[PATCH 01/10] Don't store UID & GID persistently in the context structure

[David Gibson <david@gibson.dropbear.id.au>]

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c->uid and c->gid are first set in conf(), and last used in check_root()
itself called from conf().  Therefore these don't need to be fields in the
long lived context structure and can instead be locals in conf().

Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au>
---
 conf.c  |  8 +++++---
 passt.h |  5 -----
 util.c  | 12 ++++++------
 util.h  |  2 +-
 4 files changed, 12 insertions(+), 15 deletions(-)

diff --git a/conf.c b/conf.c
index 2edb4ae..0fe5266 100644
--- a/conf.c
+++ b/conf.c
@@ -1086,6 +1086,8 @@ void conf(struct ctx *c, int argc, char **argv)
 	uint32_t *dns4 = c->ip4.dns;
 	int name, ret, mask, b, i;
 	unsigned int ifi = 0;
+	uid_t uid = 0;
+	gid_t gid = 0;
 
 	if (c->mode == MODE_PASTA)
 		c->no_dhcp_dns = c->no_dhcp_dns_search = 1;
@@ -1208,12 +1210,12 @@ void conf(struct ctx *c, int argc, char **argv)
 			c->trace = c->debug = c->foreground = 1;
 			break;
 		case 12:
-			if (c->uid || c->gid) {
+			if (uid || gid) {
 				err("Multiple --runas options given");
 				usage(argv[0]);
 			}
 
-			if (conf_runas(optarg, &c->uid, &c->gid)) {
+			if (conf_runas(optarg, &uid, &gid)) {
 				err("Invalid --runas option: %s", optarg);
 				usage(argv[0]);
 			}
@@ -1497,7 +1499,7 @@ void conf(struct ctx *c, int argc, char **argv)
 		}
 	} while (name != -1);
 
-	check_root(c);
+	check_root(&uid, &gid);
 
 	if (c->mode == MODE_PASTA) {
 		if (*netns && optind != argc) {
diff --git a/passt.h b/passt.h
index 347e7c1..3035430 100644
--- a/passt.h
+++ b/passt.h
@@ -144,8 +144,6 @@ struct ip6_ctx {
  * @sock_path:		Path for UNIX domain socket
  * @pcap:		Path for packet capture file
  * @pid_file:		Path to PID file, empty string if not configured
- * @uid:		UID we should drop to, if started as root
- * @gid:		GID we should drop to, if started as root
  * @pasta_netns_fd:	File descriptor for network namespace in pasta mode
  * @pasta_userns_fd:	Descriptor for user namespace to join, -1 once joined
  * @netns_only:		In pasta mode, don't join or create a user namespace
@@ -198,9 +196,6 @@ struct ctx {
 	char pcap[PATH_MAX];
 	char pid_file[PATH_MAX];
 
-	uid_t uid;
-	uid_t gid;
-
 	int pasta_netns_fd;
 	int pasta_userns_fd;
 	int netns_only;
diff --git a/util.c b/util.c
index 7e10deb..b2ccb3d 100644
--- a/util.c
+++ b/util.c
@@ -485,7 +485,7 @@ void drop_caps(void)
 /**
  * check_root() - Check if root in init ns, exit if we can't drop to user
  */
-void check_root(struct ctx *c)
+void check_root(uid_t *uid, gid_t *gid)
 {
 	const char root_uid_map[] = "         0          0 4294967295";
 	struct passwd *pw;
@@ -506,7 +506,7 @@ void check_root(struct ctx *c)
 
 	close(fd);
 
-	if (!c->uid) {
+	if (!*uid) {
 		fprintf(stderr, "Don't run as root. Changing to nobody...\n");
 #ifndef GLIBC_NO_STATIC_NSS
 		pw = getpwnam("nobody");
@@ -515,17 +515,17 @@ void check_root(struct ctx *c)
 			exit(EXIT_FAILURE);
 		}
 
-		c->uid = pw->pw_uid;
-		c->gid = pw->pw_gid;
+		*uid = pw->pw_uid;
+		*gid = pw->pw_gid;
 #else
 		(void)pw;
 
 		/* Common value for 'nobody', not really specified */
-		c->uid = c->gid = 65534;
+		*uid = *gid = 65534;
 #endif
 	}
 
-	if (!setgroups(0, NULL) && !setgid(c->gid) && !setuid(c->uid))
+	if (!setgroups(0, NULL) && !setgid(*gid) && !setuid(*uid))
 		return;
 
 	fprintf(stderr, "Can't change user/group, exiting");
diff --git a/util.h b/util.h
index 8297bec..58312fb 100644
--- a/util.h
+++ b/util.h
@@ -234,7 +234,7 @@ char *line_read(char *buf, size_t len, int fd);
 void procfs_scan_listen(struct ctx *c, uint8_t proto, int ip_version, int ns,
 			uint8_t *map, uint8_t *exclude);
 void drop_caps(void);
-void check_root(struct ctx *c);
+void check_root(uid_t *uid, gid_t *gid);
 int ns_enter(const struct ctx *c);
 void write_pidfile(int fd, pid_t pid);
 int __daemon(int pidfile_fd, int devnull_fd);
-- 
@@ -234,7 +234,7 @@ char *line_read(char *buf, size_t len, int fd);
 void procfs_scan_listen(struct ctx *c, uint8_t proto, int ip_version, int ns,
 			uint8_t *map, uint8_t *exclude);
 void drop_caps(void);
-void check_root(struct ctx *c);
+void check_root(uid_t *uid, gid_t *gid);
 int ns_enter(const struct ctx *c);
 void write_pidfile(int fd, pid_t pid);
 int __daemon(int pidfile_fd, int devnull_fd);
-- 
2.37.3