Pass command exit status via sideband to client.
[paraslash.git] / crypt.c
1 /*
2 * Copyright (C) 2005-2012 Andre Noll <maan@systemlinux.org>
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
19 #include "para.h"
20 #include "error.h"
21 #include "string.h"
22 #include "crypt.h"
23 #include "fd.h"
24 #include "crypt_backend.h"
25
26 struct asymmetric_key {
27 RSA *rsa;
28 };
29
30 void get_random_bytes_or_die(unsigned char *buf, int num)
31 {
32 unsigned long err;
33
34 /* RAND_bytes() returns 1 on success, 0 otherwise. */
35 if (RAND_bytes(buf, num) == 1)
36 return;
37 err = ERR_get_error();
38 PARA_EMERG_LOG("%s\n", ERR_reason_error_string(err));
39 exit(EXIT_FAILURE);
40 }
41
42 /*
43 * Read 64 bytes from /dev/urandom and adds them to the SSL PRNG. Seed the PRNG
44 * used by random() with a random seed obtained from SSL. If /dev/random is not
45 * readable the function calls exit().
46 *
47 * \sa RAND_load_file(3), \ref get_random_bytes_or_die(), srandom(3),
48 * random(3), \ref para_random().
49 */
50 void init_random_seed_or_die(void)
51 {
52 int seed, ret = RAND_load_file("/dev/urandom", 64);
53
54 if (ret != 64) {
55 PARA_EMERG_LOG("could not seed PRNG (ret = %d)\n", ret);
56 exit(EXIT_FAILURE);
57 }
58 get_random_bytes_or_die((unsigned char *)&seed, sizeof(seed));
59 srandom(seed);
60 }
61
62 static EVP_PKEY *load_key(const char *file, int private)
63 {
64 BIO *key;
65 EVP_PKEY *pkey = NULL;
66 int ret = check_key_file(file, private);
67
68 if (ret < 0) {
69 PARA_ERROR_LOG("%s\n", para_strerror(-ret));
70 return NULL;
71 }
72 key = BIO_new(BIO_s_file());
73 if (!key)
74 return NULL;
75 if (BIO_read_filename(key, file) > 0) {
76 if (private == LOAD_PRIVATE_KEY)
77 pkey = PEM_read_bio_PrivateKey(key, NULL, NULL, NULL);
78 else
79 pkey = PEM_read_bio_PUBKEY(key, NULL, NULL, NULL);
80 }
81 BIO_free(key);
82 return pkey;
83 }
84
85 static int get_openssl_key(const char *key_file, RSA **rsa, int private)
86 {
87 EVP_PKEY *key = load_key(key_file, private);
88
89 if (!key)
90 return (private == LOAD_PRIVATE_KEY)? -E_PRIVATE_KEY
91 : -E_PUBLIC_KEY;
92 *rsa = EVP_PKEY_get1_RSA(key);
93 EVP_PKEY_free(key);
94 if (!*rsa)
95 return -E_RSA;
96 return RSA_size(*rsa);
97 }
98
99 /*
100 * The public key loading functions below were inspired by corresponding code
101 * of openssh-5.2p1, Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo,
102 * Finland. However, not much of the original code remains.
103 */
104
105 static int read_bignum(const unsigned char *buf, size_t len, BIGNUM **result)
106 {
107 const unsigned char *p = buf, *end = buf + len;
108 uint32_t bnsize;
109 BIGNUM *bn;
110
111 if (p + 4 < p)
112 return -E_BIGNUM;
113 if (p + 4 > end)
114 return -E_BIGNUM;
115 bnsize = read_ssh_u32(p);
116 PARA_DEBUG_LOG("bnsize: %u\n", bnsize);
117 p += 4;
118 if (p + bnsize < p)
119 return -E_BIGNUM;
120 if (p + bnsize > end)
121 return -E_BIGNUM;
122 if (bnsize > 8192)
123 return -E_BIGNUM;
124 bn = BN_bin2bn(p, bnsize, NULL);
125 if (!bn)
126 return -E_BIGNUM;
127 *result = bn;
128 return bnsize + 4;
129 }
130
131 static int read_rsa_bignums(const unsigned char *blob, int blen, RSA **result)
132 {
133 int ret;
134 RSA *rsa;
135 const unsigned char *p = blob, *end = blob + blen;
136
137 rsa = RSA_new();
138 if (!rsa)
139 return -E_BIGNUM;
140 ret = read_bignum(p, end - p, &rsa->e);
141 if (ret < 0)
142 goto fail;
143 p += ret;
144 ret = read_bignum(p, end - p, &rsa->n);
145 if (ret < 0)
146 goto fail;
147 *result = rsa;
148 return 1;
149 fail:
150 if (rsa)
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 stream_cipher {
264 RC4_KEY key;
265 };
266
267 struct stream_cipher *sc_new(const unsigned char *data, int len)
268 {
269 struct stream_cipher *sc = para_malloc(sizeof(*sc));
270 RC4_set_key(&sc->key, len, data);
271 return sc;
272 }
273
274 void sc_free(struct stream_cipher *sc)
275 {
276 free(sc);
277 }
278
279 /**
280 * The RC4() implementation of openssl apparently reads and writes data in
281 * blocks of 8 bytes. So we have to make sure our buffer sizes are a multiple
282 * of this.
283 */
284 #define RC4_ALIGN 8
285
286 int sc_send_bin_buffer(struct stream_cipher_context *scc, char *buf,
287 size_t len)
288 {
289 int ret;
290 unsigned char *tmp;
291 static unsigned char remainder[RC4_ALIGN];
292 size_t l1 = ROUND_DOWN(len, RC4_ALIGN), l2 = ROUND_UP(len, RC4_ALIGN);
293
294 assert(len);
295 tmp = para_malloc(l2);
296 RC4(&scc->send->key, l1, (const unsigned char *)buf, tmp);
297 if (len > l1) {
298 memcpy(remainder, buf + l1, len - l1);
299 RC4(&scc->send->key, len - l1, remainder, tmp + l1);
300 }
301 ret = xwrite(scc->fd, (char *)tmp, len);
302 free(tmp);
303 return ret;
304 }
305
306 int sc_recv_bin_buffer(struct stream_cipher_context *scc, char *buf,
307 size_t size)
308 {
309 unsigned char *tmp = para_malloc(ROUND_UP(size, RC4_ALIGN));
310 ssize_t ret = recv(scc->fd, tmp, size, 0);
311
312 if (ret > 0)
313 RC4(&scc->recv->key, ret, tmp, (unsigned char *)buf);
314 else if (ret < 0)
315 ret = -ERRNO_TO_PARA_ERROR(errno);
316 free(tmp);
317 return ret;
318 }
319
320 void sc_crypt(struct stream_cipher *sc, struct iovec *src, struct iovec *dst)
321 {
322 RC4_KEY *key = &sc->key;
323
324 *dst = (typeof(*dst)) {
325 /*
326 * Add one for the terminating zero byte. Integer overflow is
327 * no problem here as para_malloc() aborts when given a zero
328 * size argument.
329 */
330 .iov_base = para_malloc(src->iov_len + 1),
331 .iov_len = src->iov_len
332 };
333 RC4(key, src->iov_len, src->iov_base, dst->iov_base);
334 ((char *)dst->iov_base)[dst->iov_len] = '\0';
335 }
336
337 void hash_function(const char *data, unsigned long len, unsigned char *hash)
338 {
339 SHA_CTX c;
340 SHA1_Init(&c);
341 SHA1_Update(&c, data, len);
342 SHA1_Final(hash, &c);
343 }