From 5f2047ece8c192d919cd97fea73759ce07b416ce Mon Sep 17 00:00:00 2001 From: Julian Andres Klode Date: Wed, 24 Sep 2014 16:47:55 +0200 Subject: DropPriv: Really call seteuid and not setuid, and add more checks The only thing we are missing is non-portable saved ids support. --- apt-pkg/contrib/fileutl.cc | 46 +++++++++++++++++++++++++++++++++++----------- 1 file 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; } -- cgit v1.2.3