+/*************************************************
+* Exim - an Internet mail transport agent *
+*************************************************/
+
+/* Copyright (c) The Exim Maintainers 2019 - 2024 */
+/* Copyright (c) University of Cambridge 1995 - 2018 */
+/* See the file NOTICE for conditions of use and distribution. */
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+/* Copyright (c) Twitter Inc 2012
+ Author: Phil Pennock <pdp@exim.org> */
+/* Copyright (c) Phil Pennock 2012 */
+
+/* Interface to GNU SASL library for generic authentication. */
+
+/* Trade-offs:
+
+GNU SASL does not provide authentication data itself, so we have to expose
+that decision to configuration. For some mechanisms, we need to act much
+like plaintext. For others, we only need to be able to provide some
+evaluated data on demand. There's no abstracted way (ie, without hardcoding
+knowledge of authenticators here) to know which need what properties; we
+can't query a session or the library for "we will need these for mechanism X".
+
+So: we always require server_condition, even if sometimes it will just be
+set as "yes". We do provide a number of other hooks, which might not make
+sense in all contexts. For some, we can do checks at init time.
+*/
+
+#include "../exim.h"
+
+#ifndef AUTH_GSASL
+/* dummy function to satisfy compilers when we link in an "empty" file. */
+static void dummy(int x);
+static void dummy2(int x) { dummy(x-1); }
+static void dummy(int x) { dummy2(x-1); }
+#else
+
+#include <gsasl.h>
+#include "gsasl.h"
+
+
+#if GSASL_VERSION_MAJOR == 2
+
+# define EXIM_GSASL_HAVE_SCRAM_SHA_256
+# define EXIM_GSASL_SCRAM_S_KEY
+# if GSASL_VERSION_MINOR >= 1
+# define EXIM_GSASL_HAVE_EXPORTER
+# elif GSASL_VERSION_PATCH >= 1
+# define EXIM_GSASL_HAVE_EXPORTER
+# endif
+
+#elif GSASL_VERSION_MAJOR == 1
+# if GSASL_VERSION_MINOR >= 10
+# define EXIM_GSASL_HAVE_SCRAM_SHA_256
+# define EXIM_GSASL_SCRAM_S_KEY
+
+# elif GSASL_VERSION_MINOR == 9
+# define EXIM_GSASL_HAVE_SCRAM_SHA_256
+
+# if GSASL_VERSION_PATCH >= 1
+# define EXIM_GSASL_SCRAM_S_KEY
+# endif
+# if GSASL_VERSION_PATCH < 2
+# define CHANNELBIND_HACK
+# endif
+
+# else
+# define CHANNELBIND_HACK
+# endif
+#endif
+
+/* Convenience for testing strings */
+
+#define STREQIC(Foo, Bar) (strcmpic((Foo), (Bar)) == 0)
+
+
+/* Authenticator-specific options. */
+/* I did have server_*_condition options for various mechanisms, but since
+we only ever handle one mechanism at a time, I didn't see the point in keeping
+that. In case someone sees a point, I've left the condition_check() API
+alone. */
+#define LOFF(field) OPT_OFF(auth_gsasl_options_block, field)
+
+optionlist auth_gsasl_options[] = {
+ { "client_authz", opt_stringptr, LOFF(client_authz) },
+ { "client_channelbinding", opt_bool, LOFF(client_channelbinding) },
+ { "client_password", opt_stringptr, LOFF(client_password) },
+ { "client_spassword", opt_stringptr, LOFF(client_spassword) },
+ { "client_username", opt_stringptr, LOFF(client_username) },
+
+ { "server_channelbinding", opt_bool, LOFF(server_channelbinding) },
+ { "server_hostname", opt_stringptr, LOFF(server_hostname) },
+#ifdef EXIM_GSASL_SCRAM_S_KEY
+ { "server_key", opt_stringptr, LOFF(server_key) },
+#endif
+ { "server_mech", opt_stringptr, LOFF(server_mech) },
+ { "server_password", opt_stringptr, LOFF(server_password) },
+ { "server_realm", opt_stringptr, LOFF(server_realm) },
+ { "server_scram_iter", opt_stringptr, LOFF(server_scram_iter) },
+ { "server_scram_salt", opt_stringptr, LOFF(server_scram_salt) },
+#ifdef EXIM_GSASL_SCRAM_S_KEY
+ { "server_skey", opt_stringptr, LOFF(server_s_key) },
+#endif
+ { "server_service", opt_stringptr, LOFF(server_service) }
+};
+
+int auth_gsasl_options_count =
+ sizeof(auth_gsasl_options)/sizeof(optionlist);
+
+/* Defaults for the authenticator-specific options. */
+auth_gsasl_options_block auth_gsasl_option_defaults = {
+ .server_service = US"smtp",
+ .server_hostname = US"$primary_hostname",
+ .server_scram_iter = US"4096",
+ /* all others zero/null */
+};
+
+
+#ifdef MACRO_PREDEF
+# include "../macro_predef.h"
+
+/* Dummy values */
+void auth_gsasl_init(driver_instance *ablock) {}
