/// <summary>
/// Re-instantiates an <see cref="Association"/> previously persisted in a database or some
/// other shared store.
/// </summary>
/// <param name="handle">
/// The <see cref="Handle"/> property of the previous <see cref="Association"/> instance.
/// </param>
/// <param name="expiresUtc">
/// The UTC value of the <see cref="Expires"/> property of the previous <see cref="Association"/> instance.
/// </param>
/// <param name="privateData">
/// The byte array returned by a call to <see cref="SerializePrivateData"/> on the previous
/// <see cref="Association"/> instance.
/// </param>
/// <returns>
/// The newly dehydrated <see cref="Association"/>, which can be returned
/// from a custom association store's
/// IRelyingPartyAssociationStore.GetAssociation method.
/// </returns>
public static Association Deserialize(string handle, DateTime expiresUtc, byte[] privateData)
{
Requires.NotNullOrEmpty(handle, "handle");
Requires.NotNull(privateData, "privateData");
expiresUtc = expiresUtc.ToUniversalTimeSafe();
TimeSpan remainingLifeLength = expiresUtc - DateTime.UtcNow;
byte[] secret = privateData; // the whole of privateData is the secret key for now.
// We figure out what derived type to instantiate based on the length of the secret.
try {
return(HmacShaAssociation.Create(handle, secret, remainingLifeLength));
} catch (ArgumentException ex) {
throw new ArgumentException(OpenIdStrings.BadAssociationPrivateData, "privateData", ex);
}
}
/// <summary>
/// Determines whether a named association fits the security requirements.
/// </summary>
/// <param name="protocol">The protocol carrying the association.</param>
/// <param name="associationType">The value of the openid.assoc_type parameter.</param>
/// <returns>
/// <c>true</c> if the association is permitted given the security requirements; otherwise, <c>false</c>.
/// </returns>
internal bool IsAssociationInPermittedRange(Protocol protocol, string associationType)
{
int lengthInBits = HmacShaAssociation.GetSecretLength(protocol, associationType) * 8;
return(lengthInBits >= this.MinimumHashBitLength && lengthInBits <= this.MaximumHashBitLength);
}