chiark / gitweb /
Add many comments to server/play.c, in advance of possible
[disorder] / lib / cookies.c
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1/*
2 * This file is part of DisOrder
5aff007d 3 * Copyright (C) 2007, 2008 Richard Kettlewell
b12be54a 4 *
e7eb3a27 5 * This program is free software: you can redistribute it and/or modify
b12be54a 6 * it under the terms of the GNU General Public License as published by
e7eb3a27 7 * the Free Software Foundation, either version 3 of the License, or
b12be54a 8 * (at your option) any later version.
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9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
b12be54a 15 * You should have received a copy of the GNU General Public License
e7eb3a27 16 * along with this program. If not, see <http://www.gnu.org/licenses/>.
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17 */
18/** @file lib/cookies.c
19 * @brief Cookie support
20 */
21
05b75f8d 22#include "common.h"
b12be54a 23
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24#include <errno.h>
25#include <time.h>
26#include <gcrypt.h>
f0feb22e 27#include <pcre.h>
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28
29#include "cookies.h"
30#include "hash.h"
31#include "mem.h"
32#include "log.h"
33#include "printf.h"
fce810c2 34#include "base64.h"
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35#include "configuration.h"
36#include "kvp.h"
f0feb22e 37#include "trackdb.h"
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38
39/** @brief Hash function used in signing HMAC */
40#define ALGO GCRY_MD_SHA1
41
42/** @brief Size of key to use */
43#define HASHSIZE 20
44
45/** @brief Signing key */
46static uint8_t signing_key[HASHSIZE];
47
48/** @brief Previous signing key */
49static uint8_t old_signing_key[HASHSIZE];
50
51/** @brief Signing key validity limit or 0 if none */
52static time_t signing_key_validity_limit;
53
54/** @brief Hash of revoked cookies */
55static hash *revoked;
56
57/** @brief Callback to expire revocation list */
58static int revoked_cleanup_callback(const char *key, void *value,
59 void *u) {
60 if(*(time_t *)value < *(time_t *)u)
61 hash_remove(revoked, key);
62 return 0;
63}
64
65/** @brief Generate a new key */
66static void newkey(void) {
67 time_t now;
68
69 time(&now);
70 memcpy(old_signing_key, signing_key, HASHSIZE);
71 gcry_randomize(signing_key, HASHSIZE, GCRY_STRONG_RANDOM);
72 signing_key_validity_limit = now + config->cookie_key_lifetime;
73 /* Now is a good time to clean up the revocation list... */
74 if(revoked)
75 hash_foreach(revoked, revoked_cleanup_callback, &now);
76}
77
82c01b31 78/** @brief Base64 mapping table for cookies
79 *
80 * Stupid Safari cannot cope with quoted cookies, so cookies had better not
81 * need quoting. We use $ to separate the parts of the cookie and +%# to where
82 * MIME uses +/=; see @ref base64.c. See http_separator() for the characters
83 * to avoid.
84 */
85static const char cookie_base64_table[] =
86 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+%#";
87
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88/** @brief Sign @p subject with @p key and return the base64 of the result
89 * @param key Key to sign with (@ref HASHSIZE bytes)
90 * @param subject Subject string
91 * @return Base64-encoded signature or NULL
92 */
93static char *sign(const uint8_t *key,
94 const char *subject) {
95 gcry_error_t e;
96 gcry_md_hd_t h;
97 uint8_t *sig;
98 char *sig64;
99
100 if((e = gcry_md_open(&h, ALGO, GCRY_MD_FLAG_HMAC))) {
101 error(0, "gcry_md_open: %s", gcry_strerror(e));
102 return 0;
103 }
104 if((e = gcry_md_setkey(h, key, HASHSIZE))) {
105 error(0, "gcry_md_setkey: %s", gcry_strerror(e));
106 gcry_md_close(h);
107 return 0;
108 }
109 gcry_md_write(h, subject, strlen(subject));
110 sig = gcry_md_read(h, ALGO);
82c01b31 111 sig64 = generic_to_base64(sig, HASHSIZE, cookie_base64_table);
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112 gcry_md_close(h);
113 return sig64;
114}
115
116/** @brief Create a login cookie
117 * @param user Username
118 * @return Cookie or NULL
119 */
120char *make_cookie(const char *user) {
f0feb22e 121 const char *password;
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122 time_t now;
123 char *b, *bp, *c, *g;
b12be54a 124
82c01b31 125 /* dollar signs aren't allowed in usernames */
126 if(strchr(user, '$')) {
127 error(0, "make_cookie for username with dollar sign");
