From 86d25d8a270f37333edc31a8f532f6502aac9d58 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Pavel=20B=C5=99ezina?= Date: Tue, 7 Jul 2020 11:05:37 +0200 Subject: [PATCH] pam: add pam_sss_gss module for gssapi authentication --- Makefile.am | 33 +- configure.ac | 1 + contrib/sssd.spec.in | 2 + src/external/libgssapi_krb5.m4 | 8 + src/man/Makefile.am | 4 +- src/man/pam_sss_gss.8.xml | 160 ++++++++ src/responder/pam/pamsrv.h | 4 + src/responder/pam/pamsrv_cmd.c | 2 + src/responder/pam/pamsrv_gssapi.c | 594 +++++++++++++++++++++++++++++ src/sss_client/pam_sss_gss.c | 477 +++++++++++++++++++++++ src/sss_client/pam_sss_gss.exports | 4 + src/sss_client/sss_cli.h | 8 + src/tests/dlopen-tests.c | 1 + 13 files changed, 1295 insertions(+), 3 deletions(-) create mode 100644 src/external/libgssapi_krb5.m4 create mode 100644 src/man/pam_sss_gss.8.xml create mode 100644 src/responder/pam/pamsrv_gssapi.c create mode 100644 src/sss_client/pam_sss_gss.c create mode 100644 src/sss_client/pam_sss_gss.exports diff --git a/Makefile.am b/Makefile.am index 97aa1ec6612..02ceee4b158 100644 --- a/Makefile.am +++ b/Makefile.am @@ -1585,12 +1585,14 @@ sssd_pam_SOURCES = \ src/responder/pam/pamsrv_cmd.c \ src/responder/pam/pamsrv_p11.c \ src/responder/pam/pamsrv_dp.c \ + src/responder/pam/pamsrv_gssapi.c \ src/responder/pam/pam_prompting_config.c \ src/sss_client/pam_sss_prompt_config.c \ src/responder/pam/pam_helpers.c \ $(SSSD_RESPONDER_OBJ) sssd_pam_CFLAGS = \ $(AM_CFLAGS) \ + $(GSSAPI_KRB5_CFLAGS) \ $(NULL) sssd_pam_LDADD = \ $(LIBADD_DL) \ @@ -1599,6 +1601,7 @@ sssd_pam_LDADD = \ $(SELINUX_LIBS) \ $(PAM_LIBS) \ $(SYSTEMD_DAEMON_LIBS) \ + $(GSSAPI_KRB5_LIBS) \ libsss_certmap.la \ $(SSSD_INTERNAL_LTLIBS) \ libsss_iface.la \ @@ -2708,6 +2711,7 @@ pam_srv_tests_SOURCES = \ src/sss_client/pam_message.c \ src/responder/pam/pamsrv_cmd.c \ src/responder/pam/pamsrv_p11.c \ + src/responder/pam/pamsrv_gssapi.c \ src/responder/pam/pam_helpers.c \ src/responder/pam/pamsrv_dp.c \ src/responder/pam/pam_LOCAL_domain.c \ @@ -2719,6 +2723,7 @@ pam_srv_tests_CFLAGS = \ -I$(abs_builddir)/src \ $(AM_CFLAGS) \ $(CMOCKA_CFLAGS) \ + $(GSSAPI_KRB5_CFLAGS) \ $(NULL) pam_srv_tests_LDFLAGS = \ -Wl,-wrap,sss_packet_get_body \ @@ -2734,6 +2739,7 @@ pam_srv_tests_LDADD = \ $(SSSD_LIBS) \ $(SSSD_INTERNAL_LTLIBS) \ $(SYSTEMD_DAEMON_LIBS) \ + $(GSSAPI_KRB5_LIBS) \ libsss_test_common.la \ libsss_idmap.la \ libsss_certmap.la \ @@ -4145,6 +4151,28 @@ pam_sss_la_LDFLAGS = \ -avoid-version \ -Wl,--version-script,$(srcdir)/src/sss_client/sss_pam.exports +pamlib_LTLIBRARIES += pam_sss_gss.la +pam_sss_gss_la_SOURCES = \ + src/sss_client/pam_sss_gss.c \ + src/sss_client/common.c \ + $(NULL) + +pam_sss_gss_la_CFLAGS = \ + $(AM_CFLAGS) \ + $(GSSAPI_KRB5_CFLAGS) \ + $(NULL) + +pam_sss_gss_la_LIBADD = \ + $(CLIENT_LIBS) \ + $(PAM_LIBS) \ + $(GSSAPI_KRB5_LIBS) \ + $(NULL) + +pam_sss_gss_la_LDFLAGS = \ + -module \ + -avoid-version \ + -Wl,--version-script,$(srcdir)/src/sss_client/pam_sss_gss.exports + if BUILD_SUDO libsss_sudo_la_SOURCES = \ @@ -4183,7 +4211,10 @@ endif dist_noinst_DATA += \ src/sss_client/sss_nss.exports \ - src/sss_client/sss_pam.exports + src/sss_client/sss_pam.exports \ + src/sss_client/pam_sss_gss.exports \ + $(NULL) + if BUILD_SUDO dist_noinst_DATA += src/sss_client/sss_sudo.exports endif diff --git a/configure.ac b/configure.ac index 1af1d1785f8..c516a8b8bac 100644 --- a/configure.ac +++ b/configure.ac @@ -181,6 +181,7 @@ m4_include([src/external/libldb.m4]) m4_include([src/external/libdhash.m4]) m4_include([src/external/libcollection.m4]) m4_include([src/external/libini_config.m4]) +m4_include([src/external/libgssapi_krb5.m4]) m4_include([src/external/pam.m4]) m4_include([src/external/ldap.m4]) m4_include([src/external/libpcre.m4]) diff --git a/contrib/sssd.spec.in b/contrib/sssd.spec.in index ed81da53569..f7e5ce13324 100644 --- a/contrib/sssd.spec.in +++ b/contrib/sssd.spec.in @@ -1166,6 +1166,7 @@ done %license src/sss_client/COPYING src/sss_client/COPYING.LESSER /%{_lib}/libnss_sss.so.2 /%{_lib}/security/pam_sss.so +/%{_lib}/security/pam_sss_gss.so %{_libdir}/krb5/plugins/libkrb5/sssd_krb5_locator_plugin.so %{_libdir}/krb5/plugins/authdata/sssd_pac_plugin.so %if (0%{?with_cifs_utils_plugin} == 1) @@ -1178,6 +1179,7 @@ done %dir %{_libdir}/%{name}/modules %{_libdir}/%{name}/modules/sssd_krb5_localauth_plugin.so %{_mandir}/man8/pam_sss.8* +%{_mandir}/man8/pam_sss_gss.8* %{_mandir}/man8/sssd_krb5_locator_plugin.8* %files -n libsss_sudo diff --git a/src/external/libgssapi_krb5.m4 b/src/external/libgssapi_krb5.m4 new file mode 100644 index 00000000000..67f3c464d8c --- /dev/null +++ b/src/external/libgssapi_krb5.m4 @@ -0,0 +1,8 @@ +AC_SUBST(GSSAPI_KRB5_CFLAGS) +AC_SUBST(GSSAPI_KRB5_LIBS) + +PKG_CHECK_MODULES(GSSAPI_KRB5, + krb5-gssapi, + , + AC_MSG_ERROR("Please install krb5-devel") + ) diff --git a/src/man/Makefile.am b/src/man/Makefile.am index 351ab80151e..c6890a792ed 100644 --- a/src/man/Makefile.am +++ b/src/man/Makefile.am @@ -69,8 +69,8 @@ man_MANS = \ sssd.8 sssd.conf.5 sssd-ldap.5 sssd-ldap-attributes.5 \ sssd-krb5.5 sssd-simple.5 sss-certmap.5 \ sssd_krb5_locator_plugin.8 \ - pam_sss.8 sss_obfuscate.8 sss_cache.8 sss_debuglevel.8 sss_seed.8 \ - sss_override.8 idmap_sss.8 sssctl.8 sssd-session-recording.5 \ + pam_sss.8 pam_sss_gss.8 sss_obfuscate.8 sss_cache.8 sss_debuglevel.8 \ + sss_seed.8 sss_override.8 idmap_sss.8 sssctl.8 sssd-session-recording.5 \ $(NULL) if BUILD_LOCAL_PROVIDER diff --git a/src/man/pam_sss_gss.8.xml b/src/man/pam_sss_gss.8.xml new file mode 100644 index 00000000000..ee1fadf9188 --- /dev/null +++ b/src/man/pam_sss_gss.8.xml @@ -0,0 +1,160 @@ + + + +SSSD Manual pages + + + + + pam_sss_gss + 8 + + + + pam_sss_gss + PAM module for SSSD GSSAPI authentication + + + + + pam_sss_gss.so + + debug + + + + + + DESCRIPTION + + pam_sss_gss.so authenticates user + over GSSAPI in cooperation with SSSD. + + + This module will try to authenticate the user using host@hostname + service ticket (which translates to host/hostname@REALM Kerberos + principal). If the ticket is already present in the Kerberos + credentials cache or if user's ticket granting ticket can be used + to get the correct service ticket then the user will be + authenticated. + + + SSSD is used to provide correct service name that should be used + for validation (host@hostname where hostname is determined from + user's domain) and later to validate the user's credentials. + + + To enable GSSAPI authentication in SSSD, set + option in [pam] or domain + section of sssd.conf. The service credentials need to be stored + in SSSD's keytab (it is already present if you use ipa or ad + provider). The keytab location can be set with + option. See + + sssd.conf + 5 + and + + sssd-krb5 + 5 + for more details on these options. + + + + + OPTIONS + + + + + + + Print debugging information. + + + + + + + MODULE TYPES PROVIDED + Only the module type is provided. + + + + RETURN VALUES + + + PAM_SUCCESS + + + The PAM operation finished successfully. + + + + + PAM_USER_UNKNOWN + + + The user is not known to the authentication service or + the GSSAPI authentication is not supported. + + + + + PAM_AUTH_ERR + + + Authentication failure. + + + + + PAM_AUTHINFO_UNAVAIL + + + Unable to access the authentication information. + This might be due to a network or hardware failure. + + + + + PAM_SYSTEM_ERR + + + A system error occurred. The SSSD log files may contain + additional information about the error. + + + + + + + + EXAMPLES + + The main use case is to provide password-less authentication in + sudo but without the need to disable authentication completely. + To achieve this, first enable GSSAPI authentication for sudo in + sssd.conf: + + +[domain/MYDOMAIN] +pam_gssapi_services = sudo, sudo-i + + + And then enable the module in desired PAM stack + (e.g. /etc/pam.d/sudo and /etc/pam.d/sudo-i). + + +... +auth sufficient pam_sss_gss.so +... + + + + + + + diff --git a/src/responder/pam/pamsrv.h b/src/responder/pam/pamsrv.h index 730dee2881f..23ba014af65 100644 --- a/src/responder/pam/pamsrv.h +++ b/src/responder/pam/pamsrv.h @@ -144,4 +144,8 @@ errno_t pam_eval_prompting_config(struct pam_ctx *pctx, struct pam_data *pd); enum pam_initgroups_scheme pam_initgroups_string_to_enum(const char *str); const char *pam_initgroup_enum_to_string(enum pam_initgroups_scheme scheme); + +int pam_cmd_gssapi_init(struct cli_ctx *cli_ctx); +int pam_cmd_gssapi_sec_ctx(struct cli_ctx *cctx); + #endif /* __PAMSRV_H__ */ diff --git a/src/responder/pam/pamsrv_cmd.c