+int auth_gsasl_server(auth_instance *ablock, uschar *data) {return 0;}
+int auth_gsasl_client(auth_instance *ablock, void * sx,
+ int timeout, uschar *buffer, int buffsize) {return 0;}
+gstring * auth_gsasl_version_report(gstring * g) {return NULL;}
+
+void
+auth_gsasl_macros(void)
+{
+# ifdef EXIM_GSASL_HAVE_SCRAM_SHA_256
+ builtin_macro_create(US"_HAVE_AUTH_GSASL_SCRAM_SHA_256");
+# endif
+# ifdef EXIM_GSASL_SCRAM_S_KEY
+ builtin_macro_create(US"_HAVE_AUTH_GSASL_SCRAM_S_KEY");
+# endif
+}
+
+#else /*!MACRO_PREDEF*/
+
+
+
+/* "Globals" for managing the gsasl interface. */
+
+static Gsasl *gsasl_ctx = NULL;
+static int
+ main_callback(Gsasl *ctx, Gsasl_session *sctx, Gsasl_property prop);
+static int
+ server_callback(Gsasl *ctx, Gsasl_session *sctx, Gsasl_property prop, auth_instance *ablock);
+static int
+ client_callback(Gsasl *ctx, Gsasl_session *sctx, Gsasl_property prop, auth_instance *ablock);
+
+static BOOL sasl_error_should_defer = FALSE;
+static Gsasl_property callback_loop = 0;
+static BOOL checked_server_condition = FALSE;
+
+enum { CURRENTLY_SERVER = 1, CURRENTLY_CLIENT = 2 };
+
+struct callback_exim_state {
+ auth_instance *ablock;
+ int currently;
+};
+
+
+/*************************************************
+* Initialization entry point *
+*************************************************/
+
+/* Called for each instance, after its options have been read, to
+enable consistency checks to be done, or anything else that needs
+to be set up. */
+
+void
+auth_gsasl_init(driver_instance * a)
+{
+auth_instance * ablock = (auth_instance *)a;
+auth_gsasl_options_block * ob = a->options_block;
+static char * once = NULL;
+int rc;
+
+/* As per existing Cyrus glue, use the authenticator's public name as
+the default for the mechanism name; we don't handle multiple mechanisms
+in one authenticator, but the same driver can be used multiple times. */
+
+if (!ob->server_mech)
+ ob->server_mech = string_copy(ablock->public_name);
+
+/* Can get multiple session contexts from one library context, so just
+initialise the once. */
+
+if (!gsasl_ctx)
+ {
+ if ((rc = gsasl_init(&gsasl_ctx)) != GSASL_OK)
+ log_write(0, LOG_PANIC_DIE|LOG_CONFIG_FOR, "%s authenticator: "
+ "couldn't initialise GNU SASL library: %s (%s)",
+ a->name, gsasl_strerror_name(rc), gsasl_strerror(rc));
+
+ gsasl_callback_set(gsasl_ctx, main_callback);
+ }
+
+/* We don't need this except to log it for debugging. */
+
+HDEBUG(D_auth) if (!once)
+ {
+ if ((rc = gsasl_server_mechlist(gsasl_ctx, &once)) != GSASL_OK)
+ log_write(0, LOG_PANIC_DIE|LOG_CONFIG_FOR, "%s authenticator: "
+ "failed to retrieve list of mechanisms: %s (%s)",
+ a->name, gsasl_strerror_name(rc), gsasl_strerror(rc));
+
+ debug_printf("GNU SASL supports: %s\n", once);
+ }
+
+if (!gsasl_client_support_p(gsasl_ctx, CCS ob->server_mech))
+ log_write(0, LOG_PANIC_DIE|LOG_CONFIG_FOR, "%s authenticator: "
+ "GNU SASL does not support mechanism \"%s\"",
+ a->name, ob->server_mech);
+
+if (ablock->server_condition)
+ ablock->server = TRUE;
+else if( ob->server_mech
+ && !STREQIC(ob->server_mech, US"EXTERNAL")
+ && !STREQIC(ob->server_mech, US"ANONYMOUS")
+ && !STREQIC(ob->server_mech, US"PLAIN")
+ && !STREQIC(ob->server_mech, US"LOGIN")
+ )
+ {
+ /* At present, for mechanisms we don't panic on absence of server_condition;
+ need to figure out the most generically correct approach to deciding when
+ it's critical and when it isn't. Eg, for simple validation (PLAIN mechanism,
+ etc) it clearly is critical.
+ */
+
+ ablock->server = FALSE;
+ HDEBUG(D_auth) debug_printf("%s authenticator: "
+ "Need server_condition for %s mechanism\n",
+ a->name, ob->server_mech);
+ }
+
+/* This does *not* scale to new SASL mechanisms. Need a better way to ask
+which properties will be needed. */
+
+if ( !ob->server_realm
+ && STREQIC(ob->server_mech, US"DIGEST-MD5"))
+ {
+ ablock->server = FALSE;
+ HDEBUG(D_auth) debug_printf("%s authenticator: "
+ "Need server_realm for %s mechanism\n",
+ a->name, ob->server_mech);
+ }
+
+ablock->client = ob->client_username && ob->client_password;
+}
+
+
+/* GNU SASL uses one top-level callback, registered at library level.
