1 /* 2 * authreadkeys.c - routines to support the reading of the key file 3 */ 4 #include <config.h> 5 #include <stdio.h> 6 #include <ctype.h> 7 8 #include "ntpd.h" /* Only for DPRINTF */ 9 #include "ntp_fp.h" 10 #include "ntp.h" 11 #include "ntp_syslog.h" 12 #include "ntp_stdlib.h" 13 #include "ntp_keyacc.h" 14 15 #ifdef OPENSSL 16 #include "openssl/objects.h" 17 #include "openssl/evp.h" 18 #endif /* OPENSSL */ 19 20 /* Forwards */ 21 static char *nexttok (char **); 22 23 /* 24 * nexttok - basic internal tokenizing routine 25 */ 26 static char * 27 nexttok( 28 char **str 29 ) 30 { 31 register char *cp; 32 char *starttok; 33 34 cp = *str; 35 36 /* 37 * Space past white space 38 */ 39 while (*cp == ' ' || *cp == '\t') 40 cp++; 41 42 /* 43 * Save this and space to end of token 44 */ 45 starttok = cp; 46 while (*cp != '\0' && *cp != '\n' && *cp != ' ' 47 && *cp != '\t' && *cp != '#') 48 cp++; 49 50 /* 51 * If token length is zero return an error, else set end of 52 * token to zero and return start. 53 */ 54 if (starttok == cp) 55 return NULL; 56 57 if (*cp == ' ' || *cp == '\t') 58 *cp++ = '\0'; 59 else 60 *cp = '\0'; 61 62 *str = cp; 63 return starttok; 64 } 65 66 67 /* TALOS-CAN-0055: possibly DoS attack by setting the key file to the 68 * log file. This is hard to prevent (it would need to check two files 69 * to be the same on the inode level, which will not work so easily with 70 * Windows or VMS) but we can avoid the self-amplification loop: We only 71 * log the first 5 errors, silently ignore the next 10 errors, and give 72 * up when when we have found more than 15 errors. 73 * 74 * This avoids the endless file iteration we will end up with otherwise, 75 * and also avoids overflowing the log file. 76 * 77 * Nevertheless, once this happens, the keys are gone since this would 78 * require a save/swap strategy that is not easy to apply due to the 79 * data on global/static level. 80 */ 81 82 static const u_int nerr_loglimit = 5u; 83 static const u_int nerr_maxlimit = 15; 84 85 static void log_maybe(u_int*, const char*, ...) NTP_PRINTF(2, 3); 86 87 typedef struct keydata KeyDataT; 88 struct keydata { 89 KeyDataT *next; /* queue/stack link */ 90 KeyAccT *keyacclist; /* key access list */ 91 keyid_t keyid; /* stored key ID */ 92 u_short keytype; /* stored key type */ 93 u_short seclen; /* length of secret */ 94 u_char secbuf[1]; /* begin of secret (formal only)*/ 95 }; 96 97 static void 98 log_maybe( 99 u_int *pnerr, 100 const char *fmt , 101 ...) 102 { 103 va_list ap; 104 if ((NULL == pnerr) || (++(*pnerr) <= nerr_loglimit)) { 105 va_start(ap, fmt); 106 mvsyslog(LOG_ERR, fmt, ap); 107 va_end(ap); 108 } 109 } 110 111 static void 112 free_keydata( 113 KeyDataT *node 114 ) 115 { 116 KeyAccT *kap; 117 118 if (node) { 119 while (node->keyacclist) { 120 kap = node->keyacclist; 121 node->keyacclist = kap->next; 122 free(kap); 123 } 124 125 /* purge secrets from memory before free()ing it */ 126 memset(node, 0, sizeof(*node) + node->seclen); 127 free(node); 128 } 129 } 130 131 /* 132 * authreadkeys - (re)read keys from a file. 133 */ 134 int 135 authreadkeys( 136 const char *file 137 ) 138 { 139 FILE *fp; 140 char *line; 141 char *token; 142 keyid_t keyno; 143 int keytype; 144 char buf[512]; /* lots of room for line */ 145 u_char keystr[32]; /* Bug 2537 */ 146 size_t len; 147 size_t j; 148 u_int nerr; 149 KeyDataT *list = NULL; 150 KeyDataT *next = NULL; 151 /* 152 * Open file. Complain and return if it can't be opened. 153 */ 154 fp = fopen(file, "r"); 155 if (fp == NULL) { 156 msyslog(LOG_ERR, "authreadkeys: file '%s': %m", 157 file); 158 goto onerror; 159 } 160 INIT_SSL(); 161 162 /* 163 * Now read lines from the file, looking for key entries. Put 164 * the data into temporary store for later propagation to avoid 165 * two-pass processing. 166 */ 167 nerr = 0; 168 while ((line = fgets(buf, sizeof buf, fp)) != NULL) { 169 if (nerr > nerr_maxlimit) 170 break; 171 token = nexttok(&line); 172 if (token == NULL) 173 continue; 174 175 /* 176 * First is key number. See if it is okay. 177 */ 178 keyno = atoi(token); 179 if (keyno < 1) { 180 log_maybe(&nerr, 181 "authreadkeys: cannot change key %s", 182 token); 183 continue; 184 } 185 186 if (keyno > NTP_MAXKEY) { 187 log_maybe(&nerr, 188 "authreadkeys: key %s > %d reserved for Autokey", 189 token, NTP_MAXKEY); 190 continue; 191 } 192 193 /* 194 * Next is keytype. See if that is all right. 