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-rw-r--r--src/util/spawn_command.c313
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diff --git a/src/util/spawn_command.c b/src/util/spawn_command.c
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+/*++
+/* NAME
+/* spawn_command 3
+/* SUMMARY
+/* run external command
+/* SYNOPSIS
+/* #include <spawn_command.h>
+/*
+/* WAIT_STATUS_T spawn_command(key, value, ...)
+/* int key;
+/* DESCRIPTION
+/* spawn_command() runs a command in a child process and returns
+/* the command exit status.
+/*
+/* Arguments:
+/* .IP key
+/* spawn_command() takes a list of macros with arguments,
+/* terminated by CA_SPAWN_CMD_END which has no arguments. The
+/* following is a listing of macros and expected argument
+/* types.
+/* .RS
+/* .IP "CA_SPAWN_CMD_COMMAND(const char *)"
+/* Specifies the command to execute as a string. The string is
+/* passed to the shell when it contains shell meta characters
+/* or when it appears to be a shell built-in command, otherwise
+/* the command is executed without invoking a shell.
+/* One of CA_SPAWN_CMD_COMMAND or CA_SPAWN_CMD_ARGV must be specified.
+/* See also the SPAWN_CMD_SHELL attribute below.
+/* .IP "CA_SPAWN_CMD_ARGV(char **)"
+/* The command is specified as an argument vector. This vector is
+/* passed without further inspection to the \fIexecvp\fR() routine.
+/* One of CA_SPAWN_CMD_COMMAND or CA_SPAWN_CMD_ARGV must be specified.
+/* .IP "CA_SPAWN_CMD_ENV(char **)"
+/* Additional environment information, in the form of a null-terminated
+/* list of name, value, name, value, ... elements. By default only the
+/* command search path is initialized to _PATH_DEFPATH.
+/* .IP "CA_SPAWN_CMD_EXPORT(char **)"
+/* Null-terminated array of names of environment parameters that can
+/* be exported. By default, everything is exported.
+/* .IP "CA_SPAWN_CMD_STDIN(int)"
+/* .IP "CA_SPAWN_CMD_STDOUT(int)"
+/* .IP "CA_SPAWN_CMD_STDERR(int)"
+/* Each of these specifies I/O redirection of one of the standard file
+/* descriptors for the command.
+/* .IP "CA_SPAWN_CMD_UID(uid_t)"
+/* The user ID to execute the command as. The value -1 is reserved
+/* and cannot be specified.
+/* .IP "CA_SPAWN_CMD_GID(gid_t)"
+/* The group ID to execute the command as. The value -1 is reserved
+/* and cannot be specified.
+/* .IP "CA_SPAWN_CMD_TIME_LIMIT(int)"
+/* The amount of time in seconds the command is allowed to run before
+/* it is terminated with SIGKILL. The default is no time limit.
+/* .IP "CA_SPAWN_CMD_SHELL(const char *)"
+/* The shell to use when executing the command specified with
+/* CA_SPAWN_CMD_COMMAND. This shell is invoked regardless of the
+/* command content.
+/* .RE
+/* DIAGNOSTICS
+/* Panic: interface violations (for example, a missing command).
+/*
+/* Fatal error: fork() failure, other system call failures.
+/*
+/* spawn_command() returns the exit status as defined by wait(2).
+/* LICENSE
+/* .ad
+/* .fi
+/* The Secure Mailer license must be distributed with this software.
