From 14928b7492abec82afa4c2b778fc03f78cd419b6 Mon Sep 17 00:00:00 2001
From: Damien Miller <djm@mindrot.org>
Date: Tue, 1 Apr 2014 14:38:07 +1100
Subject:  - (djm) On platforms that support it, use prctl() to prevent
 sftp-server     from accessing /proc/self/{mem,maps}; patch from jann AT
 thejh.net

---
 sftp-server.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

(limited to 'sftp-server.c')

diff --git a/sftp-server.c b/sftp-server.c
index b8eb59c36..77834117c 100644
--- a/sftp-server.c
+++ b/sftp-server.c
@@ -29,6 +29,9 @@
 #ifdef HAVE_SYS_STATVFS_H
 #include <sys/statvfs.h>
 #endif
+#ifdef HAVE_SYS_PRCTL_H
+#include <sys/prctl.h>
+#endif
 
 #include <dirent.h>
 #include <errno.h>
@@ -1523,6 +1526,17 @@ sftp_server_main(int argc, char **argv, struct passwd *user_pw)
 
 	log_init(__progname, log_level, log_facility, log_stderr);
 
+#ifdef HAVE_PRCTL
+	/*
+	 * On Linux, we should try to avoid making /proc/self/{mem,maps}
+	 * available to the user so that sftp access doesn't automatically
+	 * imply arbitrary code execution access that will break
+	 * restricted configurations.
+	 */
+	if (prctl(PR_SET_DUMPABLE, 0) != 0)
+		fatal("unable to make the process undumpable");
+#endif
+
 	if ((cp = getenv("SSH_CONNECTION")) != NULL) {
 		client_addr = xstrdup(cp);
 		if ((cp = strchr(client_addr, ' ')) == NULL) {
-- 
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