krb5: Use new function to validate ccaches

This function replaces and combines check_for_valid_tgt() and type specific
functions that checked for ccache existence by using generic krb5 cache
function and executing them as the target user (implicitly validate the
target use rcan properly access the ccache).

Resolves:
https://fedorahosted.org/sssd/ticket/2061

3 files changed, 88 insertions, 371 deletions

diff --git a/src/providers/krb5/krb5_auth.c b/src/providers/krb5/krb5_auth.c
index ca00ce7a..1ea179be 100644
--- a/src/providers/krb5/krb5_auth.c
+++ b/src/providers/krb5/krb5_auth.c
@@ -59,27 +59,25 @@ static errno_t
 check_old_ccache(const char *old_ccache, struct krb5child_req *kr,
                  const char *realm, bool *active, bool *valid)
 {
-    struct sss_krb5_cc_be *old_cc_ops;
     errno_t ret;
 
-    /* ccache file might be of a different type if the user changed
-     * configuration
-     */
-    old_cc_ops = get_cc_be_ops_ccache(old_ccache);
-    if (old_cc_ops == NULL) {
-        DEBUG(SSSDBG_CRIT_FAILURE,
-              ("Cannot get operations on saved ccache %s\n", old_ccache));
-        return EINVAL;
-    }
+    *active = false;
+    *valid = false;
 
-    ret = old_cc_ops->check_existing(old_ccache, kr->uid, realm, kr->upn,
-                                     valid);
-    if (ret == ENOENT) {
+    ret = sss_krb5_cc_verify_ccache(old_ccache,
+                                    kr->uid, kr->gid,
+                                    realm, kr->upn);
+    switch (ret) {
+    case ERR_NOT_FOUND:
         DEBUG(SSSDBG_TRACE_FUNC,
               ("Saved ccache %s doesn't exist.\n", old_ccache));
-        return ret;
-    }
-    if (ret != EOK) {
+        return ENOENT;
+    case EINVAL:
+        /* cache found but no tgt or expired */
+    case EOK:
+        *valid = true;
+        break;
+    default:
         DEBUG(SSSDBG_OP_FAILURE,
               ("Cannot check if saved ccache %s is valid\n",
                old_ccache));
diff --git a/src/providers/krb5/krb5_utils.c b/src/providers/krb5/krb5_utils.c
index 463a5eb4..c4849e74 100644
--- a/src/providers/krb5/krb5_utils.c
+++ b/src/providers/krb5/krb5_utils.c
@@ -761,136 +761,6 @@ done:
     return ret;
 }
 
