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-rw-r--r--src/spawn/spawn.c373
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diff --git a/src/spawn/spawn.c b/src/spawn/spawn.c
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+/*++
+/* NAME
+/* spawn 8
+/* SUMMARY
+/* Postfix external command spawner
+/* SYNOPSIS
+/* \fBspawn\fR [generic Postfix daemon options] command_attributes...
+/* DESCRIPTION
+/* The \fBspawn\fR(8) daemon provides the Postfix equivalent
+/* of \fBinetd\fR.
+/* It listens on a port as specified in the Postfix \fBmaster.cf\fR file
+/* and spawns an external command whenever a connection is established.
+/* The connection can be made over local IPC (such as UNIX-domain
+/* sockets) or over non-local IPC (such as TCP sockets).
+/* The command's standard input, output and error streams are connected
+/* directly to the communication endpoint.
+/*
+/* This daemon expects to be run from the \fBmaster\fR(8) process
+/* manager.
+/* COMMAND ATTRIBUTE SYNTAX
+/* .ad
+/* .fi
+/* The external command attributes are given in the \fBmaster.cf\fR
+/* file at the end of a service definition. The syntax is as follows:
+/* .IP "\fBuser\fR=\fIusername\fR (required)"
+/* .IP "\fBuser\fR=\fIusername\fR:\fIgroupname\fR"
+/* The external command is executed with the rights of the
+/* specified \fIusername\fR. The software refuses to execute
+/* commands with root privileges, or with the privileges of the
+/* mail system owner. If \fIgroupname\fR is specified, the
+/* corresponding group ID is used instead of the group ID
+/* of \fIusername\fR.
+/* .IP "\fBargv\fR=\fIcommand\fR... (required)"
+/* The command to be executed. This must be specified as the
+/* last command attribute.
+/* The command is executed directly, i.e. without interpretation of
+/* shell meta characters by a shell command interpreter.
+/* BUGS
+/* In order to enforce standard Postfix process resource controls,
+/* the \fBspawn\fR(8) daemon runs only one external command at a time.
+/* As such, it presents a noticeable overhead by wasting precious
+/* process resources. The \fBspawn\fR(8) daemon is expected to be
+/* replaced by a more structural solution.
+/* DIAGNOSTICS
+/* The \fBspawn\fR(8) daemon reports abnormal child exits.
+/* Problems are logged to \fBsyslogd\fR(8) or \fBpostlogd\fR(8).
+/* SECURITY
+/* .fi
+/* .ad
+/* This program needs root privilege in order to execute external
+/* commands as the specified user. It is therefore security sensitive.
+/* However the \fBspawn\fR(8) daemon does not talk to the external command
+/* and thus is not vulnerable to data-driven attacks.
+/* CONFIGURATION PARAMETERS
+/* .ad
+/* .fi
+/* Changes to \fBmain.cf\fR are picked up automatically as \fBspawn\fR(8)
+/* processes run for only a limited amount of time. Use the command
+/* "\fBpostfix reload\fR" to speed up a change.
+/*
+/* The text below provides only a parameter summary. See
+/* \fBpostconf\fR(5) for more details including examples.
+/*
+/* In the text below, \fItransport\fR is the first field of the entry
+/* in the \fBmaster.cf\fR file.
+/* RESOURCE AND RATE CONTROL
+/* .ad
+/* .fi
+/* .IP "\fBtransport_time_limit ($command_time_limit)\fR"
+/* A transport-specific override for the command_time_limit parameter
+/* value, where \fItransport\fR is the master.cf name of the message
+/* delivery transport.
+/* MISCELLANEOUS
+/* .ad
+/* .fi
+/* .IP "\fBconfig_directory (see 'postconf -d' output)\fR"
+/* The default location of the Postfix main.cf and master.cf
+/* configuration files.
+/* .IP "\fBdaemon_timeout (18000s)\fR"
+/* How much time a Postfix daemon process may take to handle a
+/* request before it is terminated by a built-in watchdog timer.
+/* .IP "\fBexport_environment (see 'postconf -d' output)\fR"
+/* The list of environment variables that a Postfix process will export
+/* to non-Postfix processes.
+/* .IP "\fBipc_timeout (3600s)\fR"
+/* The time limit for sending or receiving information over an internal
+/* communication channel.
+/* .IP "\fBmail_owner (postfix)\fR"
+/* The UNIX system account that owns the Postfix queue and most Postfix
+/* daemon processes.
+/* .IP "\fBmax_idle (100s)\fR"
+/* The maximum amount of time that an idle Postfix daemon process waits
+/* for an incoming connection before terminating voluntarily.
