| Current File : //root/postfix-3.2.0/src/global/pipe_command.c |
/*++
/* NAME
/* pipe_command 3
/* SUMMARY
/* deliver message to external command
/* SYNOPSIS
/* #include <pipe_command.h>
/*
/* int pipe_command(src, why, key, value, ...)
/* VSTREAM *src;
/* DSN_BUF *why;
/* int key;
/* DESCRIPTION
/* pipe_command() runs a command with a message as standard
/* input. A limited amount of standard output and standard error
/* output is captured for diagnostics purposes.
/*
/* If the command invokes exit() with a non-zero status,
/* the delivery status is taken from an RFC 3463-style code
/* at the beginning of command output. If that information is
/* unavailable, the delivery status is taken from the command
/* exit status as per <sysexits.h>.
/*
/* Arguments:
/* .IP src
/* An open message queue file, positioned at the start of the actual
/* message content.
/* .IP why
/* Delivery status information. The reason attribute may contain
/* a limited portion of command output, among other free text.
/* .IP key
/* Specifies what value will follow. pipe_command() takes a list
/* of macros with arguments, terminated by CA_PIPE_CMD_END which
/* has no argument. The following is a listing of macros and
/* expected argument types.
/* .RS
/* .IP "CA_PIPE_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_PIPE_CMD_COMMAND or CA_PIPE_CMD_ARGV must be specified.
/* See also the CA_PIPE_CMD_SHELL attribute below.
/* .IP "CA_PIPE_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_PIPE_CMD_COMMAND or CA_PIPE_CMD_ARGV must be specified.
/* .IP "CA_PIPE_CMD_CHROOT(const char *)"
/* Root and working directory for command execution. This takes
/* effect before CA_PIPE_CMD_CWD. A null pointer means don't
/* change root and working directory anyway. Failure to change
/* directory causes mail delivery to be deferred.
/* .IP "CA_PIPE_CMD_CWD(const char *)"
/* Working directory for command execution, after changing process
/* privileges to CA_PIPE_CMD_UID and CA_PIPE_CMD_GID. A null pointer means
/* don't change directory anyway. Failure to change directory
/* causes mail delivery to be deferred.
/* .IP "CA_PIPE_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_PIPE_CMD_EXPORT(char **)"
/* Null-terminated array with names of environment parameters
/* that can be exported. By default, everything is exported.
/* .IP "CA_PIPE_CMD_COPY_FLAGS(int)"
/* Flags that are passed on to the \fImail_copy\fR() routine.
/* The default flags value is 0 (zero).
/* .IP "CA_PIPE_CMD_SENDER(const char *)"
/* The envelope sender address, which is passed on to the
/* \fImail_copy\fR() routine.
/* .IP "CA_PIPE_CMD_ORIG_RCPT(const char *)"
/* The original recipient envelope address, which is passed on
/* to the \fImail_copy\fR() routine.
/* .IP "CA_PIPE_CMD_DELIVERED(const char *)"
/* The recipient envelope address, which is passed on to the
/* \fImail_copy\fR() routine.
/* .IP "CA_PIPE_CMD_EOL(const char *)"
/* End-of-line delimiter. The default is to use the newline character.
/* .IP "CA_PIPE_CMD_UID(uid_t)"
/* The user ID to execute the command as. The default is
/* the user ID corresponding to the \fIdefault_privs\fR
/* configuration parameter. The user ID must be non-zero.
/* .IP "CA_PIPE_CMD_GID(gid_t)"
/* The group ID to execute the command as. The default is
/* the group ID corresponding to the \fIdefault_privs\fR
/* configuration parameter. The group ID must be non-zero.
/* .IP "CA_PIPE_CMD_TIME_LIMIT(int)"
/* The amount of time the command is allowed to run before it
/* is terminated with SIGKILL. A non-negative CA_PIPE_CMD_TIME_LIMIT
/* value must be specified.
/* .IP "CA_PIPE_CMD_SHELL(const char *)"
/* The shell to use when executing the command specified with
/* CA_PIPE_CMD_COMMAND. This shell is invoked regardless of the
/* command content.
/* .RE
/* DIAGNOSTICS
/* Panic: interface violations (for example, a zero-valued
/* user ID or group ID, or a missing command).
/*
/* pipe_command() returns one of the following status codes:
/* .IP PIPE_STAT_OK
/* The command has taken responsibility for further delivery of
/* the message.
