diff options
author | Damien Miller <djm@mindrot.org> | 2012-11-04 23:21:40 +1100 |
---|---|---|
committer | Damien Miller <djm@mindrot.org> | 2012-11-04 23:21:40 +1100 |
commit | a6e3f01d1e230b8acfdd6b4cf3096459d2a325e0 (patch) | |
tree | 577022d2b31e9519d26bc614c3f5396e17d58ec6 | |
parent | d0d1099b3b8a766480ce6df215631bf0af6e6bcd (diff) |
- djm@cvs.openbsd.org 2012/11/04 11:09:15
[auth.h auth1.c auth2.c monitor.c servconf.c servconf.h sshd.c]
[sshd_config.5]
Support multiple required authentication via an AuthenticationMethods
option. This option lists one or more comma-separated lists of
authentication method names. Successful completion of all the methods in
any list is required for authentication to complete;
feedback and ok markus@
-rw-r--r-- | ChangeLog | 8 | ||||
-rw-r--r-- | auth.h | 7 | ||||
-rw-r--r-- | auth1.c | 7 | ||||
-rw-r--r-- | auth2.c | 218 | ||||
-rw-r--r-- | monitor.c | 35 | ||||
-rw-r--r-- | servconf.c | 26 | ||||
-rw-r--r-- | servconf.h | 7 | ||||
-rw-r--r-- | sshd.c | 23 | ||||
-rw-r--r-- | sshd_config.5 | 25 |
9 files changed, 328 insertions, 28 deletions
@@ -7,6 +7,14 @@ [auth2-pubkey.c sshd.c sshd_config.5] Remove default of AuthorizedCommandUser. Administrators are now expected to explicitly specify a user. feedback and ok markus@ + - djm@cvs.openbsd.org 2012/11/04 11:09:15 + [auth.h auth1.c auth2.c monitor.c servconf.c servconf.h sshd.c] + [sshd_config.5] + Support multiple required authentication via an AuthenticationMethods + option. This option lists one or more comma-separated lists of + authentication method names. Successful completion of all the methods in + any list is required for authentication to complete; + feedback and ok markus@ 20121030 - (djm) OpenBSD CVS Sync @@ -1,4 +1,4 @@ -/* $OpenBSD: auth.h,v 1.70 2012/10/30 21:29:54 djm Exp $ */ +/* $OpenBSD: auth.h,v 1.71 2012/11/04 11:09:15 djm Exp $ */ /* * Copyright (c) 2000 Markus Friedl. All rights reserved. @@ -64,6 +64,8 @@ struct Authctxt { #ifdef BSD_AUTH auth_session_t *as; #endif + char **auth_methods; /* modified from server config */ + u_int num_auth_methods; #ifdef KRB5 krb5_context krb5_ctx; krb5_ccache krb5_fwd_ccache; @@ -152,6 +154,9 @@ void userauth_send_banner(const char *); int auth_root_allowed(char *); char *auth2_read_banner(void); +int auth2_methods_valid(const char *, int); +int auth2_update_methods_lists(Authctxt *, const char *); +int auth2_setup_methods_lists(Authctxt *); void privsep_challenge_enable(void); @@ -1,4 +1,4 @@ -/* $OpenBSD: auth1.c,v 1.75 2010/08/31 09:58:37 djm Exp $ */ +/* $OpenBSD: auth1.c,v 1.76 2012/11/04 11:09:15 djm Exp $ */ /* * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland * All rights reserved @@ -406,6 +406,11 @@ do_authentication(Authctxt *authctxt) authctxt->pw = fakepw(); } + /* Configuration may have changed as a result of Match */ + if (options.num_auth_methods != 0) + fatal("AuthenticationMethods is not supported with SSH " + "protocol 1"); + setproctitle("%s%s", authctxt->valid ? user : "unknown", use_privsep ? " [net]" : ""); @@ -1,4 +1,4 @@ -/* $OpenBSD: auth2.c,v 1.124 2011/12/07 05:44:38 djm Exp $ */ +/* $OpenBSD: auth2.c,v 1.125 2012/11/04 11:09:15 djm Exp $ */ /* * Copyright (c) 2000 Markus Friedl. All rights reserved. * @@ -96,8 +96,10 @@ 