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111 lines (89 sloc) 2.27 KB
/*
* Taken from https://github.com/ncopa/su-exec
*/
/* set user and group id and exec */
#include <sys/types.h>
#include <err.h>
#include <errno.h>
#include <grp.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
static char *argv0;
static void usage(int exitcode)
{
printf("Usage: %s user-spec command [args]\n", argv0);
exit(exitcode);
}
int main(int argc, char *argv[])
{
char *user, *group, **cmdargv;
char *end;
uid_t uid = getuid();
gid_t gid = getgid();
argv0 = argv[0];
if (argc < 3)
usage(0);
user = argv[1];
group = strchr(user, ':');
if (group)
*group++ = '\0';
cmdargv = &argv[2];
struct passwd *pw = NULL;
if (user[0] != '\0') {
pw = getpwnam(user);
uid_t nuid = strtol(user, &end, 10);
if (*end == '\0')
uid = nuid;
}
if (pw == NULL) {
pw = getpwuid(uid);
}
if (pw != NULL) {
uid = pw->pw_uid;
gid = pw->pw_gid;
}
setenv("HOME", pw != NULL ? pw->pw_dir : "/", 1);
if (group && group[0] != '\0') {
/* group was specified, ignore grouplist for setgroups later */
pw = NULL;
struct group *gr = getgrnam(group);
if (gr == NULL) {
gid_t ngid = strtol(group, &end, 10);
if (*end == '\0') {
gr = getgrgid(ngid);
if (gr == NULL)
gid = ngid;
}
}
if (gr != NULL)
gid = gr->gr_gid;
}
if (pw == NULL) {
if (setgroups(1, &gid) < 0)
err(1, "setgroups(%i)", gid);
} else {
int ngroups = 0;
gid_t *glist = NULL;
while (1) {
int r = getgrouplist(pw->pw_name, gid, glist, &ngroups);
if (r >= 0) {
if (setgroups(ngroups, glist) < 0)
err(1, "setgroups");
break;
}
glist = realloc(glist, ngroups * sizeof(gid_t));
if (glist == NULL)
err(1, "malloc");
}
}
if (setgid(gid) < 0)
err(1, "setgid(%i)", gid);
if (setuid(uid) < 0)
err(1, "setuid(%i)", uid);
execvp(cmdargv[0], cmdargv);
err(1, "%s", cmdargv[0]);
return 1;
}