+/*
+ * Command-line options.
+ */
+static option_t chapms_option_list[] = {
+#ifdef MSLANMAN
+ { "ms-lanman", o_bool, &ms_lanman,
+ "Use LanMan passwd when using MS-CHAP", 1 },
+#endif
+#ifdef DEBUGMPPEKEY
+ { "mschap-challenge", o_string, &mschap_challenge,
+ "specify CHAP challenge" },
+ { "mschap2-peer-challenge", o_string, &mschap2_peer_challenge,
+ "specify CHAP peer challenge" },
+#endif
+ { NULL }
+};
+
+/*
+ * chapms_generate_challenge - generate a challenge for MS-CHAP.
+ * For MS-CHAP the challenge length is fixed at 8 bytes.
+ * The length goes in challenge[0] and the actual challenge starts
+ * at challenge[1].
+ */
+static void
+chapms_generate_challenge(unsigned char *challenge)
+{
+ *challenge++ = 8;
+#ifdef DEBUGMPPEKEY
+ if (mschap_challenge && strlen(mschap_challenge) == 8)
+ memcpy(challenge, mschap_challenge, 8);
+ else
+#endif
+ random_bytes(challenge, 8);
+}
+
+static void
+chapms2_generate_challenge(unsigned char *challenge)
+{
+ *challenge++ = 16;
+#ifdef DEBUGMPPEKEY
+ if (mschap_challenge && strlen(mschap_challenge) == 16)
+ memcpy(challenge, mschap_challenge, 16);
+ else
+#endif
+ random_bytes(challenge, 16);
+}
+
+static int
+chapms_verify_response(int id, char *name,
+ unsigned char *secret, int secret_len,
+ unsigned char *challenge, unsigned char *response,
+ char *message, int message_space)
+{
+ unsigned char md[MS_CHAP_RESPONSE_LEN];
+ int diff;
+ int challenge_len, response_len;
+
+ challenge_len = *challenge++; /* skip length, is 8 */
+ response_len = *response++;
+ if (response_len != MS_CHAP_RESPONSE_LEN)
+ goto bad;
+
+#ifndef MSLANMAN
+ if (!response[MS_CHAP_USENT]) {
+ /* Should really propagate this into the error packet. */
+ notice("Peer request for LANMAN auth not supported");
+ goto bad;
+ }
+#endif
+
+ /* Generate the expected response. */
+ ChapMS(challenge, (char *)secret, secret_len, md);
+
+#ifdef MSLANMAN
+ /* Determine which part of response to verify against */
+ if (!response[MS_CHAP_USENT])
+ diff = memcmp(&response[MS_CHAP_LANMANRESP],
+ &md[MS_CHAP_LANMANRESP], MS_CHAP_LANMANRESP_LEN);
+ else
+#endif
+ diff = memcmp(&response[MS_CHAP_NTRESP], &md[MS_CHAP_NTRESP],
+ MS_CHAP_NTRESP_LEN);
+
+ if (diff == 0) {
+ slprintf(message, message_space, "Access granted");
+ return 1;
+ }
+
+ bad:
+ /* See comments below for MS-CHAP V2 */
+ slprintf(message, message_space, "E=691 R=1 C=%0.*B V=0",
+ challenge_len, challenge);
+ return 0;
+}
+
+static int
+chapms2_verify_response(int id, char *name,
+ unsigned char *secret, int secret_len,
+ unsigned char *challenge, unsigned char *response,
+ char *message, int message_space)
+{
+ unsigned char md[MS_CHAP2_RESPONSE_LEN];
+ char saresponse[MS_AUTH_RESPONSE_LENGTH+1];
+ int challenge_len, response_len;
+
+ challenge_len = *challenge++; /* skip length, is 16 */
+ response_len = *response++;
+ if (response_len != MS_CHAP2_RESPONSE_LEN)
+ goto bad; /* not even the right length */
+
+ /* Generate the expected response and our mutual auth. */
+ ChapMS2(challenge, &response[MS_CHAP2_PEER_CHALLENGE], name,
+ (char *)secret, secret_len, md,
+ (unsigned char *)saresponse, MS_CHAP2_AUTHENTICATOR);
+
+ /* compare MDs and send the appropriate status */
+ /*
+ * Per RFC 2759, success message must be formatted as
+ * "S=<auth_string> M=<message>"
+ * where
+ * <auth_string> is the Authenticator Response (mutual auth)
+ * <message> is a text message
+ *
+ * However, some versions of Windows (win98 tested) do not know
+ * about the M=<message> part (required per RFC 2759) and flag
+ * it as an error (reported incorrectly as an encryption error
+ * to the user). Since the RFC requires it, and it can be
+ * useful information, we supply it if the peer is a conforming
+ * system. Luckily (?), win98 sets the Flags field to 0x04
+ * (contrary to RFC requirements) so we can use that to
+ * distinguish between conforming and non-conforming systems.
