contrib/ntp/libntp/authreadkeys.c

   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 (++(*pnerr) <= nerr_loglimit) {
 105                 va_start(ap, fmt);
 106                 mvsyslog(LOG_ERR, fmt, ap);
 107                 va_end(ap);
 108         }
 109 }
 110
 111 /*
 112  * authreadkeys - (re)read keys from a file.
 113  */
 114 int
 115 authreadkeys(
 116         const char *file
 117         )
 118 {
 119         FILE    *fp;
 120         char    *line;
 121         char    *token;
 122         keyid_t keyno;
 123         int     keytype;
 124         char    buf[512];               /* lots of room for line */
 125         u_char  keystr[32];             /* Bug 2537 */
 126         size_t  len;
 127         size_t  j;
 128         u_int   nerr;
 129         KeyDataT *list = NULL;
 130         KeyDataT *next = NULL;
 131         /*
 132          * Open file.  Complain and return if it can't be opened.
 133          */
 134         fp = fopen(file, "r");
 135         if (fp == NULL) {
 136                 msyslog(LOG_ERR, "authreadkeys: file '%s': %m",
 137                     file);
 138                 goto onerror;
 139         }
 140         INIT_SSL();
 141
 142         /*
 143          * Now read lines from the file, looking for key entries. Put
 144          * the data into temporary store for later propagation to avoid
 145          * two-pass processing.
 146          */
 147         nerr = 0;
 148         while ((line = fgets(buf, sizeof buf, fp)) != NULL) {
 149                 if (nerr > nerr_maxlimit)
 150                         break;
 151                 token = nexttok(&line);
 152                 if (token == NULL)
 153                         continue;
 154
 155                 /*
 156                  * First is key number.  See if it is okay.
 157                  */
 158                 keyno = atoi(token);
 159                 if (keyno == 0) {
 160                         log_maybe(&nerr,
 161                                   "authreadkeys: cannot change key %s",
 162                                   token);
 163                         continue;
 164                 }
 165
 166                 if (keyno > NTP_MAXKEY) {
 167                         log_maybe(&nerr,
 168                                   "authreadkeys: key %s > %d reserved for Autokey",
 169                                   token, NTP_MAXKEY);
 170                         continue;
 171                 }
 172
 173                 /*
 174                  * Next is keytype. See if that is all right.
 175                  */
 176                 token = nexttok(&line);
 177                 if (token == NULL) {
 178                         log_maybe(&nerr,
 179                                   "authreadkeys: no key type for key %d",
 180                                   keyno);
 181                         continue;
 182                 }
 183 #ifdef OPENSSL
 184                 /*
 185                  * The key type is the NID used by the message digest
 186                  * algorithm. There are a number of inconsistencies in
 187                  * the OpenSSL database. We attempt to discover them
 188                  * here and prevent use of inconsistent data later.
 189                  */
 190                 keytype = keytype_from_text(token, NULL);
 191                 if (keytype == 0) {
 192                         log_maybe(&nerr,
 193                                   "authreadkeys: invalid type for key %d",
 194                                   keyno);
 195                         continue;
 196                 }
 197                 if (EVP_get_digestbynid(keytype) == NULL) {
 198                         log_maybe(&nerr,
 199                                   "authreadkeys: no algorithm for key %d",
 200                                   keyno);
 201                         continue;
 202                 }
 203 #else   /* !OPENSSL follows */
 204
 205                 /*
 206                  * The key type is unused, but is required to be 'M' or
 207                  * 'm' for compatibility.
 208                  */
 209                 if (!(*token == 'M' || *token == 'm')) {
 210                         log_maybe(&nerr,
 211                                   "authreadkeys: invalid type for key %d",
 212                                   keyno);
 213                         continue;
 214                 }
 215                 keytype = KEY_TYPE_MD5;
 216 #endif  /* !OPENSSL */
 217
 218                 /*
 219                  * Finally, get key and insert it. If it is longer than 20
 220                  * characters, it is a binary string encoded in hex;
 221                  * otherwise, it is a text string of printable ASCII
 222                  * characters.
