Merge branch 't/allow_zero_btr_add'
[paraslash.git] / crypt.h
1 /*
2 * Copyright (C) 2005-2013 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 * Encrypt or decrypt a buffer using a stream cipher.
133 *
134 * \param sc Crypto key.
135 * \param src The source buffer and length.
136 * \param dst The destination buffer and length, filled out by the function.
137 *
138 * It is up to the implementation to decide whether the crypt operation is
139 * performed in place. The caller can tell by looking if the buffers given by
140 * \a src and \a dst coincide after the call. If (and only if) the crypt
141 * operation was not performed in place, the function allocated a new buffer
142 * for the result, so dst->iov_base is different from src->iov_base. In this
143 * case, the destination buffer must be freed by the caller when it is no
144 * longer needed.
145 */
146 void sc_crypt(struct stream_cipher *sc, struct iovec *src, struct iovec *dst);
147
148 /**
149 * Wrapper for \ref sc_crypt() that can be used as a sideband transformation.
150 *
151 * \param src Passed verbatim to \ref sc_crypt().
152 * \param dst Passed verbatim to \ref sc_crypt().
153 * \param trafo_context Must point to an initialized stream cipher.
154 */
155 _static_inline_ void sc_trafo(struct iovec *src, struct iovec *dst,
156 void *trafo_context)
157 {
158 sc_crypt(trafo_context, src, dst);
159 }
160
161 /**
162 * Deallocate a stream cipher structure.
163 *
164 * \param sc A stream cipher previously obtained by sc_new().
165 */
166 void sc_free(struct stream_cipher *sc);
167
168 /**
169 * Encrypt and send a buffer.
170 *
171 * \param scc The context.
172 * \param buf The buffer to send.
173 * \param len The size of \a buf in bytes.
174 *
175 * \return The return value of the underyling call to write_all().
176 *
177 * \sa \ref write_all(), RC4(3).
178 */
179 int sc_send_bin_buffer(struct stream_cipher_context *scc, char *buf,
180 size_t len);
181
182 /**
183 * Encrypt and send a \p NULL-terminated buffer.
184 *
185 * \param scc The context.
186 * \param buf The buffer to send.
187 *
188 * \return The return value of the underyling call to sc_send_bin_buffer().
189 */
190 int sc_send_buffer(struct stream_cipher_context *scc, char *buf);
191
192 /**
193 * Format, encrypt and send a buffer.
194 *
195 * \param scc The context.
196 * \param fmt A format string.
197 *
198 * \return The return value of the underyling call to sc_send_buffer().
199 */
200 __printf_2_3 int sc_send_va_buffer(struct stream_cipher_context *scc,
201 const char *fmt, ...);
202
203 /**
204 * Receive a buffer and decrypt it.
205 *
206 * \param scc The context.
207 * \param buf The buffer to write the decrypted data to.
208 * \param size The size of \a buf.
209 *
210 * \return The number of bytes received on success, negative on errors, zero if
211 * the peer has performed an orderly shutdown.
212 *
213 * \sa recv(2), RC4(3).
214 */
215 int sc_recv_bin_buffer(struct stream_cipher_context *scc, char *buf,
216 size_t size);
217
218 /**
219 * Receive a buffer, decrypt it and write terminating NULL byte.
220 *
221 * \param scc The context.
222 * \param buf The buffer to write the decrypted data to.
223 * \param size The size of \a buf.
224 *
225 * Read at most \a size - 1 bytes from file descriptor given by \a scc, decrypt
226 * the received data and write a NULL byte at the end of the decrypted data.
227 *
228 * \return The return value of the underlying call to \ref
229 * sc_recv_bin_buffer().
230 */
231 int sc_recv_buffer(struct stream_cipher_context *scc, char *buf, size_t size);
232
233 /** Size of the hash value in bytes. */
234 #define HASH_SIZE 20
235
236
237 /**
238 * Compute the hash of the given input data.
239 *
240 * \param data Pointer to the data to compute the hash value from.
241 * \param len The length of \a data in bytes.
242 * \param hash Result pointer.
243 *
244 * \a hash must point to an area at least \p HASH_SIZE bytes large.
245 *
246 * \sa sha(3), openssl(1).
247 * */
248 void hash_function(const char *data, unsigned long len, unsigned char *hash);
249
250 /**
251 * Convert a hash value to ascii format.
252 *
253 * \param hash the hash value.
254 * \param asc Result pointer.
255 *
256 * \a asc must point to an area of at least 2 * \p HASH_SIZE + 1 bytes which
257 * will be filled by the function with the ascii representation of the hash
258 * value given by \a hash, and a terminating \p NULL byte.
259 */
260 void hash_to_asc(unsigned char *hash, char *asc);
261
262 /**
263 * Compare two hashes.
264 *
265 * \param h1 Pointer to the first hash value.
266 * \param h2 Pointer to the second hash value.
267 *
268 * \return 1, -1, or zero, depending on whether \a h1 is greater than,
269 * less than or equal to h2, respectively.
270 */
271 int hash_compare(unsigned char *h1, unsigned char *h2);