Move half of sshcommon.c out into sshutils.c.

Like other 'utils' modules, the point is that sshutils.c has no
external dependencies, so it's safe to include in a tool without
requiring you to bring in a cascade of other modules you didn't really
want.

Right now I'm only planning to use this change in an out-of-tree
experiment, but it's harmless to commit the change itself here.

Recipe

@@ -262,7 +262,7 @@ SSHCRYPTO = ARITH sshmd5 sshsha sshsh256 sshsh512
          + sshdes sshblowf sshaes sshccp ssharcf
          + sshdh sshcrc sshcrcda sshauxcrypt
          + sshhmac
-SSHCOMMON = sshcommon sshprng sshrand SSHCRYPTO
+SSHCOMMON = sshcommon sshutils sshprng sshrand SSHCRYPTO
          + sshverstring
          + sshpubk sshzlib
          + sshmac marshal nullplug

sshcommon.c

@@ -356,109 +356,6 @@ static bool zombiechan_want_close(Channel *chan, bool sent_eof, bool rcvd_eof)
     return true;
 }
 
-/* ----------------------------------------------------------------------
- * Centralised standard methods for other channel implementations to
- * borrow.
- */
-
-void chan_remotely_opened_confirmation(Channel *chan)
-{
-    unreachable("this channel type should never receive OPEN_CONFIRMATION");
-}
-
-void chan_remotely_opened_failure(Channel *chan, const char *errtext)
-{
-    unreachable("this channel type should never receive OPEN_FAILURE");
-}
-
-bool chan_default_want_close(
-    Channel *chan, bool sent_local_eof, bool rcvd_remote_eof)
-{
-    /*
-     * Default close policy: we start initiating the CHANNEL_CLOSE
-     * procedure as soon as both sides of the channel have seen EOF.
-     */
-    return sent_local_eof && rcvd_remote_eof;
-}
-
-bool chan_no_exit_status(Channel *chan, int status)
-{
-    return false;
-}
-
-bool chan_no_exit_signal(
-    Channel *chan, ptrlen signame, bool core_dumped, ptrlen msg)
-{
-    return false;
-}
-
-bool chan_no_exit_signal_numeric(
-    Channel *chan, int signum, bool core_dumped, ptrlen msg)
-{
-    return false;
-}
-
-bool chan_no_run_shell(Channel *chan)
-{
-    return false;
-}
-
-bool chan_no_run_command(Channel *chan, ptrlen command)
-{
-    return false;
-}
-
-bool chan_no_run_subsystem(Channel *chan, ptrlen subsys)
-{
-    return false;
-}
-
-bool chan_no_enable_x11_forwarding(
-    Channel *chan, bool oneshot, ptrlen authproto, ptrlen authdata,
-    unsigned screen_number)
-{
-    return false;
-}
-
-bool chan_no_enable_agent_forwarding(Channel *chan)
-{
-    return false;
-}
-
-bool chan_no_allocate_pty(
-    Channel *chan, ptrlen termtype, unsigned width, unsigned height,
-    unsigned pixwidth, unsigned pixheight, struct ssh_ttymodes modes)
-{
-    return false;
-}
-
-bool chan_no_set_env(Channel *chan, ptrlen var, ptrlen value)
-{
-    return false;
-}
-
-bool chan_no_send_break(Channel *chan, unsigned length)
-{
-    return false;
-}
-
-bool chan_no_send_signal(Channel *chan, ptrlen signame)
-{
-    return false;
-}
-
-bool chan_no_change_window_size(
-    Channel *chan, unsigned width, unsigned height,
-    unsigned pixwidth, unsigned pixheight)
-{
-    return false;
-}
-
-void chan_no_request_response(Channel *chan, bool success)
-{
-    unreachable("this channel type should never send a want-reply request");
-}
-
 /* ----------------------------------------------------------------------
  * Common routines for handling SSH tty modes.
  */
@@ -1047,17 +944,3 @@ void ssh1_compute_session_id(
     put_data(hash, cookie, 8);
     ssh_hash_final(hash, session_id);
 }
-
-/* ----------------------------------------------------------------------
- * Other miscellaneous utility functions.
- */
-
-void free_rportfwd(struct ssh_rportfwd *rpf)
-{
-    if (rpf) {
-        sfree(rpf->log_description);
-        sfree(rpf->shost);
-        sfree(rpf->dhost);
-        sfree(rpf);
-    }
-}