+/* SEE ALSO
+/* exec_command(3) execute command
+/* AUTHOR(S)
+/* Wietse Venema
+/* IBM T.J. Watson Research
+/* P.O. Box 704
+/* Yorktown Heights, NY 10598, USA
+/*--*/
+
+/* System library. */
+
+#include <sys_defs.h>
+#include <sys/wait.h>
+#include <signal.h>
+#include <unistd.h>
+#include <errno.h>
+#include <stdarg.h>
+#include <stdlib.h>
+#ifdef USE_PATHS_H
+#include <paths.h>
+#endif
+#include <syslog.h>
+
+/* Utility library. */
+
+#include <msg.h>
+#include <timed_wait.h>
+#include <set_ugid.h>
+#include <argv.h>
+#include <spawn_command.h>
+#include <exec_command.h>
+#include <clean_env.h>
+
+/* Application-specific. */
+
+struct spawn_args {
+ char **argv; /* argument vector */
+ char *command; /* or a plain string */
+ int stdin_fd; /* read stdin here */
+ int stdout_fd; /* write stdout here */
+ int stderr_fd; /* write stderr here */
+ uid_t uid; /* privileges */
+ gid_t gid; /* privileges */
+ char **env; /* extra environment */
+ char **export; /* exportable environment */
+ char *shell; /* command shell */
+ int time_limit; /* command time limit */
+};
+
+/* get_spawn_args - capture the variadic argument list */
+
+static void get_spawn_args(struct spawn_args * args, int init_key, va_list ap)
+{
+ const char *myname = "get_spawn_args";
+ int key;
+
+ /*
+ * First, set the default values.
+ */
+ args->argv = 0;
+ args->command = 0;
+ args->stdin_fd = -1;
+ args->stdout_fd = -1;
+ args->stderr_fd = -1;
+ args->uid = (uid_t) - 1;
+ args->gid = (gid_t) - 1;
+ args->env = 0;
+ args->export = 0;
+ args->shell = 0;
+ args->time_limit = 0;
+
+ /*
+ * Then, override the defaults with user-supplied inputs.
+ */
+ for (key = init_key; key != SPAWN_CMD_END; key = va_arg(ap, int)) {
+ switch (key) {
+ case SPAWN_CMD_ARGV:
+ if (args->command)
+ msg_panic("%s: specify SPAWN_CMD_ARGV or SPAWN_CMD_COMMAND",
+ myname);
+ args->argv = va_arg(ap, char **);
+ break;
+ case SPAWN_CMD_COMMAND:
+ if (args->argv)
+ msg_panic("%s: specify SPAWN_CMD_ARGV or SPAWN_CMD_COMMAND",
+ myname);
+ args->command = va_arg(ap, char *);
+ break;
+ case SPAWN_CMD_STDIN:
+ args->stdin_fd = va_arg(ap, int);
+ break;
+ case SPAWN_CMD_STDOUT:
+ args->stdout_fd = va_arg(ap, int);
+ break;
+ case SPAWN_CMD_STDERR:
+ args->stderr_fd = va_arg(ap, int);
+ break;
+ case SPAWN_CMD_UID:
+ args->uid = va_arg(ap, uid_t);
+ if (args->uid == (uid_t) (-1))
+ msg_panic("spawn_command: request with reserved user ID: -1");
+ break;
+ case SPAWN_CMD_GID:
+ args->gid = va_arg(ap, gid_t);
+ if (args->gid == (gid_t) (-1))
+ msg_panic("spawn_command: request with reserved group ID: -1");
+ break;
+ case SPAWN_CMD_TIME_LIMIT:
+ args->time_limit = va_arg(ap, int);
+ break;
+ case SPAWN_CMD_ENV:
+ args->env = va_arg(ap, char **);
+ break;
+ case SPAWN_CMD_EXPORT:
+ args->export = va_arg(ap, char **);
+ break;
+ case SPAWN_CMD_SHELL:
+ args->shell = va_arg(ap, char *);
+ break;
+ default:
+ msg_panic("%s: unknown key: %d", myname, key);
+ }
+ }
+ if (args->command == 0 && args->argv == 0)
+ msg_panic("%s: missing SPAWN_CMD_ARGV or SPAWN_CMD_COMMAND", myname);
+ if (args->command == 0 && args->shell != 0)
+ msg_panic("%s: SPAWN_CMD_ARGV cannot be used with SPAWN_CMD_SHELL",
+ myname);
+}
+
+/* spawn_command - execute command with extreme prejudice */
+
+WAIT_STATUS_T spawn_command(int key,...)
