browser-client-SAMLResponse: Parse response query string to get SAMLResponse key value pair

[NemindaPiyasena]

• Previously SAMLResponse=xxxx key value pair was selected from the POST request response data. It looked for a return of a SAMLResponse=xxxx examining the browser events.
• This approach works fine until the browser response doesn't send any other data in the response.
• But some SAML providers sends out other information like RelayState=xxxx. If this key value pair is in the response after the SAMLResponse=xxxx , the captured string from the browser events would look like SAMLResponse=xxxx&RelayState=xxxx. This would result in a base64 decoding error becase of the & character.
• Made changes to capture only the SAMLResponse=xxxx key value pair using regex.

[mmmorris1975]

Thank you for taking the time to make this contribution. Since the payload you are seeing is starting to look like a URL query string, would it make more sense to do something like:

qs, err := url.ParseQuery(ev.Request.PostData)
if err != nil {
    c.Logger.Errorf("Error parsing SAMLResponse: %v", err)
    return
}
escsaml := qs.Get("SAMLResponse")

I think either approach will work, but wanted to propose an alternative to see if one feels like a better solution compared to the other. For what we're trying to accomplish here, I don't see a clear preference for how this is addressed.

[NemindaPiyasena]

Hi @mmmorris1975

Thank you for your input. Parsing as a query string makes more sense in the context. I have made the changes accordingly.

[mmmorris1975]

Thanks again for taking time to make aws-runas better! I'll work on getting this added in a new release