b/src/responder/pam/pamsrv_cmd.c index acbfc0c39f4..9ea488be4f4 100644 --- a/src/responder/pam/pamsrv_cmd.c +++ b/src/responder/pam/pamsrv_cmd.c @@ -2401,6 +2401,8 @@ struct sss_cmd_table *get_pam_cmds(void) {SSS_PAM_CHAUTHTOK, pam_cmd_chauthtok}, {SSS_PAM_CHAUTHTOK_PRELIM, pam_cmd_chauthtok_prelim}, {SSS_PAM_PREAUTH, pam_cmd_preauth}, + {SSS_GSSAPI_INIT, pam_cmd_gssapi_init}, + {SSS_GSSAPI_SEC_CTX, pam_cmd_gssapi_sec_ctx}, {SSS_CLI_NULL, NULL} }; diff --git a/src/responder/pam/pamsrv_gssapi.c b/src/responder/pam/pamsrv_gssapi.c new file mode 100644 index 00000000000..39364e2c880 --- /dev/null +++ b/src/responder/pam/pamsrv_gssapi.c @@ -0,0 +1,594 @@ +/* + Authors: + Pavel Březina + + Copyright (C) 2020 Red Hat + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see . +*/ + +#include +#include +#include +#include +#include +#include + +#include "responder/common/responder_packet.h" +#include "responder/common/responder.h" +#include "responder/common/cache_req/cache_req.h" +#include "responder/pam/pamsrv.h" +#include "sss_client/sss_cli.h" +#include "util/util.h" +#include "util/sss_utf8.h" + +static errno_t read_str(size_t body_len, + uint8_t *body, + size_t *pctr, + const char **_str) +{ + size_t i; + + for (i = *pctr; i < body_len; i++) { + if (body[i] == '\0') { + break; + } + } + + if (i >= body_len) { + return EINVAL; + } + + if (!sss_utf8_check(&body[*pctr], i - *pctr)) { + DEBUG(SSSDBG_CRIT_FAILURE, "Body is not UTF-8 string!\n"); + return EINVAL; + } + + *_str = (const char *)&body[*pctr]; + *pctr = i + 1; + + return EOK; +} + +static bool pam_gssapi_allowed(struct pam_ctx *pam_ctx, + struct sss_domain_info *domain, + const char *service) +{ + char **list = pam_ctx->gssapi_services; + + if (domain->gssapi_services != NULL) { + list = domain->gssapi_services; + } + + return string_in_list(service, list, true); +} + + static char *pam_gssapi_target(TALLOC_CTX *mem_ctx, + struct sss_domain_info *domain) +{ + return talloc_asprintf(mem_ctx, "host@%s", domain->hostname); +} + +static errno_t pam_gssapi_init_parse(struct cli_protocol *pctx, + const char **_service, + const char **_username) +{ + size_t body_len; + uint8_t *body; + size_t pctr; + errno_t ret; + + sss_packet_get_body(pctx->creq->in, &body, &body_len); + if (body == NULL) { + DEBUG(SSSDBG_CRIT_FAILURE, "Invalid input\n"); + return EINVAL; + } + + pctr = 0; + ret = read_str(body_len, body, &pctr, _service); + if (ret != EOK) { + return ret; + } + + ret = read_str(body_len, body, &pctr, _username); + if (ret != EOK) { + return ret; + } + + return EOK; +} + +static errno_t pam_gssapi_init_reply(struct cli_protocol *pctx, + const char *domain, + const char *target) +{ + size_t reply_len; + size_t body_len; + size_t pctr; + uint8_t *body; + errno_t ret; + + ret = sss_packet_new(pctx->creq, 0, sss_packet_get_cmd(pctx->creq->in), + &pctx->creq->out); + if (ret != EOK) { + DEBUG(SSSDBG_CRIT_FAILURE, "Unable to create a new packet [%d]; %s\n", + ret, sss_strerror(ret)); + return ret; + } + + reply_len = strlen(domain) + 1 + strlen(target) + 1; + + ret = sss_packet_grow(pctx->creq->out, reply_len); + if (ret != EOK) { + DEBUG(SSSDBG_CRIT_FAILURE, "Unable to create response: %s\n", + sss_strerror(ret)); + return ret; + } + + sss_packet_get_body(pctx->creq->out, &body, &body_len); + + pctr = 0; + SAFEALIGN_SETMEM_STRING(&body[pctr], domain, strlen(domain) + 1, &pctr); + SAFEALIGN_SETMEM_STRING(&body[pctr], target, strlen(target) + 1, &pctr); + + return EOK; +} + +struct gssapi_init_state { + struct cli_ctx *cli_ctx; + const char *username; + const char *service; +}; + +static void pam_cmd_gssapi_init_done(struct tevent_req *req); + +int pam_cmd_gssapi_init(struct cli_ctx *cli_ctx) +{ + struct gssapi_init_state *state; + struct cli_protocol *pctx; + struct tevent_req *req; + const char *username; + const char *service; + errno_t ret; + + state = talloc_zero(cli_ctx, struct gssapi_init_state); + if (state == NULL) { + return ENOMEM; + } + + pctx = talloc_get_type(cli_ctx->protocol_ctx, struct cli_protocol); + + ret = pam_gssapi_init_parse(pctx, &service, &username); + if (ret != EOK) { + DEBUG(SSSDBG_CRIT_FAILURE, "Unable to parse input [%d]: %s\n", + ret, sss_strerror(ret)); + goto done; + } + + state->cli_ctx = cli_ctx; + state->service = service; + state->username = username; + + DEBUG(SSSDBG_TRACE_ALL, + "Requesting GSSAPI authentication of [%s] in service [%s]\n", + username, service); + + req = cache_req_user_by_name_send(cli_ctx, cli_ctx->ev, cli_ctx->rctx, + cli_ctx->rctx->ncache, 0, + CACHE_REQ_POSIX_DOM, NULL, username); + if (req == NULL) { + DEBUG(SSSDBG_CRIT_FAILURE, "Out of memory!