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From 366631d15723db68fdb5c47e18ff9253689648ab Mon Sep 17 00:00:00 2001
From: Jakub Hrozek <jhrozek@redhat.com>
Date: Fri, 24 Jul 2015 13:13:08 +0200
Subject: [PATCH 57/57] IPA: Always re-fetch the keytab from the IPA server
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Even if a keytab for one-way trust exists, re-fetch the keytab again and
try to use it. Fall back to the previous one if it exists.

This is in order to allow the admin to re-establish the trust keytabs
with a simple sssd restart.

Reviewed-by: Pavel Březina <pbrezina@redhat.com>
---
 Makefile.am                                   |   2 +
 src/providers/ipa/ipa_subdomains.c            |   4 +-
 src/providers/ipa/ipa_subdomains_server.c     |  83 +++++++++----
 src/tests/cmocka/test_ipa_subdomains_server.c | 166 ++++++++++++++++++++++++--
 4 files changed, 221 insertions(+), 34 deletions(-)

diff --git a/Makefile.am b/Makefile.am
index 8b64317d6dce9a1ee8614916395b9afd9f11f382..ed107fd5dc76b768176a3d7236b0bf1c75f212bf 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -2550,6 +2550,8 @@ test_ipa_subdom_server_LDFLAGS = \
     -Wl,-wrap,krb5_kt_default \
     -Wl,-wrap,execle \
     -Wl,-wrap,execve \
+    -Wl,-wrap,rename \
+    -Wl,-wrap,sss_unique_filename \
     $(NULL)
 test_ipa_subdom_server_LDADD = \
     $(PAM_LIBS) \
diff --git a/src/providers/ipa/ipa_subdomains.c b/src/providers/ipa/ipa_subdomains.c
index cec8b3918b8f832e2c7376a867448fe876da6ffc..b2e2fec353f7b168d28a880cb0f1b6181abb1ccb 100644
--- a/src/providers/ipa/ipa_subdomains.c
+++ b/src/providers/ipa/ipa_subdomains.c
@@ -264,7 +264,7 @@ static errno_t ipa_ranges_parse_results(TALLOC_CTX *mem_ctx,
         ret = get_idmap_data_from_range(r, domain_name, &name1, &sid1, &rid1,
                                         &range1, &mapping1);
         if (ret != EOK) {
-            DEBUG(SSSDBG_OP_FAILURE, ("get_idmap_data_from_range failed.\n"));
+            DEBUG(SSSDBG_OP_FAILURE, "get_idmap_data_from_range failed.\n");
             goto done;
         }
         for (d = 0; d < c; d++) {
@@ -272,7 +272,7 @@ static errno_t ipa_ranges_parse_results(TALLOC_CTX *mem_ctx,
                                             &sid2, &rid2, &range2, &mapping2);
             if (ret != EOK) {
                 DEBUG(SSSDBG_OP_FAILURE,
-                      ("get_idmap_data_from_range failed.\n"));
+                      "get_idmap_data_from_range failed.\n");
                 goto done;
             }
 
diff --git a/src/providers/ipa/ipa_subdomains_server.c b/src/providers/ipa/ipa_subdomains_server.c
index 4bfea61e6dd0a02f6b723a39f7ba236c914009b0..dfecab1bc362b5772379bae6d51f9cef8443f225 100644
--- a/src/providers/ipa/ipa_subdomains_server.c
+++ b/src/providers/ipa/ipa_subdomains_server.c
@@ -445,6 +445,17 @@ static void ipa_getkeytab_exec(const char *ccache,
         exit(1);
     }
 
+    /* ipa-getkeytab cannot add keys to an empty file, let's unlink it and only
+     * use the filename */
+    ret = unlink(keytab_path);
+    if (ret == -1) {
+        ret = errno;
+        DEBUG(SSSDBG_CRIT_FAILURE,
+              "Failed to unlink the temporary ccname [%d][%s]\n",
+              ret, sss_strerror(ret));
+        exit(1);
+    }
+
     errno = 0;
     ret = execle(IPA_GETKEYTAB_PATH, IPA_GETKEYTAB_PATH,
                  "-r", "-s", server, "-p", principal, "-k", keytab_path, NULL,
@@ -561,6 +572,7 @@ struct ipa_server_trust_add_state {
     uint32_t direction;
     const char *forest;
     const char *keytab;
+    char *new_keytab;
     const char *principal;
     const char *forest_realm;
     const char *ccache;
@@ -660,21 +672,20 @@ static errno_t ipa_server_trust_add_1way(struct tevent_req *req)
         return EIO;
     }
 
