From 9624d92a65520b982f107ede35c085f9daee5fda Mon Sep 17 00:00:00 2001
From: Florian Dold <florian@dold.me>
Date: Tue, 27 Jul 2021 12:04:52 +0200
Subject: secmod: use umask, as fchmod is undefined on sockets

---
 src/util/secmod_common.c               | 26 +++++++++++++++-----------
 src/util/secmod_common.h               |  3 +++
 src/util/taler-exchange-secmod-eddsa.c |  4 ++++
 src/util/taler-exchange-secmod-rsa.c   |  2 ++
 4 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/src/util/secmod_common.c b/src/util/secmod_common.c
index cc2def19f..2e73e44b1 100644
--- a/src/util/secmod_common.c
+++ b/src/util/secmod_common.c
@@ -26,6 +26,15 @@ struct GNUNET_NETWORK_Handle *
 TES_open_socket (const char *unixpath)
 {
   int sock;
+  mode_t old_umask;
+  struct GNUNET_NETWORK_Handle *ret = NULL;
+
+  /* Change permissions so that group read/writes are allowed.
+   * We need this for multi-user exchange deployment with privilege
+   * separation, where taler-exchange-httpd is part of a group
+   * that allows it to talk to secmod.
+   */
+  old_umask = umask (S_IROTH | S_IWOTH | S_IXOTH);
 
   sock = socket (PF_UNIX,
                  SOCK_DGRAM,
@@ -34,16 +43,8 @@ TES_open_socket (const char *unixpath)
   {
     GNUNET_log_strerror (GNUNET_ERROR_TYPE_ERROR,
                          "socket");
-    return NULL;
+    goto cleanup;
   }
-  /* Change permissions so that group read/writes are allowed.
-   * We need this for multi-user exchange deployment with privilege
-   * separation, where taler-exchange-httpd is part of a group
-   * that allows it to talk to secmod.
-   *
-   * Importantly, we do this before binding the socket.
-   */
-  GNUNET_assert (0 == fchmod (sock, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP));
   {
     struct sockaddr_un un;
 
@@ -76,8 +77,11 @@ TES_open_socket (const char *unixpath)
                                 "bind",
                                 unixpath);
       GNUNET_break (0 == close (sock));
-      return NULL;
+      goto cleanup;
     }
+    ret = GNUNET_NETWORK_socket_box_native (sock);
   }
-  return GNUNET_NETWORK_socket_box_native (sock);
+cleanup:
+  (void) umask (old_umask);
+  return ret;
 }
diff --git a/src/util/secmod_common.h b/src/util/secmod_common.h
index c1eea655c..ca1270fa8 100644
--- a/src/util/secmod_common.h
+++ b/src/util/secmod_common.h
@@ -28,6 +28,9 @@
 /**
  * Create the listen socket for a secmod daemon.
  *
+ * This function is not thread-safe, as it changes and
+ * restores the process umask.
+ *
  * @param unixpath socket path
  */
 struct GNUNET_NETWORK_Handle *
diff --git a/src/util/taler-exchange-secmod-eddsa.c b/src/util/taler-exchange-secmod-eddsa.c
index 8f9964439..ac4bfc61b 100644
--- a/src/util/taler-exchange-secmod-eddsa.c
+++ b/src/util/taler-exchange-secmod-eddsa.c
@@ -40,6 +40,7 @@
 #include <sys/eventfd.h>
 #include "taler_error_codes.h"
 #include "taler_signatures.h"
+#include "secmod_common.h"
 
 
 /**
@@ -1633,6 +1634,9 @@ main (int argc,
   };
   int ret;
 
+  /* Restrict permissions for the key files that we create. */
+  (void) umask (S_IWGRP | S_IROTH | S_IWOTH | S_IXOTH);
+
   /* force linker to link against libtalerutil; if we do
    not do this, the linker may "optimize" libtalerutil
    away and skip #TALER_OS_init(), which we do need */
diff --git a/src/util/taler-exchange-secmod-rsa.c b/src/util/taler-exchange-secmod-rsa.c
index b6729b66b..3c1f81c26 100644
--- a/src/util/taler-exchange-secmod-rsa.c
+++ b/src/util/taler-exchange-secmod-rsa.c
@@ -2031,7 +2031,9 @@ main (int argc,
   };
   int ret;
 
+  /* Restrict permissions for the key files that we create. */
   (void) umask (S_IWGRP | S_IROTH | S_IWOTH | S_IXOTH);
+
   /* force linker to link against libtalerutil; if we do
    not do this, the linker may "optimize" libtalerutil
    away and skip #TALER_OS_init(), which we do need */
-- 
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