+We dispatch to client and server functions instead. */
+
+static int
+main_callback(Gsasl *ctx, Gsasl_session *sctx, Gsasl_property prop)
+{
+int rc = 0;
+struct callback_exim_state *cb_state =
+ (struct callback_exim_state *)gsasl_session_hook_get(sctx);
+
+if (!cb_state)
+ {
+ HDEBUG(D_auth) debug_printf("gsasl callback (%d) not from our server/client processing\n", prop);
+#ifdef CHANNELBIND_HACK
+ if (prop == GSASL_CB_TLS_UNIQUE)
+ {
+ uschar * s;
+ if ((s = gsasl_callback_hook_get(ctx))) /* Gross hack for early lib vers */
+ {
+ HDEBUG(D_auth) debug_printf("GSASL_CB_TLS_UNIQUE from ctx hook\n");
+ gsasl_property_set(sctx, GSASL_CB_TLS_UNIQUE, CS s);
+ }
+ else
+ {
+ HDEBUG(D_auth) debug_printf("GSASL_CB_TLS_UNIQUE! dummy for now\n");
+ gsasl_property_set(sctx, GSASL_CB_TLS_UNIQUE, "");
+ }
+ return GSASL_OK;
+ }
+#endif
+ return GSASL_NO_CALLBACK;
+ }
+
+HDEBUG(D_auth)
+ debug_printf("GNU SASL Callback entered, prop=%d (loop prop=%d)\n",
+ prop, callback_loop);
+
+if (callback_loop > 0)
+ {
+ /* Most likely is that we were asked for property FOO, and to
+ expand the string we asked for property BAR to put into an auth
+ variable, but property BAR is not supplied for this mechanism. */
+ HDEBUG(D_auth)
+ debug_printf("Loop, asked for property %d while handling property %d\n",
+ prop, callback_loop);
+ return GSASL_NO_CALLBACK;
+ }
+callback_loop = prop;
+
+if (cb_state->currently == CURRENTLY_CLIENT)
+ rc = client_callback(ctx, sctx, prop, cb_state->ablock);
+else if (cb_state->currently == CURRENTLY_SERVER)
+ rc = server_callback(ctx, sctx, prop, cb_state->ablock);
+else
+ log_write(0, LOG_PANIC_DIE|LOG_CONFIG_FOR, "%s authenticator: "
+ "unhandled callback state, bug in Exim", cb_state->ablock->drinst.name);
+ /* NOTREACHED */
+
+callback_loop = 0;
+return rc;
+}
+
+
+/*************************************************
+* Debug service function *
+*************************************************/
+static const uschar *
+gsasl_prop_code_to_name(Gsasl_property prop)
+{
+switch (prop)
+ {
+ case GSASL_AUTHID: return US"AUTHID";
+ case GSASL_AUTHZID: return US"AUTHZID";
+ case GSASL_PASSWORD: return US"PASSWORD";
+ case GSASL_ANONYMOUS_TOKEN: return US"ANONYMOUS_TOKEN";
+ case GSASL_SERVICE: return US"SERVICE";
+ case GSASL_HOSTNAME: return US"HOSTNAME";
+ case GSASL_GSSAPI_DISPLAY_NAME: return US"GSSAPI_DISPLAY_NAME";
+ case GSASL_PASSCODE: return US"PASSCODE";
+ case GSASL_SUGGESTED_PIN: return US"SUGGESTED_PIN";
+ case GSASL_PIN: return US"PIN";
+ case GSASL_REALM: return US"REALM";
+ case GSASL_DIGEST_MD5_HASHED_PASSWORD: return US"DIGEST_MD5_HASHED_PASSWORD";
+ case GSASL_QOPS: return US"QOPS";
+ case GSASL_QOP: return US"QOP";
+ case GSASL_SCRAM_ITER: return US"SCRAM_ITER";
+ case GSASL_SCRAM_SALT: return US"SCRAM_SALT";
+ case GSASL_SCRAM_SALTED_PASSWORD: return US"SCRAM_SALTED_PASSWORD";
+#ifdef EXIM_GSASL_SCRAM_S_KEY
+ case GSASL_SCRAM_STOREDKEY: return US"SCRAM_STOREDKEY";
+ case GSASL_SCRAM_SERVERKEY: return US"SCRAM_SERVERKEY";
+#endif
+#ifdef EXIM_GSASL_HAVE_EXPORTER /* v. 2.1.0 */
+ case GSASL_CB_TLS_EXPORTER: return US"CB_TLS_EXPORTER";
+#endif
+ case GSASL_CB_TLS_UNIQUE: return US"CB_TLS_UNIQUE";
+ case GSASL_SAML20_IDP_IDENTIFIER: return US"SAML20_IDP_IDENTIFIER";
+ case GSASL_SAML20_REDIRECT_URL: return US"SAML20_REDIRECT_URL";
+ case GSASL_OPENID20_REDIRECT_URL: return US"OPENID20_REDIRECT_URL";
+ case GSASL_OPENID20_OUTCOME_DATA: return US"OPENID20_OUTCOME_DATA";
+ case GSASL_SAML20_AUTHENTICATE_IN_BROWSER: return US"SAML20_AUTHENTICATE_IN_BROWSER";
+ case GSASL_OPENID20_AUTHENTICATE_IN_BROWSER: return US"OPENID20_AUTHENTICATE_IN_BROWSER";
+ case GSASL_VALIDATE_SIMPLE: return US"VALIDATE_SIMPLE";
+ case GSASL_VALIDATE_EXTERNAL: return US"VALIDATE_EXTERNAL";
+ case GSASL_VALIDATE_ANONYMOUS: return US"VALIDATE_ANONYMOUS";
+ case GSASL_VALIDATE_GSSAPI: return US"VALIDATE_GSSAPI";
+ case GSASL_VALIDATE_SECURID: return US"VALIDATE_SECURID";
+ case GSASL_VALIDATE_SAML20: return US"VALIDATE_SAML20";
+ case GSASL_VALIDATE_OPENID20: return US"VALIDATE_OPENID20";
+ }
+return CUS string_sprintf("(unknown prop: %d)", (int)prop);
+}
+
+static void
+preload_prop(Gsasl_session * sctx, Gsasl_property propcode, const uschar * val)