-    ret = ipa_check_keytab(state->keytab,
-                           state->id_ctx->server_mode->kt_owner_uid,
-                           state->id_ctx->server_mode->kt_owner_gid);
-    if (ret == EOK) {
-        DEBUG(SSSDBG_TRACE_FUNC,
-              "Keytab already present, can add the trust\n");
-        return EOK;
-    } else if (ret != ENOENT) {
-        DEBUG(SSSDBG_OP_FAILURE,
-              "Failed to check for keytab: %d\n", ret);
+    state->new_keytab = talloc_asprintf(state, "%sXXXXXX", state->keytab);
+    if (state->new_keytab == NULL) {
+        DEBUG(SSSDBG_CRIT_FAILURE, "Cannot set up ipa_get_keytab\n");
+        return ENOMEM;
+    }
+
+    ret = sss_unique_filename(state, state->new_keytab);
+    if (ret != EOK) {
+        DEBUG(SSSDBG_CRIT_FAILURE, "Cannot create temporary keytab name\n");
         return ret;
     }
 
     DEBUG(SSSDBG_TRACE_FUNC,
-          "No keytab for %s\n", state->subdom->name);
+          "Will re-fetch keytab for %s\n", state->subdom->name);
 
     hostname = dp_opt_get_string(state->id_ctx->ipa_options->basic,
                                  IPA_HOSTNAME);
@@ -691,7 +702,7 @@ static errno_t ipa_server_trust_add_1way(struct tevent_req *req)
                                 state->ccache,
                                 hostname,
                                 state->principal,
-                                state->keytab);
+                                state->new_keytab);
     if (subreq == NULL) {
         return ENOMEM;
     }
@@ -710,23 +721,49 @@ static void ipa_server_trust_1way_kt_done(struct tevent_req *subreq)
     ret = ipa_getkeytab_recv(subreq, NULL);
     talloc_zfree(subreq);
     if (ret != EOK) {
-        DEBUG(SSSDBG_OP_FAILURE, "ipa_getkeytab_recv failed: %d\n", ret);
-        tevent_req_error(req, ret);
-        return;
+        /* Do not fail here, but try to check and use the previous keytab,
+         * if any */
+        DEBUG(SSSDBG_MINOR_FAILURE, "ipa_getkeytab_recv failed: %d\n", ret);
+    } else {
+        DEBUG(SSSDBG_TRACE_FUNC,
+              "Keytab successfully retrieved to %s\n", state->new_keytab);
     }
 
-    DEBUG(SSSDBG_TRACE_FUNC,
-          "Keytab successfully retrieved to %s\n", state->keytab);
-
-    ret = ipa_check_keytab(state->keytab,
+    ret = ipa_check_keytab(state->new_keytab,
                            state->id_ctx->server_mode->kt_owner_uid,
                            state->id_ctx->server_mode->kt_owner_gid);
-    if (ret != EOK) {
-        DEBUG(SSSDBG_OP_FAILURE, "ipa_check_keytab failed: %d\n", ret);
-        tevent_req_error(req, ret);
-        return;
+    if (ret == EOK) {
+        ret = rename(state->new_keytab, state->keytab);
+        if (ret == -1) {
+            ret = errno;
+            DEBUG(SSSDBG_CRIT_FAILURE,
+                "rename failed [%d][%s].\n", ret, strerror(ret));
+            tevent_req_error(req, ret);
+            return;
+        }
+        DEBUG(SSSDBG_TRACE_INTERNAL, "Keytab renamed to %s\n", state->keytab);
+    } else if (ret != EOK) {
+        DEBUG(SSSDBG_MINOR_FAILURE,
+              "Trying to recover and use the previous keytab, if available\n");
+        ret = ipa_check_keytab(state->keytab,
+                               state->id_ctx->server_mode->kt_owner_uid,
+                               state->id_ctx->server_mode->kt_owner_gid);
+        if (ret == EOK) {
+            DEBUG(SSSDBG_TRACE_FUNC,
+                  "The previous keytab %s contains the expected principal\n",
+                  state->keytab);
+        } else {
+            DEBUG(SSSDBG_OP_FAILURE,
+                  "Cannot use the old keytab: %d\n", ret);
+            /* Nothing we can do now */
+            tevent_req_error(req, ret);
+            return;
+        }
     }
 
+    DEBUG(SSSDBG_TRACE_FUNC,
+          "Keytab %s contains the expected principals\n", state->new_keytab);
+
     ret = ipa_server_trust_add_step(req);
     if (ret != EOK) {
         DEBUG(SSSDBG_OP_FAILURE,
diff --git a/src/tests/cmocka/test_ipa_subdomains_server.c b/src/tests/cmocka/test_ipa_subdomains_server.c
index a4cb8c2b7538dc84b74e0227205b73780844b652..fb9bd80e299c05fa230599d442fa361ae757dcd3 100644
--- a/src/tests/cmocka/test_ipa_subdomains_server.c
+++ b/src/tests/cmocka/test_ipa_subdomains_server.c
@@ -66,33 +66,79 @@
 #define ONEWAY_PRINC    DOM_FLAT"$"
 #define ONEWAY_AUTHID   ONEWAY_PRINC"@"SUBDOM_REALM
 