/* .IP PIPE_STAT_DEFER
/* The command failed with a "try again" type error.
/* The reason is given via the \fIwhy\fR argument.
/* .IP PIPE_STAT_BOUNCE
/* The command indicated that the message was not acceptable,
/* or the command did not finish within the time limit.
/* The reason is given via the \fIwhy\fR argument.
/* .IP PIPE_STAT_CORRUPT
/* The queue file is corrupted.
/* SEE ALSO
/* mail_copy(3) deliver to any.
/* mark_corrupt(3) mark queue file as corrupt.
/* sys_exits(3) sendmail-compatible exit status codes.
/* LICENSE
/* .ad
/* .fi
/* The Secure Mailer license must be distributed with this software.
/* 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 <fcntl.h>
#include <stdlib.h>
#ifdef USE_PATHS_H
#include <paths.h>
#endif
#include <syslog.h>
/* Utility library. */
#include <msg.h>
#include <vstream.h>
#include <msg_vstream.h>
#include <vstring.h>
#include <stringops.h>
#include <iostuff.h>
#include <timed_wait.h>
#include <set_ugid.h>
#include <set_eugid.h>
#include <argv.h>
#include <chroot_uid.h>
/* Global library. */
#include <mail_params.h>
#include <mail_copy.h>
#include <clean_env.h>
#include <pipe_command.h>
#include <exec_command.h>
#include <sys_exits.h>
#include <dsn_util.h>
#include <dsn_buf.h>
/* Application-specific. */
struct pipe_args {
int flags; /* see mail_copy.h */
char *sender; /* envelope sender */
char *orig_rcpt; /* original recipient */
char *delivered; /* envelope recipient */
char *eol; /* carriagecontrol */
char **argv; /* either an array */
char *command; /* or a plain string */
uid_t uid; /* privileges */
gid_t gid; /* privileges */
char **env; /* extra environment */
char **export; /* exportable environment */
char *shell; /* command shell */
char *cwd; /* preferred working directory */
char *chroot; /* root directory */
};
static int pipe_command_timeout; /* command has timed out */
static int pipe_command_maxtime; /* available time to complete */
/* get_pipe_args - capture the variadic argument list */
static void get_pipe_args(struct pipe_args * args, va_list ap)
{
const char *myname = "get_pipe_args";
int key;
/*
* First, set the default values.
*/
args->flags = 0;
args->sender = 0;
args->orig_rcpt = 0;
args->delivered = 0;
args->eol = "\n";
args->argv = 0;
args->command = 0;
args->uid = var_default_uid;
args->gid = var_default_gid;
args->env = 0;
args->export = 0;
args->shell = 0;
args->cwd = 0;
args->chroot = 0;
pipe_command_maxtime = -1;
/*
* Then, override the defaults with user-supplied inputs.
*/
while ((key = va_arg(ap, int)) != PIPE_CMD_END) {
switch (key) {
case PIPE_CMD_COPY_FLAGS:
args->flags |= va_arg(ap, int);
break;
case PIPE_CMD_SENDER:
args->sender = va_arg(ap, char *);
break;
case PIPE_CMD_ORIG_RCPT:
args->orig_rcpt = va_arg(ap, char *);
break;
case PIPE_CMD_DELIVERED:
args->delivered = va_arg(ap, char *);
break;
case PIPE_CMD_EOL:
args->eol = va_arg(ap, char *);
break;
case PIPE_CMD_ARGV:
if (args->command)
msg_panic("%s: got PIPE_CMD_ARGV and PIPE_CMD_COMMAND", myname);
args->argv = va_arg(ap, char **);
break;
case PIPE_CMD_COMMAND:
if (args->argv)
msg_panic("%s: got PIPE_CMD_ARGV and PIPE_CMD_COMMAND", myname);
args->command = va_arg(ap, char *);
break;
case PIPE_CMD_UID:
args->uid = va_arg(ap, uid_t); /* in case uid_t is short */
break;
case PIPE_CMD_GID:
args->gid = va_arg(ap, gid_t); /* in case gid_t is short */
break;
case PIPE_CMD_TIME_LIMIT:
pipe_command_maxtime = va_arg(ap, int);
break;
case PIPE_CMD_ENV:
args->env = va_arg(ap, char **);
break;
case PIPE_CMD_EXPORT:
args->export = va_arg(ap, char **);
break;
case PIPE_CMD_SHELL:
args->shell = va_arg(ap, char *);
break;
case PIPE_CMD_CWD:
args->cwd = va_arg(ap, char *);
break;
case PIPE_CMD_CHROOT:
args->chroot = 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 PIPE_CMD_ARGV or PIPE_CMD_COMMAND", myname);
if (args->uid == 0)
msg_panic("%s: privileged uid", myname);
if (args->gid == 0)
msg_panic("%s: privileged gid", myname);
if (pipe_command_maxtime < 0)
msg_panic("%s: missing or invalid PIPE_CMD_TIME_LIMIT", myname);
}
/* pipe_command_write - write to command with time limit */
static ssize_t pipe_command_write(int fd, void *buf, size_t len,
int unused_timeout,
void *unused_context)
{
int maxtime = (pipe_command_timeout == 0) ? pipe_command_maxtime : 0;
const char *myname = "pipe_command_write";
/*
* Don't wait when all available time was already used up.