\n"); + ret = ENOMEM; + goto done; + } + + tevent_req_set_callback(req, pam_cmd_gssapi_init_done, state); + + ret = EOK; + +done: + if (ret != EOK) { + sss_cmd_send_error(cli_ctx, ret); + sss_cmd_done(cli_ctx, NULL); + } + + return EOK; +} + +static void pam_cmd_gssapi_init_done(struct tevent_req *req) +{ + struct gssapi_init_state *state; + struct cache_req_result *result; + struct cli_protocol *pctx; + struct pam_ctx *pam_ctx; + char *target; + errno_t ret; + + state = tevent_req_callback_data(req, struct gssapi_init_state); + pctx = talloc_get_type(state->cli_ctx->protocol_ctx, struct cli_protocol); + pam_ctx = talloc_get_type(state->cli_ctx->rctx->pvt_ctx, struct pam_ctx); + + ret = cache_req_user_by_name_recv(state, req, &result); + talloc_zfree(req); + if (ret == ENOENT || ret == ERR_DOMAIN_NOT_FOUND) { + ret = ENOENT; + goto done; + } else if (ret != EOK) { + goto done; + } + + if (!pam_gssapi_allowed(pam_ctx, result->domain, state->service)) { + ret = ENOTSUP; + goto done; + } + + target = pam_gssapi_target(state, result->domain); + if (target == NULL) { + ret = ENOMEM; + goto done; + } + + ret = pam_gssapi_init_reply(pctx, result->domain->name, target); + if (ret != EOK) { + DEBUG(SSSDBG_CRIT_FAILURE, "Unable to construct reply [%d]: %s\n", + ret, sss_strerror(ret)); + goto done; + } + +done: + DEBUG(SSSDBG_TRACE_FUNC, "Returning [%d]: %s\n", ret, sss_strerror(ret)); + + if (ret == EOK) { + sss_packet_set_error(pctx->creq->out, EOK); + } else { + sss_cmd_send_error(state->cli_ctx, ret); + } + + sss_cmd_done(state->cli_ctx, state); +} + +static void gssapi_log_status(int type, OM_uint32 status_code) +{ + gss_buffer_desc buf; + OM_uint32 message_context; + OM_uint32 minor; + + message_context = 0; + do { + gss_display_status(&minor, status_code, type, GSS_C_NO_OID, + &message_context, &buf); + DEBUG(SSSDBG_OP_FAILURE, "GSSAPI: %.*s\n", (int)buf.length, + (char *)buf.value); + gss_release_buffer(&minor, &buf); + } while (message_context != 0); +} + +static char * gssapi_get_name(TALLOC_CTX *mem_ctx, gss_name_t gss_name) +{ + gss_buffer_desc buf; + OM_uint32 major; + OM_uint32 minor; + char *exported; + + major = gss_display_name(&minor, gss_name, &buf, NULL); + if (major != GSS_S_COMPLETE) { + DEBUG(SSSDBG_CRIT_FAILURE, "Unable to export name\n"); + return NULL; + } + + exported = talloc_strndup(mem_ctx, buf.value, buf.length); + gss_release_buffer(&minor, &buf); + + if (exported == NULL) { + DEBUG(SSSDBG_CRIT_FAILURE, "Out of memory!\n"); + return NULL; + } + + return exported; +} + +struct gssapi_state { + bool established; + gss_ctx_id_t ctx; +}; + +int gssapi_state_destructor(struct gssapi_state *state) +{ + OM_uint32 minor; + + gss_delete_sec_context(&minor, &state->ctx, NULL); + + return 0; +} + +static struct gssapi_state * gssapi_get_state(struct cli_ctx *cli_ctx) +{ + struct gssapi_state *state; + + state = talloc_get_type(cli_ctx->state_ctx, struct gssapi_state); + if (state == NULL) { + state = talloc_zero(cli_ctx, struct gssapi_state); + if (state == NULL) { + return NULL; + } + + state->ctx = GSS_C_NO_CONTEXT; + talloc_set_destructor(state, gssapi_state_destructor); + + cli_ctx->state_ctx = state; + } + + return state; +} + +static errno_t gssapi_get_creds(const char *keytab, + const char *target, + gss_cred_id_t *_creds) +{ + gss_key_value_set_desc cstore = {0, NULL}; + gss_key_value_element_desc el; + gss_buffer_desc name_buf; + gss_name_t name = GSS_C_NO_NAME; + OM_uint32 major; + OM_uint32 minor; + errno_t ret; + + if (keytab != NULL) { + el.key = "keytab"; + el.value = keytab; + cstore.count = 1; + cstore.elements = ⪙ + } + + if (target != NULL) { + name_buf.value = discard_const(target); + name_buf.length = strlen(target); + + major = gss_import_name(&minor, &name_buf, GSS_C_NT_HOSTBASED_SERVICE, + &name); + if (GSS_ERROR(major)) { + DEBUG(SSSDBG_OP_FAILURE, "Could not import name [%s] " + "[maj:0x%x, min:0x%x]\n", target, major, minor); + + gssapi_log_status(GSS_C_GSS_CODE, major); + gssapi_log_status(GSS_C_MECH_CODE, minor); + + ret = EIO; + goto done; + } + } + + major = gss_acquire_cred_from(&minor, name, GSS_C_INDEFINITE, + GSS_C_NO_OID_SET, GSS_C_ACCEPT, &cstore, + _creds, NULL, NULL); + if (GSS_ERROR(major)) { + DEBUG(SSSDBG_OP_FAILURE, "Unable to read credentials from [%s] " + "[maj:0x%x, min:0x%x]\n", keytab, major, minor); + + gssapi_log_status(GSS_C_GSS_CODE, major); + gssapi_log_status(GSS_C_MECH_CODE, minor); + + ret = EIO; + goto done; + } + + ret = EOK; + +done: + gss_release_name(&minor, &name); + + return ret; +} + +static errno_t +gssapi_handshake(struct gssapi_state *state, + struct cli_protocol *pctx, + const char *keytab, + const char *target, + uint8_t *gss_data, + size_t gss_data_len) +{ + OM_uint32 flags = GSS_C_MUTUAL_FLAG; + gss_buffer_desc output = GSS_C_EMPTY_BUFFER; + gss_buffer_desc input; + gss_name_t client_name; + gss_cred_id_t creds; + OM_uint32 ret_flags; + gss_OID mech_type; + OM_uint32 major; + OM_uint32 minor; + char *display_name; + errno_t ret; + + input.value = gss_data; + input.length = gss_data_len; + + ret = gssapi_get_creds(keytab, target, &creds); + if (ret != EOK) { + return ret; + } + + major = gss_accept_sec_context(&minor, &state->ctx, creds, + &input, NULL, &client_name, &mech_type, + &output, &ret_flags, NULL, NULL); + + if (major == GSS_S_CONTINUE_NEEDED || output.length > 0) { + ret = sss_packet_set_body(pctx->creq->out, output.value, output.length); + if (ret != EOK) { + goto done; + } + } + + if (GSS_ERROR(major)) { + DEBUG(SSSDBG_OP_FAILURE, "Unable to establish GSS context " + "[maj:0x%x, min:0x%x]\n", major, minor); + + gssapi_log_status(GSS_C_GSS_CODE, major); + gssapi_log_status(GSS_C_MECH_CODE, minor); + ret = EIO; + goto done; + } + + switch (major) { + case GSS_S_COMPLETE: + if ((ret_flags & flags) != flags) { + DEBUG(SSSDBG_MINOR_FAILURE, + "Negotiated context does not support requested flags\n"); + state->established = false; + ret = EIO; + break; + } + + display_name = gssapi_get_name(state, client_name); + if (display_name == NULL) { + state->established = false; + ret = ENOMEM; + break; + } + + DEBUG(SSSDBG_TRACE_FUNC, "Security context established with [%s]\n", + display_name); + talloc_free(display_name); + + state->established = true; + ret = EOK; + break; + case GSS_S_CONTINUE_NEEDED: + ret = EOK; + break; + default: + DEBUG(SSSDBG_OP_FAILURE, "Unable to establish GSS context, unexpected " + "value: 0x%x\n", major); + ret = EIO; + break; + } + +done: + gss_release_cred(&minor, &creds); + gss_release_buffer(&minor, &output); + + return ret; +} + +static errno_t pam_cmd_gssapi_sec_ctx_parse(struct cli_protocol *pctx, + const char **_pam_service, + const char **_domain, + uint8_t **_gss_data, + size_t *_gss_data_len) +{ + size_t body_len; + uint8_t *body; + size_t pctr; + errno_t ret; + + sss_packet_get_body(pctx->creq->in, &body, &body_len); + if (body == NULL) { + DEBUG(SSSDBG_CRIT_FAILURE, "Invalid input\n"); + return EINVAL; + } + + pctr = 0; + ret = read_str(body_len, body, &pctr, _pam_service); + if (ret != EOK) { + return ret; + } + + ret = read_str(body_len, body, &pctr, _domain); + if (ret != EOK) { + return ret; + } + + *_gss_data = body_len - pctr == 0 ? NULL : body + pctr; + *_gss_data_len = body_len - pctr; + + return EOK; +} + +int +pam_cmd_gssapi_sec_ctx(struct cli_ctx *cli_ctx) +{ + struct sss_domain_info *domain; + struct gssapi_state *state; + struct cli_protocol *pctx; + struct pam_ctx *pam_ctx; + const char *pam_service; + const char *domain_name; + char *target; + size_t gss_data_len; + uint8_t *gss_data; + errno_t ret; + + pctx = talloc_get_type(cli_ctx->protocol_ctx, struct cli_protocol); + pam_ctx = talloc_get_type(cli_ctx->rctx->pvt_ctx, struct pam_ctx); + + ret = sss_packet_new(pctx->creq, 0, sss_packet_get_cmd(pctx->creq->in), + &pctx->creq->out); + if (ret != EOK) { + DEBUG(SSSDBG_CRIT_FAILURE, "Unable to create a new packet [%d]; %s\n", + ret, sss_strerror(ret)); + return ret; + } + + ret = pam_cmd_gssapi_sec_ctx_parse(pctx, &pam_service, &domain_name, + &gss_data, &gss_data_len); + if (ret != EOK) { + DEBUG(SSSDBG_OP_FAILURE, "Unable to parse input data [%d]: %s\n", + ret, sss_strerror(ret)); + goto