+ *
+ * Special thanks to Alex Swiridov <say@real.kharkov.ua> for
+ * help debugging this.
+ */
+ if (memcmp(&md[MS_CHAP2_NTRESP], &response[MS_CHAP2_NTRESP],
+ MS_CHAP2_NTRESP_LEN) == 0) {
+ if (response[MS_CHAP2_FLAGS])
+ slprintf(message, message_space, "S=%s", saresponse);
+ else
+ slprintf(message, message_space, "S=%s M=%s",
+ saresponse, "Access granted");
+ return 1;
+ }
+
+ bad:
+ /*
+ * Failure message must be formatted as
+ * "E=e R=r C=c V=v M=m"
+ * where
+ * e = error code (we use 691, ERROR_AUTHENTICATION_FAILURE)
+ * r = retry (we use 1, ok to retry)
+ * c = challenge to use for next response, we reuse previous
+ * v = Change Password version supported, we use 0
+ * m = text message
+ *
+ * The M=m part is only for MS-CHAPv2. Neither win2k nor
+ * win98 (others untested) display the message to the user anyway.
+ * They also both ignore the E=e code.
+ *
+ * Note that it's safe to reuse the same challenge as we don't
+ * actually accept another response based on the error message
+ * (and no clients try to resend a response anyway).
+ *
+ * Basically, this whole bit is useless code, even the small
+ * implementation here is only because of overspecification.
+ */
+ slprintf(message, message_space, "E=691 R=1 C=%0.*B V=0 M=%s",
+ challenge_len, challenge, "Access denied");
+ return 0;
+}
+
+static void
+chapms_make_response(unsigned char *response, int id, char *our_name,
+ unsigned char *challenge, char *secret, int secret_len,
+ unsigned char *private)
+{
+ challenge++; /* skip length, should be 8 */
+ *response++ = MS_CHAP_RESPONSE_LEN;
+ ChapMS(challenge, secret, secret_len, response);
+}
+
+struct chapms2_response_cache_entry {
+ int id;
+ unsigned char challenge[16];
+ unsigned char response[MS_CHAP2_RESPONSE_LEN];
+ unsigned char auth_response[MS_AUTH_RESPONSE_LENGTH];
+};
+
+#define CHAPMS2_MAX_RESPONSE_CACHE_SIZE 10
+static struct chapms2_response_cache_entry
+ chapms2_response_cache[CHAPMS2_MAX_RESPONSE_CACHE_SIZE];
+static int chapms2_response_cache_next_index = 0;
+static int chapms2_response_cache_size = 0;
+
+static void
+chapms2_add_to_response_cache(int id, unsigned char *challenge,
+ unsigned char *response,
+ unsigned char *auth_response)
+{
+ int i = chapms2_response_cache_next_index;
+
+ chapms2_response_cache[i].id = id;
+ memcpy(chapms2_response_cache[i].challenge, challenge, 16);
+ memcpy(chapms2_response_cache[i].response, response,
+ MS_CHAP2_RESPONSE_LEN);
+ memcpy(chapms2_response_cache[i].auth_response,
+ auth_response, MS_AUTH_RESPONSE_LENGTH);
+ chapms2_response_cache_next_index =
+ (i + 1) % CHAPMS2_MAX_RESPONSE_CACHE_SIZE;
+ if (chapms2_response_cache_next_index > chapms2_response_cache_size)
+ chapms2_response_cache_size = chapms2_response_cache_next_index;
+ dbglog("added response cache entry %d", i);
+}
+
+static struct chapms2_response_cache_entry*
+chapms2_find_in_response_cache(int id, unsigned char *challenge,
+ unsigned char *auth_response)
+{
+ int i;
+
+ for (i = 0; i < chapms2_response_cache_size; i++) {
+ if (id == chapms2_response_cache[i].id
+ && (!challenge
+ || memcmp(challenge,
+ chapms2_response_cache[i].challenge,
+ 16) == 0)
+ && (!auth_response
+ || memcmp(auth_response,
+ chapms2_response_cache[i].auth_response,
+ MS_AUTH_RESPONSE_LENGTH) == 0)) {
+ dbglog("response found in cache (entry %d)", i);
+ return &chapms2_response_cache[i];
+ }
+ }
