Uppity: configurable SSH-2 authentication banner.

I've had to test banner handling several times recently, what with
trust sigils and the fix for CONF_ssh_show_banner. So it's the thing
I've most wanted to keep reconfiguring about Uppity so far.

ssh2userauth-server.c

@@ -127,6 +127,13 @@ static void ssh2_userauth_server_process_queue(PacketProtocolLayer *ppl)
 
     s->session_id = ssh2_transport_get_session_id(s->transport_layer);
 
+    if (s->ssc->banner.ptr) {
+        pktout = ssh_bpp_new_pktout(s->ppl.bpp, SSH2_MSG_USERAUTH_BANNER);
+        put_stringpl(pktout, s->ssc->banner);
+        put_stringz(pktout, ""); /* language tag */
+        pq_push(s->ppl.out_pq, pktout);
+    }
+
     while (1) {
         crMaybeWaitUntilV((pktin = ssh2_userauth_server_pop(s)) != NULL);
         if (pktin->type != SSH2_MSG_USERAUTH_REQUEST) {

sshserver.h

@@ -1,7 +1,7 @@
 typedef struct AuthPolicy AuthPolicy;
 
 struct SshServerConfig {
-    int dummy;                         /* no fields in here yet */
+    ptrlen banner;        /* banner.ptr == NULL indicates no banner */
 };
 
 Plug *ssh_server_plug(

unix/uxserver.c

@@ -510,6 +510,23 @@ int main(int argc, char **argv)
                         "(%s)\n", appname, val, key_type_to_str(keytype));
                 exit(1);
             }
+        } else if (longoptarg(arg, "--bannerfile", &val, &argc, &argv)) {
+            FILE *fp = fopen(val, "r");
+            if (!fp) {
+                fprintf(stderr, "%s: %s: open: %s\n", appname,
+                        val, strerror(errno));
+                exit(1);
+            }
+            strbuf *sb = strbuf_new();
+            if (!read_file_into(BinarySink_UPCAST(sb), fp)) {
+                fprintf(stderr, "%s: %s: read: %s\n", appname,
+                        val, strerror(errno));
+                exit(1);
+            }
+            fclose(fp);
+            ssc.banner = ptrlen_from_strbuf(sb);
+        } else if (longoptarg(arg, "--bannertext", &val, &argc, &argv)) {
+            ssc.banner = ptrlen_from_asciz(val);
         } else if (longoptarg(arg, "--sshlog", &val, &argc, &argv) ||
                    longoptarg(arg, "-sshlog", &val, &argc, &argv)) {
             Filename *logfile = filename_from_str(val);