*/
if (write_wait(fd, maxtime) < 0) {
if (pipe_command_timeout == 0) {
msg_warn("%s: write time limit exceeded", myname);
pipe_command_timeout = 1;
}
return (0);
} else {
return (write(fd, buf, len));
}
}
/* pipe_command_read - read from command with time limit */
static ssize_t pipe_command_read(int fd, void *buf, size_t len,
int unused_timeout,
void *unused_context)
{
int maxtime = (pipe_command_timeout == 0) ? pipe_command_maxtime : 0;
const char *myname = "pipe_command_read";
/*
* Don't wait when all available time was already used up.
*/
if (read_wait(fd, maxtime) < 0) {
if (pipe_command_timeout == 0) {
msg_warn("%s: read time limit exceeded", myname);
pipe_command_timeout = 1;
}
return (0);
} else {
return (read(fd, buf, len));
}
}
/* kill_command - terminate command forcibly */
static void kill_command(pid_t pid, int sig, uid_t kill_uid, gid_t kill_gid)
{
uid_t saved_euid = geteuid();
gid_t saved_egid = getegid();
/*
* Switch privileges to that of the child process. Terminate the child
* and its offspring.
*/
set_eugid(kill_uid, kill_gid);
if (kill(-pid, sig) < 0 && kill(pid, sig) < 0)
msg_warn("cannot kill process (group) %lu: %m",
(unsigned long) pid);
set_eugid(saved_euid, saved_egid);
}
/* pipe_command_wait_or_kill - wait for command with time limit, or kill it */
static int pipe_command_wait_or_kill(pid_t pid, WAIT_STATUS_T *statusp, int sig,
uid_t kill_uid, gid_t kill_gid)
{
int maxtime = (pipe_command_timeout == 0) ? pipe_command_maxtime : 1;
const char *myname = "pipe_command_wait_or_kill";
int n;
/*
* Don't wait when all available time was already used up.
*/
if ((n = timed_waitpid(pid, statusp, 0, maxtime)) < 0 && errno == ETIMEDOUT) {
if (pipe_command_timeout == 0) {
msg_warn("%s: child wait time limit exceeded", myname);
pipe_command_timeout = 1;
}
kill_command(pid, sig, kill_uid, kill_gid);
n = waitpid(pid, statusp, 0);
}
return (n);
}
/* pipe_child_cleanup - child fatal error handler */
static void pipe_child_cleanup(void)
{
/*
* WARNING: don't place code here. This code may run as mail_owner, as
* root, or as the user/group specified with the "user" attribute. The
* only safe action is to terminate.
*
* Future proofing. If you need exit() here then you broke Postfix.
*/
_exit(EX_TEMPFAIL);
}
/* pipe_command - execute command with extreme prejudice */
int pipe_command(VSTREAM *src, DSN_BUF *why,...)
{
const char *myname = "pipe_command";
va_list ap;
VSTREAM *cmd_in_stream;
VSTREAM *cmd_out_stream;
char log_buf[VSTREAM_BUFSIZE + 1];
ssize_t log_len;
pid_t pid;
int write_status;
int write_errno;
WAIT_STATUS_T wait_status;
int cmd_in_pipe[2];
int cmd_out_pipe[2];
struct pipe_args args;
char **cpp;
ARGV *argv;
DSN_SPLIT dp;
const SYS_EXITS_DETAIL *sp;
/*
* Process the variadic argument list. This also does sanity checks on
* what data the caller is passing to us.