+ return NULL; /* not found */
+}
+
+static void
+chapms2_make_response(unsigned char *response, int id, char *our_name,
+ unsigned char *challenge, char *secret, int secret_len,
+ unsigned char *private)
+{
+ const struct chapms2_response_cache_entry *cache_entry;
+ unsigned char auth_response[MS_AUTH_RESPONSE_LENGTH];
+
+ challenge++; /* skip length, should be 16 */
+ *response++ = MS_CHAP2_RESPONSE_LEN;
+ cache_entry = chapms2_find_in_response_cache(id, challenge, NULL);
+ if (cache_entry) {
+ memcpy(response, cache_entry->response, MS_CHAP2_RESPONSE_LEN);
+ return;
+ }
+ ChapMS2(challenge,
+#ifdef DEBUGMPPEKEY
+ mschap2_peer_challenge,
+#else
+ NULL,
+#endif
+ our_name, secret, secret_len, response, auth_response,
+ MS_CHAP2_AUTHENTICATEE);
+ chapms2_add_to_response_cache(id, challenge, response, auth_response);
+}
+
+static int
+chapms2_check_success(int id, unsigned char *msg, int len)
+{
+ if ((len < MS_AUTH_RESPONSE_LENGTH + 2) ||
+ strncmp((char *)msg, "S=", 2) != 0) {
+ /* Packet does not start with "S=" */
+ error("MS-CHAPv2 Success packet is badly formed.");
+ return 0;
+ }
+ msg += 2;
+ len -= 2;
+ if (len < MS_AUTH_RESPONSE_LENGTH
+ || !chapms2_find_in_response_cache(id, NULL /* challenge */, msg)) {
+ /* Authenticator Response did not match expected. */
+ error("MS-CHAPv2 mutual authentication failed.");
+ return 0;
+ }
+ /* Authenticator Response matches. */
+ msg += MS_AUTH_RESPONSE_LENGTH; /* Eat it */
+ len -= MS_AUTH_RESPONSE_LENGTH;
+ if ((len >= 3) && !strncmp((char *)msg, " M=", 3)) {
+ msg += 3; /* Eat the delimiter */
+ } else if (len) {
+ /* Packet has extra text which does not begin " M=" */
+ error("MS-CHAPv2 Success packet is badly formed.");
+ return 0;
+ }
+ return 1;
+}
+
+static void
+chapms_handle_failure(unsigned char *inp, int len)
+{
+ int err;
+ char *p, *msg;
+
+ /* We want a null-terminated string for strxxx(). */
+ msg = malloc(len + 1);
+ if (!msg) {
+ notice("Out of memory in chapms_handle_failure");
+ return;
+ }
+ BCOPY(inp, msg, len);
+ msg[len] = 0;
+ p = msg;
+
+ /*
+ * Deal with MS-CHAP formatted failure messages; just print the
+ * M=<message> part (if any). For MS-CHAP we're not really supposed
+ * to use M=<message>, but it shouldn't hurt. See
+ * chapms[2]_verify_response.
+ */
+ if (!strncmp(p, "E=", 2))
+ err = strtol(p+2, NULL, 10); /* Remember the error code. */
+ else
+ goto print_msg; /* Message is badly formatted. */
+
+ if (len && ((p = strstr(p, " M=")) != NULL)) {
+ /* M=<message> field found. */
+ p += 3;
+ } else {
+ /* No M=<message>; use the error code. */
+ switch (err) {
+ case MS_CHAP_ERROR_RESTRICTED_LOGON_HOURS:
+ p = "E=646 Restricted logon hours";
+ break;
+
+ case MS_CHAP_ERROR_ACCT_DISABLED:
+ p = "E=647 Account disabled";
+ break;
+
+ case MS_CHAP_ERROR_PASSWD_EXPIRED:
+ p = "E=648 Password expired";
+ break;
+
+ case MS_CHAP_ERROR_NO_DIALIN_PERMISSION:
+ p = "E=649 No dialin permission";
+ break;
+
+ case MS_CHAP_ERROR_AUTHENTICATION_FAILURE:
+ p = "E=691 Authentication failure";
+ break;
+
+ case MS_CHAP_ERROR_CHANGING_PASSWORD:
+ /* Should never see this, we don't support Change Password. */
+ p = "E=709 Error changing password";
+ break;
+
+ default:
+ free(msg);
+ error("Unknown MS-CHAP authentication failure: %.*v",
+ len, inp);
+ return;
+ }
+ }
+print_msg:
+ if (p != NULL)
+ error("MS-CHAP authentication failed: %v", p);
+ free(msg);
+}
+