upstream commit

add AuthorizedPrincipalsCommand that allows getting
 authorized_principals from a subprocess rather than a file, which is quite
 useful in deployments with large userbases

feedback and ok markus@

Upstream-ID: aa1bdac7b16fc6d2fa3524ef08f04c7258d247f6

1 files changed, 127 insertions, 23 deletions

diff --git a/auth2-pubkey.c b/auth2-pubkey.c
index 553144c7b..c4e80b01b 100644
--- a/auth2-pubkey.c
+++ b/auth2-pubkey.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: auth2-pubkey.c,v 1.50 2015/05/21 06:38:35 djm Exp $ */
+/* $OpenBSD: auth2-pubkey.c,v 1.51 2015/05/21 06:43:30 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  *
@@ -554,19 +554,13 @@ match_principals_option(const char *principal_list, struct sshkey_cert *cert)
 }
 
 static int
-match_principals_file(char *file, struct passwd *pw, struct sshkey_cert *cert)
+process_principals(FILE *f, char *file, struct passwd *pw,
+    struct sshkey_cert *cert)
 {
-        FILE *f;
         char line[SSH_MAX_PUBKEY_BYTES], *cp, *ep, *line_opts;
         u_long linenum = 0;
         u_int i;
 
-        temporarily_use_uid(pw);
-        debug("trying authorized principals file %s", file);
-        if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) {
-                restore_uid();
-                return 0;
-        }
         while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
                 /* Skip leading whitespace. */
                 for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
@@ -594,24 +588,128 @@ match_principals_file(char *file, struct passwd *pw, struct sshkey_cert *cert)
                 }
                 for (i = 0; i < cert->nprincipals; i++) {
                         if (strcmp(cp, cert->principals[i]) == 0) {
-                                debug3("matched principal \"%.100s\" "
-                                    "from file \"%s\" on line %lu",
-                                    cert->principals[i], file, linenum);
+                                debug3("%s:%lu: matched principal \"%.100s\"",
+                                    file == NULL ? "(command)" : file,
+                                    linenum, cert->principals[i]);
                                 if (auth_parse_options(pw, line_opts,
                                     file, linenum) != 1)
                                         continue;
-                                fclose(f);
-                                restore_uid();
                                 return 1;
                         }
                 }
         }
+        return 0;
+}
+
+static int
+match_principals_file(char *file, struct passwd *pw, struct sshkey_cert *cert)
+{
+        FILE *f;
+        int success;
+
+        temporarily_use_uid(pw);
+        debug("trying authorized principals file %s", file);
+        if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) {
+                restore_uid();
+                return 0;
+        }
+        success = process_principals(f, file, pw, cert);
         fclose(f);
         restore_uid();
-        return 0;
+        return success;
 }
 
 /*
+ * Checks whether principal is allowed in output of command.
+ * returns 1 if the principal is allowed or 0 otherwise.
+ */
+static int
+match_principals_command(struct passwd *user_pw, struct sshkey *key)
+{
+        FILE *f = NULL;
+        int ok, found_principal = 0;
+        struct passwd *pw;
+        int i, ac = 0, uid_swapped = 0;
+        pid_t pid;
+        char *tmp, *username = NULL, *command = NULL, **av = NULL;
+        void (*osigchld)(int);
+
+        if (options.authorized_principals_command == NULL)
+                return 0;
+        if (options.authorized_principals_command_user == NULL) {
+                error("No user for AuthorizedPrincipalsCommand specified, "
+                    "skipping");
+                return 0;
+        }
+
+        /*
+         * NB. all returns later this function should go via "out" to
+         * ensure the original SIGCHLD handler is restored properly.
+         */
+        osigchld = signal(SIGCHLD, SIG_DFL);
+
+        /* Prepare and verify the user for the command */
+        username = percent_expand(options.authorized_principals_command_user,
+            "u", user_pw->pw_name, (char *)NULL);
+        pw = getpwnam(username);
+        if (pw == NULL) {
+                error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s",
+                    username, strerror(errno));
+                goto out;
+        }
+
+        /* Turn the command into an argument vector */
+        if (split_argv(options.authorized_principals_command, &ac, &av) != 0) {
+                error("AuthorizedPrincipalsCommand \"%s\" contains "
+                    "invalid quotes", command);
+                goto out;
+        }
+        if (ac == 0) {
+                error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments",
+                    command);
+                goto out;
+        }
+        for (i = 1; i < ac; i++) {
+                tmp = percent_expand(av[i],
+                    "u", user_pw->pw_name,
+                    "h", user_pw->pw_dir,
+                    (char *)NULL);
+                if (tmp == NULL)
+                        fatal("%s: percent_expand failed", __func__);
+                free(av[i]);
+                av[i] = tmp;
+        }
+        /* Prepare a printable command for logs, etc. */
+        command = assemble_argv(ac, av);
+
+        if ((pid = subprocess("AuthorizedPrincipalsCommand", pw, command,
+            ac, av, &f)) == 0)
+                goto out;
+
+        uid_swapped = 1;
+        temporarily_use_uid(pw);
+
+        ok = process_principals(f, NULL, pw, key->cert);
+
+        if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command) != 0)
+                goto out;
+
+        /* Read completed successfully */
+        found_principal = ok;
+ out:
+        if (f != NULL)
+                fclose(f);
+        signal(SIGCHLD, osigchld);
+        for (i = 0; i < ac; i++)
+                free(av[i]);
+        free(av);
+        if (uid_swapped)
+                restore_uid();
+        free(command);
+        free(username);
+        return found_principal;
+}
+/*
  * Checks whether key is allowed in authorized_keys-format file,
  * returns 1 if the key is allowed or 0 otherwise.
  */
@@ -733,7 +831,7 @@ user_cert_trusted_ca(struct passwd *pw, Key *key)
 {
         char *ca_fp, *principals_file = NULL;
         const char *reason;
-        int ret = 0;
+        int ret = 0, found_principal = 0;
 
         if (!key_is_cert(key) || options.trusted_user_ca_keys == NULL)
                 return 0;
@@ -755,14 +853,20 @@ user_cert_trusted_ca(struct passwd *pw, Key *key)
          * against the username.
          */
         if ((principals_file = authorized_principals_file(pw)) != NULL) {
-                if (!match_principals_file(principals_file, pw, key->cert)) {
-                        reason = "Certificate does not contain an "
-                            "authorized principal";
+                if (match_principals_file(principals_file, pw, key->cert))
+                        found_principal = 1;
+        }
+        /* Try querying command if specified */
+        if (!found_principal && match_principals_command(pw, key))
+                found_principal = 1;
+        /* If principals file or command specify, then require a match here */
+        if (!found_principal && (principals_file != NULL ||
+            options.authorized_principals_command != NULL)) {
+                reason = "Certificate does not contain an authorized principal";
  fail_reason:
-                        error("%s", reason);
-                        auth_debug_add("%s", reason);
-                        goto out;
-                }
+                error("%s", reason);
+                auth_debug_add("%s", reason);
+                goto out;
         }
         if (key_cert_check_authority(key, 0, 1,
             principals_file == NULL ? pw->pw_name : NULL, &reason) != 0)