done; + } + + domain = find_domain_by_name(cli_ctx->rctx->domains, domain_name, false); + if (domain == NULL) { + ret = EINVAL; + goto done; + } + + if (!pam_gssapi_allowed(pam_ctx, domain, pam_service)) { + ret = ENOTSUP; + goto done; + } + + target = pam_gssapi_target(cli_ctx, domain); + if (target == NULL) { + ret = ENOMEM; + goto done; + } + + state = gssapi_get_state(cli_ctx); + if (state == NULL) { + return ENOMEM; + } + + if (state->established) { + DEBUG(SSSDBG_MINOR_FAILURE, + "Security context is already established\n"); + ret = EPERM; + goto done; + } + + ret = gssapi_handshake(state, pctx, domain->krb5_keytab, target, gss_data, + gss_data_len); + +done: + DEBUG(SSSDBG_TRACE_FUNC, "Returning [%d]: %s\n", ret, sss_strerror(ret)); + + if (ret == EOK) { + sss_packet_set_error(pctx->creq->out, EOK); + } else { + sss_cmd_send_error(cli_ctx, ret); + } + + sss_cmd_done(cli_ctx, NULL); + return EOK; +} diff --git a/src/sss_client/pam_sss_gss.c b/src/sss_client/pam_sss_gss.c new file mode 100644 index 00000000000..f44c6e1b042 --- /dev/null +++ b/src/sss_client/pam_sss_gss.c @@ -0,0 +1,477 @@ +/* + Authors: + Pavel Březina + + Copyright (C) 2020 Red Hat + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see . +*/ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include "util/sss_format.h" +#include "sss_client/sss_cli.h" + +bool debug_enabled; + +#define TRACE(pamh, fmt, ...) do { \ + if (debug_enabled) { \ + pam_info(pamh, "pam_sss_gss: " fmt, ## __VA_ARGS__); \ + } \ +} while (0) + +#define ERROR(pamh, fmt, ...) do { \ + if (debug_enabled) { \ + pam_error(pamh, "pam_sss_gss: " fmt, ## __VA_ARGS__); \ + } \ +} while (0) + +static bool switch_euid(pam_handle_t *pamh, uid_t current, uid_t desired) +{ + int ret; + + if (current == desired) { + return true; + } + + TRACE(pamh, "Switching euid from %" SPRIuid " to %" SPRIuid, current, + desired); + + ret = seteuid(desired); + if (ret != 0) { + ERROR(pamh, "Unable to set euid to %" SPRIuid, desired); + return false; + } + + return true; +} + +static const char *get_item_as_string(pam_handle_t *pamh, int item) +{ + const char *str; + int ret; + + ret = pam_get_item(pamh, item, (void *)&str); + if (ret != PAM_SUCCESS || str == NULL || str[0] == '\0') { + return NULL; + } + + return str; +} + +static errno_t string_to_gss_name(pam_handle_t *pamh, + const char *target, + gss_name_t *_name) +{ + gss_buffer_desc name_buf; + OM_uint32 major; + OM_uint32 minor; + + name_buf.value = (void *)(uintptr_t)target; + name_buf.length = strlen(target); + major = gss_import_name(&minor, &name_buf, GSS_C_NT_HOSTBASED_SERVICE, + _name); + if (GSS_ERROR(major)) { + ERROR(pamh, "Could not convert target to GSS name"); + return EIO; + } + + return EOK; +} + +static void gssapi_log_status(pam_handle_t *pamh, + int type, + OM_uint32 status_code) +{ + gss_buffer_desc buf; + OM_uint32 message_context; + OM_uint32 minor; + + message_context = 0; + do { + gss_display_status(&minor, status_code, type, GSS_C_NO_OID, + &message_context, &buf); + ERROR(pamh, "GSSAPI: %.*s", (int)buf.length, (char *)buf.value); + gss_release_buffer(&minor, &buf); + } while (message_context != 0); +} + +static errno_t sssd_gssapi_init_send(pam_handle_t *pamh, + const char *pam_service, + const char *pam_user, + uint8_t **_reply, + size_t *_reply_len) +{ + struct sss_cli_req_data req_data; + size_t service_len; + size_t user_len; + uint8_t *data; + errno_t ret; + int ret_errno; + + if (pam_service == NULL || pam_user == NULL) { + return EINVAL; + } + + service_len = strlen(pam_service) + 1; + user_len = strlen(pam_user) + 1; + + req_data.len = (service_len + user_len) * sizeof(char); + data = (uint8_t*)malloc(req_data.len); + if (data == NULL) { + return ENOMEM; + } + + memcpy(data, pam_service, service_len); + memcpy(data + service_len, pam_user, user_len); + + req_data.data = data; + + ret = sss_pam_make_request(SSS_GSSAPI_INIT, &req_data, _reply, _reply_len, + &ret_errno); + free(data); + if (ret != PAM_SUCCESS) { + ERROR(pamh, "Communication error [%d, %d]: %s", ret, ret_errno, + pam_strerror(pamh, ret)); + return ret_errno != EOK ? ret_errno : EIO; + } + + return ret_errno; +} + +static errno_t sssd_gssapi_init_recv(pam_handle_t *pamh, + uint8_t *reply, + size_t