+/* .IP "\fBmax_use (100)\fR"
+/* The maximal number of incoming connections that a Postfix daemon
+/* process will service before terminating voluntarily.
+/* .IP "\fBprocess_id (read-only)\fR"
+/* The process ID of a Postfix command or daemon process.
+/* .IP "\fBprocess_name (read-only)\fR"
+/* The process name of a Postfix command or daemon process.
+/* .IP "\fBqueue_directory (see 'postconf -d' output)\fR"
+/* The location of the Postfix top-level queue directory.
+/* .IP "\fBsyslog_facility (mail)\fR"
+/* The syslog facility of Postfix logging.
+/* .IP "\fBsyslog_name (see 'postconf -d' output)\fR"
+/* A prefix that is prepended to the process name in syslog
+/* records, so that, for example, "smtpd" becomes "prefix/smtpd".
+/* .PP
+/* Available in Postfix 3.3 and later:
+/* .IP "\fBservice_name (read-only)\fR"
+/* The master.cf service name of a Postfix daemon process.
+/* SEE ALSO
+/* postconf(5), configuration parameters
+/* master(8), process manager
+/* postlogd(8), Postfix logging
+/* syslogd(8), system logging
+/* 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
+/*
+/* Wietse Venema
+/* Google, Inc.
+/* 111 8th Avenue
+/* New York, NY 10011, USA
+/*--*/
+
+/* System library. */
+
+#include <sys_defs.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <pwd.h>
+#include <grp.h>
+#include <fcntl.h>
+#ifdef STRCASECMP_IN_STRINGS_H
+#include <strings.h>
+#endif
+
+/* Utility library. */
+
+#include <msg.h>
+#include <argv.h>
+#include <dict.h>
+#include <mymalloc.h>
+#include <spawn_command.h>
+#include <split_at.h>
+#include <timed_wait.h>
+#include <set_eugid.h>
+
+/* Global library. */
+
+#include <mail_version.h>
+
+/* Single server skeleton. */
+
+#include <mail_params.h>
+#include <mail_server.h>
+#include <mail_conf.h>
+#include <mail_parm_split.h>
+
+/* Application-specific. */
+
+ /*
+ * Tunable parameters. Values are taken from the config file, after
+ * prepending the service name to _name, and so on.
+ */
+int var_command_maxtime; /* system-wide */
+
+ /*
+ * For convenience. Instead of passing around lists of parameters, bundle
+ * them up in convenient structures.
+ */
+typedef struct {
+ char **argv; /* argument vector */
+ uid_t uid; /* command privileges */
+ gid_t gid; /* command privileges */
+ int time_limit; /* per-service time limit */
+} SPAWN_ATTR;
+
+/* get_service_attr - get service attributes */
+
+static void get_service_attr(SPAWN_ATTR *attr, char *service, char **argv)
+{
+ const char *myname = "get_service_attr";
+ struct passwd *pwd;
+ struct group *grp;
+ char *user; /* user name */
+ char *group; /* group name */
+
+ /*
+ * Initialize.
+ */
+ user = 0;
+ group = 0;
+ attr->argv = 0;
+
+ /*
+ * Figure out the command time limit for this transport.
+ */
+ attr->time_limit =
+ get_mail_conf_time2(service, _MAXTIME, var_command_maxtime, 's', 1, 0);
+
+ /*
+ * Iterate over the command-line attribute list.
+ */
+ for ( /* void */ ; *argv != 0; argv++) {
+
+ /*
+ * user=username[:groupname]
+ */
+ if (strncasecmp("user=", *argv, sizeof("user=") - 1) == 0) {
+ user = *argv + sizeof("user=") - 1;
+ if ((group = split_at(user, ':')) != 0) /* XXX clobbers argv */
+ if (*group == 0)
+ group = 0;
+ if ((pwd = getpwnam(user)) == 0)
+ msg_fatal("unknown user name: %s", user);
+ attr->uid = pwd->pw_uid;
+ if (group != 0) {
+ if ((grp = getgrnam(group)) == 0)
+ msg_fatal("unknown group name: %s", group);
+ attr->gid = grp->gr_gid;
+ } else {
+ attr->gid = pwd->pw_gid;
+ }
+ }
+
+ /*
+ * argv=command...
+ */
+ else if (strncasecmp("argv=", *argv, sizeof("argv=") - 1) == 0) {
+ *argv += sizeof("argv=") - 1; /* XXX clobbers argv */
+ attr->argv = argv;
+ break;
+ }
+
+ /*
+ * Bad.
+ */
+ else
+ msg_fatal("unknown attribute name: %s", *argv);
+ }
+
+ /*
+ * Sanity checks. Verify that every member has an acceptable value.
