#include "container.h"
#include "userns.h"

int handle_child_uid_map(pid_t child_pid, int fd)
{
	int uid_map = 0;
	int has_userns = -1;
	if (read(fd, &has_userns, sizeof(has_userns)) != sizeof(has_userns)) {
		fprintf(stderr, "couldn't read from child!\n");
		return -1;
	}
	if (has_userns) {
		char path[PATH_MAX] = {0};
		for (char **file = (char *[]) { "uid_map", "gid_map", 0 }; *file; file++) {
			if (snprintf(path, sizeof(path), "/proc/%d/%s", child_pid, *file)
			    > sizeof(path)) {
				fprintf(stderr, "snprintf too big? %m\n");
				return -1;
			}
			fprintf(stderr, "writing %s...", path);
			if ((uid_map = open(path, O_WRONLY)) == -1) {
				fprintf(stderr, "open failed: %m\n");
				return -1;
			}
			if (dprintf(uid_map, "0 %d %d\n", USERNS_OFFSET, USERNS_COUNT) == -1) {
				fprintf(stderr, "dprintf failed: %m\n");
				close(uid_map);
				return -1;
			}
			close(uid_map);
		}
	}
	if (write(fd, & (int) { 0 }, sizeof(int)) != sizeof(int)) {
		fprintf(stderr, "couldn't write: %m\n");
		return -1;
	}
	return 0;
}

int userns(struct child_config *config)
{
	fprintf(stderr, "=> trying a user namespace...");
	int has_userns = !unshare(CLONE_NEWUSER);
	if (write(config->fd, &has_userns, sizeof(has_userns)) != sizeof(has_userns)) {
		fprintf(stderr, "couldn't write: %m\n");
		return -1;
	}
	int result = 0;
	if (read(config->fd, &result, sizeof(result)) != sizeof(result)) {
		fprintf(stderr, "couldn't read: %m\n");
		return -1;
	}
	if (result) return -1;
	if (has_userns) {
		fprintf(stderr, "done.\n");
	} else {
		fprintf(stderr, "unsupported? continuing.\n");
	}
	fprintf(stderr, "=> switching to uid %d / gid %d...", config->uid, config->uid);
	if (setgroups(1, & (gid_t) { config->uid }) ||
	    setresgid(config->uid, config->uid, config->uid) ||
	    setresuid(config->uid, config->uid, config->uid)) {
		fprintf(stderr, "%m\n");
		return -1;
	}
	fprintf(stderr, "done.\n");
	return 0;
}