+{
+DEBUG(D_auth) debug_printf("preloading prop %s val %s\n",
+ gsasl_prop_code_to_name(propcode), val);
+gsasl_property_set(sctx, propcode, CCS val);
+}
+
+/*************************************************
+* Server entry point *
+*************************************************/
+
+/* For interface, see auths/README */
+
+int
+auth_gsasl_server(auth_instance * ablock, uschar * initial_data)
+{
+auth_gsasl_options_block * ob = ablock->drinst.options_block;
+const uschar * auname = ablock->drinst.name;
+uschar * tmps;
+char * to_send, * received;
+Gsasl_session * sctx = NULL;
+struct callback_exim_state cb_state;
+int rc, auth_result, exim_error, exim_error_override;
+
+HDEBUG(D_auth)
+ debug_printf("GNU SASL: initialising session for %s, mechanism %s\n",
+ auname, ob->server_mech);
+
+#ifndef DISABLE_TLS
+if (tls_in.channelbinding && ob->server_channelbinding)
+ {
+# ifndef DISABLE_TLS_RESUME
+ if (!tls_in.ext_master_secret && tls_in.resumption == RESUME_USED)
+ { /* per RFC 7677 section 4 */
+ HDEBUG(D_auth) debug_printf(
+ "channel binding not usable on resumed TLS without extended-master-secret");
+ return FAIL;
+ }
+# endif
+# ifdef CHANNELBIND_HACK
+/* This is a gross hack to get around the library before 1.9.2
+a) requiring that c-b was already set, at the _start() call, and
+b) caching a b64'd version of the binding then which it never updates. */
+
+ gsasl_callback_hook_set(gsasl_ctx, tls_in.channelbinding);
+# endif
+ }
+#endif
+
+if ((rc = gsasl_server_start(gsasl_ctx, CCS ob->server_mech, &sctx)) != GSASL_OK)
+ {
+ auth_defer_msg = string_sprintf("GNU SASL: session start failure: %s (%s)",
+ gsasl_strerror_name(rc), gsasl_strerror(rc));
+ HDEBUG(D_auth) debug_printf("%s\n", auth_defer_msg);
+ return DEFER;
+ }
+/* Hereafter: gsasl_finish(sctx) please */
+
+cb_state.ablock = ablock;
+cb_state.currently = CURRENTLY_SERVER;
+gsasl_session_hook_set(sctx, &cb_state);
+
+tmps = expand_string(ob->server_service);
+preload_prop(sctx, GSASL_SERVICE, tmps);
+tmps = expand_string(ob->server_hostname);
+preload_prop(sctx, GSASL_HOSTNAME, tmps);
+if (ob->server_realm)
+ {
+ tmps = expand_string(ob->server_realm);
+ if (tmps && *tmps)
+ preload_prop(sctx, GSASL_REALM, tmps);
+ }
+/* We don't support protection layers. */
+preload_prop(sctx, GSASL_QOPS, US "qop-auth");
+
+#ifndef DISABLE_TLS
+if (tls_in.channelbinding)
+ {
+ /* Some auth mechanisms can ensure that both sides are talking withing the
+ same security context; for TLS, this means that even if a bad certificate
+ has been accepted, they remain MitM-proof because both sides must be within
+ the same negotiated session; if someone is terminating one session and
+ proxying data on within a second, authentication will fail.
+
+ We might not have this available, depending upon TLS implementation,
+ ciphersuite, phase of moon ...
+
+ If we do, it results in extra SASL mechanisms being available; here,
+ Exim's one-mechanism-per-authenticator potentially causes problems.
+ It depends upon how GNU SASL will implement the PLUS variants of GS2
+ and whether it automatically mandates a switch to the bound PLUS
+ if the data is available. Since default-on, despite being more secure,
+ would then result in mechanism name changes on a library update, we
+ have little choice but to default it off and let the admin choose to
+ enable it. *sigh*
+
+ Earlier library versions need this set early, during the _start() call,
+ so we had to misuse gsasl_callback_hook_set/get() as a data transfer
+ mech for the callback done at that time to get the bind-data. More recently
+ the callback is done (if needed) during the first gsasl_stop(). We know
+ the bind-data here so can set it (and should not get a callback).
+ */
+ if (ob->server_channelbinding)
+ {
+ HDEBUG(D_auth) debug_printf("Auth %s: Enabling channel-binding\n",
+ auname);
+# ifndef CHANNELBIND_HACK
+ preload_prop(sctx,
+# ifdef EXIM_GSASL_HAVE_EXPORTER
+ tls_in.channelbind_exporter ? GSASL_CB_TLS_EXPORTER :
+# endif
+ GSASL_CB_TLS_UNIQUE,
+ tls_in.channelbinding);
+# endif
+ }
+ else
+ HDEBUG(D_auth)
+ debug_printf("Auth %s: Not enabling channel-binding (data available)\n",
+ auname);
+ }
+else
+ HDEBUG(D_auth)