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128 return 0;
129 }
130 /* look up the password */
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131 password = trackdb_get_password(user);
132 if(!password) {
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133 error(0, "make_cookie for nonexistent user");
134 return 0;
135 }
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136 /* make sure we have a valid signing key */
137 time(&now);
138 if(now >= signing_key_validity_limit)
139 newkey();
140 /* construct the subject */
82c01b31 141 byte_xasprintf(&b, "%jx$%s$", (intmax_t)now + config->cookie_login_lifetime,
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142 urlencodestring(user));
143 byte_xasprintf(&bp, "%s%s", b, password);
144 /* sign it */
145 if(!(g = sign(signing_key, bp)))
146 return 0;
147 /* put together the final cookie */
148 byte_xasprintf(&c, "%s%s", b, g);
149 return c;
150}
151
152/** @brief Verify a cookie
153 * @param cookie Cookie to verify
eb5dc014 154 * @param rights Where to store rights value
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155 * @return Verified user or NULL
156 */
eb5dc014 157char *verify_cookie(const char *cookie, rights_type *rights) {
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158 char *c1, *c2;
159 intmax_t t;
160 time_t now;
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161 char *user, *bp, *sig;
162 const char *password;
eb5dc014 163 struct kvp *k;
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164
165 /* check the revocation list */
166 if(revoked && hash_find(revoked, cookie)) {
167 error(0, "attempt to log in with revoked cookie");
168 return 0;
169 }
170 /* parse the cookie */
171 errno = 0;
172 t = strtoimax(cookie, &c1, 16);
173 if(errno) {
174 error(errno, "error parsing cookie timestamp");
175 return 0;
176 }
82c01b31 177 if(*c1 != '$') {
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178 error(0, "invalid cookie timestamp");
179 return 0;
180 }
82c01b31 181 /* There'd better be two dollar signs */
182 c2 = strchr(c1 + 1, '$');
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183 if(c2 == 0) {
184 error(0, "invalid cookie syntax");
185 return 0;
186 }
187 /* Extract the username */
188 user = xstrndup(c1 + 1, c2 - (c1 + 1));
189 /* check expiry */
190 time(&now);
191 if(now >= t) {
192 error(0, "cookie has expired");
193 return 0;
194 }
195 /* look up the password */
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196 k = trackdb_getuserinfo(user);
197 if(!k) {
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198 error(0, "verify_cookie for nonexistent user");
199 return 0;
200 }
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201 password = kvp_get(k, "password");
202 if(!password) password = "";
0f55e905 203 if(parse_rights(kvp_get(k, "rights"), rights, 1))
eb5dc014 204 return 0;
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205 /* construct the expected subject. We re-encode the timestamp and the
206 * password. */
82c01b31 207 byte_xasprintf(&bp, "%jx$%s$%s", t, urlencodestring(user), password);
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208 /* Compute the expected signature. NB we base64 the expected signature and
209 * compare that rather than exposing our base64 parser to the cookie. */
210 if(!(sig = sign(signing_key, bp)))
211 return 0;
212 if(!strcmp(sig, c2 + 1))
213 return user;
214 /* that didn't match, try the old key */
215 if(!(sig = sign(old_signing_key, bp)))
216 return 0;
217 if(!strcmp(sig, c2 + 1))
218 return user;
219 /* that didn't match either */
220 error(0, "cookie signature does not match");
221 return 0;
222}
223
224/** @brief Revoke a cookie
225 * @param cookie Cookie to revoke
226 *
227 * Further attempts to log in with @p cookie will fail.
228 */
229void revoke_cookie(const char *cookie) {
230 time_t when;
231 char *ptr;
232
233 /* find the cookie's expiry time */
234 errno = 0;
235 when = (time_t)strtoimax(cookie, &ptr, 16);
236 /* reject bogus cookies */
237 if(errno)
238 return;
82c01b31 239 if(*ptr != '$')
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240 return;
241 /* make sure the revocation list exists */
242 if(!revoked)
243 revoked = hash_new(sizeof(time_t));
244 /* add the cookie to it; its value is the expiry time */
245 hash_add(revoked, cookie, &when, HASH_INSERT);
246}
247
248/*
249Local Variables:
250c-basic-offset:2
251comment-column:40
252fill-column:79
253indent-tabs-mode:nil
254End:
255*/