-static krb5_error_code check_for_valid_tgt(krb5_context context,
-                                           krb5_ccache ccache,
-                                           const char *realm,
-                                           const char *client_princ_str,
-                                           bool *result)
-{
-    krb5_error_code krberr;
-    TALLOC_CTX *tmp_ctx = NULL;
-    krb5_creds mcred;
-    krb5_creds cred;
-    char *server_name = NULL;
-    krb5_principal client_principal = NULL;
-    krb5_principal server_principal = NULL;
-
-    *result = false;
-
-    tmp_ctx = talloc_new(NULL);
-    if (tmp_ctx == NULL) {
-        DEBUG(1, ("talloc_new failed.\n"));
-        return ENOMEM;
-    }
-
-    server_name = talloc_asprintf(tmp_ctx, "krbtgt/%s@%s", realm, realm);
-    if (server_name == NULL) {
-        DEBUG(1, ("talloc_asprintf failed.\n"));
-        krberr = ENOMEM;
-        goto done;
-    }
-
-    krberr = krb5_parse_name(context, server_name, &server_principal);
-    if (krberr != 0) {
-        DEBUG(1, ("krb5_parse_name failed.\n"));
-        goto done;
-    }
-
-    krberr = krb5_parse_name(context, client_princ_str, &client_principal);
-    if (krberr != 0) {
-        DEBUG(1, ("krb5_parse_name failed.\n"));
-        goto done;
-    }
-
-    memset(&mcred, 0, sizeof(mcred));
-    memset(&cred, 0, sizeof(mcred));
-    mcred.client = client_principal;
-    mcred.server = server_principal;
-
-    krberr = krb5_cc_retrieve_cred(context, ccache, 0, &mcred, &cred);
-    if (krberr != 0) {
-        DEBUG(1, ("krb5_cc_retrieve_cred failed.\n"));
-        krberr = 0;
-        goto done;
-    }
-
-    DEBUG(7, ("TGT end time [%d].\n", cred.times.endtime));
-
-    if (cred.times.endtime > time(NULL)) {
-        DEBUG(3, ("TGT is valid.\n"));
-        *result = true;
-    }
-    krb5_free_cred_contents(context, &cred);
-
-    krberr = 0;
-
-done:
-    if (client_principal != NULL) {
-        krb5_free_principal(context, client_principal);
-    }
-    if (server_principal != NULL) {
-        krb5_free_principal(context, server_principal);
-    }
-    talloc_free(tmp_ctx);
-    return krberr;
-}
-
-static errno_t
-check_cc_validity(const char *location,
-                  const char *realm,
-                  const char *princ,
-                  bool *_valid)
-{
-    errno_t ret;
-    bool valid = false;
-    krb5_ccache ccache = NULL;
-    krb5_context context = NULL;
-    krb5_error_code krberr;
-
-    krberr = krb5_init_context(&context);
-    if (krberr) {
-        DEBUG(SSSDBG_CRIT_FAILURE, ("Failed to init kerberos context\n"));
-        return EIO;
-    }
-
-    krberr = krb5_cc_resolve(context, location, &ccache);
-    if (krberr == KRB5_FCC_NOFILE || ccache == NULL) {
-        /* KRB5_FCC_NOFILE would be returned if the directory components
-         * of the DIR cache do not exist, which is the case in /run
-         * after a reboot
-         */
-        DEBUG(SSSDBG_TRACE_FUNC,
-              ("ccache %s is missing or empty\n", location));
-        valid = false;
-        ret = EOK;
-        goto done;
-    } else if (krberr != 0) {
-        KRB5_DEBUG(SSSDBG_OP_FAILURE, context, krberr);
-        DEBUG(SSSDBG_CRIT_FAILURE, ("krb5_cc_resolve failed.\n"));
-        ret = EIO;
-        goto done;
-    }
-
-    krberr = check_for_valid_tgt(context, ccache, realm, princ, &valid);
-    if (krberr != EOK) {
-        KRB5_DEBUG(SSSDBG_OP_FAILURE, context, krberr);
-        DEBUG(SSSDBG_CRIT_FAILURE,
-              ("Could not check if ccache contains a valid principal\n"));
-        ret = EIO;
-        goto done;
-    }
-
-    ret = EOK;
-
-done:
-    if (ret == EOK) {
-        *_valid = valid;
-    }
-    if (ccache) krb5_cc_close(context, ccache);
-    krb5_free_context(context);
-    return ret;
-}
-
 
 struct sss_krb5_ccache {
     struct sss_creds *creds;
@@ -1085,6 +955,78 @@ done:
     return ret;
 }
 