*/
va_start(ap, why);
get_pipe_args(&args, ap);
va_end(ap);
/*
* For convenience...
*/
if (args.command == 0)
args.command = args.argv[0];
/*
* Set up pipes that connect us to the command input and output streams.
* We're using a rather disgusting hack to capture command output: set
* the output to non-blocking mode, and don't attempt to read the output
* until AFTER the process has terminated. The rationale for this is: 1)
* the command output will be used only when delivery fails; 2) the
* amount of output is expected to be small; 3) the output can be
* truncated without too much loss. I could even argue that truncating
* the amount of diagnostic output is a good thing to do, but I won't go
* that far.
*
* Turn on non-blocking writes to the child process so that we can enforce
* timeouts after partial writes.
*
* XXX Too much trouble with different systems returning weird write()
* results when a pipe is writable.
*/
if (pipe(cmd_in_pipe) < 0 || pipe(cmd_out_pipe) < 0)
msg_fatal("%s: pipe: %m", myname);
non_blocking(cmd_out_pipe[1], NON_BLOCKING);
#if 0
non_blocking(cmd_in_pipe[1], NON_BLOCKING);
#endif
/*
* 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_warn("fork: %m");
dsb_unix(why, "4.3.0", sys_exits_detail(EX_OSERR)->text,
"Delivery failed: %m");
return (PIPE_STAT_DEFER);
/*
* Child. Run the child in a separate process group so that the
* parent can kill not just the child but also its offspring.
*
* Redirect fatal exits to our own fatal exit handler (never leave the
* parent's handler enabled :-) so we can replace random exit status
* codes by EX_TEMPFAIL.
*/
case 0:
(void) msg_cleanup(pipe_child_cleanup);
/*
* In order to chroot it is necessary to switch euid back to root.
* Right after chroot we call set_ugid() so all privileges will be
* dropped again.
*
* XXX For consistency we use chroot_uid() to change root+current
* directory. However, we must not use chroot_uid() to change process
* privileges (assuming a version that accepts numeric privileges).
* That would create a maintenance problem, because we would have two
* different code paths to set the external command's privileges.
*/
if (args.chroot) {
seteuid(0);
chroot_uid(args.chroot, (char *) 0);
}
/*
* XXX If we put code before the set_ugid() call, then the code that
* changes root directory must switch back to the mail_owner UID,
* otherwise we'd be running with root privileges.
*/
set_ugid(args.uid, args.gid);
if (setsid() < 0)
msg_warn("setsid failed: %m");
/*
* Pipe plumbing.
*/
close(cmd_in_pipe[1]);
close(cmd_out_pipe[0]);
if (DUP2(cmd_in_pipe[0], STDIN_FILENO) < 0
|| DUP2(cmd_out_pipe[1], STDOUT_FILENO) < 0
|| DUP2(cmd_out_pipe[1], STDERR_FILENO) < 0)
msg_fatal("%s: dup2: %m", myname);
close(cmd_in_pipe[0]);
close(cmd_out_pipe[1]);
/*
* Working directory plumbing.
*/
if (args.cwd && chdir(args.cwd) < 0)
msg_fatal("cannot change directory to \"%s\" for uid=%lu gid=%lu: %m",
args.cwd, (unsigned long) args.uid,
(unsigned long) args.gid);
/*
* 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.
*
* As a safety for buggy libraries, we close the syslog socket.
* Otherwise we could leak a file descriptor that was created by a
* privileged process.
*
* XXX To avoid losing fatal error messages we open a VSTREAM and
* capture the output in the parent process.
*/
closelog();
msg_vstream_init(var_procname, VSTREAM_ERR);
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:
close(cmd_in_pipe[0]);
close(cmd_out_pipe[1]);
cmd_in_stream = vstream_fdopen(cmd_in_pipe[1], O_WRONLY);
cmd_out_stream = vstream_fdopen(cmd_out_pipe[0], O_RDONLY);
/*
* Give the command a limited amount of time to run, by enforcing
* timeouts on all I/O from and to it.
