private bool DoVerify(
AsymmetricKeyParameter key)
{
string digestName = Helper.GetDigestAlgName(this.DigestAlgOid);
IDigest digest = Helper.GetDigestInstance(digestName);
DerObjectIdentifier sigAlgOid = this.encryptionAlgorithm.Algorithm;
Asn1Encodable sigParams = this.encryptionAlgorithm.Parameters;
ISigner sig;
if (sigAlgOid.Equals(Asn1.Pkcs.PkcsObjectIdentifiers.IdRsassaPss))
{
// RFC 4056 2.2
// When the id-RSASSA-PSS algorithm identifier is used for a signature,
// the AlgorithmIdentifier parameters field MUST contain RSASSA-PSS-params.
if (sigParams == null)
{
throw new CmsException("RSASSA-PSS signature must specify algorithm parameters");
}
try
{
// TODO Provide abstract configuration mechanism
// (via alternate SignerUtilities.GetSigner method taking ASN.1 params)
Asn1.Pkcs.RsassaPssParameters pss = Asn1.Pkcs.RsassaPssParameters.GetInstance(
sigParams.ToAsn1Object());
if (!pss.HashAlgorithm.Algorithm.Equals(this.digestAlgorithm.Algorithm))
{
throw new CmsException("RSASSA-PSS signature parameters specified incorrect hash algorithm");
}
if (!pss.MaskGenAlgorithm.Algorithm.Equals(Asn1.Pkcs.PkcsObjectIdentifiers.IdMgf1))
{
throw new CmsException("RSASSA-PSS signature parameters specified unknown MGF");
}
IDigest pssDigest = DigestUtilities.GetDigest(pss.HashAlgorithm.Algorithm);
int saltLength = pss.SaltLength.Value.IntValue;
byte trailerField = (byte)pss.TrailerField.Value.IntValue;
// RFC 4055 3.1
// The value MUST be 1, which represents the trailer field with hexadecimal value 0xBC
if (trailerField != 1)
{
throw new CmsException("RSASSA-PSS signature parameters must have trailerField of 1");
}
sig = new PssSigner(new RsaBlindedEngine(), pssDigest, saltLength);
}
catch (Exception e)
{
throw new CmsException("failed to set RSASSA-PSS signature parameters", e);
}
}
else
{
// TODO Probably too strong a check at the moment
// if (sigParams != null)
// throw new CmsException("unrecognised signature parameters provided");
string signatureName = digestName + "with" + Helper.GetEncryptionAlgName(this.EncryptionAlgOid);
sig = Helper.GetSignatureInstance(signatureName);
//sig = Helper.GetSignatureInstance(this.EncryptionAlgOid);
//sig = SignerUtilities.GetSigner(sigAlgOid);
}
try
{
if (digestCalculator != null)
{
resultDigest = digestCalculator.GetDigest();
}
else
{
if (content != null)
{
content.Write(new DigOutputStream(digest));
}
else if (signedAttributeSet == null)
{
// TODO Get rid of this exception and just treat content==null as empty not missing?
throw new CmsException("data not encapsulated in signature - use detached constructor.");
}
resultDigest = DigestUtilities.DoFinal(digest);
}
}
catch (IOException e)
{
throw new CmsException("can't process mime object to create signature.", e);
}
// RFC 3852 11.1 Check the content-type attribute is correct
{
Asn1Object validContentType = GetSingleValuedSignedAttribute(
CmsAttributes.ContentType, "content-type");
if (validContentType == null)
{
if (!isCounterSignature && signedAttributeSet != null)
{
throw new CmsException("The content-type attribute type MUST be present whenever signed attributes are present in signed-data");
}
}
else
{
if (isCounterSignature)
{
throw new CmsException("[For counter signatures,] the signedAttributes field MUST NOT contain a content-type attribute");
}
if (!(validContentType is DerObjectIdentifier))
{
throw new CmsException("content-type attribute value not of ASN.1 type 'OBJECT IDENTIFIER'");
}
DerObjectIdentifier signedContentType = (DerObjectIdentifier)validContentType;
if (!signedContentType.Equals(contentType))
{
throw new CmsException("content-type attribute value does not match eContentType");
}
}
}
// RFC 3852 11.2 Check the message-digest attribute is correct
{
Asn1Object validMessageDigest = GetSingleValuedSignedAttribute(
CmsAttributes.MessageDigest, "message-digest");
if (validMessageDigest == null)
{
if (signedAttributeSet != null)
{
throw new CmsException("the message-digest signed attribute type MUST be present when there are any signed attributes present");
}
}
else
{
if (!(validMessageDigest is Asn1OctetString))
{
throw new CmsException("message-digest attribute value not of ASN.1 type 'OCTET STRING'");