+errno_t sss_krb5_cc_verify_ccache(const char *ccname, uid_t uid, gid_t gid,
+                                  const char *realm, const char *principal)
+{
+    struct sss_krb5_ccache *cc = NULL;
+    TALLOC_CTX *tmp_ctx = NULL;
+    krb5_principal tgt_princ = NULL;
+    krb5_principal princ = NULL;
+    char *tgt_name;
+    krb5_creds mcred = { 0 };
+    krb5_creds cred = { 0 };
+    krb5_error_code kerr;
+    errno_t ret;
+
+    tmp_ctx = talloc_new(NULL);
+    if (tmp_ctx == NULL) {
+        DEBUG(SSSDBG_CRIT_FAILURE, ("talloc_new failed.\n"));
+        return ENOMEM;
+    }
+
+    ret = sss_open_ccache_as_user(tmp_ctx, ccname, uid, gid, &cc);
+    if (ret) {
+        goto done;
+    }
+
+    tgt_name = talloc_asprintf(tmp_ctx, "krbtgt/%s@%s", realm, realm);
+    if (!tgt_name) {
+        DEBUG(SSSDBG_CRIT_FAILURE, ("talloc_new failed.\n"));
+        ret = ENOMEM;
+        goto done;
+    }
+
+    kerr = krb5_parse_name(cc->context, tgt_name, &tgt_princ);
+    if (kerr) {
+        KRB5_DEBUG(SSSDBG_CRIT_FAILURE, cc->context, kerr);
+        if (kerr == KRB5_PARSE_MALFORMED) ret = EINVAL;
+        else ret = ERR_INTERNAL;
+        goto done;
+    }
+
+    kerr = krb5_parse_name(cc->context, principal, &princ);
+    if (kerr) {
+        KRB5_DEBUG(SSSDBG_CRIT_FAILURE, cc->context, kerr);
+        if (kerr == KRB5_PARSE_MALFORMED) ret = EINVAL;
+        else ret = ERR_INTERNAL;
+        goto done;
+    }
+
+    mcred.client = princ;
+    mcred.server = tgt_princ;
+    mcred.times.endtime = time(NULL);
+
+    kerr = krb5_cc_retrieve_cred(cc->context, cc->ccache,
+                                 KRB5_TC_MATCH_TIMES, &mcred, &cred);
+    if (kerr) {
+        if (kerr == KRB5_CC_NOTFOUND) {
+            DEBUG(SSSDBG_TRACE_INTERNAL, ("TGT not found or expired.\n"));
+            ret = EINVAL;
+        } else {
+            KRB5_DEBUG(SSSDBG_CRIT_FAILURE, cc->context, kerr);
+            ret = ERR_INTERNAL;
+        }
+    }
+    krb5_free_cred_contents(cc->context, &cred);
+
+done:
+    if (tgt_princ) krb5_free_principal(cc->context, tgt_princ);
+    if (princ) krb5_free_principal(cc->context, princ);
+    talloc_free(tmp_ctx);
+    return ret;
+}
+
+
 /*======== ccache back end utilities ========*/
 struct sss_krb5_cc_be *
 get_cc_be_ops(enum sss_krb5_cc_type type)
@@ -1139,105 +1081,9 @@ cc_file_create(const char *location, pcre *illegal_re,
     return create_ccache_dir_head(filename, illegal_re, uid, gid, private_path);
 }
 
-static errno_t
-cc_residual_exists(uid_t uid, const char *ccname,
-                   enum sss_krb5_cc_type type)
-{
-    int ret;
-    struct stat stat_buf;
-
-    if (ccname == NULL || *ccname == '\0') {
-        return EINVAL;
-    }
-
-    ret = lstat(ccname, &stat_buf);
-
-    if (ret == -1) {
-        ret = errno;
-        if (ret == ENOENT) {
-            DEBUG(SSSDBG_FUNC_DATA, ("Cache file [%s] does not exist, "
-                                     "it will be recreated\n", ccname));
-            return ENOENT;
-        }
-
-        DEBUG(SSSDBG_OP_FAILURE,
-              ("stat failed [%d][%s].\n", ret, strerror(ret)));
-        return ret;
-    }
-
-    if (stat_buf.st_uid != uid) {
-        DEBUG(SSSDBG_OP_FAILURE,
-              ("Cache file [%s] exists, but is owned by [%d] instead of "
-               "[%d].\n", ccname, stat_buf.st_uid, uid));
-        return EINVAL;
-    }
-
-    switch (type) {
-#ifdef HAVE_KRB5_CC_COLLECTION
-        case SSS_KRB5_TYPE_DIR:
-            ret = S_ISDIR(stat_buf.st_mode);
-            break;
-#endif /* HAVE_KRB5_CC_COLLECTION */
-        case SSS_KRB5_TYPE_FILE:
-            ret = S_ISREG(stat_buf.st_mode);
-            break;
-        default:
-            DEBUG(SSSDBG_CRIT_FAILURE, ("Unsupported ccache type\n"));
-            return EINVAL;
-    }
-
-    if (ret == 0) {
-        DEBUG(SSSDBG_OP_FAILURE,
-              ("Cache file [%s] exists, but is not the expected type\n",
-              ccname));
-        return EINVAL;
-    }
-
-    return EOK;
-}
-
-errno_t
-cc_file_check_existing(const char *location, uid_t uid,
-                       const char *realm, const char *princ,
-                       bool *_valid)
-{
-    errno_t ret;
-    bool valid;
-    const char *filename;
-
-    filename = sss_krb5_residual_check_type(location, SSS_KRB5_TYPE_FILE);
-    if (!filename) {
-        DEBUG(SSSDBG_CRIT_FAILURE, ("%s is not of type FILE:\n", location));
-        return EINVAL;
-    }
-
-    if (filename[0] != '/') {
-        DEBUG(SSSDBG_OP_FAILURE, ("Only absolute path names are allowed.\n"));
-        return EINVAL;
-    }
-
-    ret = cc_residual_exists(uid, filename, SSS_KRB5_TYPE_FILE);
-    if (ret != EOK) {
-        if (ret != ENOENT) {
-            DEBUG(SSSDBG_OP_FAILURE,
-                  ("Could not check if ccache is active.\n"));
-        }
-        return ret;
-    }
-
-    ret = check_cc_validity(location, realm, princ, &valid);
-    if (ret != EOK) {
-        return ret;
-    }
-
-    *_valid = valid;
-    return EOK;
-}
-
 struct sss_krb5_cc_be file_cc = {
     .type               = SSS_KRB5_TYPE_FILE,
     .create             = cc_file_create,
-    .check_existing     = cc_file_check_existing,
 };
 