+ */
+ if (user == 0)
+ msg_fatal("missing user= attribute");
+ if (attr->argv == 0)
+ msg_fatal("missing argv= attribute");
+ if (attr->uid == 0)
+ msg_fatal("request to deliver as root");
+ if (attr->uid == var_owner_uid)
+ msg_fatal("request to deliver as mail system owner");
+ if (attr->gid == 0)
+ msg_fatal("request to use privileged group id %ld", (long) attr->gid);
+ if (attr->gid == var_owner_gid)
+ msg_fatal("request to use mail system owner group id %ld", (long) attr->gid);
+ if (attr->uid == (uid_t) (-1))
+ msg_fatal("user must not have user ID -1");
+ if (attr->gid == (gid_t) (-1))
+ msg_fatal("user must not have group ID -1");
+
+ /*
+ * Give the poor tester a clue of what is going on.
+ */
+ if (msg_verbose)
+ msg_info("%s: uid %ld, gid %ld; time %d",
+ myname, (long) attr->uid, (long) attr->gid, attr->time_limit);
+}
+
+/* spawn_service - perform service for client */
+
+static void spawn_service(VSTREAM *client_stream, char *service, char **argv)
+{
+ const char *myname = "spawn_service";
+ static SPAWN_ATTR attr;
+ WAIT_STATUS_T status;
+ ARGV *export_env;
+
+ /*
+ * This routine runs whenever a client connects to the UNIX-domain socket
+ * dedicated to running an external command.
+ */
+ if (msg_verbose)
+ msg_info("%s: service=%s, command=%s...", myname, service, argv[0]);
+
+ /*
+ * Look up service attributes and config information only once. This is
+ * safe since the information comes from a trusted source.
+ */
+ if (attr.argv == 0) {
+ get_service_attr(&attr, service, argv);
+ }
+
+ /*
+ * Execute the command.
+ */
+ export_env = mail_parm_split(VAR_EXPORT_ENVIRON, var_export_environ);
+ status = spawn_command(CA_SPAWN_CMD_STDIN(vstream_fileno(client_stream)),
+ CA_SPAWN_CMD_STDOUT(vstream_fileno(client_stream)),
+ CA_SPAWN_CMD_STDERR(vstream_fileno(client_stream)),
+ CA_SPAWN_CMD_UID(attr.uid),
+ CA_SPAWN_CMD_GID(attr.gid),
+ CA_SPAWN_CMD_ARGV(attr.argv),
+ CA_SPAWN_CMD_TIME_LIMIT(attr.time_limit),
+ CA_SPAWN_CMD_EXPORT(export_env->argv),
+ CA_SPAWN_CMD_END);
+ argv_free(export_env);
+
+ /*
+ * Warn about unsuccessful completion.
+ */
+ if (!NORMAL_EXIT_STATUS(status)) {
+ if (WIFEXITED(status))
+ msg_warn("command %s exit status %d",
+ attr.argv[0], WEXITSTATUS(status));
+ if (WIFSIGNALED(status))
+ msg_warn("command %s killed by signal %d",
+ attr.argv[0], WTERMSIG(status));
+ }
+}
+
+/* pre_accept - see if tables have changed */
+
+static void pre_accept(char *unused_name, char **unused_argv)
+{
+ const char *table;
+
+ if ((table = dict_changed_name()) != 0) {
+ msg_info("table %s has changed -- restarting", table);
+ exit(0);
+ }
+}
+
+/* drop_privileges - drop privileges most of the time */
+
+static void drop_privileges(char *unused_name, char **unused_argv)
+{
+ set_eugid(var_owner_uid, var_owner_gid);
+}
+
+MAIL_VERSION_STAMP_DECLARE;
+
+/* main - pass control to the single-threaded skeleton */
+
+int main(int argc, char **argv)
+{
+ static const CONFIG_TIME_TABLE time_table[] = {
+ VAR_COMMAND_MAXTIME, DEF_COMMAND_MAXTIME, &var_command_maxtime, 1, 0,
+ 0,
+ };
+
+ /*
+ * Fingerprint executables and core dumps.
+ */
+ MAIL_VERSION_STAMP_ALLOCATE;
+
+ single_server_main(argc, argv, spawn_service,
+ CA_MAIL_SERVER_TIME_TABLE(time_table),
+ CA_MAIL_SERVER_POST_INIT(drop_privileges),
+ CA_MAIL_SERVER_PRE_ACCEPT(pre_accept),
+ CA_MAIL_SERVER_PRIVILEGED,
+ 0);
+}
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