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su: Use setgroups() to switch over to the target user's extra GIDs

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Before this, su would leave the process's extra GIDs untouched,
simply inheriting them from whoever spawned su.

Now we grab the target user's groups from /etc/group and setgroups().
This commit is contained in:
Andreas Kling 2020-01-04 13:48:55 +01:00
parent 5abc30e057
commit c663b1034a
1 changed files with 27 additions and 2 deletions
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29
Userland/su.cpp
View file

@ -1,3 +1,4 @@
#include <AK/Vector.h>
#include <alloca.h>
#include <grp.h>
#include <pwd.h>
@ -10,8 +11,9 @@ int main(int argc, char** argv)
{
uid_t uid = 0;
gid_t gid = 0;
struct passwd* pwd = nullptr;
if (argc > 1) {
auto* pwd = getpwnam(argv[1]);
pwd = getpwnam(argv[1]);
if (!pwd) {
fprintf(stderr, "No such user: %s\n", argv[1]);
return 1;
@ -19,7 +21,30 @@ int main(int argc, char** argv)
uid = pwd->pw_uid;
gid = pwd->pw_gid;
}
int rc = setgid(uid);
if (!pwd)
pwd = getpwuid(0);
if (!pwd) {
fprintf(stderr, "No passwd entry.\n");
return 1;
}
Vector<gid_t> extra_gids;
for (auto* group = getgrent(); group; group = getgrent()) {
for (size_t i = 0; group->gr_mem[i]; ++i) {
if (!strcmp(pwd->pw_name, group->gr_mem[i]))
extra_gids.append(group->gr_gid);
}
}
endgrent();
int rc = setgroups(extra_gids.size(), extra_gids.data());
if (rc < 0) {
perror("setgroups");
return 1;
}
rc = setgid(uid);
if (rc < 0) {
perror("setgid");
return 1;