 223                  */
 224                 token = nexttok(&line);
 225                 if (token == NULL) {
 226                         log_maybe(&nerr,
 227                                   "authreadkeys: no key for key %d", keyno);
 228                         continue;
 229                 }
 230                 next = NULL;
 231                 len = strlen(token);
 232                 if (len <= 20) {        /* Bug 2537 */
 233                         next = emalloc(sizeof(KeyDataT) + len);
 234                         next->keyacclist = NULL;
 235                         next->keyid   = keyno;
 236                         next->keytype = keytype;
 237                         next->seclen  = len;
 238                         memcpy(next->secbuf, token, len);
 239                 } else {
 240                         static const char hex[] = "0123456789abcdef";
 241                         u_char  temp;
 242                         char    *ptr;
 243                         size_t  jlim;
 244
 245                         jlim = min(len, 2 * sizeof(keystr));
 246                         for (j = 0; j < jlim; j++) {
 247                                 ptr = strchr(hex, tolower((unsigned char)token[j]));
 248                                 if (ptr == NULL)
 249                                         break;  /* abort decoding */
 250                                 temp = (u_char)(ptr - hex);
 251                                 if (j & 1)
 252                                         keystr[j / 2] |= temp;
 253                                 else
 254                                         keystr[j / 2] = temp << 4;
 255                         }
 256                         if (j < jlim) {
 257                                 log_maybe(&nerr,
 258                                           "authreadkeys: invalid hex digit for key %d",
 259                                           keyno);
 260                                 continue;
 261                         }
 262                         len = jlim/2; /* hmmmm.... what about odd length?!? */
 263                         next = emalloc(sizeof(KeyDataT) + len);
 264                         next->keyacclist = NULL;
 265                         next->keyid   = keyno;
 266                         next->keytype = keytype;
 267                         next->seclen  = len;
 268                         memcpy(next->secbuf, keystr, len);
 269                 }
 270
 271                 token = nexttok(&line);
 272 DPRINTF(0, ("authreadkeys: full access list <%s>\n", (token) ? token : "NULL"));
 273                 if (token != NULL) {    /* A comma-separated IP access list */
 274                         char *tp = token;
 275
 276                         while (tp) {
 277                                 char *i;
 278                                 KeyAccT ka;
 279
 280                                 i = strchr(tp, (int)',');
 281                                 if (i)
 282                                         *i = '\0';
 283 DPRINTF(0, ("authreadkeys: access list:  <%s>\n", tp));
 284
 285                                 if (is_ip_address(tp, AF_UNSPEC, &ka.addr)) {
 286                                         KeyAccT *kap;
 287
 288                                         kap = emalloc(sizeof(KeyAccT));
 289                                         memcpy(kap, &ka, sizeof ka);
 290                                         kap->next = next->keyacclist;
 291                                         next->keyacclist = kap;
 292                                 } else {
 293                                         log_maybe(&nerr,
 294                                                   "authreadkeys: invalid IP address <%s> for key %d",
 295                                                   tp, keyno);
 296                                 }
 297
 298                                 if (i) {
 299                                         tp = i + 1;
 300                                 } else {
 301                                         tp = 0;
 302                                 }
 303                         }
 304                 }
 305
 306                 INSIST(NULL != next);
 307                 next->next = list;
 308                 list = next;
 309         }
 310         fclose(fp);
 311         if (nerr > nerr_maxlimit) {
 312                 msyslog(LOG_ERR,
 313                         "authreadkeys: rejecting file '%s' after %u errors (emergency break)",
 314                         file, nerr);
 315                 goto onerror;
 316         }
 317         if (nerr > 0) {
 318                 msyslog(LOG_ERR,
 319                         "authreadkeys: rejecting file '%s' after %u error(s)",
 320                         file, nerr);
 321                 goto onerror;
 322         }
 323
 324         /* first remove old file-based keys */
 325         auth_delkeys();
 326         /* insert the new key material */
 327         while (NULL != (next = list)) {
 328                 list = next->next;
 329                 MD5auth_setkey(next->keyid, next->keytype,
 330                                next->secbuf, next->seclen, next->keyacclist);
 331                 /* purge secrets from memory before free()ing it */
 332                 memset(next, 0, sizeof(*next) + next->seclen);
 333                 free(next);
 334         }
 335         return (1);
 336
 337   onerror:
 338         /* Mop up temporary storage before bailing out. */
 339         while (NULL != (next = list)) {
 340                 list = next->next;
 341
 342                 while (next->keyacclist) {
 343                         KeyAccT *kap = next->keyacclist;
 344
 345                         next->keyacclist = kap->next;
 346                         free(kap);
 347                 }
 348
 349                 /* purge secrets from memory before free()ing it */
 350                 memset(next, 0, sizeof(*next) + next->seclen);
 351                 free(next);
 352         }
 353         return (0);
 354 }