diff options
Diffstat (limited to 'crypto/openssh/auth2.c')
| -rw-r--r-- | crypto/openssh/auth2.c | 239 |
1 files changed, 212 insertions, 27 deletions
diff --git a/crypto/openssh/auth2.c b/crypto/openssh/auth2.c index 234ca3b..7e50bf7 100644 --- a/crypto/openssh/auth2.c +++ b/crypto/openssh/auth2.c @@ -1,4 +1,4 @@ -/* $OpenBSD: auth2.c,v 1.124 2011/12/07 05:44:38 djm Exp $ */ +/* $OpenBSD: auth2.c,v 1.126 2012/12/02 20:34:09 djm Exp $ */ /* * Copyright (c) 2000 Markus Friedl. All rights reserved. * @@ -98,8 +98,10 @@ static void input_service_request(int, u_int32_t, void *); static void input_userauth_request(int, u_int32_t, void *); /* helper */ -static Authmethod *authmethod_lookup(const char *); -static char *authmethods_get(void); +static Authmethod *authmethod_lookup(Authctxt *, const char *); +static char *authmethods_get(Authctxt *authctxt); +static int method_allowed(Authctxt *, const char *); +static int list_starts_with(const char *, const char *); char * auth2_read_banner(void) @@ -264,6 +266,8 @@ input_userauth_request(int type, u_int32_t seq, void *ctxt) 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: " @@ -307,12 +311,12 @@ input_userauth_request(int type, u_int32_t seq, void *ctxt) authctxt->server_caused_failure = 0; /* try to authenticate user */ - m = authmethod_lookup(method); + 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); + userauth_finish(authctxt, authenticated, method, NULL); xfree(service); xfree(user); @@ -320,13 +324,17 @@ input_userauth_request(int type, u_int32_t seq, void *ctxt) } void -userauth_finish(Authctxt *authctxt, int authenticated, char *method) +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 && @@ -337,6 +345,19 @@ userauth_finish(Authctxt *authctxt, int authenticated, char *method) #endif } + if (authenticated && options.num_auth_methods != 0) { + if (!auth2_update_methods_lists(authctxt, method)) { + authenticated = 0; + partial = 1; + } + } + + /* Log before sending the reply */ + auth_log(authctxt, authenticated, partial, method, submethod, " ssh2"); + + if (authctxt->postponed) + return; + #ifdef USE_PAM if (options.use_pam && authenticated) { if (!PRIVSEP(do_pam_account())) { @@ -355,17 +376,10 @@ userauth_finish(Authctxt *authctxt, int authenticated, char *method) #ifdef _UNICOS if (authenticated && cray_access_denied(authctxt->user)) { authenticated = 0; - fatal("Access denied for user %s.",authctxt->user); + fatal("Access denied for user %s.", authctxt->user); } #endif /* _UNICOS */ - /* Log before sending the reply */ - auth_log(authctxt, authenticated, method, " ssh2"); - - if (authctxt->postponed) - return; - - /* XXX todo: check if multiple auth methods are needed */ if (authenticated == 1) { /* turn off userauth */ dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore); @@ -386,34 +400,61 @@ userauth_finish(Authctxt *authctxt, int authenticated, char *method) #endif packet_disconnect(AUTH_FAIL_MSG, authctxt->user); } - methods = authmethods_get(); + 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(0); /* XXX partial success, unused */ + packet_put_char(partial); packet_send(); packet_write_wait(); xfree(methods); } } +/* + * Checks whether method is allowed by at least one AuthenticationMethods + * methods list. Returns 1 if allowed, or no methods lists configured. + * 0 otherwise. + */ +static int +method_allowed(Authctxt *authctxt, const char *method) +{ + 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)) + return 1; + } + return 0; +} + static char * -authmethods_get(void) +authmethods_get(Authctxt *authctxt) { Buffer b; char *list; - int i; + 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) { - if (buffer_len(&b) > 0) - buffer_append(&b, ",", 1); - buffer_append(&b, authmethods[i]->name, - strlen(authmethods[i]->name)); - } + if (authmethods[i]->enabled == NULL || + *(authmethods[i]->enabled) == 0) + continue; + if (!method_allowed(authctxt, authmethods[i]->name)) + 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)); @@ -422,7 +463,7 @@ authmethods_get(void) } static Authmethod * -authmethod_lookup(const char *name) +authmethod_lookup(Authctxt *authctxt, const char *name) { int i; @@ -430,10 +471,154 @@ authmethod_lookup(const char *name) for (i = 0; authmethods[i] != NULL; i++) if (authmethods[i]->enabled != NULL && *(authmethods[i]->enabled) != 0 && - strcmp(name, authmethods[i]->name) == 0) + strcmp(name, authmethods[i]->name) == 0 && + method_allowed(authctxt, authmethods[i]->name)) 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; + 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 (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) +{ + size_t l = strlen(method); + + if (strncmp(methods, method, l) != 0) + return 0; + if (methods[l] != ',' && methods[l] != '\0') + return 0; + return 1; +} + +/* + * 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) +{ + char *omethods = *methods; + size_t l = strlen(method); + + if (!list_starts_with(omethods, method)) + return 0; + *methods = xstrdup(omethods + l + (omethods[l] == ',' ? 1 : 0)); + 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) +{ + 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)) + 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; +} + + |
