/* $OpenBSD: auth2.c,v 1.135 2015/01/19 20:07:45 markus Exp $ */ /* * Copyright (c) 2000 Markus Friedl. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #include "includes.h" __RCSID("$FreeBSD$"); #include #include #include #include #include #include #include #include #include "atomicio.h" #include "xmalloc.h" #include "ssh2.h" #include "packet.h" #include "log.h" #include "buffer.h" #include "misc.h" #include "servconf.h" #include "compat.h" #include "key.h" #include "hostfile.h" #include "auth.h" #include "dispatch.h" #include "pathnames.h" #include "buffer.h" #include "canohost.h" #include "blacklist_client.h" #ifdef GSSAPI #include "ssh-gss.h" #endif #include "monitor_wrap.h" /* import */ extern ServerOptions options; extern u_char *session_id2; extern u_int session_id2_len; extern Buffer loginmsg; /* methods */ extern Authmethod method_none; extern Authmethod method_pubkey; extern Authmethod method_passwd; extern Authmethod method_kbdint; extern Authmethod method_hostbased; #ifdef GSSAPI extern Authmethod method_gssapi; #endif Authmethod *authmethods[] = { &method_none, &method_pubkey, #ifdef GSSAPI &method_gssapi, #endif &method_passwd, &method_kbdint, &method_hostbased, NULL }; /* protocol */ static int input_service_request(int, u_int32_t, void *); static int input_userauth_request(int, u_int32_t, void *); /* helper */ static Authmethod *authmethod_lookup(Authctxt *, const char *); static char *authmethods_get(Authctxt *authctxt); #define MATCH_NONE 0 /* method or submethod mismatch */ #define MATCH_METHOD 1 /* method matches (no submethod specified) */ #define MATCH_BOTH 2 /* method and submethod match */ #define MATCH_PARTIAL 3 /* method matches, submethod can't be checked */ static int list_starts_with(const char *, const char *, const char *); char * auth2_read_banner(void) { struct stat st; char *banner = NULL; size_t len, n; int fd; if ((fd = open(options.banner, O_RDONLY)) == -1) return (NULL); if (fstat(fd, &st) == -1) { close(fd); return (NULL); } if (st.st_size <= 0 || st.st_size > 1*1024*1024) { close(fd); return (NULL); } len = (size_t)st.st_size; /* truncate */ banner = xmalloc(len + 1); n = atomicio(read, fd, banner, len); close(fd); if (n != len) { free(banner); return (NULL); } banner[n] = '\0'; return (banner); } void userauth_send_banner(const char *msg) { if (datafellows & SSH_BUG_BANNER) return; packet_start(SSH2_MSG_USERAUTH_BANNER); packet_put_cstring(msg); packet_put_cstring(""); /* language, unused */ packet_send(); debug("%s: sent", __func__); } static void userauth_banner(void) { char *banner = NULL; if (options.banner == NULL || (datafellows & SSH_BUG_BANNER) != 0) return; if ((banner = PRIVSEP(auth2_read_banner())) == NULL) goto done; userauth_send_banner(banner); done: free(banner); } /* * loop until authctxt->success == TRUE */ void do_authentication2(Authctxt *authctxt) { dispatch_init(&dispatch_protocol_error); dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request); dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt); } /*ARGSUSED*/ static int input_service_request(int type, u_int32_t seq, void *ctxt) { Authctxt *authctxt = ctxt; u_int len; int acceptit = 0; char *service = packet_get_cstring(&len); packet_check_eom(); if (authctxt == NULL) fatal("input_service_request: no authctxt"); if (strcmp(service, "ssh-userauth") == 0) { if (!authctxt->success) { acceptit = 1; /* now we can handle user-auth requests */ dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request); } } /* XXX all other service requests are denied */ if (acceptit) { packet_start(SSH2_MSG_SERVICE_ACCEPT); packet_put_cstring(service); packet_send(); packet_write_wait(); } else { debug("bad service request %s", service); packet_disconnect("bad service