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 ((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 }