+static bool global_rename_called;
+
 krb5_error_code __wrap_krb5_kt_default(krb5_context context, krb5_keytab *id)
 {
     return krb5_kt_resolve(context, KEYTAB_PATH, id);
 }
 
-static void create_dummy_keytab(void)
+static void create_dummy_keytab(const char *dummy_kt)
 {
     errno_t ret;
 
-    assert_non_null(ONEWAY_KEYTAB);
+    assert_non_null(dummy_kt);
     mock_keytab_with_contents(global_talloc_context,
-                              ONEWAY_KEYTAB, ONEWAY_AUTHID);
+                              dummy_kt, ONEWAY_AUTHID);
 
-    ret = access(ONEWAY_KEYTAB, R_OK);
+    ret = access(dummy_kt, R_OK);
     assert_int_equal(ret, 0);
 }
 
+static int wrap_exec(void)
+{
+    const char *test_kt;
+    const char *fail_creating_kt;
+
+    test_kt = getenv("TEST_KT_ENV");
+    if (test_kt == NULL) {
+        _exit(1);
+    }
+    unsetenv("TEST_KT_ENV");
+
+    fail_creating_kt = getenv("KT_CREATE_FAIL");
+    if (fail_creating_kt != NULL) {
+        _exit(1);
+    }
+
+    create_dummy_keytab(test_kt);
+    _exit(0);
+
+    return 1;   /* Should not happen */
+}
+
 int __wrap_execle(const char *path, const char *arg, ...)
 {
-    create_dummy_keytab();
-    _exit(0);
+    return wrap_exec();
 }
 
 int __wrap_execve(const char *path, const char *arg, ...)
 {
-    create_dummy_keytab();
-    _exit(0);
+    return wrap_exec();
+}
+
+errno_t __real_sss_unique_filename(TALLOC_CTX *owner, char *path_tmpl);
+
+errno_t __wrap_sss_unique_filename(TALLOC_CTX *owner, char *path_tmpl)
+{
+    int ret;
+    int sret;
+
+    ret = __real_sss_unique_filename(owner, path_tmpl);
+    if (ret == EOK) {
+
+        sret = setenv("TEST_KT_ENV", path_tmpl, 1);
+        assert_int_equal(sret, 0);
+    }
+    return ret;
+}
+
+int __real_rename(const char *old, const char *new);
+
+int __wrap_rename(const char *old, const char *new)
+{
+    global_rename_called = true;
+    return __real_rename(old, new);
 }
 
 struct trust_test_ctx {
@@ -100,6 +146,7 @@ struct trust_test_ctx {
     struct be_ctx *be_ctx;
 
     struct ipa_id_ctx *ipa_ctx;
+    bool expect_rename;
 };
 
 static struct ipa_id_ctx *mock_ipa_ctx(TALLOC_CTX *mem_ctx,
@@ -244,6 +291,8 @@ static int test_ipa_server_create_trusts_setup(void **state)
 
     mock_keytab_with_contents(test_ctx, KEYTAB_PATH, KEYTAB_TEST_PRINC);
 
+    global_rename_called = false;
+
     *state = test_ctx;
     return 0;
 }
@@ -260,6 +309,11 @@ static int test_ipa_server_create_trusts_teardown(void **state)
     unlink(ONEWAY_KEYTAB);
     /* Ignore failures */
 
+    /* If a test needs this variable, it should be set again in
+     * each test
+     */
+    unsetenv("KT_CREATE_FAIL");
+
     talloc_free(test_ctx);
     return 0;
 }
@@ -612,6 +666,8 @@ static void test_ipa_server_create_oneway(void **state)
 
     assert_null(test_ctx->ipa_ctx->server_mode->trusts);
 
+    test_ctx->expect_rename = true;
+
     req = ipa_server_create_trusts_send(test_ctx,
                                         test_ctx->tctx->ev,
                                         test_ctx->be_ctx,
@@ -635,6 +691,8 @@ static void test_ipa_server_create_trusts_oneway(struct tevent_req *req)
     talloc_zfree(req);
     assert_int_equal(ret, EOK);
 
+    assert_true(test_ctx->expect_rename == global_rename_called);
+
     ret = access(ONEWAY_KEYTAB, R_OK);
     assert_int_equal(ret, 0);
 
@@ -674,10 +732,46 @@ static void test_ipa_server_create_oneway_kt_exists(void **state)
 
     add_test_1way_subdomains(test_ctx);
 
