwise the public key.
394 * \param result The key structure is returned here.
396 * \return The size of the key on success, negative on errors.
398 * \sa openssl(1), rsa(1).
400 int get_asymmetric_key(const char *key_file, int private,
401 struct asymmetric_key **result)
403 struct asymmetric_key *key = NULL;
405 unsigned char *blob = NULL;
406 size_t map_size, blob_size;
410 key = para_malloc(sizeof(*key));
412 ret = get_openssl_key(key_file, &key->rsa, LOAD_PRIVATE_KEY);
415 ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
418 ret = is_ssh_rsa_key(map, map_size);
420 ret = para_munmap(map, map_size);
424 ret = get_openssl_key(key_file, &key->rsa, LOAD_PUBLIC_KEY);
428 PARA_INFO_LOG("decoding public rsa-ssh key %s\n", key_file);
429 ret = -ERRNO_TO_PARA_ERROR(EOVERFLOW);
430 if (map_size > INT_MAX / 4)
432 blob_size = 2 * map_size;
433 blob = para_malloc(blob_size);
434 ret = uudecode(cp, blob, blob_size);
437 ret = read_rsa_bignums(blob, ret, &key->rsa);
440 ret = RSA_size(key->rsa);
442 ret2 = para_munmap(map, map_size);
443 if (ret >= 0 && ret2 < 0)
448 PARA_ERROR_LOG("key %s: %s\n", key_file, para_strerror(-ret));
456 * Deallocate an asymmetric key structure.
458 * \param key Pointer to the key structure to free.
460 * This must be called for any key obtained by get_asymmetric_key().
462 void free_asymmetric_key(struct asymmetric_key *key)
471 * Decrypt a buffer using a private key.
473 * \param key_file Full path of the key.
474 * \param outbuf The output buffer.
475 * \param inbuf The encrypted input buffer.
476 * \param inlen The length of \a inbuf in bytes.
478 * The \a outbuf must be large enough to hold at least \a rsa_inlen bytes.
480 * \return The size of the recovered plaintext on success, negative on errors.
482 * \sa RSA_private_decrypt(3)
484 int priv_decrypt(const char *key_file, unsigned char *outbuf,
485 unsigned char *inbuf, int inlen)
487 struct asymmetric_key *priv;
492 ret = get_asymmetric_key(key_file, LOAD_PRIVATE_KEY, &priv);
496 * RSA is vulnerable to timing attacks. Generate a random blinding
497 * factor to protect against this kind of attack.
500 if (RSA_blinding_on(priv->rsa, NULL) == 0)
502 ret = RSA_private_decrypt(inlen, inbuf, outbuf, priv->rsa,
503 RSA_PKCS1_OAEP_PADDING);
504 RSA_blinding_off(priv->rsa);
508 free_asymmetric_key(priv);
513 * Encrypt a buffer using an RSA key
515 * \param pub: The public key.
516 * \param inbuf The input buffer.
517 * \param len The length of \a inbuf.
518 * \param outbuf The output buffer.
520 * \return The size of the encrypted data on success, negative on errors.
522 * \sa RSA_public_encrypt(3)
524 int pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf,
525 unsigned len, unsigned char *outbuf)
527 int ret, flen = len; /* RSA_public_encrypt expects a signed int */
531 ret = RSA_public_encrypt(flen, inbuf, outbuf, pub->rsa,
532 RSA_PKCS1_OAEP_PADDING);
533 return ret < 0? -E_ENCRYPT : ret;
536 struct stream_cipher {
541 * Allocate and initialize a stream cipher structure.
543 * \param data The key.
544 * \param len The size of the key.
546 * \return A new stream cipher structure.
548 struct stream_cipher *sc_new(const unsigned char *data, int len)
550 struct stream_cipher *sc = para_malloc(sizeof(*sc));
551 RC4_set_key(&sc->key, len, data);
556 * Deallocate a stream cipher structure.
558 * \param sc A stream cipher previously obtained by sc_new().
560 void sc_free(struct stream_cipher *sc)
566 * The RC4() implementation of openssl apparently reads and writes data in
567 * blocks of 8 bytes. So we have to make sure our buffer sizes are a multiple
573 * Encrypt and send a buffer.
575 * \param scc The context.
576 * \param buf The buffer to send.
577 * \param len The size of \a buf in bytes.
579 * \return The return value of the underyling call to write_all().
581 * \sa \ref write_all(), RC4(3).
583 int sc_send_bin_buffer(struct stream_cipher_context *scc, const char *buf,
588 static unsigned char remainder[RC4_ALIGN];
589 size_t l1 = ROUND_DOWN(len, RC4_ALIGN), l2 = ROUND_UP(len, RC4_ALIGN);
592 tmp = para_malloc(l2);
593 RC4(&scc->send->key, l1, (const unsigned char *)buf, tmp);
595 memcpy(remainder, buf + l1, len - l1);
596 RC4(&scc->send->key, len - l1, remainder, tmp + l1);
598 ret = write_all(scc->fd, (char *)tmp, &len);
604 * Encrypt and send a \p NULL-terminated buffer.
606 * \param scc The context.
607 * \param buf The buffer to send.
609 * \return The return value of the underyling call to sc_send_bin_buffer().
611 int sc_send_buffer(struct stream_cipher_context *scc, const char *buf)
613 return sc_send_bin_buffer(scc, buf, strlen(buf));
617 * Format, encrypt and send a buffer.
619 * \param scc The context.
620 * \param fmt A format string.
622 * \return The return value of the underyling call to sc_send_buffer().
624 __printf_2_3 int sc_send_va_buffer(struct stream_cipher_context *scc,
625 const char *fmt, ...)
630 PARA_VSPRINTF(fmt, msg);
631 ret = sc_send_buffer(scc, msg);
637 * Receive a buffer and decrypt it.
639 * \param scc The context.
640 * \param buf The buffer to write the decrypted data to.
641 * \param size The size of \a buf.
643 * \return The number of bytes received on success, negative on errors, zero if
644 * the peer has performed an orderly shutdown.
646 * \sa recv(2), RC4(3).
648 int sc_recv_bin_buffer(struct stream_cipher_context *scc, char *buf,
651 unsigned char *tmp = para_malloc(size);
652 ssize_t ret = recv(scc->fd, tmp, size, 0);
655 RC4(&scc->recv->key, ret, tmp, (unsigned char *)buf);
657 ret = -ERRNO_TO_PARA_ERROR(errno);
663 * Receive a buffer, decrypt it and write terminating NULL byte.
665 * \param scc The context.
666 * \param buf The buffer to write the decrypted data to.
667 * \param size The size of \a buf.
669 * Read at most \a size - 1 bytes from file descriptor given by \a scc, decrypt
670 * the received data and write a NULL byte at the end of the decrypted data.
672 * \return The return value of the underlying call to \ref
673 * sc_recv_bin_buffer().
675 int sc_recv_buffer(struct stream_cipher_context *scc, char *buf, size_t size)
680 n = sc_recv_bin_buffer(scc, buf, size - 1);
689 * Compute the hash of the given input data.
691 * \param data Pointer to the data to compute the hash value from.
692 * \param len The length of \a data in bytes.
693 * \param hash Result pointer.
695 * \a hash must point to an area at least \p HASH_SIZE bytes large.
697 * \sa sha(3), openssl(1).
699 void hash_function(const char *data, unsigned long len, unsigned char *hash)
703 SHA1_Update(&c, data, len);
704 SHA1_Final(hash, &c);