+{
+ const char *myname = "spawn_comand";
+ va_list ap;
+ pid_t pid;
+ WAIT_STATUS_T wait_status;
+ struct spawn_args args;
+ char **cpp;
+ ARGV *argv;
+ int err;
+
+ /*
+ * Process the variadic argument list. This also does sanity checks on
+ * what data the caller is passing to us.
+ */
+ va_start(ap, key);
+ get_spawn_args(&args, key, ap);
+ va_end(ap);
+
+ /*
+ * For convenience...
+ */
+ if (args.command == 0)
+ args.command = args.argv[0];
+
+ /*
+ * Spawn off a child process and irrevocably change privilege to the
+ * user. This includes revoking all rights on open files (via the close
+ * on exec flag). If we cannot run the command now, try again some time
+ * later.
+ */
+ switch (pid = fork()) {
+
+ /*
+ * Error. Instead of trying again right now, back off, give the
+ * system a chance to recover, and try again later.
+ */
+ case -1:
+ msg_fatal("fork: %m");
+
+ /*
+ * Child. Run the child in a separate process group so that the
+ * parent can kill not just the child but also its offspring.
+ */
+ case 0:
+ if (args.uid != (uid_t) - 1 || args.gid != (gid_t) - 1)
+ set_ugid(args.uid, args.gid);
+ setsid();
+
+ /*
+ * Pipe plumbing.
+ */
+ if ((args.stdin_fd >= 0 && DUP2(args.stdin_fd, STDIN_FILENO) < 0)
+ || (args.stdout_fd >= 0 && DUP2(args.stdout_fd, STDOUT_FILENO) < 0)
+ || (args.stderr_fd >= 0 && DUP2(args.stderr_fd, STDERR_FILENO) < 0))
+ msg_fatal("%s: dup2: %m", myname);
+
+ /*
+ * Environment plumbing. Always reset the command search path. XXX
+ * That should probably be done by clean_env().
+ */
+ if (args.export)
+ clean_env(args.export);
+ if (setenv("PATH", _PATH_DEFPATH, 1))
+ msg_fatal("%s: setenv: %m", myname);
+ if (args.env)
+ for (cpp = args.env; *cpp; cpp += 2)
+ if (setenv(cpp[0], cpp[1], 1))
+ msg_fatal("setenv: %m");
+
+ /*
+ * Process plumbing. If possible, avoid running a shell.
+ */
+ closelog();
+ if (args.argv) {
+ execvp(args.argv[0], args.argv);
+ msg_fatal("%s: execvp %s: %m", myname, args.argv[0]);
+ } else if (args.shell && *args.shell) {
+ argv = argv_split(args.shell, CHARS_SPACE);
+ argv_add(argv, args.command, (char *) 0);
+ argv_terminate(argv);
+ execvp(argv->argv[0], argv->argv);
+ msg_fatal("%s: execvp %s: %m", myname, argv->argv[0]);
+ } else {
+ exec_command(args.command);
+ }
+ /* NOTREACHED */
+
+ /*
+ * Parent.
+ */
+ default:
+
+ /*
+ * Be prepared for the situation that the child does not terminate.
+ * Make sure that the child terminates before the parent attempts to
+ * retrieve its exit status, otherwise the parent could become stuck,
+ * and the mail system would eventually run out of exec daemons. Do a
+ * thorough job, and kill not just the child process but also its
+ * offspring.
+ */
+ if ((err = timed_waitpid(pid, &wait_status, 0, args.time_limit)) < 0
+ && errno == ETIMEDOUT) {
+ msg_warn("%s: process id %lu: command time limit exceeded",
+ args.command, (unsigned long) pid);
+ kill(-pid, SIGKILL);
+ err = waitpid(pid, &wait_status, 0);
+ }
+ if (err < 0)
+ msg_fatal("wait: %m");
+ return (wait_status);
+ }
+}
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