6d394530ffe19a5ab9294fb6f6021d0bf0490410
[paraslash.git] / crypt.c
1 /*
2 * Copyright (C) 2005-2007 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
14 static EVP_PKEY *load_key(const char *file, int private)
15 {
16 BIO *key;
17 EVP_PKEY *pkey = NULL;
18
19 key = BIO_new(BIO_s_file());
20 if (!key)
21 return NULL;
22 if (BIO_read_filename(key, file) > 0) {
23 if (private == LOAD_PRIVATE_KEY)
24 pkey = PEM_read_bio_PrivateKey(key, NULL, NULL, NULL);
25 else
26 pkey = PEM_read_bio_PUBKEY(key, NULL, NULL, NULL);
27 }
28 BIO_free(key);
29 return pkey;
30 }
31
32 /**
33 * read an RSA key from a file
34 *
35 * \param key_file the file containing the key
36 * \param rsa RSA structure is returned here
37 * \param private if non-zero, read the private key, otherwise the public key
38 *
39 * \return The size of the RSA key on success, negative on errors.
40 *
41 * \sa openssl(1), rsa(1).
42 */
43 int get_rsa_key(char *key_file, RSA **rsa, int private)
44 {
45 EVP_PKEY *key = load_key(key_file, private);
46
47 if (!key)
48 return (private == LOAD_PRIVATE_KEY)? -E_PRIVATE_KEY
49 : -E_PUBLIC_KEY;
50 *rsa = EVP_PKEY_get1_RSA(key);
51 EVP_PKEY_free(key);
52 if (!*rsa)
53 return -E_RSA;
54 return RSA_size(*rsa);
55 }
56
57 /**
58 * free an RSA structure
59 *
60 * \param rsa pointer to the RSA struct to free
61 *
62 * This must be called for any key obtained by get_rsa_key().
63 */
64 void rsa_free(RSA *rsa)
65 {
66 if (rsa)
67 RSA_free(rsa);
68 }
69
70 /**
71 * decrypt a buffer using an RSA key
72 *
73 * \param key_file full path of the rsa key
74 * \param outbuf the output buffer
75 * \param inbuf the encrypted input buffer
76 * \param rsa_inlen the length of \a inbuf
77 *
78 * The \a outbuf must be large enough to hold at least \a rsa_inlen bytes.
79 *
80 * \return The size of the recovered plaintext on success, negative on errors.
81 *
82 * \sa RSA_private_decrypt(3)
83 **/
84 int para_decrypt_buffer(char *key_file, unsigned char *outbuf, unsigned char *inbuf,
85 unsigned rsa_inlen)
86 {
87 RSA *rsa;
88 int ret, inlen = rsa_inlen;
89
90 if (inlen < 0)
91 return -E_RSA;
92 ret = get_rsa_key(key_file, &rsa, LOAD_PRIVATE_KEY);
93 if (ret < 0)
94 return ret;
95 ret = RSA_private_decrypt(inlen, inbuf, outbuf, rsa, RSA_PKCS1_PADDING);
96 rsa_free(rsa);
97 return (ret > 0)? ret : -E_DECRYPT;
98 }
99
100 /**
101 * decrypt the challenge number sent by para_server
102 *
103 * \param key_file full path of the rsa key
104 * \param challenge_nr result is stored here
105 * \param inbuf the input buffer
106 * \param rsa_inlen the length of \a inbuf
107 *
108 * \return positive on success, negative on errors
109 *
110 * \sa para_decrypt_buffer()
111 */
112 int para_decrypt_challenge(char *key_file, long unsigned *challenge_nr,
113 unsigned char *inbuf, unsigned rsa_inlen)
114 {
115 unsigned char *rsa_out = OPENSSL_malloc(rsa_inlen + 1);
116 int ret = para_decrypt_buffer(key_file, rsa_out, inbuf, rsa_inlen);
117
118 if (ret >= 0) {
119 rsa_out[ret] = '\0';
120 ret = sscanf((char *)rsa_out, "%lu", challenge_nr) == 1?
121 1 : -E_CHALLENGE;
122 }
123 OPENSSL_free(rsa_out);
124 return ret;
125 }
126
127 /**
128 * encrypt a buffer using an RSA key
129 *
130 * \param rsa: public rsa key
131 * \param inbuf the input buffer
132 * \param len the length of \a inbuf
133 * \param outbuf the output buffer
134 *
135 * \return The size of the encrypted data on success, negative on errors
136 *
137 * \sa RSA_public_encrypt(3)
138 */
139 int para_encrypt_buffer(RSA *rsa, unsigned char *inbuf,
140 unsigned len, unsigned char *outbuf)
141 {
142 int ret, flen = len; /* RSA_public_encrypt expects a signed int */
143
144 if (flen < 0)
145 return -E_ENCRYPT;
146 ret = RSA_public_encrypt(flen, inbuf, outbuf, rsa, RSA_PKCS1_PADDING);
147 return ret < 0? -E_ENCRYPT : ret;
148 }
149
150 /**
151 * encrypt the given challenge number
152 *
153 * \param rsa: public rsa key
154 * \param challenge_nr the number to be encrypted
155 * \param outbuf the output buffer
156 *
157 * \a outbuf must be at least 64 bytes long
158 *
159 * \return The size of the encrypted data on success, negative on errors
160 *
161 * \sa para_encrypt_buffer()
162 *
163 */
164 int para_encrypt_challenge(RSA* rsa, long unsigned challenge_nr,
165 unsigned char *outbuf)
166 {
167 unsigned char *inbuf = (unsigned char*) make_message("%lu", challenge_nr);
168 int ret = para_encrypt_buffer(rsa, inbuf, strlen((char *)inbuf), outbuf);
169 free(inbuf);
170 return ret;
171 }
172