From a559fcf156f4ee8c98daac52fcf3447993b9ba14 Mon Sep 17 00:00:00 2001
From: Jeremy Allison <jra@samba.org>
Date: Tue, 3 Jul 2012 12:39:23 -0700
Subject: [PATCH] Add function set_thread_credentials_permanently(). Panic if
 fail.

Not yet used.
---
 source3/include/proto.h |  4 ++++
 source3/lib/util_sec.c  | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/source3/include/proto.h b/source3/include/proto.h
index 4080f237384..308283016c5 100644
--- a/source3/include/proto.h
+++ b/source3/include/proto.h
@@ -544,6 +544,10 @@ void save_re_gid(void);
 void restore_re_gid(void);
 int set_re_uid(void);
 void become_user_permanently(uid_t uid, gid_t gid);
+int set_thread_credentials_permanently(uid_t uid,
+				gid_t gid,
+				size_t setlen,
+				const gid_t *gidset);
 bool is_setuid_root(void) ;
 
 /* The following definitions come from lib/util_sid.c  */
diff --git a/source3/lib/util_sec.c b/source3/lib/util_sec.c
index 11d85a102a5..7c05f17de57 100644
--- a/source3/lib/util_sec.c
+++ b/source3/lib/util_sec.c
@@ -410,6 +410,54 @@ void become_user_permanently(uid_t uid, gid_t gid)
 	assert_gid(gid, gid);
 }
 
+/**********************************************************
+ Function to set thread specific credentials in an
+ irreversible way. Must be thread-safe code.
+**********************************************************/
+
+int set_thread_credentials_permanently(uid_t uid,
+				gid_t gid,
+				size_t setlen,
+				const gid_t *gidset)
+{
+#if defined(USE_LINUX_THREAD_CREDENTIALS)
+	/*
+	 * With Linux thread-specific credentials
+	 * we know we have setresuid/setresgid
+	 * available.
+	 */
+
+	/* Become root. */
+	/* Set ru=0, eu=0 */
+	if (samba_setresuid(0, 0, -1) != 0) {
+		return -1;
+	}
+	/* Set our primary gid. */
+	/* Set rg=gid, eg=gid, sg=gid */
+	if (samba_setresgid(gid, gid, gid) != 0) {
+		return -1;
+	}
+	/* Set extra groups list. */
+	if (samba_setgroups(setlen, gidset) != 0) {
+		return -1;
+	}
+	/* Become the requested user. No way back after this. */
+	/* Set ru=uid, eu=uid, su=uid */
+	if (samba_setresuid(uid, uid, uid) != 0) {
+		return -1;
+	}
+	if (geteuid() != uid || getuid() != uid ||
+			getegid() != gid || getgid() != gid) {
+		smb_panic("set_thread_credentials_permanently failed\n");
+		return -1;
+	}
+	return 0;
+#else
+	errno = ENOSYS;
+	return -1;
+#endif
+}
+
 #ifdef AUTOCONF_TEST
 
 /****************************************************************************
-- 
2.11.4.GIT