+ debug_printf("Auth %s: no channel-binding data available\n",
+ auname);
+#endif
+
+checked_server_condition = FALSE;
+
+received = CS initial_data;
+to_send = NULL;
+exim_error = exim_error_override = OK;
+
+do {
+ switch (rc = gsasl_step64(sctx, received, &to_send))
+ {
+ case GSASL_OK:
+ if (!to_send)
+ goto STOP_INTERACTION;
+ break;
+
+ case GSASL_NEEDS_MORE:
+ break;
+
+ case GSASL_AUTHENTICATION_ERROR:
+ case GSASL_INTEGRITY_ERROR:
+ case GSASL_NO_AUTHID:
+ case GSASL_NO_ANONYMOUS_TOKEN:
+ case GSASL_NO_AUTHZID:
+ case GSASL_NO_PASSWORD:
+ case GSASL_NO_PASSCODE:
+ case GSASL_NO_PIN:
+ case GSASL_BASE64_ERROR:
+ HDEBUG(D_auth) debug_printf("GNU SASL permanent error: %s (%s)\n",
+ gsasl_strerror_name(rc), gsasl_strerror(rc));
+ log_write(0, LOG_REJECT, "%s authenticator (%s):\n "
+ "GNU SASL permanent failure: %s (%s)",
+ auname, ob->server_mech,
+ gsasl_strerror_name(rc), gsasl_strerror(rc));
+ if (rc == GSASL_BASE64_ERROR)
+ exim_error_override = BAD64;
+ goto STOP_INTERACTION;
+
+ default:
+ auth_defer_msg = string_sprintf("GNU SASL temporary error: %s (%s)",
+ gsasl_strerror_name(rc), gsasl_strerror(rc));
+ HDEBUG(D_auth) debug_printf("%s\n", auth_defer_msg);
+ exim_error_override = DEFER;
+ goto STOP_INTERACTION;
+ }
+
+ /*XXX having our caller send the final smtp "235" is unfortunate; wastes a roundtrip */
+ if ((rc == GSASL_NEEDS_MORE) || (to_send && *to_send))
+ exim_error = auth_get_no64_data(USS &received, US to_send);
+
+ if (to_send)
+ {
+ free(to_send);
+ to_send = NULL;
+ }
+
+ if (exim_error)
+ break; /* handles * cancelled check */
+
+ } while (rc == GSASL_NEEDS_MORE);
+
+STOP_INTERACTION:
+auth_result = rc;
+
+HDEBUG(D_auth)
+ {
+ const uschar * s;
+ if ((s = CUS gsasl_property_fast(sctx, GSASL_SCRAM_ITER)))
+ debug_printf(" - itercnt: '%s'\n", s);
+ if ((s = CUS gsasl_property_fast(sctx, GSASL_SCRAM_SALT)))
+ debug_printf(" - salt: '%s'\n", s);
+#ifdef EXIM_GSASL_SCRAM_S_KEY
+ if ((s = CUS gsasl_property_fast(sctx, GSASL_SCRAM_SERVERKEY)))
+ debug_printf(" - ServerKey: '%s'\n", s);
+ if ((s = CUS gsasl_property_fast(sctx, GSASL_SCRAM_STOREDKEY)))
+ debug_printf(" - StoredKey: '%s'\n", s);
+#endif
+ }
+
+gsasl_finish(sctx);
+
+/* Can return: OK DEFER FAIL CANCELLED BAD64 UNEXPECTED */
+
+if (exim_error != OK)
+ return exim_error;
+
+if (auth_result != GSASL_OK)
+ {
+ HDEBUG(D_auth) debug_printf("authentication returned %s (%s)\n",
+ gsasl_strerror_name(auth_result), gsasl_strerror(auth_result));
+ if (exim_error_override != OK)
+ return exim_error_override; /* might be DEFER */
+ if (sasl_error_should_defer) /* overriding auth failure SASL error */
+ return DEFER;
+ return FAIL;
+ }
+
+/* Auth succeeded, check server_condition unless already done in callback */
+return checked_server_condition ? OK : auth_check_serv_cond(ablock);
+}
+
+
+/* returns the GSASL status of expanding the Exim string given */
+static int
+condition_check(auth_instance *ablock, uschar *label, uschar *condition_string)
+{
+int exim_rc = auth_check_some_cond(ablock, label, condition_string, FAIL);
+switch (exim_rc)
+ {
+ case OK: return GSASL_OK;
+ case DEFER: sasl_error_should_defer = TRUE;
+ return GSASL_AUTHENTICATION_ERROR;
+ case FAIL: return GSASL_AUTHENTICATION_ERROR;
+ default: log_write(0, LOG_PANIC_DIE|LOG_CONFIG_FOR, "%s authenticator: "
+ "Unhandled return from checking %s: %d",
+ ablock->drinst.name, label, exim_rc);
+ }
+
+/* NOTREACHED */
+return GSASL_AUTHENTICATION_ERROR;
+}
+
+
+/* Set the "next" $auth[n] and increment expand_nmax */
+
+static void
+set_exim_authvar_from_prop(Gsasl_session * sctx, Gsasl_property prop)
+{
+uschar * propval = US gsasl_property_fast(sctx, prop);
+int i = expand_nmax, j = i + 1;
+propval = propval ? string_copy(propval) : US"";
+HDEBUG(D_auth) debug_printf("auth[%d] <= %s'%s'\n",
+ j, gsasl_prop_code_to_name(prop), propval);
+expand_nstring[j] = propval;
+expand_nlength[j] = Ustrlen(propval);
+if (i < AUTH_VARS) auth_vars[i] = propval;
+expand_nmax = j;
+}
+
+static void
+set_exim_authvars_from_a_az_r_props(Gsasl_session * sctx)
+{
+if (expand_nmax > 0 ) return;
+
+/* Asking for GSASL_AUTHZID calls back into us if we use
+gsasl_property_get(), thus the use of gsasl_property_fast().
