From bcf1a938298486e474a6e94d67aaed6f822ec7e1 Mon Sep 17 00:00:00 2001
From: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
Date: Tue, 11 Aug 2015 20:28:26 -0400
Subject: [PATCH] Avoid simple memory dumps via ptrace

This avoids needing to setgid gpg-agent.  It probably doesn't defend
against all possible attacks, but it defends against one specific (and
easy) one.  If there are other protections we should do them too.

This will make it slightly harder to debug the agent because the
normal user won't be able to attach gdb to it directly while it runs.

The remaining options for debugging are:

 * launch the agent from gdb directly
 * connect gdb to a running agent as the superuser

Upstream bug: https://dev.gnupg.org/T1211

Gbp-Pq: Topic block-ptrace-on-secret-daemons
Gbp-Pq: Name Avoid-simple-memory-dumps-via-ptrace.patch
---
 agent/gpg-agent.c | 8 ++++++++
 configure.ac      | 1 +
 scd/scdaemon.c    | 9 +++++++++
 3 files changed, 18 insertions(+)

diff --git a/agent/gpg-agent.c b/agent/gpg-agent.c
index 1fdc94d..7d0d906 100644
--- a/agent/gpg-agent.c
+++ b/agent/gpg-agent.c
@@ -48,6 +48,9 @@
 # include <signal.h>
 #endif
 #include <npth.h>
+#ifdef HAVE_PRCTL
+# include <sys/prctl.h>
+#endif
 
 #define GNUPG_COMMON_NEED_AFLOCAL
 #include "agent.h"
@@ -1006,6 +1009,11 @@ main (int argc, char **argv )
 
   early_system_init ();
 
+#if defined(HAVE_PRCTL) && defined(PR_SET_DUMPABLE)
+  /* Disable ptrace on Linux without sgid bit */
+  prctl(PR_SET_DUMPABLE, 0);
+#endif
+
   /* Before we do anything else we save the list of currently open
      file descriptors and the signal mask.  This info is required to
      do the exec call properly.  We don't need it on Windows.  */
diff --git a/configure.ac b/configure.ac
index f77317f..50e9355 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1379,6 +1379,7 @@ AC_CHECK_FUNCS([strerror strlwr tcgetattr mmap canonicalize_file_name])
 AC_CHECK_FUNCS([strcasecmp strncasecmp ctermid times gmtime_r strtoull])
 AC_CHECK_FUNCS([setenv unsetenv fcntl ftruncate inet_ntop])
 AC_CHECK_FUNCS([canonicalize_file_name])
+AC_CHECK_FUNCS([prctl])
 AC_CHECK_FUNCS([gettimeofday getrusage getrlimit setrlimit clock_gettime])
 AC_CHECK_FUNCS([atexit raise getpagesize strftime nl_langinfo setlocale])
 AC_CHECK_FUNCS([waitpid wait4 sigaction sigprocmask pipe getaddrinfo])
diff --git a/scd/scdaemon.c b/scd/scdaemon.c
index 8f8a026..e427b9e 100644
--- a/scd/scdaemon.c
+++ b/scd/scdaemon.c
@@ -36,6 +36,9 @@
 #include <unistd.h>
 #include <signal.h>
 #include <npth.h>
+#ifdef HAVE_PRCTL
+# include <sys/prctl.h>
+#endif
 
 #define GNUPG_COMMON_NEED_AFLOCAL
 #include "scdaemon.h"
@@ -438,6 +441,12 @@ main (int argc, char **argv )
   npth_t pipecon_handler;
 
   early_system_init ();
+
+#if defined(HAVE_PRCTL) && defined(PR_SET_DUMPABLE)
+  /* Disable ptrace on Linux without sgid bit */
+  prctl(PR_SET_DUMPABLE, 0);
+#endif
+
   set_strusage (my_strusage);
   gcry_control (GCRYCTL_SUSPEND_SECMEM_WARN);
   /* Please note that we may running SUID(ROOT), so be very CAREFUL
-- 
2.30.2