*/
vstream_control(cmd_in_stream,
CA_VSTREAM_CTL_WRITE_FN(pipe_command_write),
CA_VSTREAM_CTL_END);
vstream_control(cmd_out_stream,
CA_VSTREAM_CTL_READ_FN(pipe_command_read),
CA_VSTREAM_CTL_END);
pipe_command_timeout = 0;
/*
* Pipe the message into the command. Examine the error report only
* if we can't recognize a more specific error from the command exit
* status or from the command output.
*/
write_status = mail_copy(args.sender, args.orig_rcpt,
args.delivered, src,
cmd_in_stream, args.flags,
args.eol, why);
write_errno = errno;
/*
* Capture a limited amount of command output, for inclusion in a
* bounce message. Turn tabs and newlines into whitespace, and
* replace other non-printable characters by underscore.
*/
log_len = vstream_fread(cmd_out_stream, log_buf, sizeof(log_buf) - 1);
(void) vstream_fclose(cmd_out_stream);
log_buf[log_len] = 0;
translit(log_buf, "\t\n", " ");
printable(log_buf, '_');
/*
* Just because the child closes its output streams, don't assume
* that it will terminate. Instead, be prepared for the situation
* that the child does not terminate, even when the parent
* experiences no read/write timeout. 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 delivery agents. Do a thorough job, and kill
* not just the child process but also its offspring.
*/
if (pipe_command_timeout)
kill_command(pid, SIGKILL, args.uid, args.gid);
if (pipe_command_wait_or_kill(pid, &wait_status, SIGKILL,
args.uid, args.gid) < 0)
msg_fatal("wait: %m");
if (pipe_command_timeout) {
dsb_unix(why, "5.3.0", log_len ?
log_buf : sys_exits_detail(EX_SOFTWARE)->text,
"Command time limit exceeded: \"%s\"%s%s",
args.command,
log_len ? ". Command output: " : "", log_buf);
return (PIPE_STAT_BOUNCE);
}
/*
* Command exits. Give special treatment to sendmail style exit
* status codes.
*/
if (!NORMAL_EXIT_STATUS(wait_status)) {
if (WIFSIGNALED(wait_status)) {
dsb_unix(why, "4.3.0", log_len ?
log_buf : sys_exits_detail(EX_SOFTWARE)->text,
"Command died with signal %d: \"%s\"%s%s",
WTERMSIG(wait_status), args.command,
log_len ? ". Command output: " : "", log_buf);
return (PIPE_STAT_DEFER);
}
/* Use "D.S.N text" command output. XXX What diagnostic code? */
else if (dsn_valid(log_buf) > 0) {
dsn_split(&dp, "5.3.0", log_buf);
dsb_unix(why, DSN_STATUS(dp.dsn), dp.text, "%s", dp.text);
return (DSN_CLASS(dp.dsn) == '4' ?
PIPE_STAT_DEFER : PIPE_STAT_BOUNCE);
}
/* Use <sysexits.h> compatible exit status. */
else if (SYS_EXITS_CODE(WEXITSTATUS(wait_status))) {
sp = sys_exits_detail(WEXITSTATUS(wait_status));
dsb_unix(why, sp->dsn,
log_len ? log_buf : sp->text, "%s%s%s", sp->text,
log_len ? ". Command output: " : "", log_buf);
return (sp->dsn[0] == '4' ?
PIPE_STAT_DEFER : PIPE_STAT_BOUNCE);
}
/*
* No "D.S.N text" or <sysexits.h> compatible status. Fake it.
*/
else {
sp = sys_exits_detail(WEXITSTATUS(wait_status));
dsb_unix(why, sp->dsn,
log_len ? log_buf : sp->text,
"Command died with status %d: \"%s\"%s%s",
WEXITSTATUS(wait_status), args.command,
log_len ? ". Command output: " : "", log_buf);
return (PIPE_STAT_BOUNCE);
}
} else if (write_status &
MAIL_COPY_STAT_CORRUPT) {
return (PIPE_STAT_CORRUPT);
} else if (write_status && write_errno != EPIPE) {
vstring_prepend(why->reason, "Command failed: ",
sizeof("Command failed: ") - 1);
vstring_sprintf_append(why->reason, ": \"%s\"", args.command);
return (PIPE_STAT_BOUNCE);
} else {
vstring_strcpy(why->reason, log_buf);
return (PIPE_STAT_OK);
}
}
}