}
Asn1OctetString signedMessageDigest = (Asn1OctetString)validMessageDigest;
if (!Arrays.AreEqual(resultDigest, signedMessageDigest.GetOctets()))
{
throw new CmsException("message-digest attribute value does not match calculated value");
}
}
}
// RFC 3852 11.4 Validate countersignature attribute(s)
{
Asn1.Cms.AttributeTable signedAttrTable = this.SignedAttributes;
if (signedAttrTable != null &&
signedAttrTable.GetAll(CmsAttributes.CounterSignature).Count > 0)
{
throw new CmsException("A countersignature attribute MUST NOT be a signed attribute");
}
Asn1.Cms.AttributeTable unsignedAttrTable = this.UnsignedAttributes;
if (unsignedAttrTable != null)
{
foreach (Asn1.Cms.Attribute csAttr in unsignedAttrTable.GetAll(CmsAttributes.CounterSignature))
{
if (csAttr.AttrValues.Count < 1)
{
throw new CmsException("A countersignature attribute MUST contain at least one AttributeValue");
}
// Note: We don't recursively validate the countersignature value
}
}
}
try
{
sig.Init(false, key);
if (signedAttributeSet == null)
{
if (digestCalculator != null)
{
// need to decrypt signature and check message bytes
return(VerifyDigest(resultDigest, key, this.GetSignature()));
}
else if (content != null)
{
// TODO Use raw signature of the hash value instead
content.Write(new SigOutputStream(sig));
}
}
else
{
byte[] tmp = this.GetEncodedSignedAttributes();
sig.BlockUpdate(tmp, 0, tmp.Length);
}
return(sig.VerifySignature(this.GetSignature()));
}
catch (InvalidKeyException e)
{
throw new CmsException("key not appropriate to signature in message.", e);
}
catch (IOException e)
{
throw new CmsException("can't process mime object to create signature.", e);
}
catch (SignatureException e)
{
throw new CmsException("invalid signature format in message: " + e.Message, e);
}
}
/**
* Return a SignerInformationStore containing the counter signatures attached to this
* signer. If no counter signatures are present an empty store is returned.
*/
public SignerInformationStore GetCounterSignatures()
{
// TODO There are several checks implied by the RFC3852 comments that are missing
/*
* The countersignature attribute MUST be an unsigned attribute; it MUST
* NOT be a signed attribute, an authenticated attribute, an
* unauthenticated attribute, or an unprotected attribute.
*/
Asn1.Cms.AttributeTable unsignedAttributeTable = UnsignedAttributes;
if (unsignedAttributeTable == null)
{
return(new SignerInformationStore(Platform.CreateArrayList(0)));
}
IList counterSignatures = Platform.CreateArrayList();
/*
* The UnsignedAttributes syntax is defined as a SET OF Attributes. The
* UnsignedAttributes in a signerInfo may include multiple instances of
* the countersignature attribute.
*/
Asn1EncodableVector allCSAttrs = unsignedAttributeTable.GetAll(CmsAttributes.CounterSignature);
foreach (Asn1.Cms.Attribute counterSignatureAttribute in allCSAttrs)
{
/*
* A countersignature attribute can have multiple attribute values. The
* syntax is defined as a SET OF AttributeValue, and there MUST be one
* or more instances of AttributeValue present.
*/
Asn1Set values = counterSignatureAttribute.AttrValues;
if (values.Count < 1)
{
// TODO Throw an appropriate exception?
}
foreach (Asn1Encodable asn1Obj in values)
{
/*
* Countersignature values have the same meaning as SignerInfo values
* for ordinary signatures, except that:
*
* 1. The signedAttributes field MUST NOT contain a content-type
* attribute; there is no content type for countersignatures.
*
* 2. The signedAttributes field MUST contain a message-digest
* attribute if it contains any other attributes.
*
* 3. The input to the message-digesting process is the contents
* octets of the DER encoding of the signatureValue field of the
* SignerInfo value with which the attribute is associated.
*/
SignerInfo si = SignerInfo.GetInstance(asn1Obj.ToAsn1Object());
string digestName = CmsSignedHelper.Instance.GetDigestAlgName(si.DigestAlgorithm.Algorithm.Id);
counterSignatures.Add(new SignerInformation(si, null, null, new CounterSignatureDigestCalculator(digestName, GetSignature())));
}
}
return(new SignerInformationStore(counterSignatures));
}
