lib/pwdutils.c

#include <stdlib.h>

#include "c.h"
#include "pwdutils.h"
#include "xalloc.h"

/* Returns allocated passwd and allocated pwdbuf to store passwd strings
 * fields. In case of error returns NULL and set errno, for unknown user set
 * errno to EINVAL
 */
struct passwd *xgetpwnam(const char *username, char **pwdbuf)
{
	struct passwd *pwd = NULL, *res = NULL;
	int rc;

	if (!pwdbuf || !username)
		return NULL;

	*pwdbuf = xmalloc(UL_GETPW_BUFSIZ);
	pwd = xcalloc(1, sizeof(struct passwd));

	errno = 0;
	rc = getpwnam_r(username, pwd, *pwdbuf, UL_GETPW_BUFSIZ, &res);
	if (rc != 0) {
		errno = rc;
		goto failed;
	}
	if (!res) {
		errno = EINVAL;
		goto failed;
	}
	return pwd;
failed:
	free(pwd);
	free(*pwdbuf);
	return NULL;
}

char *xgetlogin(void)
{
	struct passwd *pw = NULL;
	uid_t ruid;
	char *user;

	user = getlogin();
	if (user)
		return xstrdup(user);

	/* GNU Hurd implementation has an extension where a process can exist in a
	 * non-conforming environment, and thus be outside the realms of POSIX
	 * process identifiers; on this platform, getuid() fails with a status of
	 * (uid_t)(-1) and sets errno if a program is run from a non-conforming
	 * environment.
	 *
	 * http://austingroupbugs.net/view.php?id=511
	 */
	errno = 0;
	ruid = getuid();

	if (errno == 0)
		pw = getpwuid(ruid);
	if (pw && pw->pw_name && *pw->pw_name)
		return xstrdup(pw->pw_name);

	return NULL;
}

#ifdef TEST_PROGRAM
int main(int argc, char *argv[])
{
	char *buf = NULL;
	struct passwd *pwd = NULL;

	if (argc != 2) {
		fprintf(stderr, "usage: %s <username>\n", argv[0]);
		return EXIT_FAILURE;
	}

	pwd = xgetpwnam(argv[1], &buf);
	if (!pwd)
		err(EXIT_FAILURE, "failed to get %s pwd entry", argv[1]);

	printf("Username: %s\n", pwd->pw_name);
	printf("UID:      %d\n", pwd->pw_uid);
	printf("HOME:     %s\n", pwd->pw_dir);
	printf("GECO:     %s\n", pwd->pw_gecos);

	free(pwd);
	free(buf);

	printf("Current:  %s\n", (buf = xgetlogin()));
	free(buf);

	return EXIT_SUCCESS;
}
#endif /* TEST_PROGRAM */