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) @@ -255,6 +257,8 @@ 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: " @@ -277,7 +281,7 @@ 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); @@ -293,6 +297,7 @@ void userauth_finish(Authctxt *authctxt, int authenticated, char *method) { char *methods; + int partial = 0; if (!authctxt->valid && authenticated) fatal("INTERNAL ERROR: authenticated invalid user %s", @@ -335,7 +340,13 @@ userauth_finish(Authctxt *authctxt, int authenticated, char *method) if (authctxt->postponed) return; - /* XXX todo: check if multiple auth methods are needed */ + if (authenticated && options.num_auth_methods != 0) { + if (!auth2_update_methods_lists(authctxt, method)) { + authenticated = 0; + partial = 1; + } + } + if (authenticated == 1) { /* turn off userauth */ dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore); @@ -356,34 +367,61 @@ 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)); @@ -392,7 +430,7 @@ authmethods_get(void) } static Authmethod * -authmethod_lookup(const char *name) +authmethod_lookup(Authctxt *authctxt, const char *name) { int i; @@ -400,10 +438,154 @@ 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; +} + + @@ -1,4 +1,4 @@ -/* $OpenBSD: monitor.c,v 1.117 2012/06/22 12:30:26 dtucker Exp $ */ +/* $OpenBSD: monitor.c,v 1.118 2012/11/04 11:09:15 djm Exp $ */ /* * Copyright 2002 Niels Provos <provos@citi.umich.edu> * Copyright 2002 Markus Friedl <markus@openbsd.org> @@ -381,6 +381,21 @@ monitor_child_preauth(Authctxt *_authctxt, struct monitor *pmonitor) while (!authenticated) { auth_method = "unknown"; authenticated = (monitor_read(pmonitor, mon_dispatch, &ent) == 1); + + /* Special handling for multiple required authentications */ + if (options.num_auth_methods != 0) { + if (!compat20) + fatal("AuthenticationMethods is not supported" + "with SSH protocol 1"); + if (authenticated && + !auth2_update_methods_lists(authctxt, + auth_method)) { + debug3("%s: method %s: partial", __func__, + auth_method); + authenticated = 0; + } + } + if (authenticated) { if (!(ent->flags & MON_AUTHDECIDE)) fatal("%s: unexpected authentication from %d", @@ -401,7 +416,6 @@ monitor_child_preauth(Authctxt *_authctxt, struct monitor *pmonitor) } #endif } - if (ent->flags & (MON_AUTHDECIDE|MON_ALOG)) { auth_log(authctxt, authenticated, auth_method, compat20 ? " ssh2" : ""); @@ -781,7 +795,17 @@ mm_answer_pwnamallow(int sock, Buffer *m) COPY_MATCH_STRING_OPTS(); #undef M_CP_STROPT #undef M_CP_STRARRAYOPT - + + /* Create valid auth method lists */ + if (compat20 && auth2_setup_methods_lists(authctxt) != 0) { + /* + * The monitor will continue long enough to let the child + * run to it's packet_disconnect(), but it must not allow any + * authentication to succeed. + */ + debug("%s: no valid authentication method lists", __func__); + } + debug3("%s: sending MONITOR_ANS_PWNAM: %d", __func__, allowed); mm_request_send(sock, MONITOR_ANS_PWNAM, m); @@ -918,7 +942,10 @@ mm_answer_bsdauthrespond(int sock, Buffer *m) debug3("%s: sending authenticated: %d", __func__, authok); mm_request_send(sock, MONITOR_ANS_BSDAUTHRESPOND, m); - auth_method = "bsdauth"; + if (compat20) + auth_method = "keyboard-interactive"; + else + auth_method = "bsdauth"; return (authok != 