+Do we really want to hardcode limits per mechanism? What happens when
+a new mechanism is added to the library. It *shouldn't* result in us
+needing to add more glue, since avoiding that is a large part of the
+point of SASL. */
+
+set_exim_authvar_from_prop(sctx, GSASL_AUTHID);
+set_exim_authvar_from_prop(sctx, GSASL_AUTHZID);
+set_exim_authvar_from_prop(sctx, GSASL_REALM);
+}
+
+
+static int
+prop_from_option(Gsasl_session * sctx, Gsasl_property prop,
+ const uschar * option)
+{
+HDEBUG(D_auth) debug_printf(" %s\n", gsasl_prop_code_to_name(prop));
+if (option)
+ {
+ set_exim_authvars_from_a_az_r_props(sctx);
+ option = expand_cstring(option);
+ HDEBUG(D_auth) debug_printf(" '%s'\n", option);
+ if (*option)
+ gsasl_property_set(sctx, prop, CCS option);
+ return GSASL_OK;
+ }
+HDEBUG(D_auth) debug_printf(" option not set\n");
+return GSASL_NO_CALLBACK;
+}
+
+static int
+server_callback(Gsasl *ctx, Gsasl_session *sctx, Gsasl_property prop,
+ auth_instance *ablock)
+{
+auth_gsasl_options_block * ob = ablock->drinst.options_block;
+char * tmps;
+uschar * s;
+int cbrc = GSASL_NO_CALLBACK;
+
+HDEBUG(D_auth) debug_printf("GNU SASL callback %s for %s/%s as server\n",
+ gsasl_prop_code_to_name(prop), ablock->drinst.name, ablock->public_name);
+
+for (int i = 0; i < AUTH_VARS; i++) auth_vars[i] = NULL;
+expand_nmax = 0;
+
+switch (prop)
+ {
+ case GSASL_VALIDATE_SIMPLE:
+ /* GSASL_AUTHID, GSASL_AUTHZID, and GSASL_PASSWORD */
+ set_exim_authvar_from_prop(sctx, GSASL_AUTHID);
+ set_exim_authvar_from_prop(sctx, GSASL_AUTHZID);
+ set_exim_authvar_from_prop(sctx, GSASL_PASSWORD);
+
+ cbrc = condition_check(ablock, US"server_condition", ablock->server_condition);
+ checked_server_condition = TRUE;
+ break;
+
+ case GSASL_VALIDATE_EXTERNAL:
+ if (!ablock->server_condition)
+ {
+ HDEBUG(D_auth) debug_printf("No server_condition supplied, to validate EXTERNAL\n");
+ cbrc = GSASL_AUTHENTICATION_ERROR;
+ break;
+ }
+ set_exim_authvar_from_prop(sctx, GSASL_AUTHZID);
+
+ cbrc = condition_check(ablock,
+ US"server_condition (EXTERNAL)", ablock->server_condition);
+ checked_server_condition = TRUE;
+ break;
+
+ case GSASL_VALIDATE_ANONYMOUS:
+ if (!ablock->server_condition)
+ {
+ HDEBUG(D_auth) debug_printf("No server_condition supplied, to validate ANONYMOUS\n");
+ cbrc = GSASL_AUTHENTICATION_ERROR;
+ break;
+ }
+ set_exim_authvar_from_prop(sctx, GSASL_ANONYMOUS_TOKEN);
+
+ cbrc = condition_check(ablock,
+ US"server_condition (ANONYMOUS)", ablock->server_condition);
+ checked_server_condition = TRUE;
+ break;
+
+ case GSASL_VALIDATE_GSSAPI:
+ /* GSASL_AUTHZID and GSASL_GSSAPI_DISPLAY_NAME
+ The display-name is authenticated as part of GSS, the authzid is claimed
+ by the SASL integration after authentication; protected against tampering
+ (if the SASL mechanism supports that, which Kerberos does) but is
+ unverified, same as normal for other mechanisms.
+ First coding, we had these values swapped, but for consistency and prior
+ to the first release of Exim with this authenticator, they've been
+ switched to match the ordering of GSASL_VALIDATE_SIMPLE. */
+
+ set_exim_authvar_from_prop(sctx, GSASL_GSSAPI_DISPLAY_NAME);
+ set_exim_authvar_from_prop(sctx, GSASL_AUTHZID);
+
+ /* In this one case, it perhaps makes sense to default back open?
+ But for consistency, let's just mandate server_condition here too. */
+
+ cbrc = condition_check(ablock,
+ US"server_condition (GSSAPI family)", ablock->server_condition);
+ checked_server_condition = TRUE;
+ break;
+
+ case GSASL_SCRAM_ITER:
+ cbrc = prop_from_option(sctx, prop, ob->server_scram_iter);
+ break;
+
+ case GSASL_SCRAM_SALT:
+ cbrc = prop_from_option(sctx, prop, ob->server_scram_salt);
+ break;
+
+#ifdef EXIM_GSASL_SCRAM_S_KEY
+ case GSASL_SCRAM_STOREDKEY:
+ cbrc = prop_from_option(sctx, prop, ob->server_s_key);
+ break;
+
+ case GSASL_SCRAM_SERVERKEY:
+ cbrc = prop_from_option(sctx, prop, ob->server_key);
+ break;
+#endif
+
+ case GSASL_PASSWORD:
+ /* SCRAM-*: GSASL_AUTHID, GSASL_AUTHZID and GSASL_REALM
+ DIGEST-MD5: GSASL_AUTHID, GSASL_AUTHZID and GSASL_REALM
+ CRAM-MD5: GSASL_AUTHID
+ PLAIN: GSASL_AUTHID and GSASL_AUTHZID
+ LOGIN: GSASL_AUTHID
+ */
+ set_exim_authvars_from_a_az_r_props(sctx);
+
+ if (!(s = ob->server_password))
+ {
+ HDEBUG(D_auth) debug_printf("option not set\n");
+ break;
+ }
+ if (!(tmps = CS expand_string(s)))
+ {
+ sasl_error_should_defer = !f.expand_string_forcedfail;
+ HDEBUG(D_auth) debug_printf("server_password expansion failed, so "
+ "can't tell GNU SASL library the password for %s\n", auth_vars[0]);
+ return GSASL_AUTHENTICATION_ERROR;
+ }
+ HDEBUG(D_auth) debug_printf(" set\n");
+ gsasl_property_set(sctx, GSASL_PASSWORD, tmps);
+
+ /* This is inadequate; don't think Exim's store stacks are geared
+ for memory wiping, so expanding strings will leave stuff laying around.