sshutils.c

@@ -0,0 +1,131 @@
+/*
+ * Supporting routines used in common by all the various components of
+ * the SSH system.
+ */
+
+#include <assert.h>
+#include <stdlib.h>
+
+#include "putty.h"
+#include "mpint.h"
+#include "ssh.h"
+#include "sshbpp.h"
+#include "sshppl.h"
+#include "sshchan.h"
+
+/* ----------------------------------------------------------------------
+ * Centralised standard methods for other channel implementations to
+ * borrow.
+ */
+
+void chan_remotely_opened_confirmation(Channel *chan)
+{
+    unreachable("this channel type should never receive OPEN_CONFIRMATION");
+}
+
+void chan_remotely_opened_failure(Channel *chan, const char *errtext)
+{
+    unreachable("this channel type should never receive OPEN_FAILURE");
+}
+
+bool chan_default_want_close(
+    Channel *chan, bool sent_local_eof, bool rcvd_remote_eof)
+{
+    /*
+     * Default close policy: we start initiating the CHANNEL_CLOSE
+     * procedure as soon as both sides of the channel have seen EOF.
+     */
+    return sent_local_eof && rcvd_remote_eof;
+}
+
+bool chan_no_exit_status(Channel *chan, int status)
+{
+    return false;
+}
+
+bool chan_no_exit_signal(
+    Channel *chan, ptrlen signame, bool core_dumped, ptrlen msg)
+{
+    return false;
+}
+
+bool chan_no_exit_signal_numeric(
+    Channel *chan, int signum, bool core_dumped, ptrlen msg)
+{
+    return false;
+}
+
+bool chan_no_run_shell(Channel *chan)
+{
+    return false;
+}
+
+bool chan_no_run_command(Channel *chan, ptrlen command)
+{
+    return false;
+}
+
+bool chan_no_run_subsystem(Channel *chan, ptrlen subsys)
+{
+    return false;
+}
+
+bool chan_no_enable_x11_forwarding(
+    Channel *chan, bool oneshot, ptrlen authproto, ptrlen authdata,
+    unsigned screen_number)
+{
+    return false;
+}
+
+bool chan_no_enable_agent_forwarding(Channel *chan)
+{
+    return false;
+}
+
+bool chan_no_allocate_pty(
+    Channel *chan, ptrlen termtype, unsigned width, unsigned height,
+    unsigned pixwidth, unsigned pixheight, struct ssh_ttymodes modes)
+{
+    return false;
+}
+
+bool chan_no_set_env(Channel *chan, ptrlen var, ptrlen value)
+{
+    return false;
+}
+
+bool chan_no_send_break(Channel *chan, unsigned length)
+{
+    return false;
+}
+
+bool chan_no_send_signal(Channel *chan, ptrlen signame)
+{
+    return false;
+}
+
+bool chan_no_change_window_size(
+    Channel *chan, unsigned width, unsigned height,
+    unsigned pixwidth, unsigned pixheight)
+{
+    return false;
+}
+
+void chan_no_request_response(Channel *chan, bool success)
+{
+    unreachable("this channel type should never send a want-reply request");
+}
+
+/* ----------------------------------------------------------------------
+ * Other miscellaneous utility functions.
+ */
+
+void free_rportfwd(struct ssh_rportfwd *rpf)
+{
+    if (rpf) {
+        sfree(rpf->log_description);
+        sfree(rpf->shost);
+        sfree(rpf->dhost);
+        sfree(rpf);
+    }
+}