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-rw-r--r--apt-pkg/contrib/fileutl.cc46
1 files changed, 35 insertions, 11 deletions
diff --git a/apt-pkg/contrib/fileutl.cc b/apt-pkg/contrib/fileutl.cc
index de67a94b9..72e2dabd5 100644
--- a/apt-pkg/contrib/fileutl.cc
+++ b/apt-pkg/contrib/fileutl.cc
@@ -2175,9 +2175,12 @@ bool Popen(const char* Args[], FileFd &Fd, pid_t &Child, FileFd::OpenMode Mode)
bool DropPrivs()
{
- if (getuid() != 0)
- return true;
+ /* uid will be 0 in the end, but gid might be different anyway */
+ uid_t old_uid = getuid();
+ gid_t old_gid = getgid();
+ if (old_uid != 0)
+ return true;
if(_config->FindB("Debug::NoDropPrivs", false) == true)
return true;
@@ -2197,22 +2200,43 @@ bool DropPrivs()
return _error->Errno("setgroups", "Failed to setgroups");
if (setegid(pw->pw_gid) != 0)
- return _error->Errno("setgid", "Failed to setgid");
+ return _error->Errno("setegid", "Failed to setegid");
+
if (setgid(pw->pw_gid) != 0)
return _error->Errno("setgid", "Failed to setgid");
-
+
if (setuid(pw->pw_uid) != 0)
return _error->Errno("setuid", "Failed to setuid");
// the seteuid() is probably uneeded (at least thats what the linux
// man-page says about setuid(2)) but we cargo culted it anyway
- if (setuid(pw->pw_uid) != 0)
- return _error->Errno("setuid", "Failed to setuid");
- // be defensive
- if(setgid(0) != -1 || setegid(0) != -1)
- return _error->Error("Could restore gid to root, privilege dropping does not work");
- if(setuid(0) != -1 || seteuid(0) != -1)
- return _error->Error("Could restore uid to root, privilege dropping does not work");
+ if (seteuid(pw->pw_uid) != 0)
+ return _error->Errno("seteuid", "Failed to seteuid");
+
+ /* Try changing GID/EGID */
+ if (pw->pw_gid != old_gid && (setgid(old_gid) != -1 || setegid(old_gid) != -1))
+ return _error->Error("Could restore a gid to root, privilege dropping did not work");
+
+ if (pw->pw_uid != old_uid && (setuid(old_uid) != -1 || seteuid(old_uid) != -1))
+ return _error->Error("Could restore a uid to root, privilege dropping did not work");
+
+ /* Verify the list of supplementary groups is what we expected */
+ gid_t groups[1];
+ if (getgroups(1, groups) != 1)
+ return _error->Errno("getgroups", "Could not get new groups");
+ if (groups[0] != pw->pw_gid)
+ return _error->Error("Could not switch group");
+ /* Verify gid, egid, uid, and euid */
+ if (getgid() != pw->pw_gid)
+ return _error->Error("Could not switch group");
+ if (getegid() != pw->pw_gid)
+ return _error->Error("Could not switch effective group");
+ if (getuid() != pw->pw_uid)
+ return _error->Error("Could not switch user");
+ if (geteuid() != pw->pw_uid)
+ return _error->Error("Could not switch effective user");
+
+ /* TODO: Check saved uid/saved gid as well */
return true;
}