+ But no need to compound the problem, so get rid of the one we can. */
+
+ if (US tmps != s) memset(tmps, '\0', strlen(tmps));
+ cbrc = GSASL_OK;
+ break;
+
+ default:
+ HDEBUG(D_auth) debug_printf(" Unrecognised callback: %d\n", prop);
+ cbrc = GSASL_NO_CALLBACK;
+ }
+
+HDEBUG(D_auth) debug_printf("Returning %s (%s)\n",
+ gsasl_strerror_name(cbrc), gsasl_strerror(cbrc));
+
+return cbrc;
+}
+
+
+/******************************************************************************/
+
+#define PROP_OPTIONAL BIT(0)
+
+static BOOL
+set_client_prop(Gsasl_session * sctx, Gsasl_property prop, uschar * val,
+ unsigned flags, uschar * buffer, int buffsize)
+{
+uschar * s;
+
+if (!val) return !!(flags & PROP_OPTIONAL);
+if (!(s = expand_string(val)) || !(flags & PROP_OPTIONAL) && !*s)
+ {
+ string_format(buffer, buffsize, "%s", expand_string_message);
+ return FALSE;
+ }
+if (*s)
+ {
+ HDEBUG(D_auth) debug_printf("%s: set %s = '%s'\n", __FUNCTION__,
+ gsasl_prop_code_to_name(prop), s);
+ gsasl_property_set(sctx, prop, CS s);
+ }
+
+return TRUE;
+}
+
+/*************************************************
+* Client entry point *
+*************************************************/
+
+/* For interface, see auths/README */
+
+int
+auth_gsasl_client(
+ auth_instance * ablock, /* authenticator block */
+ void * sx, /* connection */
+ int timeout, /* command timeout */
+ uschar * buffer, /* buffer for reading response */
+ int buffsize) /* size of buffer */
+{
+auth_gsasl_options_block * ob = ablock->drinst.options_block;
+const uschar * auname = ablock->drinst.name;
+Gsasl_session * sctx = NULL;
+struct callback_exim_state cb_state;
+uschar * s;
+BOOL initial = TRUE;
+int rc, yield = FAIL;
+
+HDEBUG(D_auth)
+ debug_printf("GNU SASL: initialising session for %s, mechanism %s\n",
+ auname, ob->server_mech);
+
+*buffer = 0;
+
+#ifndef DISABLE_TLS
+if (tls_out.channelbinding && ob->client_channelbinding)
+ {
+# ifndef DISABLE_TLS_RESUME
+ if (!tls_out.ext_master_secret && tls_out.resumption == RESUME_USED)
+ { /* Per RFC 7677 section 4. See also RFC 7627, "Triple Handshake"
+ vulnerability, and https://www.mitls.org/pages/attacks/3SHAKE */
+ string_format(buffer, buffsize, "%s",
+ "channel binding not usable on resumed TLS without extended-master-secret");
+ return FAIL;
+ }
+# endif
+# ifdef CHANNELBIND_HACK
+ /* This is a gross hack to get around the library before 1.9.2
+ a) requiring that c-b was already set, at the _start() call, and
+ b) caching a b64'd version of the binding then which it never updates. */
+
+ gsasl_callback_hook_set(gsasl_ctx, tls_out.channelbinding);
+# endif
+ }
+#endif
+
+if ((rc = gsasl_client_start(gsasl_ctx, CCS ob->server_mech, &sctx)) != GSASL_OK)
+ {
+ string_format(buffer, buffsize, "GNU SASL: session start failure: %s (%s)",
+ gsasl_strerror_name(rc), gsasl_strerror(rc));
+ HDEBUG(D_auth) debug_printf("%s\n", buffer);
+ return ERROR;
+ }
+
+cb_state.ablock = ablock;
+cb_state.currently = CURRENTLY_CLIENT;
+gsasl_session_hook_set(sctx, &cb_state);
+
+/* Set properties */
+
+if ( !set_client_prop(sctx, GSASL_PASSWORD, ob->client_password,
+ 0, buffer, buffsize)
+ || !set_client_prop(sctx, GSASL_AUTHID, ob->client_username,
+ 0, buffer, buffsize)
+ || !set_client_prop(sctx, GSASL_AUTHZID, ob->client_authz,
+ PROP_OPTIONAL, buffer, buffsize)
+ )
+ return ERROR;
+
+#ifndef DISABLE_TLS
+if (tls_out.channelbinding)
+ if (ob->client_channelbinding)
+ {
+ HDEBUG(D_auth) debug_printf("Auth %s: Enabling channel-binding\n",
+ auname);
+# ifndef CHANNELBIND_HACK
+ preload_prop(sctx,
+# ifdef EXIM_GSASL_HAVE_EXPORTER
+ tls_out.channelbind_exporter ? GSASL_CB_TLS_EXPORTER :
+# endif
+ GSASL_CB_TLS_UNIQUE,
+ tls_out.channelbinding);
+# endif
+ }
+ else
+ HDEBUG(D_auth)
+ debug_printf("Auth %s: Not enabling channel-binding (data available)\n",
+ auname);
+#endif
+
+/* Run the SASL conversation with the server */
+
+for(s = NULL; ;)
+ {
+ uschar * outstr;
+ BOOL fail = TRUE;
+
+ rc = gsasl_step64(sctx, CS s, CSS &outstr);
+
