feat: Add IMAP4rev1 capability check to imap-login proxy

The imap-login proxy now checks if the remote server advertises the IMAP4rev1 capability. If the capability is not found, the proxying will fail with an error message.

diff --git a/src/imap-login/imap-proxy.c b/src/imap-login/imap-proxy.c
index 34ed1b24e8313701bbff13c2389636a41986f0ed..3074a4670d73ee065f2ab6679fa953e5991d485e 100644 (file)
--- a/src/imap-login/imap-proxy.c
+++ b/src/imap-login/imap-proxy.c
@@ -206,6 +206,13 @@ static int proxy_input_banner(struct imap_client *client,
        str = t_str_new(128);
        if (str_begins_icase(line, "[CAPABILITY ", &suffix)) {
                capabilities = t_strsplit(t_strcut(suffix, ']'), " ");
+               if (!str_array_icase_find(capabilities, "IMAP4rev1")) {
+                       login_proxy_failed(client->common.login_proxy,
+                               login_proxy_get_event(client->common.login_proxy),
+                               LOGIN_PROXY_FAILURE_TYPE_PROTOCOL,
+                               "Remote server doesn't support IMAP4rev1");
+                       return -1;
+               }
                if (str_array_icase_find(capabilities, "SASL-IR"))
                        client->proxy_sasl_ir = TRUE;
                if (str_array_icase_find(capabilities, "LOGINDISABLED"))
@@ -464,6 +471,15 @@ int imap_proxy_parse_line(struct client *client, const char *line)
                                   failure_type, log_line);
                return -1;
        } else if (str_begins_icase(line, "* CAPABILITY ", &line)) {
+               const char *const *capabilities = t_strsplit(line, " ");
+
+               if (!str_array_icase_find(capabilities, "IMAP4rev1")) {
+                       login_proxy_failed(client->login_proxy,
+                               login_proxy_get_event(client->login_proxy),
+                               LOGIN_PROXY_FAILURE_TYPE_PROTOCOL,
+                               "Remote server doesn't support IMAP4rev1");
+                       return -1;
+               }
                i_free(imap_client->proxy_backend_capability);
                imap_client->proxy_backend_capability = i_strdup(line);
                return 0;