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Make dropped root privileges permanent

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seteuid sets the effective uid but at the same time retains the old
effective uid as a so called saved uid, which allows the process to go
back to root at a later point in time. As we don't want that, we use
the function setresuid and setresgid instead, allowing to set the
real, effective and saved uid/gid. We keep the real uid/gid unchanged,
but set the effective and saved uid/gid to the value of the real uid.
This forbids us to not regain root priviliges.
This commit is contained in:
madmaurice 2021-01-15 20:22:22 +01:00
parent 5fe9ba36a2
commit 650a576c56
1 changed files with 5 additions and 3 deletions
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8
main.c
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@ -13,15 +13,17 @@
pid_t pid_child;
void drop_root(void) {
uid_t uid = getuid();
// Drop root privileges
if (seteuid(getuid()) == -1)
if (setresuid(-1,uid,uid) == -1)
{
int err = errno;
printf("Failed to drop root privileges with seteuid (%d)\n", err);
printf("Failed to drop root privileges with setresuid (%d)\n", err);
exit(err);
}
if (setegid(getgid()) == -1)
gid_t gid = getgid();
if (setresgid(-1,gid,gid) == -1)
{
int err = errno;
printf("Failed to drop root privileges with setegid (%d)\n", err);