HttpHelpers.getUrlString allows NullPointerException due to null response body

[digitalapps21]

I’m encountering a crash in the Ably Java/Android SDK related to HttpHelpers.getUrlString.

Issue

When getUrlString calls new String(getUrl(...)), if getUrl returns null (e.g. empty response, network error), this results in:

Fatal Exception: java.lang.NullPointerException
Attempt to get length of null array
at java.lang.StringFactory.newStringFromBytes(StringFactory.java:46)
at io.ably.lib.http.HttpHelpers.getUrlString(HttpHelpers.java:45)

Stack trace

io.ably.lib.http.HttpHelpers.getUrlString(HttpHelpers.java:45)
io.ably.lib.transport.ConnectionManager.checkConnectivity
io.ably.lib.transport.ConnectionManager.checkFallback
io.ably.lib.transport.ConnectionManager.onTransportUnavailable
io.ably.lib.transport.WebSocketTransport$WsClient.onError
org.java_websocket.client.WebSocketClient.onWebsocketError
...

Analysis

getUrlString doesn’t check for null before passing the byte array to new String(...).

This can happen if HttpCore.Response.body is null.

We observed this during network failures or fallback host issues.

Suggested fix

In getUrlString, add a check:

public static String getUrlString(HttpCore httpCore, String url) throws AblyException {
    byte[] bytes = getUrl(httpCore, url);
    if (bytes == null) {
        throw AblyException.fromErrorInfo(new ErrorInfo("Empty response body", 50000, 500));
    }
    return new String(bytes);
}

or similar logic.

┆Issue is synchronized with this Jira Task by Unito

[ttypic]

Hi @digitalapps21,

Thanks for reporting this! we are working on a fix