107c3998c3
4.2.8p12 --> 4.2.8p13 MFC after: immediately Security: CVE-2019-8936 VuXML: c2576e14-36e2-11e9-9eda-206a8a720317 Obtained from: nwtime.org
408 lines
9.1 KiB
C
408 lines
9.1 KiB
C
/*
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* authreadkeys.c - routines to support the reading of the key file
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*/
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#include <config.h>
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#include <stdio.h>
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#include <ctype.h>
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//#include "ntpd.h" /* Only for DPRINTF */
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//#include "ntp_fp.h"
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#include "ntp.h"
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#include "ntp_syslog.h"
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#include "ntp_stdlib.h"
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#include "ntp_keyacc.h"
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#ifdef OPENSSL
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#include "openssl/objects.h"
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#include "openssl/evp.h"
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#endif /* OPENSSL */
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/* Forwards */
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static char *nexttok (char **);
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/*
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* nexttok - basic internal tokenizing routine
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*/
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static char *
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nexttok(
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char **str
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)
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{
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register char *cp;
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char *starttok;
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cp = *str;
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/*
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* Space past white space
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*/
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while (*cp == ' ' || *cp == '\t')
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cp++;
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/*
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* Save this and space to end of token
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*/
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starttok = cp;
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while (*cp != '\0' && *cp != '\n' && *cp != ' '
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&& *cp != '\t' && *cp != '#')
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cp++;
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/*
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* If token length is zero return an error, else set end of
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* token to zero and return start.
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*/
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if (starttok == cp)
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return NULL;
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if (*cp == ' ' || *cp == '\t')
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*cp++ = '\0';
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else
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*cp = '\0';
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*str = cp;
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return starttok;
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}
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/* TALOS-CAN-0055: possibly DoS attack by setting the key file to the
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* log file. This is hard to prevent (it would need to check two files
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* to be the same on the inode level, which will not work so easily with
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* Windows or VMS) but we can avoid the self-amplification loop: We only
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* log the first 5 errors, silently ignore the next 10 errors, and give
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* up when when we have found more than 15 errors.
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*
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* This avoids the endless file iteration we will end up with otherwise,
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* and also avoids overflowing the log file.
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*
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* Nevertheless, once this happens, the keys are gone since this would
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* require a save/swap strategy that is not easy to apply due to the
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* data on global/static level.
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*/
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static const u_int nerr_loglimit = 5u;
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static const u_int nerr_maxlimit = 15;
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static void log_maybe(u_int*, const char*, ...) NTP_PRINTF(2, 3);
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typedef struct keydata KeyDataT;
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struct keydata {
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KeyDataT *next; /* queue/stack link */
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KeyAccT *keyacclist; /* key access list */
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keyid_t keyid; /* stored key ID */
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u_short keytype; /* stored key type */
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u_short seclen; /* length of secret */
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u_char secbuf[1]; /* begin of secret (formal only)*/
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};
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static void
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log_maybe(
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u_int *pnerr,
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const char *fmt ,
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...)
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{
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va_list ap;
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if ((NULL == pnerr) || (++(*pnerr) <= nerr_loglimit)) {
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va_start(ap, fmt);
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mvsyslog(LOG_ERR, fmt, ap);
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va_end(ap);
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}
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}
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static void
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free_keydata(
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KeyDataT *node
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)
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{
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KeyAccT *kap;
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if (node) {
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while (node->keyacclist) {
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kap = node->keyacclist;
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node->keyacclist = kap->next;
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free(kap);
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}
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/* purge secrets from memory before free()ing it */
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memset(node, 0, sizeof(*node) + node->seclen);
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free(node);
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}
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}
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/*
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* authreadkeys - (re)read keys from a file.
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*/
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int
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authreadkeys(
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const char *file
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)
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{
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FILE *fp;
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char *line;
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char *token;
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keyid_t keyno;
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int keytype;
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char buf[512]; /* lots of room for line */
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u_char keystr[32]; /* Bug 2537 */
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size_t len;
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size_t j;
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u_int nerr;
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KeyDataT *list = NULL;
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KeyDataT *next = NULL;
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/*
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* Open file. Complain and return if it can't be opened.
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*/
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fp = fopen(file, "r");
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if (fp == NULL) {
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msyslog(LOG_ERR, "authreadkeys: file '%s': %m",
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file);
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goto onerror;
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}
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INIT_SSL();
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/*
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* Now read lines from the file, looking for key entries. Put
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* the data into temporary store for later propagation to avoid
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* two-pass processing.
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*/
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nerr = 0;
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while ((line = fgets(buf, sizeof buf, fp)) != NULL) {
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if (nerr > nerr_maxlimit)
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break;
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token = nexttok(&line);
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if (token == NULL)
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continue;
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/*
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* First is key number. See if it is okay.
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*/
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keyno = atoi(token);
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if (keyno < 1) {
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log_maybe(&nerr,
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"authreadkeys: cannot change key %s",
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token);
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continue;
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}
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if (keyno > NTP_MAXKEY) {
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log_maybe(&nerr,
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"authreadkeys: key %s > %d reserved for Autokey",
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token, NTP_MAXKEY);
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continue;
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}
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/*
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* Next is keytype. See if that is all right.
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*/
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token = nexttok(&line);
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if (token == NULL) {
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log_maybe(&nerr,
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"authreadkeys: no key type for key %d",
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keyno);
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continue;
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}
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/* We want to silently ignore keys where we do not
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* support the requested digest type. OTOH, we want to
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* make sure the file is well-formed. That means we
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* have to process the line completely and have to
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* finally throw away the result... This is a bit more
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* work, but it also results in better error detection.
