Merge branch 't/clang_analyzer_fixes'
[paraslash.git] / crypt.h
1 /*
2 * Copyright (C) 2005-2011 Andre Noll <maan@systemlinux.org>
3 *
4 * Licensed under the GPL v2. For licencing details see COPYING.
5 */
6
7 /** \file crypt.h Public crypto interface. */
8
9
10 /* These are used to distinguish between loading of private/public key. */
11
12 /** The key to load is a public key. */
13 #define LOAD_PUBLIC_KEY 0
14 /** The key to load is a private key. */
15 #define LOAD_PRIVATE_KEY 1
16 /** The size of the challenge sent to the client. */
17 #define CHALLENGE_SIZE 64
18
19 /** Opaque structure for public and private keys. */
20 struct asymmetric_key;
21
22 /**
23 * Encrypt a buffer using asymmetric keys.
24 *
25 * \param pub: The public key.
26 * \param inbuf The input buffer.
27 * \param len The length of \a inbuf.
28 * \param outbuf The output buffer.
29 *
30 * \return The size of the encrypted data on success, negative on errors.
31 */
32 int pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf,
33 unsigned len, unsigned char *outbuf);
34
35 /**
36 * Decrypt a buffer using a private key.
37 *
38 * \param key_file Full path of the key.
39 * \param outbuf The output buffer.
40 * \param inbuf The encrypted input buffer.
41 * \param inlen The length of \a inbuf.
42 *
43 * The \a outbuf must be large enough to hold at least 512 bytes.
44 *
45 * \return The size of the recovered plaintext on success, negative on errors.
46 */
47 int priv_decrypt(const char *key_file, unsigned char *outbuf,
48 unsigned char *inbuf, int inlen);
49
50 /**
51 * Read an asymmetric key from a file.
52 *
53 * \param key_file The file containing the key.
54 * \param private if non-zero, read the private key, otherwise the public key.
55 * \param result The key structure is returned here.
56 *
57 * \return The size of the key on success, negative on errors.
58 */
59 int get_asymmetric_key(const char *key_file, int private,
60 struct asymmetric_key **result);
61
62 /**
63 * Deallocate an asymmetric key structure.
64 *
65 * \param key Pointer to the key structure to free.
66 *
67 * This must be called for any key obtained by get_asymmetric_key().
68 */
69 void free_asymmetric_key(struct asymmetric_key *key);
70
71
72 /**
73 * Fill a buffer with random content.
74 *
75 * \param buf The buffer to fill.
76 * \param num The size of \a buf in bytes.
77 *
78 * This function puts \a num cryptographically strong pseudo-random bytes into
79 * buf. If it can not guarantee an unpredictable byte sequence (for example
80 * because the PRNG has not been seeded with enough randomness) the function
81 * logs an error message and calls exit().
82 */
83 void get_random_bytes_or_die(unsigned char *buf, int num);
84
85 /**
86 * Seed pseudo random number generators.
87 *
88 * This function seeds the PRNG used by random() with a random seed obtained
89 * from the crypto implementation. On errors, an error message is logged and
90 * the function calls exit().
91 *
92 * \sa \ref get_random_bytes_or_die(), srandom(3), random(3), \ref
93 * para_random().
94 */
95 void init_random_seed_or_die(void);
96
97
98 /** Opaque structure for stream ciphers. */
99 struct stream_cipher;
100
101 /** Number of bytes of the session key for stream ciphers. */
102 #define SESSION_KEY_LEN 32
103
104 /**
105 * Used for client-server communication encryption.
106 *
107 * The traffic between (the forked child of) para_server and the remote client
108 * process is crypted by a symmetric session key. This structure contains the
109 * keys for the stream cipher and the file descriptor for which these keys
110 * should be used.
111 */
112 struct stream_cipher_context {
113 /** The socket file descriptor. */
114 int fd;
115 /** Key used for receiving data. */
116 struct stream_cipher *recv;
117 /** Key used for sending data. */
118 struct stream_cipher *send;
119 };
120
121 /**
122 * Allocate and initialize a stream cipher structure.
