Bug#448775: Uses too much entropy (Debian Bug #343085)

[Andreas Metzler]

On 2008-01-08 Werner Koch <wk at gnupg.org> wrote:
> On Fri,  4 Jan 2008 17:01, simon at josefsson.org said:

> > Right.  So what should applications like exim do exactly?  Is there

> My suggestion is:
[...]

Hello,

which yields this stripped down version for exim:
------------------------------
diff -urNad exim4-4.68~/build-tree/src/tls-gnu.c exim4-4.68/build-tree/src/tls-gnu.c
--- exim4-4.68~/build-tree/src/tls-gnu.c	2007-08-30 14:31:06.000000000 +0000
+++ exim4-4.68/build-tree/src/tls-gnu.c	2008-01-27 18:42:00.000000000 +0000
@@ -20,6 +20,7 @@
 #include <gnutls/gnutls.h>
 #include <gnutls/x509.h>
 
+#include <gcrypt.h>
 
 #define UNKNOWN_NAME "unknown"
 #define DH_BITS      1024
@@ -440,10 +441,32 @@
   uschar *crl)
 {
 int rc;
+uschar filename[200];
 uschar *cert_expanded, *key_expanded, *cas_expanded, *crl_expanded;
+gcry_error_t gcr_rc;
 
 initialized = (host == NULL)? INITIALIZED_SERVER : INITIALIZED_CLIENT;
 
+/* Use a random_seed file for gcrypt's RNG */
+if (host_number_string != NULL)
+  {
+  if (!string_format(filename, sizeof(filename), "%s/random.seed%s",
+    spool_directory, host_number_string))
+  return tls_error(US"overlong filename spool_directory/random.seedlocalhost_number", host, 0);
+  } 
+else
+  {
+  if (!string_format(filename, sizeof(filename), "%s/random.seed",
+    spool_directory))
+  return tls_error(US"overlong filename spool_directory/random.seed", host, 0);
+  }
+
+gcr_rc = gcry_control (GCRYCTL_SET_RANDOM_SEED_FILE,filename);
+if (gcr_rc)
+  return tls_error(US"Failure to set random_seed file", host, gcr_rc);
+
+gcry_control (GCRYCTL_INITIALIZATION_FINISHED, 0);
+
 rc = gnutls_global_init();
 if (rc < 0) return tls_error(US"tls-init", host, rc);
 
@@ -1303,8 +1326,19 @@
 void
 tls_close(BOOL shutdown)
 {
+gcry_error_t gcr_rc;
+
 if (tls_active < 0) return;  /* TLS was not active */
 
+gcr_rc = gcry_control (GCRYCTL_UPDATE_RANDOM_SEED_FILE);
+
+if (gcr_rc)
+  {
+  DEBUG(D_tls) debug_printf(
+    "GCRYCTL_UPDATE_RANDOM_SEED_FILE failed: (%d): (%s)\n",
+    gcr_rc,gcry_strerror(gcr_rc));
+  }
+
 if (shutdown)
   {
   DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS\n");
------------------------------

Any obvious breakage? Exim does not use any threading. I have not
included an gcry_check_version(NULL) since I thought gcry_control()
would fail as reliably as gcry_check_version() would, if gcrypt was
not available.

thanks, cu andreas
-- 
`What a good friend you are to him, Dr. Maturin. His other friends are
so grateful to you.'
`I sew his ears on from time to time, sure'