195 */ 196 token = nexttok(&line); 197 if (token == NULL) { 198 log_maybe(&nerr, 199 "authreadkeys: no key type for key %d", 200 keyno); 201 continue; 202 } 203 204 /* We want to silently ignore keys where we do not 205 * support the requested digest type. OTOH, we want to 206 * make sure the file is well-formed. That means we 207 * have to process the line completely and have to 208 * finally throw away the result... This is a bit more 209 * work, but it also results in better error detection. 210 */ 211 #ifdef OPENSSL 212 /* 213 * The key type is the NID used by the message digest 214 * algorithm. There are a number of inconsistencies in 215 * the OpenSSL database. We attempt to discover them 216 * here and prevent use of inconsistent data later. 217 */ 218 keytype = keytype_from_text(token, NULL); 219 if (keytype == 0) { 220 log_maybe(NULL, 221 "authreadkeys: invalid type for key %d", 222 keyno); 223 } else if (EVP_get_digestbynid(keytype) == NULL) { 224 log_maybe(NULL, 225 "authreadkeys: no algorithm for key %d", 226 keyno); 227 keytype = 0; 228 } 229 #else /* !OPENSSL follows */ 230 /* 231 * The key type is unused, but is required to be 'M' or 232 * 'm' for compatibility. 233 */ 234 if (!(*token == 'M' || *token == 'm')) { 235 log_maybe(NULL, 236 "authreadkeys: invalid type for key %d", 237 keyno); 238 keytype = 0; 239 } else { 240 keytype = KEY_TYPE_MD5; 241 } 242 #endif /* !OPENSSL */ 243 244 /* 245 * Finally, get key and insert it. If it is longer than 20 246 * characters, it is a binary string encoded in hex; 247 * otherwise, it is a text string of printable ASCII 248 * characters. 249 */ 250 token = nexttok(&line); 251 if (token == NULL) { 252 log_maybe(&nerr, 253 "authreadkeys: no key for key %d", keyno); 254 continue; 255 } 256 next = NULL; 257 len = strlen(token); 258 if (len <= 20) { /* Bug 2537 */ 259 next = emalloc(sizeof(KeyDataT) + len); 260 next->keyacclist = NULL; 261 next->keyid = keyno; 262 next->keytype = keytype; 263 next->seclen = len; 264 memcpy(next->secbuf, token, len); 265 } else { 266 static const char hex[] = "0123456789abcdef"; 267 u_char temp; 268 char *ptr; 269 size_t jlim; 270 271 jlim = min(len, 2 * sizeof(keystr)); 272 for (j = 0; j < jlim; j++) { 273 ptr = strchr(hex, tolower((unsigned char)token[j])); 274 if (ptr == NULL) 275 break; /* abort decoding */ 276 temp = (u_char)(ptr - hex); 277 if (j & 1) 278 keystr[j / 2] |= temp; 279 else 280 keystr[j / 2] = temp << 4; 281 } 282 if (j < jlim) { 283 log_maybe(&nerr, 284 "authreadkeys: invalid hex digit for key %d", 285 keyno); 286 continue; 287 } 288 len = jlim/2; /* hmmmm.... what about odd length?!? */ 289 next = emalloc(sizeof(KeyDataT) + len); 290 next->keyacclist = NULL; 291 next->keyid = keyno; 292 next->keytype = keytype; 293 next->seclen = len; 294 memcpy(next->secbuf, keystr, len); 295 } 296 297 token = nexttok(&line); 298 DPRINTF(0, ("authreadkeys: full access list <%s>\n", (token) ? token : "NULL")); 299 if (token != NULL) { /* A comma-separated IP access list */ 300 char *tp = token; 301 302 while (tp) { 303 char *i; 304 sockaddr_u addr; 305 306 i = strchr(tp, (int)','); 307 if (i) 308 *i = '\0'; 309 DPRINTF(0, ("authreadkeys: access list: <%s>\n", tp)); 310 311 if (is_ip_address(tp, AF_UNSPEC, &addr)) { 312 next->keyacclist = keyacc_new_push( 313 next->keyacclist, &addr); 314 } else { 315 log_maybe(&nerr, 316 "authreadkeys: invalid IP address <%s> for key %d", 317 tp, keyno); 318 } 319 320 if (i) { 321 tp = i + 1; 322 } else { 323 tp = 0; 324 } 325 } 326 } 327 328 /* check if this has to be weeded out... */ 329 if (0 == keytype) { 330 free_keydata(next); 331 next = NULL; 332 continue; 333 } 334 335 INSIST(NULL != next); 336 next->next = list; 337 list = next; 338 } 339 fclose(fp); 340 if (nerr > 0) { 341 const char * why = ""; 342 if (nerr > nerr_maxlimit) 343 why = " (emergency break)"; 344 msyslog(LOG_ERR, 345 "authreadkeys: rejecting file '%s' after %u error(s)%s", 346 file, nerr, why); 347 goto onerror; 348 } 349 350 /* first remove old file-based keys */ 351 auth_delkeys(); 352 /* insert the new key material */ 353 while (NULL != (next = list)) { 354 list = next->next; 355 MD5auth_setkey(next->keyid, next->keytype, 356 next->secbuf, next->seclen, next->keyacclist); 357 next->keyacclist = NULL; /* consumed by MD5auth_setkey */ 358 free_keydata(next); 359 } 360 return (1); 361 362 onerror: 363 /* Mop up temporary storage before bailing out. */ 364 while (NULL != (next = list)) { 365 list = next->next; 366 free_keydata(next); 367 } 368 return (0); 369 } 370