reply_len, + char **_domain, + char **_target) +{ + char *domain = NULL; + char *target = NULL; + const char *buf; + size_t dlen; + size_t pctr; + errno_t ret; + + domain = malloc(reply_len * sizeof(char*)); + target = malloc(reply_len * sizeof(char*)); + if (domain == NULL || target == NULL) { + return ENOMEM; + } + + buf = (const char*)reply; + pctr = 0; + + dlen = reply_len; + ret = sss_readrep_copy_string(buf, &pctr, &reply_len, &dlen, &domain, NULL); + if (ret != EOK) { + goto done; + } + + dlen = reply_len; + ret = sss_readrep_copy_string(buf, &pctr, &reply_len, &dlen, &target, NULL); + if (ret != EOK) { + goto done; + } + + *_domain = domain; + *_target = target; + +done: + if (ret != EOK) { + free(domain); + free(target); + } + + return ret; +} + +static errno_t sssd_gssapi_init(pam_handle_t *pamh, + const char *pam_service, + const char *pam_user, + char **_domain, + char **_target) +{ + size_t reply_len; + uint8_t *reply; + errno_t ret; + + ret = sssd_gssapi_init_send(pamh, pam_service, pam_user, &reply, + &reply_len); + if (ret != EOK) { + return ret; + } + + ret = sssd_gssapi_init_recv(pamh, reply, reply_len, _domain, _target); + free(reply); + + return ret; +} + +static errno_t sssd_establish_sec_ctx_send(pam_handle_t *pamh, + const char *pam_service, + const char *domain, + const void *gss_data, + size_t gss_data_len, + void **_reply, + size_t *_reply_len) +{ + struct sss_cli_req_data req_data; + size_t service_len; + size_t domain_len; + uint8_t *data; + int ret_errno; + int ret; + + service_len = strlen(pam_service) + 1; + domain_len = strlen(domain) + 1; + + req_data.len = (service_len + domain_len) * sizeof(char) + gss_data_len; + data = (uint8_t*)malloc(req_data.len); + if (data == NULL) { + return ENOMEM; + } + + memcpy(data, pam_service, service_len); + memcpy(data + service_len, domain, domain_len); + memcpy(data + service_len + domain_len, gss_data, gss_data_len); + + req_data.data = data; + ret = sss_pam_make_request(SSS_GSSAPI_SEC_CTX, &req_data, (uint8_t**)_reply, + _reply_len, &ret_errno); + free(data); + if (ret != PAM_SUCCESS) { + ERROR(pamh, "Communication error [%d, %d]: %s", ret, ret_errno, + pam_strerror(pamh, ret)); + return ret_errno != EOK ? ret_errno : EIO; + } + + return ret_errno; +} + +static int sssd_establish_sec_ctx(pam_handle_t *pamh, + const char *pam_service, + const char *domain, + const char *target) +{ + bool established; + gss_ctx_id_t ctx = GSS_C_NO_CONTEXT; + gss_buffer_desc input = GSS_C_EMPTY_BUFFER; + gss_buffer_desc output = GSS_C_EMPTY_BUFFER; + OM_uint32 flags = GSS_C_MUTUAL_FLAG; + gss_name_t gss_name; + OM_uint32 ret_flags; + OM_uint32 major; + OM_uint32 minor; + int ret; + + ret = string_to_gss_name(pamh, target, &gss_name); + if (ret != 0) { + return ret; + } + + /* Do the handshake. */ + established = false; + while (!established) { + major = gss_init_sec_context(&minor, GSS_C_NO_CREDENTIAL, &ctx, + gss_name, GSS_C_NO_OID, flags, 0, NULL, + &input, NULL, &output, + &ret_flags, NULL); + + free(input.value); + memset(&input, 0, sizeof(gss_buffer_desc)); + + if (major == GSS_S_CONTINUE_NEEDED || output.length > 0) { + ret = sssd_establish_sec_ctx_send(pamh, pam_service, domain, + output.value, output.length, + &input.value, &input.length); + if (ret != EOK) { + goto done; + } + } + + gss_release_buffer(NULL, &output); + + if (GSS_ERROR(major)) { + ERROR(pamh, "Unable to establish GSS context [maj:0x%x, min:0x%x]", + major, minor); + gssapi_log_status(pamh, GSS_C_GSS_CODE, major); + gssapi_log_status(pamh, GSS_C_MECH_CODE, minor); + ret = EIO; + goto done; + } + + switch (major) + { + case GSS_S_COMPLETE: + established = true; + break; + case GSS_S_CONTINUE_NEEDED: + break; + default: + ERROR(pamh, "Context is not established but major has " + "unexpected value: %x\n", major); + ret = EIO; + goto done; + } + } + + if ((ret_flags & flags) != flags) { + ERROR(pamh, "Negotiated context does not support requested flags\n"); + ret = EIO; + goto done; + } + + ret = EOK; + +done: + gss_delete_sec_context(&minor, &ctx, NULL); + gss_release_name(&minor, &gss_name); + + return ret; +} + +static int errno_to_pam(pam_handle_t *pamh, errno_t ret) +{ + switch (ret) { + case EOK: + TRACE(pamh, "Authentication successful"); + return PAM_SUCCESS; + case