From b4e8bb4725066a979276997ffd3cbf055f14f85b Mon Sep 17 00:00:00 2001
From: Marko Kreen <markokr@gmail.com>
Date: Tue, 4 Mar 2008 12:43:34 +0000
Subject: [PATCH] Cmdline option and config param to support user switching.

Original patch from Jason Coby, applied with minor modifications.
---
 include/system.h |  2 ++
 src/main.c       | 21 ++++++++++++++++++++-
 src/system.c     | 25 +++++++++++++++++++++++++
 3 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/include/system.h b/include/system.h
index 48e45e7..6e07e38 100644
--- a/include/system.h
+++ b/include/system.h
@@ -144,6 +144,8 @@ int getpeereid(int fd, uid_t *uid_p, gid_t *gid_p) _MUSTCHECK;
 const char *basename(const char *path);
 #endif
 
+void change_user(const char *user);
+
 /*
  * memcpy() optimization - improves hash.c.
  *
diff --git a/src/main.c b/src/main.c
index d8b19c9..5fcb5bb 100644
--- a/src/main.c
+++ b/src/main.c
@@ -39,6 +39,7 @@ static const char *usage_str =
 "  -R            Do a online restart\n"
 "  -q            Run quietly\n"
 "  -v            Increase verbosity\n"
+"  -u <username> Assume identity of <username>\n"
 "  -V            Show version\n"
 "  -h            Show this help screen and exit\n";
 
@@ -59,6 +60,7 @@ int cf_pause_mode = P_NONE;
 int cf_shutdown = 0;
 int cf_reboot = 0;
 int cf_syslog = 0;
+char *cf_username = "";
 char *cf_syslog_facility = "daemon";
 static char *cf_config_file;
 
@@ -133,6 +135,7 @@ ConfElem bouncer_params[] = {
 {"default_pool_size",	true, CF_INT, &cf_default_pool_size},
 {"syslog",		true, CF_INT, &cf_syslog},
 {"syslog_facility",	true, CF_STR, &cf_syslog_facility},
+{"user",		false, CF_STR, &cf_username},
 
 {"server_reset_query",	true, CF_STR, &cf_server_reset_query},
 {"server_check_query",	true, CF_STR, &cf_server_check_query},
@@ -563,9 +566,10 @@ int main(int argc, char *argv[])
 {
 	int c;
 	bool did_takeover = false;
+	char *arg_username = NULL;
 
 	/* parse cmdline */
-	while ((c = getopt(argc, argv, "avhdVR")) != EOF) {
+	while ((c = getopt(argc, argv, "avhdVRu:")) != EOF) {
 		switch (c) {
 		case 'R':
 			cf_reboot = 1;
@@ -582,6 +586,9 @@ int main(int argc, char *argv[])
 		case 'q':
 			cf_quiet = 1;
 			break;
+		case 'u':
+			arg_username = optarg;
+			break;
 		case 'h':
 			usage(0, argv[0]);
 		default:
@@ -597,6 +604,18 @@ int main(int argc, char *argv[])
 	init_caches();
 	admin_setup();
 
+	/* prefer cmdline over config for username */
+	if (arg_username)
+		cf_username = arg_username;
+
+	/* switch user is needed */
+	if (*cf_username)
+		change_user(cf_username);
+
+	/* disallow running as root */
+	if (getuid() == 0)
+		fatal("PgBouncer should not run as root");
+
 	/* need to do that after loading config */
 	check_limits();
 
diff --git a/src/system.c b/src/system.c
index 5107001..ce81948 100644
--- a/src/system.c
+++ b/src/system.c
@@ -29,6 +29,8 @@
 #include <sys/ucred.h>
 #endif
 
+#include <pwd.h>
+
 /*
  * Minimal spec-conforming implementations of strlcpy(), strlcat().
  */
@@ -101,3 +103,26 @@ const char *basename(const char *path)
 }
 #endif
 
+void change_user(const char *user)
+{
+	const struct passwd *pw;
+	gid_t gset[1];
+
+	/* check for a valid username */
+	pw = getpwnam(user);
+	if (pw == NULL)
+		fatal("could not find user '%s' to switch to", user);
+	
+	gset[0] = pw->pw_gid;
+	if (getuid() == 0) {
+		if (setgroups(1, gset) < 0)
+			fatal_perror("failed to reset groups");
+	}
+
+	if (setgid(pw->pw_gid) < 0 || setuid(pw->pw_uid) < 0)
+		fatal_perror("failed to assume identity of user '%s'", user);
+
+	if (getuid() != pw->pw_uid || geteuid() != pw->pw_uid)
+		fatal("setuid() failed to work");
+}
+
-- 
2.40.0