diff options
Diffstat (limited to 'apt-pkg/contrib')
| -rw-r--r-- | apt-pkg/contrib/fileutl.cc | 85 | ||||
| -rw-r--r-- | apt-pkg/contrib/fileutl.h | 12 |
2 files changed, 92 insertions, 5 deletions
diff --git a/apt-pkg/contrib/fileutl.cc b/apt-pkg/contrib/fileutl.cc index 6b8f04dea..e81f32a52 100644 --- a/apt-pkg/contrib/fileutl.cc +++ b/apt-pkg/contrib/fileutl.cc @@ -48,6 +48,7 @@ #include <errno.h> #include <glob.h> #include <pwd.h> +#include <grp.h> #include <set> #include <algorithm> @@ -64,6 +65,10 @@ #include <endian.h> #include <stdint.h> +#if __gnu_linux__ +#include <sys/prctl.h> +#endif + #include <apti18n.h> /*}}}*/ @@ -2170,17 +2175,89 @@ bool Popen(const char* Args[], FileFd &Fd, pid_t &Child, FileFd::OpenMode Mode) bool DropPrivs() { - if (getuid() != 0) + // 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; - const std::string nobody = _config->Find("APT::User::Nobody", "nobody"); - struct passwd *pw = getpwnam(nobody.c_str()); + const std::string toUser = _config->Find("APT::Sandbox::User", "_apt"); + struct passwd *pw = getpwnam(toUser.c_str()); if (pw == NULL) - return _error->Warning("No user %s, can not drop rights", nobody.c_str()); + return _error->Error("No user %s, can not drop rights", toUser.c_str()); + +#if __gnu_linux__ + // see prctl(2), needs linux3.5 + int ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0,0, 0); + if(ret < 0) + _error->Warning("PR_SET_NO_NEW_PRIVS failed with %i", ret); +#endif + // Do not change the order here, it might break things + if (setgroups(1, &pw->pw_gid)) + return _error->Errno("setgroups", "Failed to setgroups"); + + if (setegid(pw->pw_gid) != 0) + 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 (seteuid(pw->pw_uid) != 0) + return _error->Errno("seteuid", "Failed to seteuid"); + + // Verify that the user has only a single group, and the correct one + 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 that gid, egid, uid, and euid changed + 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"); + +#ifdef HAVE_GETRESUID + // verify that the saved set-user-id was changed as well + uid_t ruid = 0; + uid_t euid = 0; + uid_t suid = 0; + if (getresuid(&ruid, &euid, &suid)) + return _error->Errno("getresuid", "Could not get saved set-user-ID"); + if (suid != pw->pw_uid) + return _error->Error("Could not switch saved set-user-ID"); +#endif + +#ifdef HAVE_GETRESGID + // verify that the saved set-group-id was changed as well + gid_t rgid = 0; + gid_t egid = 0; + gid_t sgid = 0; + if (getresgid(&rgid, &egid, &sgid)) + return _error->Errno("getresuid", "Could not get saved set-group-ID"); + if (sgid != pw->pw_gid) + return _error->Error("Could not switch saved set-group-ID"); +#endif + + // Check that uid and gid changes do not work anymore + 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"); + return true; } diff --git a/apt-pkg/contrib/fileutl.h b/apt-pkg/contrib/fileutl.h index a8e255b86..9dd29eb9e 100644 --- a/apt-pkg/contrib/fileutl.h +++ b/apt-pkg/contrib/fileutl.h @@ -199,7 +199,17 @@ bool ExecWait(pid_t Pid,const char *Name,bool Reap = false); // check if the given file starts with a PGP cleartext signature bool StartsWithGPGClearTextSignature(std::string const &FileName); -// process releated +/** + * \brief Drop privileges + * + * Drop the privileges to the user _apt (or the one specified in + * APT::Sandbox::User). This does not set the supplementary group + * ids up correctly, it only uses the default group. Also prevent + * the process from gaining any new privileges afterwards, at least + * on Linux. + * + * \return true on success, false on failure with _error set + */ bool DropPrivs(); // File string manipulators |