ENOENT: + TRACE(pamh, "User not found"); + return PAM_USER_UNKNOWN; + case ENOTSUP: + TRACE(pamh, "GSSAPI authentication is not enabled " + "for given user and service"); + return PAM_USER_UNKNOWN; + case ESSS_NO_SOCKET: + TRACE(pamh, "SSSD socket does not exist"); + return PAM_AUTHINFO_UNAVAIL; + case EPERM: + TRACE(pamh, "Authentication failed"); + return PAM_AUTH_ERR; + default: + TRACE(pamh, "System error [%d]: %s", + ret, strerror(ret)); + return PAM_SYSTEM_ERR; + } +} + +int pam_sm_authenticate(pam_handle_t *pamh, + int flags, + int argc, + const char **argv) +{ + const char *pam_service; + const char *pam_user; + char *domain = NULL; + char *target = NULL; + uid_t uid; + uid_t euid; + errno_t ret; + int i; + + debug_enabled = false; + for (i = 0; i < argc; i++) { + if (strcmp(argv[i], "debug") == 0) { + debug_enabled = true; + break; + } + } + + uid = getuid(); + euid = geteuid(); + + /* Read PAM data. */ + pam_service = get_item_as_string(pamh, PAM_SERVICE); + pam_user = get_item_as_string(pamh, PAM_USER); + if (pam_service == NULL || pam_user == NULL) { + ERROR(pamh, "Unable to get PAM data!"); + ret = EINVAL; + goto done; + } + + /* Initialize GSSAPI authentication with SSSD. Get user domain + * and target GSS service name. */ + TRACE(pamh, "Initializing GSSAPI authentication with SSSD"); + ret = sssd_gssapi_init(pamh, pam_service, pam_user, &domain, &target); + if (ret != EOK) { + goto done; + } + + /* PAM is often called from set-user-id applications (sudo, su). we want to + * make sure that we access credentials of the caller (real uid). */ + if (!switch_euid(pamh, euid, uid)) { + ret = EFAULT; + goto done; + } + + /* Authenticate the user by estabilishing security context. Authorization is + * expected to be done by other modules through pam_access. */ + TRACE(pamh, "Trying to establish security context"); + TRACE(pamh, "User domain: %s, Target name: %s", domain, target); + ret = sssd_establish_sec_ctx(pamh, pam_service, domain, target); + + /* Restore original euid. */ + if (!switch_euid(pamh, uid, euid)) { + ret = EFAULT; + goto done; + } + +done: + sss_pam_close_fd(); + free(domain); + free(target); + + return errno_to_pam(pamh, ret); +} + +int pam_sm_setcred(pam_handle_t *pamh, int flags, int argc, const char **argv) +{ + return PAM_IGNORE; +} + +int pam_sm_acct_mgmt(pam_handle_t *pamh, int flags, int argc, const char **argv) +{ + return PAM_IGNORE; +} + +int pam_sm_open_session(pam_handle_t *pamh, + int flags, + int argc, + const char **argv) +{ + return PAM_IGNORE; +} + +int pam_sm_close_session(pam_handle_t *pamh, + int flags, + int argc, + const char **argv) +{ + return PAM_IGNORE; +} + +int pam_sm_chauthtok(pam_handle_t *pamh, int flags, int argc, const char **argv) +{ + return PAM_IGNORE; +} diff --git a/src/sss_client/pam_sss_gss.exports b/src/sss_client/pam_sss_gss.exports new file mode 100644 index 00000000000..9afa106be96 --- /dev/null +++ b/src/sss_client/pam_sss_gss.exports @@ -0,0 +1,4 @@ +{ + global: + *; +}; diff --git a/src/sss_client/sss_cli.h b/src/sss_client/sss_cli.h index d897f43b74f..2c3c71bc41a 100644 --- a/src/sss_client/sss_cli.h +++ b/src/sss_client/sss_cli.h @@ -233,6 +233,8 @@ enum sss_cli_command { * an authentication request to find * out which authentication methods * are available for the given user. */ + SSS_GSSAPI_INIT = 0x00FA, /**< Initialize GSSAPI authentication. */ + SSS_GSSAPI_SEC_CTX = 0x00FB, /**< Establish GSSAPI security ctx. */ /* PAC responder calls */ SSS_PAC_ADD_PAC_USER = 0x0101, @@ -721,4 +723,10 @@ errno_t sss_readrep_copy_string(const char *in, char **out, size_t *size); +enum pam_gssapi_cmd { + PAM_GSSAPI_GET_NAME, + PAM_GSSAPI_INIT, + PAM_GSSAPI_SENTINEL +}; + #endif /* _SSSCLI_H */ diff --git a/src/tests/dlopen-tests.c b/src/tests/dlopen-tests.c index ccf52abe9c1..bffa021884a 100644 --- a/src/tests/dlopen-tests.c +++ b/src/tests/dlopen-tests.c @@ -47,6 +47,7 @@ struct so { { "libnss_sss.so", { LIBPFX"libnss_sss.so", NULL } }, { "libsss_certmap.so", { LIBPFX"libsss_certmap.so", NULL } }, { "pam_sss.so", { LIBPFX"pam_sss.so", NULL } }, + { "pam_sss_gss.so", { LIBPFX"pam_sss_gss.so", NULL } }, #ifdef BUILD_WITH_LIBSECRET { "libsss_secrets.so", { LIBPFX"libsss_secrets.so", NULL } }, #endif /* BUILD_WITH_LIBSECRET */