Permit configuring RSA signature types in certificates.

As distinct from the type of signature generated by the SSH server
itself from the host key, this lets you exclude (and by default does
exclude) the old "ssh-rsa" SHA-1 signature type from the signature of
the CA on the certificate.

ssh/ca-config.c

@@ -11,15 +11,19 @@
 
 const bool has_ca_config_box = true;
 
+#define NRSATYPES 3
+
 struct ca_state {
     dlgcontrol *ca_name_edit;
     dlgcontrol *ca_reclist;
     dlgcontrol *ca_pubkey_edit;
     dlgcontrol *ca_wclist;
     dlgcontrol *ca_wc_edit;
+    dlgcontrol *rsa_type_checkboxes[NRSATYPES];
     char *name, *pubkey, *wc;
     tree234 *ca_names;                 /* stores plain 'char *' */
     tree234 *host_wcs;                 /* stores plain 'char *' */
+    ca_options opts;
 };
 
 static int ca_name_compare(void *av, void *bv)
@@ -68,6 +72,29 @@ static void ca_refresh_name_list(struct ca_state *st)
     }
 }
 
+static void set_from_hca(struct ca_state *st, host_ca *hca)
+{
+    sfree(st->name);
+    st->name = dupstr(hca->name);
+
+    sfree(st->pubkey);
+    if (hca->ca_public_key)
+        st->pubkey = strbuf_to_str(
+            base64_encode_sb(ptrlen_from_strbuf(hca->ca_public_key), 0));
+    else
+        st->pubkey = dupstr("");
+
+    clear_string_tree(st->host_wcs);
+    for (size_t i = 0; i < hca->n_hostname_wildcards; i++) {
+        char *name = dupstr(hca->hostname_wildcards[i]);
+        char *added = add234(st->host_wcs, name);
+        if (added != name)
+            sfree(name);               /* de-duplicate, just in case */
+    }
+
+    st->opts = hca->opts;              /* structure copy */
+}
+
 static void ca_load_selected_record(struct ca_state *st, dlgparam *dp)
 {
     int i = dlg_listbox_index(st->ca_reclist, dp);
@@ -88,26 +115,14 @@ static void ca_load_selected_record(struct ca_state *st, dlgparam *dp)
         return;
     }
 
-    sfree(st->name);
-    st->name = dupstr(hca->name);
-
-    sfree(st->pubkey);
-    st->pubkey = strbuf_to_str(
-        base64_encode_sb(ptrlen_from_strbuf(hca->ca_public_key), 0));
-
-    clear_string_tree(st->host_wcs);
-    for (size_t i = 0; i < hca->n_hostname_wildcards; i++) {
-        char *name = dupstr(hca->hostname_wildcards[i]);
-        char *added = add234(st->host_wcs, name);
-        if (added != name)
-            sfree(name);               /* de-duplicate, just in case */
-    }
-
+    set_from_hca(st, hca);
     host_ca_free(hca);
 
     dlg_refresh(st->ca_name_edit, dp);
     dlg_refresh(st->ca_pubkey_edit, dp);
     dlg_refresh(st->ca_wclist, dp);
+    for (size_t i = 0; i < NRSATYPES; i++)
+        dlg_refresh(st->rsa_type_checkboxes[i], dp);
 }
 
 static void ca_ok_handler(dlgcontrol *ctrl, dlgparam *dp,
@@ -214,6 +229,8 @@ static void ca_save_handler(dlgcontrol *ctrl, dlgparam *dp,
         hca->hostname_wildcards = snewn(hca->n_hostname_wildcards, char *);
         for (size_t i = 0; i < hca->n_hostname_wildcards; i++)
             hca->hostname_wildcards[i] = dupstr(index234(st->host_wcs, i));
+        hca->opts = st->opts;          /* structure copy */
+
         char *error = host_ca_save(hca);
         host_ca_free(hca);
 
@@ -363,6 +380,20 @@ static void ca_wc_rem_handler(dlgcontrol *ctrl, dlgparam *dp,
     }
 }
 
+static void ca_rsa_type_handler(dlgcontrol *ctrl, dlgparam *dp,
+                                void *data, int event)
+{
+    struct ca_state *st = (struct ca_state *)ctrl->context.p;
+    size_t offset = ctrl->context2.i;
+    bool *option = (bool *)((char *)&st->opts + offset);
+
+    if (event == EVENT_REFRESH) {
+        dlg_checkbox_set(ctrl, dp, *option);
+    } else if (event == EVENT_VALCHANGE) {
+        *option = dlg_checkbox_get(ctrl, dp);
+    }
+}
+
 void setup_ca_config_box(struct controlbox *b)
 {
     struct controlset *s;
@@ -372,12 +403,17 @@ void setup_ca_config_box(struct controlbox *b)
     struct ca_state *st = (struct ca_state *)ctrl_alloc_with_free(
         b, sizeof(struct ca_state), ca_state_free);
     memset(st, 0, sizeof(*st));
-    st->name = dupstr("");
-    st->pubkey = dupstr("");
     st->ca_names = newtree234(ca_name_compare);
     st->host_wcs = newtree234(ca_name_compare);
     ca_refresh_name_list(st);
 
+    /* Initialise the settings to a default blank host_ca */
+    {
+        host_ca *hca = host_ca_new();
+        set_from_hca(st, hca);
+        host_ca_free(hca);
+    }
+
     /* Action area, with the Done button in it */
     s = ctrl_getset(b, "", "", "");
     ctrl_columns(s, 5, 20, 20, 20, 20, 20);
@@ -442,4 +478,25 @@ void setup_ca_config_box(struct controlbox *b)
     c = ctrl_pushbutton(s, "Remove", NO_SHORTCUT, HELPCTX(no_help),
                         ca_wc_rem_handler, P(st));
     c->column = 2;
+    ctrl_columns(s, 1, 100);
+
+    ctrl_columns(s, 4, 44, 18, 18, 18);
+    c = ctrl_text(s, "Signature types (RSA keys only):", HELPCTX(no_help));
+    c->column = 0;
+    c = ctrl_checkbox(s, "SHA-1", NO_SHORTCUT, HELPCTX(no_help),
+                      ca_rsa_type_handler, P(st));
+    c->column = 1;
+    c->context2 = I(offsetof(ca_options, permit_rsa_sha1));
+    st->rsa_type_checkboxes[0] = c;
+    c = ctrl_checkbox(s, "SHA-256", NO_SHORTCUT, HELPCTX(no_help),
+                      ca_rsa_type_handler, P(st));
+    c->column = 2;
+    c->context2 = I(offsetof(ca_options, permit_rsa_sha256));
+    st->rsa_type_checkboxes[1] = c;
+    c = ctrl_checkbox(s, "SHA-512", NO_SHORTCUT, HELPCTX(no_help),
+                      ca_rsa_type_handler, P(st));
+    c->column = 3;
+    c->context2 = I(offsetof(ca_options, permit_rsa_sha512));
+    st->rsa_type_checkboxes[2] = c;
+    ctrl_columns(s, 1, 100);
 }

ssh/kex2-client.c

@@ -912,6 +912,7 @@ void ssh2kex_coroutine(struct ssh2_transport_state *s, bool *aborted)
                         true, /* host certificate */
                         ptrlen_from_asciz(s->savedhost),
                         time(NULL),
+                        &hca_found->opts,
                         BinarySink_UPCAST(error));
                 }
                 if (cert_ok) {