 #ifdef HAVE_KRB5_CC_COLLECTION
@@ -1257,107 +1103,9 @@ cc_dir_create(const char *location, pcre *illegal_re,
     return create_ccache_dir_head(dir_name, illegal_re, uid, gid, private_path);
 }
 
-errno_t
-cc_dir_check_existing(const char *location, uid_t uid,
-                      const char *realm, const char *princ,
-                      bool *_valid)
-{
-    bool valid;
-    enum sss_krb5_cc_type type;
-    const char *filename;
-    const char *dir;
-    char *tmp;
-    char *primary_file;
-    errno_t ret;
-    TALLOC_CTX *tmp_ctx;
-
-    type = sss_krb5_get_type(location);
-    if (type != SSS_KRB5_TYPE_DIR) {
-        DEBUG(SSSDBG_CRIT_FAILURE, ("%s is not of type DIR:\n", location));
-        return EINVAL;
-    }
-
-    filename = sss_krb5_cc_file_path(location);
-    if (!filename) {
-        DEBUG(SSSDBG_CRIT_FAILURE,
-              ("Existing ccname does not contain path into the collection"));
-        return EINVAL;
-    }
-
-    if (filename[0] != '/') {
-        DEBUG(SSSDBG_CRIT_FAILURE,
-              ("Only absolute path names are allowed.\n"));
-        return EINVAL;
-    }
-
-    tmp_ctx = talloc_new(NULL);
-    if (tmp_ctx == NULL) {
-        DEBUG(SSSDBG_OP_FAILURE, ("talloc_new failed.\n"));
-        return ENOMEM;
-    }
-
-    tmp = talloc_strdup(tmp_ctx, filename);
-    if (!tmp) {
-        DEBUG(SSSDBG_CRIT_FAILURE, ("talloc_strdup failed.\n"));
-        ret = ENOMEM;
-        goto done;
-    }
-
-    if (0 == strncmp(location, "DIR::", 5)) {
-        dir = dirname(tmp);
-        if (!dir) {
-            DEBUG(SSSDBG_CRIT_FAILURE,
-                  ("Cannot get base directory of %s.\n", tmp));
-            ret = EINVAL;
-            goto done;
-        }
-    } else {
-        dir = tmp;
-    }
-
-    ret = cc_residual_exists(uid, dir, SSS_KRB5_TYPE_DIR);
-    if (ret != EOK) {
-        if (ret != ENOENT) {
-            DEBUG(SSSDBG_OP_FAILURE,
-                  ("Could not check if ccache is active.\n"));
-        }
-        goto done;
-    }
-
-    /* If primary file isn't in ccache dir, we will ignore it.
-     * But if primary file has wrong permissions, we will fail.
-     */
-    primary_file = talloc_asprintf(tmp_ctx, "%s/primary", dir);
-    if (!primary_file) {
-        DEBUG(SSSDBG_CRIT_FAILURE, ("talloc_asprintf failed.\n"));
-        ret = ENOMEM;
-        goto done;
-    }
-    ret = cc_residual_exists(uid, primary_file, SSS_KRB5_TYPE_FILE);
-    if (ret != EOK && ret != ENOENT) {
-        DEBUG(SSSDBG_OP_FAILURE,
-              ("Could not check if file 'primary' [%s] in dir ccache"
-               " is active.\n", primary_file));
-        goto done;
-    }
-
-    ret = check_cc_validity(location, realm, princ, &valid);
-    if (ret != EOK) {
-        goto done;
-    }
-
-    *_valid = valid;
-    ret = EOK;
-
-done:
-    talloc_free(tmp_ctx);
-    return ret;
-}
-
 struct sss_krb5_cc_be dir_cc = {
     .type               = SSS_KRB5_TYPE_DIR,
     .create             = cc_dir_create,
-    .check_existing     = cc_dir_check_existing,
 };
 