123 *
124 * \param data The key.
125 * \param len The size of the key.
126 *
127 * \return A new stream cipher structure.
128 */
129 struct stream_cipher *sc_new(const unsigned char *data, int len);
130
131 /**
132 * Deallocate a stream cipher structure.
133 *
134 * \param sc A stream cipher previously obtained by sc_new().
135 */
136 void sc_free(struct stream_cipher *sc);
137
138 /**
139 * Encrypt and send a buffer.
140 *
141 * \param scc The context.
142 * \param buf The buffer to send.
143 * \param len The size of \a buf in bytes.
144 *
145 * \return The return value of the underyling call to write_all().
146 *
147 * \sa \ref write_all(), RC4(3).
148 */
149 int sc_send_bin_buffer(struct stream_cipher_context *scc, char *buf,
150 size_t len);
151
152 /**
153 * Encrypt and send a \p NULL-terminated buffer.
154 *
155 * \param scc The context.
156 * \param buf The buffer to send.
157 *
158 * \return The return value of the underyling call to sc_send_bin_buffer().
159 */
160 int sc_send_buffer(struct stream_cipher_context *scc, char *buf);
161
162 /**
163 * Format, encrypt and send a buffer.
164 *
165 * \param scc The context.
166 * \param fmt A format string.
167 *
168 * \return The return value of the underyling call to sc_send_buffer().
169 */
170 __printf_2_3 int sc_send_va_buffer(struct stream_cipher_context *scc,
171 const char *fmt, ...);
172
173 /**
174 * Receive a buffer and decrypt it.
175 *
176 * \param scc The context.
177 * \param buf The buffer to write the decrypted data to.
178 * \param size The size of \a buf.
179 *
180 * \return The number of bytes received on success, negative on errors, zero if
181 * the peer has performed an orderly shutdown.
182 *
183 * \sa recv(2), RC4(3).
184 */
185 int sc_recv_bin_buffer(struct stream_cipher_context *scc, char *buf,
186 size_t size);
187
188 /**
189 * Receive a buffer, decrypt it and write terminating NULL byte.
190 *
191 * \param scc The context.
192 * \param buf The buffer to write the decrypted data to.
193 * \param size The size of \a buf.
194 *
195 * Read at most \a size - 1 bytes from file descriptor given by \a scc, decrypt
196 * the received data and write a NULL byte at the end of the decrypted data.
197 *
198 * \return The return value of the underlying call to \ref
199 * sc_recv_bin_buffer().
200 */
201 int sc_recv_buffer(struct stream_cipher_context *scc, char *buf, size_t size);
202
203
204 /** Size of the hash value in bytes. */
205 #define HASH_SIZE 20
206
207
208 /**
209 * Compute the hash of the given input data.
210 *
211 * \param data Pointer to the data to compute the hash value from.
212 * \param len The length of \a data in bytes.
213 * \param hash Result pointer.
214 *
215 * \a hash must point to an area at least \p HASH_SIZE bytes large.
216 *
217 * \sa sha(3), openssl(1).
218 * */
219 void hash_function(const char *data, unsigned long len, unsigned char *hash);
220
221 /**
222 * Convert a hash value to ascii format.
223 *
224 * \param hash the hash value.
225 * \param asc Result pointer.
226 *
227 * \a asc must point to an area of at least 2 * \p HASH_SIZE + 1 bytes which
228 * will be filled by the function with the ascii representation of the hash
229 * value given by \a hash, and a terminating \p NULL byte.
230 */
231 void hash_to_asc(unsigned char *hash, char *asc);
232
233 /**
234 * Compare two hashes.
235 *
236 * \param h1 Pointer to the first hash value.
237 * \param h2 Pointer to the second hash value.
238 *
239 * \return 1, -1, or zero, depending on whether \a h1 is greater than,
240 * less than or equal to h2, respectively.
241 */
242 int hash_compare(unsigned char *h1, unsigned char *h2);