Move para_tmpname() to file_write.c and make it static.
[paraslash.git] / crypt.c
1 /*
2 * Copyright (C) 2005-2009 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 RSA encryption/decryption routines */
8
9 #include "para.h"
10 #include "error.h"
11 #include "string.h"
12 #include "crypt.h"
13 #include <openssl/rand.h>
14 #include <openssl/err.h>
15
16 /**
17 * Fill a buffer with random content.
18 *
19 * \param buf The buffer to fill.
20 * \param num The size of \a buf in bytes.
21 *
22 * This function puts \a num cryptographically strong pseudo-random bytes into
23 * buf. If libssl can not guarantee an unpredictable byte sequence (for example
24 * because the PRNG has not been seeded with enough randomness) the function
25 * logs an error message and calls exit().
26 */
27 void get_random_bytes_or_die(unsigned char *buf, int num)
28 {
29 unsigned long err;
30
31 /* RAND_bytes() returns 1 on success, 0 otherwise. */
32 if (RAND_bytes(buf, num) == 1)
33 return;
34 err = ERR_get_error();
35 PARA_EMERG_LOG("%s\n", ERR_reason_error_string(err));
36 exit(EXIT_FAILURE);
37 }
38
39 /**
40 * Seed pseudo random number generators.
41 *
42 * This function reads 64 bytes from /dev/urandom and adds them to the SSL
43 * PRNG. It also seeds the PRNG used by random() with a random seed obtained
44 * from SSL. If /dev/random could not be read, an error message is logged and
45 * 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
67 key = BIO_new(BIO_s_file());
68 if (!key)
69 return NULL;
70 if (BIO_read_filename(key, file) > 0) {
71 if (private == LOAD_PRIVATE_KEY)
72 pkey = PEM_read_bio_PrivateKey(key, NULL, NULL, NULL);
73 else
74 pkey = PEM_read_bio_PUBKEY(key, NULL, NULL, NULL);
75 }
76 BIO_free(key);
77 return pkey;
78 }
79
80 /**
81 * read an RSA key from a file
82 *
83 * \param key_file the file containing the key
84 * \param rsa RSA structure is returned here
85 * \param private if non-zero, read the private key, otherwise the public key
86 *
87 * \return The size of the RSA key on success, negative on errors.
88 *
89 * \sa openssl(1), rsa(1).
90 */
91 int get_rsa_key(char *key_file, RSA **rsa, int private)
92 {
93 EVP_PKEY *key = load_key(key_file, private);
94
95 if (!key)
96 return (private == LOAD_PRIVATE_KEY)? -E_PRIVATE_KEY
97 : -E_PUBLIC_KEY;
98 *rsa = EVP_PKEY_get1_RSA(key);
99 EVP_PKEY_free(key);
100 if (!*rsa)
101 return -E_RSA;
102 return RSA_size(*rsa);
103 }
104
105 /**
106 * free an RSA structure
107 *
108 * \param rsa pointer to the RSA struct to free
109 *
110 * This must be called for any key obtained by get_rsa_key().
111 */
112 void rsa_free(RSA *rsa)
113 {
114 if (rsa)
115 RSA_free(rsa);
116 }
117
118 /**
119 * decrypt a buffer using an RSA key
120 *
121 * \param key_file full path of the rsa key
122 * \param outbuf the output buffer
123 * \param inbuf the encrypted input buffer
124 * \param rsa_inlen the length of \a inbuf
125 *
126 * The \a outbuf must be large enough to hold at least \a rsa_inlen bytes.
127 *
128 * \return The size of the recovered plaintext on success, negative on errors.
129 *
130 * \sa RSA_private_decrypt(3)
131 **/
132 int para_decrypt_buffer(char *key_file, unsigned char *outbuf, unsigned char *inbuf,
133 unsigned rsa_inlen)
134 {
135 RSA *rsa;
136 int ret, inlen = rsa_inlen;
137
138 if (inlen < 0)
139 return -E_RSA;
140 ret = get_rsa_key(key_file, &rsa, LOAD_PRIVATE_KEY);
141 if (ret < 0)
142 return ret;
143 ret = RSA_private_decrypt(inlen, inbuf, outbuf, rsa, RSA_PKCS1_PADDING);
144 rsa_free(rsa);
145 return (ret > 0)? ret : -E_DECRYPT;
146 }
147
148 /**
149 * decrypt the challenge number sent by para_server
150 *
151 * \param key_file full path of the rsa key
152 * \param challenge_nr result is stored here
153 * \param inbuf the input buffer
154 * \param rsa_inlen the length of \a inbuf
155 *
156 * \return positive on success, negative on errors
157 *
158 * \sa para_decrypt_buffer()
159 */
160 int para_decrypt_challenge(char *key_file, long unsigned *challenge_nr,
161 unsigned char *inbuf, unsigned rsa_inlen)
162 {
163 unsigned char *rsa_out = OPENSSL_malloc(rsa_inlen + 1);
164 int ret = para_decrypt_buffer(key_file, rsa_out, inbuf, rsa_inlen);
165
166 if (ret >= 0) {
167 rsa_out[ret] = '\0';
168 ret = sscanf((char *)rsa_out, "%lu", challenge_nr) == 1?
169 1 : -E_CHALLENGE;
170 }
171 OPENSSL_free(rsa_out);
172 return ret;
173 }
174
175 /**
176 * encrypt a buffer using an RSA key
177 *
178 * \param rsa: public rsa key
179 * \param inbuf the input buffer
180 * \param len the length of \a inbuf
181 * \param outbuf the output buffer
182 *
183 * \return The size of the encrypted data on success, negative on errors
184 *
185 * \sa RSA_public_encrypt(3)
186 */
187 int para_encrypt_buffer(RSA *rsa, unsigned char *inbuf,
188 unsigned len, unsigned char *outbuf)
189 {
190 int ret, flen = len; /* RSA_public_encrypt expects a signed int */
191
192 if (flen < 0)
193 return -E_ENCRYPT;
194 ret = RSA_public_encrypt(flen, inbuf, outbuf, rsa, RSA_PKCS1_PADDING);
195 return ret < 0? -E_ENCRYPT : ret;
196 }
197
198 /**
199 * encrypt the given challenge number
200 *
201 * \param rsa: public rsa key
202 * \param challenge_nr the number to be encrypted
203 * \param outbuf the output buffer
204 *
205 * \a outbuf must be at least 64 bytes long
206 *
207 * \return The size of the encrypted data on success, negative on errors
208 *
209 * \sa para_encrypt_buffer()
210 *
211 */
212 int para_encrypt_challenge(RSA* rsa, long unsigned challenge_nr,
213 unsigned char *outbuf)
214 {
215 unsigned char *inbuf = (unsigned char*) make_message("%lu", challenge_nr);
216 int ret = para_encrypt_buffer(rsa, inbuf, strlen((char *)inbuf), outbuf);
217 free(inbuf);
218 return ret;
219 }
220