-    create_dummy_keytab();
+    create_dummy_keytab(ONEWAY_KEYTAB);
     ret = access(ONEWAY_KEYTAB, R_OK);
     assert_int_equal(ret, 0);
 
+    test_ctx->expect_rename = true;
+
+    assert_null(test_ctx->ipa_ctx->server_mode->trusts);
+
+    req = ipa_server_create_trusts_send(test_ctx,
+                                        test_ctx->tctx->ev,
+                                        test_ctx->be_ctx,
+                                        test_ctx->ipa_ctx,
+                                        test_ctx->be_ctx->domain);
+    assert_non_null(req);
+
+    tevent_req_set_callback(req, test_ipa_server_create_trusts_oneway, test_ctx);
+
+    ret = test_ev_loop(test_ctx->tctx);
+    assert_int_equal(ret, ERR_OK);
+}
+
+/* Test scenario where a keytab already exists, but refresh fails. In this case,
+ * sssd should attempt to reuse the previous keytab
+ */
+static void test_ipa_server_create_oneway_kt_refresh_fallback(void **state)
+{
+    struct trust_test_ctx *test_ctx =
+        talloc_get_type(*state, struct trust_test_ctx);
+    struct tevent_req *req;
+    errno_t ret;
+
+    add_test_1way_subdomains(test_ctx);
+
+    create_dummy_keytab(ONEWAY_KEYTAB);
+    ret = access(ONEWAY_KEYTAB, R_OK);
+    assert_int_equal(ret, 0);
+
+    setenv("KT_CREATE_FAIL", "1", 1);
+    test_ctx->expect_rename = false;
+
     assert_null(test_ctx->ipa_ctx->server_mode->trusts);
 
     req = ipa_server_create_trusts_send(test_ctx,
@@ -693,6 +787,54 @@ static void test_ipa_server_create_oneway_kt_exists(void **state)
     assert_int_equal(ret, ERR_OK);
 }
 
+/* Tests case where there's no keytab and retrieving fails. Just fail the
+ * request in that case
+ */
+static void test_ipa_server_create_trusts_oneway_fail(struct tevent_req *req);
+
+static void test_ipa_server_create_oneway_kt_refresh_fail(void **state)
+{
+    struct trust_test_ctx *test_ctx =
+        talloc_get_type(*state, struct trust_test_ctx);
+    struct tevent_req *req;
+    errno_t ret;
+
+    add_test_1way_subdomains(test_ctx);
+
+    setenv("KT_CREATE_FAIL", "1", 1);
+    test_ctx->expect_rename = false;
+
+    assert_null(test_ctx->ipa_ctx->server_mode->trusts);
+
+    req = ipa_server_create_trusts_send(test_ctx,
+                                        test_ctx->tctx->ev,
+                                        test_ctx->be_ctx,
+                                        test_ctx->ipa_ctx,
+                                        test_ctx->be_ctx->domain);
+    assert_non_null(req);
+
+    tevent_req_set_callback(req,
+                            test_ipa_server_create_trusts_oneway_fail,
+                            test_ctx);
+
+    ret = test_ev_loop(test_ctx->tctx);
+    assert_int_equal(ret, ERR_OK);
+}
+
+static void test_ipa_server_create_trusts_oneway_fail(struct tevent_req *req)
+{
+    struct trust_test_ctx *test_ctx = \
+        tevent_req_callback_data(req, struct trust_test_ctx);
+    errno_t ret;
+
+    ret = ipa_server_create_trusts_recv(req);
+    assert_int_not_equal(ret, EOK);
+
+    assert_true(test_ctx->expect_rename == global_rename_called);
+
+    test_ev_done(test_ctx->tctx, EOK);
+}
+
 static void test_ipa_server_trust_oneway_init(void **state)
 {
     struct trust_test_ctx *test_ctx =
@@ -749,6 +891,12 @@ int main(int argc, const char *argv[])
         cmocka_unit_test_setup_teardown(test_ipa_server_create_oneway_kt_exists,
                                         test_ipa_server_create_trusts_setup,
                                         test_ipa_server_create_trusts_teardown),
+        cmocka_unit_test_setup_teardown(test_ipa_server_create_oneway_kt_refresh_fallback,
+                                        test_ipa_server_create_trusts_setup,
+                                        test_ipa_server_create_trusts_teardown),
+        cmocka_unit_test_setup_teardown(test_ipa_server_create_oneway_kt_refresh_fail,
+                                        test_ipa_server_create_trusts_setup,
+                                        test_ipa_server_create_trusts_teardown),
         cmocka_unit_test_setup_teardown(test_ipa_server_trust_oneway_init,
                                         test_ipa_server_create_trusts_setup,
                                         test_ipa_server_create_trusts_teardown),
-- 
2.4.3