[balsa/gtk3] Obfuscate the message-id header (Albrecht Dr eß)

[Peter Bloomfield <peterb src gnome org>]

commit 306b30023b5b234e9c7c120a46840631dd158ef9
Author: Peter Bloomfield <PeterBloomfield bellsouth net>
Date:   Sun Mar 1 14:49:13 2015 -0500

    Obfuscate the message-id header (Albrecht Dreß)
    
        * libbalsa/send.c (libbalsa_set_message_id): obfuscate the
        message-id header (in response to bgo #738155).

 ChangeLog       |    7 ++++++
 libbalsa/send.c |   63 ++++++++++++++++++++++++++++++++++++------------------
 2 files changed, 49 insertions(+), 21 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index fb5a59f..e68f48a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2015-03-01  Albrecht Dreß
+
+       Obfuscate the message-id header
+
+       * libbalsa/send.c (libbalsa_set_message_id): obfuscate the
+       message-id header (in response to bgo #738155).
+
 2015-03-01  Peter Bloomfield  <pbloomfield bellsouth net>
 
        Use pan-down-symbolic instead of balsa-drop-down
diff --git a/libbalsa/send.c b/libbalsa/send.c
index def8cb5..b7e3460 100644
--- a/libbalsa/send.c
+++ b/libbalsa/send.c
@@ -2046,29 +2046,50 @@ libbalsa_message_postpone(LibBalsaMessage * message,
 static void
 libbalsa_set_message_id(GMimeMessage * mime_message)
 {
-    struct utsname utsbuf;
-    const gchar *host = "localhost";
+    static GMutex mutex;       /* as to make me thread-safe... */
+    static GRand *rand = NULL;
+    static struct {
+       gint64 now_monotonic;
+       gdouble randval;
+       char user_name[16];
+       char host_name[16];
+    } id_data;
+    GHmac *msg_id_hash;
+    guint8 buffer[32];
+    gsize buflen;
     gchar *message_id;
-#if defined(_GNU_SOURCE) && defined(HAVE_STRUCT_UTSNAME_DOMAINNAME)
-    gchar *fqdn;
-    const gchar *domain = "localdomain";
-
-    /* In an ideal world, uname() allows us to make a FQDN. */
-    if (uname(&utsbuf) == 0) {
-       if (*utsbuf.nodename)
-           host = utsbuf.nodename;
-       if (*utsbuf.domainname)
-           domain = utsbuf.domainname;
+
+    g_mutex_lock(&mutex);
+    if (rand == NULL) {
+       /* initialise some stuff on first-time use... */
+       rand = g_rand_new_with_seed((guint32) time(NULL));
+       strncpy(id_data.user_name, g_get_user_name(),
+                sizeof(id_data.user_name));
+       strncpy(id_data.host_name, g_get_host_name(),
+                sizeof(id_data.host_name));
     }
-    fqdn = g_strconcat(host, ".", domain, NULL);
-    message_id = g_mime_utils_generate_message_id(fqdn);
-    g_free(fqdn);
-#else                          /* _GNU_SOURCE */
-
-    if (uname(&utsbuf) == 0 && *utsbuf.nodename)
-       host = utsbuf.nodename;
-    message_id = g_mime_utils_generate_message_id(host);
-#endif                         /* _GNU_SOURCE */
+
+    /* get some randomness... */
+    id_data.now_monotonic = g_get_monotonic_time();
+    id_data.randval = g_rand_double(rand);
+
+    /* hash the buffer */
+    msg_id_hash =
+        g_hmac_new(G_CHECKSUM_SHA256, (const guchar *) &id_data,
+                   sizeof(id_data));
+    buflen = sizeof(buffer);
+    g_hmac_get_digest(msg_id_hash, buffer, &buflen);
+    g_hmac_unref(msg_id_hash);
+    g_mutex_unlock(&mutex);
+
+    /* create a msg id string
+     * Note: RFC 5322, sect. 3.6.4 explicitly allows the form
+     *    dot-atom-text "@" dot-atom-text
+     * where dot-atom-text may include all base64 (RFC 1421) chars,
+     * including '+' and '/' */
+    message_id = g_base64_encode(buffer, buflen);
+    memmove(message_id + 23, message_id + 22, strlen(message_id) - 23);
+    message_id[22] = '@';
 
     g_mime_message_set_message_id(mime_message, message_id);
     g_free(message_id);