0); } @@ -1,5 +1,5 @@ -/* $OpenBSD: servconf.c,v 1.231 2012/10/30 21:29:54 djm Exp $ */ +/* $OpenBSD: servconf.c,v 1.232 2012/11/04 11:09:15 djm Exp $ */ /* * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland * All rights reserved @@ -48,6 +48,8 @@ #include "groupaccess.h" #include "canohost.h" #include "packet.h" +#include "hostfile.h" +#include "auth.h" static void add_listen_addr(ServerOptions *, char *, int); static void add_one_listen_addr(ServerOptions *, char *, int); @@ -332,6 +334,7 @@ typedef enum { sRevokedKeys, sTrustedUserCAKeys, sAuthorizedPrincipalsFile, sKexAlgorithms, sIPQoS, sVersionAddendum, sAuthorizedKeysCommand, sAuthorizedKeysCommandUser, + sAuthenticationMethods, sDeprecated, sUnsupported } ServerOpCodes; @@ -459,6 +462,7 @@ static struct { { "authorizedkeyscommand", sAuthorizedKeysCommand, SSHCFG_ALL }, { "authorizedkeyscommanduser", sAuthorizedKeysCommandUser, SSHCFG_ALL }, { "versionaddendum", sVersionAddendum, SSHCFG_GLOBAL }, + { "authenticationmethods", sAuthenticationMethods, SSHCFG_ALL }, { NULL, sBadOption, 0 } }; @@ -1522,6 +1526,24 @@ process_server_config_line(ServerOptions *options, char *line, *charptr = xstrdup(arg); break; + case sAuthenticationMethods: + if (*activep && options->num_auth_methods == 0) { + while ((arg = strdelim(&cp)) && *arg != '\0') { + if (options->num_auth_methods >= + MAX_AUTH_METHODS) + fatal("%s line %d: " + "too many authentication methods.", + filename, linenum); + if (auth2_methods_valid(arg, 0) != 0) + fatal("%s line %d: invalid " + "authentication method list.", + filename, linenum); + options->auth_methods[ + options->num_auth_methods++] = xstrdup(arg); + } + } + return 0; + case sDeprecated: logit("%s line %d: Deprecated option %s", filename, linenum, arg); @@ -1953,6 +1975,8 @@ dump_config(ServerOptions *o) dump_cfg_strarray(sAllowGroups, o->num_allow_groups, o->allow_groups); dump_cfg_strarray(sDenyGroups, o->num_deny_groups, o->deny_groups); dump_cfg_strarray(sAcceptEnv, o->num_accept_env, o->accept_env); + dump_cfg_strarray_oneline(sAuthenticationMethods, + o->num_auth_methods, o->auth_methods); /* other arguments */ for (i = 0; i < o->num_subsystems; i++) @@ -1,4 +1,4 @@ -/* $OpenBSD: servconf.h,v 1.104 2012/10/30 21:29:55 djm Exp $ */ +/* $OpenBSD: servconf.h,v 1.105 2012/11/04 11:09:15 djm Exp $ */ /* * Author: Tatu Ylonen <ylo@cs.hut.fi> @@ -28,6 +28,7 @@ #define MAX_ACCEPT_ENV 256 /* Max # of env vars. */ #define MAX_MATCH_GROUPS 256 /* Max # of groups for Match. */ #define MAX_AUTHKEYS_FILES 256 /* Max # of authorized_keys files. */ +#define MAX_AUTH_METHODS 256 /* Max # of AuthenticationMethods. */ /* permit_root_login */ #define PERMIT_NOT_SET -1 @@ -170,6 +171,9 @@ typedef struct { char *authorized_keys_command_user; char *version_addendum; /* Appended to SSH banner */ + + u_int num_auth_methods; + char *auth_methods[MAX_AUTH_METHODS]; } ServerOptions; /* Information about the incoming connection as used by Match */ @@ -199,6 +203,7 @@ struct connection_info { M_CP_STRARRAYOPT(allow_groups, num_allow_groups); \ M_CP_STRARRAYOPT(deny_groups, num_deny_groups); \ M_CP_STRARRAYOPT(accept_env, num_accept_env); \ + M_CP_STRARRAYOPT(auth_methods, num_auth_methods); \ } while (0) struct connection_info *get_connection_info(int, int); @@ -1,4 +1,4 @@ -/* $OpenBSD: sshd.c,v 1.395 2012/11/04 10:38:43 djm Exp $ */ +/* $OpenBSD: sshd.c,v 1.396 2012/11/04 11:09:15 djm Exp $ */ /* * Author: Tatu Ylonen <ylo@cs.hut.fi> * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland @@ -1337,6 +1337,7 @@ main(int ac, char **av) int remote_port; char *line; int config_s[2] = { -1 , -1 }; + u_int n; u_int64_t ibytes, obytes; mode_t new_umask; Key *key; @@ -1566,6 +1567,26 @@ main(int ac, char **av) fatal("AuthorizedKeysCommand set without " "AuthorizedKeysCommandUser"); + /* + * Check whether there is any path through configured auth methods. + * Unfortunately it is not possible to verify this generally before + * daemonisation in the presence of Match block, but this catches + * and warns for trivial misconfigurations that could break login. + */ + if (options.num_auth_methods != 0) { + if ((options.protocol & SSH_PROTO_1)) + fatal("AuthenticationMethods is not supported with " + "SSH protocol 1"); + for (n = 0; n < options.num_auth_methods; n++) { + if (auth2_methods_valid(options.auth_methods[n], + 1) == 0) + break; + } + if (n >= options.num_auth_methods) + fatal("AuthenticationMethods cannot be satisfied by " + "enabled authentication methods"); + } + /* set default channel AF */ channel_set_af(options.address_family); diff --git a/sshd_config.5 b/sshd_config.5 index 0fb0b837..05f3374f 100644 --- a/sshd_config.5 +++ b/sshd_config.5 @@ -33,7 +33,7 @@ .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. .\" -.\" $OpenBSD: sshd_config.5,v 1.148 2012/11/04 10:38:43 djm Exp $ +.\" $OpenBSD: sshd_config.5,v 1.149 2012/11/04 11:09:15 djm Exp $ .Dd $Mdocdate: November 4 2012 $ .Dt SSHD_CONFIG 5 .Os @@ -151,6 +151,28 @@ See in .Xr ssh_config 5 for more information on patterns. +.It Cm AuthenticationMethods +Specifies the authentication methods that must be successfully completed +for a user to be granted access. +This option must be followed by one or more comma-separated lists of +authentication method names. +Successful authentication requires completion of every method in at least +one of these lists. +.Pp +For example, an argument of +.Dq publickey,password publickey,keyboard-interactive +would require the user to complete public key authentication, followed by +either password or keyboard interactive authentication. +Only methods that are next in one or more lists are offered at each stage, +so for this example, it would not be possible to attempt password or +keyboard-interactive authentication before public key. +.Pp +This option is only available for SSH protocol 2 and will yield a fatal +error if enabled if protocol 1 is also enabled. +Note that each authentication method listed should also be explicitly enabled +in the configuration. +The default is not to require multiple authentication; successful completion +of a single authentication method is sufficient. .It Cm AuthorizedKeysCommand Specifies a program to be used to look up the user's public keys. The program will be invoked with a single argument of the username @@ -728,6 +750,7 @@ Available keywords are .Cm AllowGroups , .Cm AllowTcpForwarding , .Cm AllowUsers , +.Cm AuthenticationMethods , .Cm AuthorizedKeysCommand , .Cm AuthorizedKeysCommandUser , .Cm AuthorizedKeysFile , |