Allow specifying uid/gid to map in user namespace

exile.c

@@ -625,6 +625,8 @@ struct exile_policy *exile_init_policy()
 	result->not_dumpable = 1;
 	result->no_new_privs = 1;
 	result->namespace_options = EXILE_UNSHARE_MOUNT | EXILE_UNSHARE_USER;
+	result->namespace_uid = 0;
+	result->namespace_gid = 0;
 	return result;
 }
 
@@ -938,7 +940,7 @@ void exile_free_policy(struct exile_policy *ctxt)
 }
 
 /* Enters the specified namespaces */
-static int enter_namespaces(int namespace_options)
+static int enter_namespaces(int namespace_options, uid_t namespace_uid, gid_t namespace_gid)
 {
 	if(namespace_options & EXILE_UNSHARE_USER)
 	{
@@ -975,7 +977,7 @@ static int enter_namespaces(int namespace_options)
 			EXILE_LOG_ERROR("Failed to open /proc/self/uid_map for writing");
 			return -1;
 		}
-		writesize = snprintf(buf, sizeof(buf), "0 %u 1\n", current_uid);
+		writesize = snprintf(buf, sizeof(buf), "%u %u 1\n", namespace_uid, current_uid);
 		writeret = write(fd, buf, writesize);
 		if(writeret < 0 || writeret < writesize)
 		{
@@ -991,7 +993,7 @@ static int enter_namespaces(int namespace_options)
 			EXILE_LOG_ERROR("Failed to open /proc/self/gid_map for writing");
 			return -1;
 		}
-		writesize = snprintf(buf, sizeof(buf), "0 %u 1\n", current_gid);
+		writesize = snprintf(buf, sizeof(buf), "%u %u 1\n", namespace_gid, current_gid);
 		writeret = write(fd, buf, writesize);
 		if(writeret < 0 || writeret < writesize)
 		{
@@ -1541,7 +1543,7 @@ int exile_enable_policy(struct exile_policy *policy)
 		close_file_fds();
 	}
 
-	if(enter_namespaces(policy->namespace_options) < 0)
+	if(enter_namespaces(policy->namespace_options, policy->namespace_uid, policy->namespace_gid) < 0)
 	{
 		EXILE_LOG_ERROR("Error while trying to enter namespaces\n");
 		return -1;

exile.h

@@ -375,6 +375,9 @@ struct exile_policy
 
 	uint64_t vow_promises;
 
+	uid_t namespace_uid;
+	gid_t namespace_gid;
+
 	/* Do not manually add policies here, use exile_append_path_policies() */
 	struct exile_path_policy *path_policies;
 	struct exile_path_policy **path_policies_tail;

test.c

@@ -755,8 +755,50 @@ int test_unshare_user()
 	}
 
 	return 0;
+}
 
+int test_unshare_user_own_uid()
+{
+	uid_t uid = getuid();
+	gid_t gid = getgid();
 
+	char uidstr[64];
+	snprintf(uidstr, sizeof(uidstr), "%u", uid);
+
+	char gidstr[64];
+	snprintf(gidstr, sizeof(gidstr), "%u", gid);
+
+	struct exile_policy *policy = exile_init_policy();
+	policy->namespace_options = EXILE_UNSHARE_USER;
+	policy->namespace_gid = gid;
+	policy->namespace_uid = uid;
+	xexile_enable_policy(policy);
+
+	if(do_test_nsuidmap("/proc/self/uid_map", uidstr, uidstr, "1") != 0)
+	{
+		LOG("/proc/self/uid_map failed\n");
+		return 1;
+	}
+
+	if(do_test_nsuidmap("/proc/self/gid_map", gidstr, gidstr, "1") != 0)
+	{
+		LOG("/proc/self/gid_map failed\n");
+		return 1;
+	}
+
+	FILE *fp = fopen("/proc/self/setgroups", "r");
+
+	char buffer[4096] = { 0 };
+	fread(buffer, sizeof(buffer), 1, fp);
+	fclose(fp);
+
+	if(strcmp(buffer, "deny\n") != 0)
+	{
+		LOG("/proc/self/setgroups does not contain 'deny'\n");
+		return 1;
+	}
+
+	return 0;
 }
 
 struct dispatcher
@@ -788,6 +830,8 @@ struct dispatcher dispatchers[] = {
 	{ "vow_from_str", &test_vows_from_str},
 	{ "clone3_nosys", &test_clone3_nosys},
 	{ "unshare-user", &test_unshare_user},
+	{ "unshare-user-own-uid", &test_unshare_user_own_uid},
+
 
 };