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*/
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#ifdef OPENSSL
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/*
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* The key type is the NID used by the message digest
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* algorithm. There are a number of inconsistencies in
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* the OpenSSL database. We attempt to discover them
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* here and prevent use of inconsistent data later.
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*/
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keytype = keytype_from_text(token, NULL);
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if (keytype == 0) {
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log_maybe(NULL,
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"authreadkeys: invalid type for key %d",
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keyno);
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# ifdef ENABLE_CMAC
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} else if (NID_cmac != keytype &&
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EVP_get_digestbynid(keytype) == NULL) {
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log_maybe(NULL,
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"authreadkeys: no algorithm for key %d",
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keyno);
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keytype = 0;
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# endif /* ENABLE_CMAC */
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}
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#else /* !OPENSSL follows */
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/*
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* The key type is unused, but is required to be 'M' or
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* 'm' for compatibility.
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*/
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if (!(*token == 'M' || *token == 'm')) {
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log_maybe(NULL,
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"authreadkeys: invalid type for key %d",
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keyno);
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keytype = 0;
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} else {
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keytype = KEY_TYPE_MD5;
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}
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#endif /* !OPENSSL */
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/*
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* Finally, get key and insert it. If it is longer than 20
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* characters, it is a binary string encoded in hex;
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* otherwise, it is a text string of printable ASCII
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* characters.
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*/
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token = nexttok(&line);
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if (token == NULL) {
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log_maybe(&nerr,
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"authreadkeys: no key for key %d", keyno);
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continue;
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}
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next = NULL;
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len = strlen(token);
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if (len <= 20) { /* Bug 2537 */
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next = emalloc(sizeof(KeyDataT) + len);
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next->keyacclist = NULL;
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next->keyid = keyno;
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next->keytype = keytype;
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next->seclen = len;
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memcpy(next->secbuf, token, len);
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} else {
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static const char hex[] = "0123456789abcdef";
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u_char temp;
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char *ptr;
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size_t jlim;
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jlim = min(len, 2 * sizeof(keystr));
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for (j = 0; j < jlim; j++) {
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ptr = strchr(hex, tolower((unsigned char)token[j]));
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if (ptr == NULL)
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break; /* abort decoding */
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temp = (u_char)(ptr - hex);
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if (j & 1)
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keystr[j / 2] |= temp;
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else
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keystr[j / 2] = temp << 4;
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}
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if (j < jlim) {
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log_maybe(&nerr,
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"authreadkeys: invalid hex digit for key %d",
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keyno);
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continue;
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}
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len = jlim/2; /* hmmmm.... what about odd length?!? */
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next = emalloc(sizeof(KeyDataT) + len);
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next->keyacclist = NULL;
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next->keyid = keyno;
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next->keytype = keytype;
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next->seclen = len;
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memcpy(next->secbuf, keystr, len);
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}
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token = nexttok(&line);
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if (token != NULL) { /* A comma-separated IP access list */
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char *tp = token;
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while (tp) {
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char *i;
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char *snp; /* subnet text pointer */
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unsigned int snbits;
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sockaddr_u addr;
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i = strchr(tp, (int)',');
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if (i) {
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*i = '\0';
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}
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snp = strchr(tp, (int)'/');
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if (snp) {
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char *sp;
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*snp++ = '\0';
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snbits = 0;
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sp = snp;
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while (*sp != '\0') {
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if (!isdigit((unsigned char)*sp))
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break;
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if (snbits > 1000)
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break; /* overflow */
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snbits = 10 * snbits + (*sp++ - '0'); /* ascii dependent */
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}
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if (*sp != '\0') {
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log_maybe(&nerr,
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"authreadkeys: Invalid character in subnet specification for <%s/%s> in key %d",
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sp, snp, keyno);
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goto nextip;
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}
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} else {
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snbits = UINT_MAX;
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}
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if (is_ip_address(tp, AF_UNSPEC, &addr)) {
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/* Make sure that snbits is valid for addr */
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if ((snbits < UINT_MAX) &&
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( (IS_IPV4(&addr) && snbits > 32) ||
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(IS_IPV6(&addr) && snbits > 128))) {
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log_maybe(NULL,
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"authreadkeys: excessive subnet mask <%s/%s> for key %d",
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tp, snp, keyno);
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}
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next->keyacclist = keyacc_new_push(
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next->keyacclist, &addr, snbits);
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} else {
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log_maybe(&nerr,
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"authreadkeys: invalid IP address <%s> for key %d",
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tp, keyno);
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}
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nextip:
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if (i) {
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tp = i + 1;
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} else {
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tp = 0;
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}
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}
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}
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/* check if this has to be weeded out... */
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if (0 == keytype) {
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free_keydata(next);
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next = NULL;
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continue;
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}
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INSIST(NULL != next);
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next->next = list;
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list = next;
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}
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fclose(fp);
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if (nerr > 0) {
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const char * why = "";
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if (nerr > nerr_maxlimit)
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why = " (emergency break)";
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msyslog(LOG_ERR,
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"authreadkeys: rejecting file '%s' after %u error(s)%s",
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file, nerr, why);
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goto onerror;
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}
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/* first remove old file-based keys */
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auth_delkeys();
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/* insert the new key material */
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while (NULL != (next = list)) {
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list = next->next;
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MD5auth_setkey(next->keyid, next->keytype,
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next->secbuf, next->seclen, next->keyacclist);
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next->keyacclist = NULL; /* consumed by MD5auth_setkey */
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free_keydata(next);
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}
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return (1);
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onerror:
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/* Mop up temporary storage before bailing out. */
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while (NULL != (next = list)) {
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list = next->next;
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free_keydata(next);
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}
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return (0);
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}
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