 
@@ -1381,36 +1129,9 @@ cc_keyring_create(const char *location, pcre *illegal_re,
     return EOK;
 }
 
-errno_t
-cc_keyring_check_existing(const char *location, uid_t uid,
-                          const char *realm, const char *princ,
-                          bool *_valid)
-{
-    errno_t ret;
-    bool valid;
-    const char *residual;
-
-    residual = sss_krb5_residual_check_type(location, SSS_KRB5_TYPE_KEYRING);
-    if (!residual) {
-        DEBUG(SSSDBG_CRIT_FAILURE,
-              ("%s is not of type KEYRING:\n", location));
-        return EINVAL;
-    }
-
-    /* Check if any user is actively using this cache */
-    ret = check_cc_validity(location, realm, princ, &valid);
-    if (ret != EOK) {
-        return ret;
-    }
-
-    *_valid = valid;
-    return EOK;
-}
-
 struct sss_krb5_cc_be keyring_cc = {
     .type               = SSS_KRB5_TYPE_KEYRING,
     .create             = cc_keyring_create,
-    .check_existing     = cc_keyring_check_existing,
 };
 
 #endif /* HAVE_KRB5_CC_COLLECTION */
diff --git a/src/providers/krb5/krb5_utils.h b/src/providers/krb5/krb5_utils.h
index e2416662..b364f87a 100644
--- a/src/providers/krb5/krb5_utils.h
+++ b/src/providers/krb5/krb5_utils.h
@@ -45,16 +45,12 @@ errno_t check_if_cached_upn_needs_update(struct sysdb_ctx *sysdb,
 /* Operations on a credential cache */
 typedef errno_t (*cc_be_create_fn)(const char *location, pcre *illegal_re,
                                    uid_t uid, gid_t gid, bool private_path);
-typedef errno_t (*cc_be_check_existing)(const char *location, uid_t uid,
-                                        const char *realm, const char *princ,
-                                        bool *valid);
 
 /* A ccache back end */
 struct sss_krb5_cc_be {
     enum sss_krb5_cc_type type;
 
     cc_be_create_fn create;
-    cc_be_check_existing check_existing;
 };
 
 extern struct sss_krb5_cc_be file_cc;
@@ -83,6 +79,8 @@ errno_t restore_creds(struct sss_creds *saved_creds);
 errno_t sss_krb5_cc_destroy(const char *ccname, uid_t uid, gid_t gid);
 errno_t sss_krb5_check_ccache_princ(uid_t uid, gid_t gid,
                                     const char *ccname, const char *principal);
+errno_t sss_krb5_cc_verify_ccache(const char *ccname, uid_t uid, gid_t gid,
+                                  const char *realm, const char *principal);
 
 errno_t get_ccache_file_data(const char *ccache_file, const char *client_name,
                              struct tgt_times *tgtt);