/// <summary>
/// Validate that a specified context token string is intended for this application based on the parameters
/// specified in web.config. Parameters used from web.config used for validation include ClientId,
/// HostedAppHostNameOverride, HostedAppHostName, ClientSecret, and Realm (if it is specified). If HostedAppHostNameOverride is present,
/// it will be used for validation. Otherwise, if the <paramref name="appHostName"/> is not
/// null, it is used for validation instead of the web.config's HostedAppHostName. If the token is invalid, an
/// exception is thrown. If the token is valid, TokenHelper's static STS metadata url is updated based on the token contents
/// and a JsonWebSecurityToken based on the context token is returned.
/// </summary>
/// <param name="contextTokenString">The context token to validate</param>
/// <param name="appHostName">The URL authority, consisting of Domain Name System (DNS) host name or IP address and the port number, to use for token audience validation.
/// If null, HostedAppHostName web.config setting is used instead. HostedAppHostNameOverride web.config setting, if present, will be used
/// for validation instead of <paramref name="appHostName"/> .</param>
/// <returns>A JsonWebSecurityToken based on the context token.</returns>
public static SharePointContextToken ReadAndValidateContextToken(string contextTokenString,
string appHostName = null)
{
JsonWebSecurityTokenHandler tokenHandler = CreateJsonWebSecurityTokenHandler();
SecurityToken securityToken = tokenHandler.ReadToken(contextTokenString);
JsonWebSecurityToken jsonToken = securityToken as JsonWebSecurityToken;
SharePointContextToken token = SharePointContextToken.Create(jsonToken);
string stsAuthority = (new Uri(token.SecurityTokenServiceUri)).Authority;
int firstDot = stsAuthority.IndexOf('.');
GlobalEndPointPrefix = stsAuthority.Substring(0, firstDot);
AcsHostUrl = stsAuthority.Substring(firstDot + 1);
tokenHandler.ValidateToken(jsonToken);
string[] acceptableAudiences;
if (!String.IsNullOrEmpty(HostedAppHostNameOverride))
{
acceptableAudiences = HostedAppHostNameOverride.Split(';');
}
else if (appHostName == null)
{
acceptableAudiences = new[] { HostedAppHostName };
}
else
{
acceptableAudiences = new[] { appHostName };
}
bool validationSuccessful = false;
string realm = Realm ?? token.Realm;
foreach (var audience in acceptableAudiences)
{
string principal = GetFormattedPrincipal(ClientId, audience, realm);
if (StringComparer.OrdinalIgnoreCase.Equals(token.Audience, principal))
{
validationSuccessful = true;
break;
}
}
if (!validationSuccessful)
{
throw new AudienceUriValidationFailedException(
String.Format(CultureInfo.CurrentCulture,
"\"{0}\" is not the intended audience \"{1}\"", String.Join(";", acceptableAudiences),
token.Audience));
}
return(token);
}