/// <summary>
/// Gets the signature type from one or more commitment-type-indication attributes.
/// </summary>
/// <param name="signedAttributes">A <see cref="SignerInfo" /> signed attributes collection.</param>
/// <remarks>Unknown OIDs are ignored.</remarks>
/// <exception cref="ArgumentNullException">Thrown if <paramref name="signedAttributes" /> is <c>null</c>.</exception>
/// <exception cref="SignatureException">Thrown if one or more attributes are invalid.</exception>
public static SignatureType GetSignatureType(CryptographicAttributeObjectCollection signedAttributes)
{
if (signedAttributes == null)
{
throw new ArgumentNullException(nameof(signedAttributes));
}
var values = signedAttributes.GetAttributes(Oids.CommitmentTypeIndication)
.SelectMany(attribute => GetCommitmentTypeIndicationRawValues(attribute))
.Distinct();
// Remove unknown values, these could be future values.
var knownValues = values.Where(e => e != SignatureType.Unknown).ToList();
if (knownValues.Count == 0)
{
return(SignatureType.Unknown);
}
// Author and repository values are mutually exclusive in the same signature.
// If multiple distinct known values exist then the attribute is invalid.
if (knownValues.Count > 1)
{
throw new SignatureException(Strings.CommitmentTypeIndicationAttributeInvalidCombination);
}
return(knownValues[0]);
}
/// <summary>
/// Gets 0 or 1 attribute with the specified OID. If more than one attribute is found, an exception is thrown.
/// </summary>
/// <param name="attributes">A collection of attributes.</param>
/// <param name="oid">The attribute OID to search for.</param>
/// <returns>Either a <see cref="CryptographicAttributeObject" /> or <c>null</c>, if no attribute was found.</returns>
/// <exception cref="ArgumentNullException">Thrown if <paramref name="attributes" /> is <c>null</c>.</exception>
/// <exception cref="ArgumentException">Thrown if <paramref name="oid" /> is either <c>null</c> or an empty string.</exception>
/// <exception cref="CryptographicException">Thrown if multiple attribute instances with the specified OID were found.</exception>
public static CryptographicAttributeObject GetAttribute(this CryptographicAttributeObjectCollection attributes, string oid)
{
if (attributes == null)
{
throw new ArgumentNullException(nameof(attributes));
}
if (string.IsNullOrEmpty(oid))
{
throw new ArgumentException(Strings.ArgumentCannotBeNullOrEmpty, nameof(oid));
}
var matches = attributes.GetAttributes(oid);
var instanceCount = matches.Count();
if (instanceCount == 0)
{
return(null);
}
if (instanceCount > 1)
{
throw new CryptographicException(string.Format(CultureInfo.CurrentCulture, Strings.MultipleAttributesDisallowed, oid));
}
return(matches.Single());
}