request %s", service); } free(service); return 0; } /*ARGSUSED*/ static int input_userauth_request(int type, u_int32_t seq, void *ctxt) { Authctxt *authctxt = ctxt; Authmethod *m = NULL; char *user, *service, *method, *style = NULL; int authenticated = 0; #ifdef HAVE_LOGIN_CAP login_cap_t *lc; const char *from_host, *from_ip; from_host = get_canonical_hostname(options.use_dns); from_ip = get_remote_ipaddr(); #endif if (authctxt == NULL) fatal("input_userauth_request: no authctxt"); user = packet_get_cstring(NULL); service = packet_get_cstring(NULL); method = packet_get_cstring(NULL); debug("userauth-request for user %s service %s method %s", user, service, method); debug("attempt %d failures %d", authctxt->attempt, authctxt->failures); if ((style = strchr(user, ':')) != NULL) *style++ = 0; if (authctxt->attempt++ == 0) { /* setup auth context */ authctxt->pw = PRIVSEP(getpwnamallow(user)); authctxt->user = xstrdup(user); if (authctxt->pw && strcmp(service, "ssh-connection")==0) { authctxt->valid = 1; debug2("input_userauth_request: setting up authctxt for %s", user); } else { logit("input_userauth_request: invalid user %s", user); authctxt->pw = fakepw(); #ifdef SSH_AUDIT_EVENTS PRIVSEP(audit_event(SSH_INVALID_USER)); #endif } #ifdef USE_PAM if (options.use_pam) PRIVSEP(start_pam(authctxt)); #endif setproctitle("%s%s", authctxt->valid ? user : "unknown", use_privsep ? " [net]" : ""); authctxt->service = xstrdup(service); authctxt->style = style ? xstrdup(style) : NULL; if (use_privsep) mm_inform_authserv(service, style); userauth_banner(); if (auth2_setup_methods_lists(authctxt) != 0) packet_disconnect("no authentication methods enabled"); } else if (strcmp(user, authctxt->user) != 0 || strcmp(service, authctxt->service) != 0) { packet_disconnect("Change of username or service not allowed: " "(%s,%s) -> (%s,%s)", authctxt->user, authctxt->service, user, service); } #ifdef HAVE_LOGIN_CAP if (authctxt->pw != NULL) { lc = login_getpwclass(authctxt->pw); if (lc == NULL) lc = login_getclassbyname(NULL, authctxt->pw); if (!auth_hostok(lc, from_host, from_ip)) { logit("Denied connection for %.200s from %.200s [%.200s].", authctxt->pw->pw_name, from_host, from_ip); packet_disconnect("Sorry, you are not allowed to connect."); } if (!auth_timeok(lc, time(NULL))) { logit("LOGIN %.200s REFUSED (TIME) FROM %.200s", authctxt->pw->pw_name, from_host); packet_disconnect("Logins not available right now."); } login_close(lc); lc = NULL; } #endif /* HAVE_LOGIN_CAP */ /* reset state */ auth2_challenge_stop(authctxt); #ifdef GSSAPI /* XXX move to auth2_gssapi_stop() */ dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); #endif authctxt->postponed = 0; authctxt->server_caused_failure = 0; /* try to authenticate user */ m = authmethod_lookup(authctxt, method); if (m != NULL && authctxt->failures < options.max_authtries) { debug2("input_userauth_request: try method %s", method); authenticated = m->userauth(authctxt); } userauth_finish(authctxt, authenticated, method, NULL); free(service); free(user); free(method); return 0; } void userauth_finish(Authctxt *authctxt, int authenticated, const char *method, const char *submethod) { char *methods; int partial = 0; if (!authctxt->valid && authenticated) fatal("INTERNAL ERROR: authenticated invalid user %s", authctxt->user); if (authenticated && authctxt->postponed) fatal("INTERNAL ERROR: authenticated and postponed"); /* Special handling for root */ if (authenticated && authctxt->pw->pw_uid == 0 && !auth_root_allowed(method)) { authenticated = 0; #ifdef SSH_AUDIT_EVENTS PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED)); #endif } if (authenticated && options.num_auth_methods != 0) { if (!auth2_update_methods_lists(authctxt, method, submethod)) { authenticated = 0; partial = 1; } } /* Log before sending the reply */ auth_log(authctxt, authenticated, partial, method, submethod); if (authctxt->postponed) return; #ifdef USE_PAM if (options.use_pam && authenticated) { if (!PRIVSEP(do_pam_account())) { /* if PAM returned a message, send it to the user */ if (buffer_len(&loginmsg) > 0) { buffer_append(&loginmsg, "\0", 1); userauth_send_banner(buffer_ptr(&loginmsg)); packet_write_wait(); } fatal("Access denied for user %s by PAM account " "configuration", authctxt->user); } } #endif #ifdef _UNICOS if (authenticated && cray_access_denied(authctxt->user)) { authenticated = 0; fatal("Access denied for user %s.", authctxt->user); } #endif /* _UNICOS */ if (authenticated == 1) { /* turn off userauth */ dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore); packet_start(SSH2_MSG_USERAUTH_SUCCESS); packet_send(); packet_write_wait(); /* now we can break out */ authctxt->success = 1; } else { /* Allow initial try of "none" auth without failure penalty */ if (!partial && !authctxt->server_caused_failure && (authctxt->attempt > 1 || strcmp(method, "none") != 0)) { authctxt->failures++; BLACKLIST_NOTIFY(BLACKLIST_AUTH_FAIL, "ssh"); } if (authctxt->failures >= options.max_authtries) { #ifdef SSH_AUDIT_EVENTS PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES)); #endif auth_maxtries_exceeded(authctxt); } methods = authmethods_get(authctxt); debug3("%s: failure partial=%d next methods=\"%s\"", __func__, partial, methods); packet_start(SSH2_MSG_USERAUTH_FAILURE); packet_put_cstring(methods); packet_put_char(partial); packet_send(); packet_write_wait(); free(methods); } } /* * Checks whether method is allowed by at least one AuthenticationMethods * methods list. Returns 1 if allowed, or no methods lists configured. * 0 otherwise. */ int auth2_method_allowed(Authctxt *authctxt, const char *method, const char *submethod) { u_int i; /* * NB. authctxt->num_auth_methods might be zero as a result of * auth2_setup_methods_lists(), so check the configuration. */ if (options.num_auth_methods == 0) return 1; for (i = 0; i < authctxt->num_auth_methods; i++) { if (list_starts_with(authctxt->auth_methods[i], method, submethod) != MATCH_NONE) return 1; } return 0; } static char * authmethods_get(Authctxt *authctxt) { Buffer b; char *list; u_int i; buffer_init(&b); for (i = 0; authmethods[i] != NULL; i++) { if (strcmp(authmethods[i]->name, "none") == 0) continue; if (authmethods[i]->enabled == NULL || *(authmethods[i]->enabled) == 0) continue; if (!auth2_method_allowed(authctxt, authmethods[i]->name, NULL)) continue; if (buffer_len(&b) > 0) buffer_append(&b, ",", 1); buffer_append(&b, authmethods[i]->name, strlen(authmethods[i]->name)); } buffer_append(&b, "\0", 1); list = xstrdup(buffer_ptr(&b)); buffer_free(&b); return list; } static Authmethod * authmethod_lookup(Authctxt *authctxt, const char *name) { int i; if (name != NULL) for (i = 0; authmethods[i] != NULL; i++) if (authmethods[i]->enabled != NULL && *(authmethods[i]->enabled) != 0 && strcmp(name, authmethods[i]->name) == 0 && auth2_method_allowed(authctxt, authmethods[i]->name, NULL)) return authmethods[i]; debug2("Unrecognized authentication method name: %s", name ? name : "NULL"); return NULL; } /* * Check a comma-separated list of methods for validity. Is need_enable is * non-zero, then also require that the methods are enabled. * Returns 0 on success or -1 if the methods list is invalid. */ int auth2_methods_valid(const char *_methods, int need_enable) { char *methods, *omethods, *method, *p; u_int i, found; int ret = -1; if (*_methods == '\0') { error("empty authentication method list"); return -1; } omethods = methods = xstrdup(_methods); while ((method = strsep(&methods, ",")) != NULL) { for (found = i = 0; !found && authmethods[i] != NULL; i++) { if ((p = strchr(method, ':')) != NULL) *p = '\0'; if (strcmp(method, authmethods[i]->name) != 0) continue; if (need_enable) { if (authmethods[i]->enabled == NULL || *(authmethods[i]->enabled) == 0) { error("Disabled method \"%s\" in " "AuthenticationMethods list \"%s\"", method, _methods); goto out; } } found = 1; break; } if (!found) { error("Unknown authentication method \"%s\" in list", method); goto out; } } ret = 0; out: free(omethods); return ret; } /* * Prune the AuthenticationMethods supplied in the configuration, removing * any methods lists that include disabled methods. Note that this might * leave authctxt->num_auth_methods == 0, even when multiple required auth * has been requested. For this reason, all tests for whether multiple is * enabled should consult options.num_auth_methods directly. */ int auth2_setup_methods_lists(Authctxt *authctxt) { u_int i; if (options.num_auth_methods == 0) return 0; debug3("%s: checking methods", __func__); authctxt->auth_methods = xcalloc(options.num_auth_methods, sizeof(*authctxt->auth_methods)); authctxt->num_auth_methods = 0; for (i = 0; i < options.num_auth_methods; i++) { if (auth2_methods_valid(options.auth_methods[i], 1) != 0) { logit("Authentication methods list \"%s\" contains " "disabled method, skipping", options.auth_methods[i]); continue; } debug("authentication methods list %d: %s", authctxt->num_auth_methods, options.auth_methods[i]); authctxt->auth_methods[authctxt->num_auth_methods++] = xstrdup(options.auth_methods[i]); } if (authctxt->num_auth_methods == 0) { error("No AuthenticationMethods left after eliminating " "disabled methods"); return -1; } return 0; } static int list_starts_with(const char *methods, const char *method, const char *submethod) { size_t l = strlen(method); int match; const char *p; if (strncmp(methods, method, l) != 0) return MATCH_NONE; p = methods + l; match = MATCH_METHOD; if (*p == ':') { if (!submethod) return MATCH_PARTIAL; l = strlen(submethod); p += 1; if (strncmp(submethod, p, l)) return MATCH_NONE; p += l; match = MATCH_BOTH; } if (*p != ',' && *p != '\0') return MATCH_NONE; return match; } /* * Remove method from the start of a comma-separated list of methods. * Returns 0 if the list of methods did not start with that method or 1 * if it did. */ static int remove_method(char **methods, const char *method, const char *submethod) { char *omethods = *methods, *p; size_t l = strlen(method); int match; match = list_starts_with(omethods, method, submethod); if (match != MATCH_METHOD && match != MATCH_BOTH) return 0; p = omethods + l; if (submethod && match == MATCH_BOTH) p += 1 + strlen(submethod); /* include colon */ if (*p == ',') p++; *methods = xstrdup(p); free(omethods); return 1; } /* * Called after successful authentication. Will remove the successful method * from the start of each list in which it occurs. If it was the last method * in any list, then authentication is deemed successful. * Returns 1 if the method completed any authentication list or 0 otherwise. */ int auth2_update_methods_lists(Authctxt *authctxt, const char *method, const char *submethod) { u_int i, found = 0; debug3("%s: updating methods list after \"%s\"", __func__, method); for (i = 0; i < authctxt->num_auth_methods; i++) { if (!remove_method(&(authctxt->auth_methods[i]), method, submethod)) continue; found = 1; if (*authctxt->auth_methods[i] == '\0') { debug2("authentication methods list %d complete", i); return 1; } debug3("authentication methods list %d remaining: \"%s\"", i, authctxt->auth_methods[i]); } /* This should not happen, but would be bad if it did */ if (!found) fatal("%s: method not in AuthenticationMethods", __func__); return 0; }