+ if (rc == GSASL_NEEDS_MORE || rc == GSASL_OK)
+ {
+ fail = initial
+ ? smtp_write_command(sx, SCMD_FLUSH,
+ outstr ? "AUTH %s %s\r\n" : "AUTH %s\r\n",
+ ablock->public_name, outstr) <= 0
+ : outstr
+ ? smtp_write_command(sx, SCMD_FLUSH, "%s\r\n", outstr) <= 0
+ : FALSE;
+ free(outstr);
+ if (fail)
+ {
+ yield = FAIL_SEND;
+ goto done;
+ }
+ initial = FALSE;
+ }
+
+ if (rc != GSASL_NEEDS_MORE)
+ {
+ if (rc != GSASL_OK)
+ {
+ string_format(buffer, buffsize, "gsasl: %s", gsasl_strerror(rc));
+ break;
+ }
+
+ /* expecting a final 2xx from the server, accepting the AUTH */
+
+ if (smtp_read_response(sx, buffer, buffsize, '2', timeout))
+ yield = OK;
+ break; /* from SASL sequence loop */
+ }
+
+ /* 2xx or 3xx response is acceptable. If 2xx, no further input */
+
+ if (!smtp_read_response(sx, buffer, buffsize, '3', timeout))
+ if (errno == 0 && buffer[0] == '2')
+ buffer[4] = '\0';
+ else
+ {
+ yield = FAIL;
+ goto done;
+ }
+ s = buffer + 4;
+ }
+
+done:
+if (yield == OK)
+ {
+ expand_nmax = 0;
+ set_exim_authvar_from_prop(sctx, GSASL_AUTHID);
+ set_exim_authvar_from_prop(sctx, GSASL_SCRAM_ITER);
+ set_exim_authvar_from_prop(sctx, GSASL_SCRAM_SALT);
+ set_exim_authvar_from_prop(sctx, GSASL_SCRAM_SALTED_PASSWORD);
+ }
+
+gsasl_finish(sctx);
+return yield;
+}
+
+static int
+client_callback(Gsasl *ctx, Gsasl_session *sctx, Gsasl_property prop, auth_instance *ablock)
+{
+HDEBUG(D_auth) debug_printf("GNU SASL callback %s for %s/%s as client\n",
+ gsasl_prop_code_to_name(prop), ablock->drinst.name, ablock->public_name);
+switch (prop)
+ {
+#ifdef EXIM_GSASL_HAVE_EXPORTER
+ case GSASL_CB_TLS_EXPORTER: /* Should never get called for this, as pre-set */
+ if (!tls_out.channelbind_exporter) break;
+ HDEBUG(D_auth) debug_printf(" filling in\n");
+ gsasl_property_set(sctx, GSASL_CB_TLS_EXPORTER, CCS tls_out.channelbinding);
+ return GSASL_OK;
+#endif
+ case GSASL_CB_TLS_UNIQUE: /* Should never get called for this, as pre-set */
+#ifdef EXIM_GSASL_HAVE_EXPORTER
+ if (tls_out.channelbind_exporter) break;
+#endif
+ HDEBUG(D_auth) debug_printf(" filling in\n");
+ gsasl_property_set(sctx, GSASL_CB_TLS_UNIQUE, CCS tls_out.channelbinding);
+ return GSASL_OK;
+ case GSASL_SCRAM_SALTED_PASSWORD:
+ {
+ uschar * client_spassword =
+ ((auth_gsasl_options_block *) ablock->drinst.options_block)->client_spassword;
+ uschar dummy[4];
+ HDEBUG(D_auth) if (!client_spassword)
+ debug_printf(" client_spassword option unset\n");
+ if (client_spassword)
+ {
+ expand_nmax = 0;
+ set_exim_authvar_from_prop(sctx, GSASL_AUTHID);
+ set_exim_authvar_from_prop(sctx, GSASL_SCRAM_ITER);
+ set_exim_authvar_from_prop(sctx, GSASL_SCRAM_SALT);
+ set_client_prop(sctx, GSASL_SCRAM_SALTED_PASSWORD, client_spassword,
+ 0, dummy, sizeof(dummy));
+ for (int i = 0; i < AUTH_VARS; i++) auth_vars[i] = NULL;
+ expand_nmax = 0;
+ }
+ break;
+ }
+ default:
+ HDEBUG(D_auth)
+ debug_printf(" not providing one\n");
+ break;
+ }
+return GSASL_NO_CALLBACK;
+}
+
+/*************************************************
+* Diagnostic API *
+*************************************************/
+
+gstring *
+auth_gsasl_version_report(gstring * g)
+{
+return string_fmt_append(g, "Library version: GNU SASL: Compile: %s\n"
+ " Runtime: %s\n",
+ GSASL_VERSION, gsasl_check_version(NULL));
+}
+
+
+
+/* Dummy */
+void auth_gsasl_macros(void) {}
+
+# ifdef DYNLOOKUP
+# define gsasl_auth_info _auth_info
+# endif
+
+auth_info gsasl_auth_info = {
+.drinfo = {
+ .driver_name = US"gsasl", /* lookup name */
+ .options = auth_gsasl_options,
+ .options_count = &auth_gsasl_options_count,
+ .options_block = &auth_gsasl_option_defaults,
+ .options_len = sizeof(auth_gsasl_options_block),
+ .init = auth_gsasl_init,
+# ifdef DYNLOOKUP
+ .dyn_magic = AUTH_MAGIC,
+# endif
+ },
+.servercode = auth_gsasl_server,
+.clientcode = auth_gsasl_client,
+.version_report = auth_gsasl_version_report,
+.macros_create = auth_gsasl_macros,
+};
+
+#endif /*!MACRO_PREDEF*/
+#endif /* AUTH_GSASL */
+
+/* End of gsasl_exim.c */
git://git.exim.org / exim.git / commitdiff