feat: cms package

internal/crypto/cms/cms.go

@@ -0,0 +1,185 @@
+// Copyright The Notary Project Authors.
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package cms verifies signatures in Cryptographic Message Syntax (CMS) / PKCS7
+// defined in RFC 5652.
+//
+// References:
+// - RFC 5652 Cryptographic Message Syntax (CMS): https://datatracker.ietf.org/doc/html/rfc5652
+package cms
+
+import (
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/asn1"
+	"math/big"
+)
+
+// ContentInfo struct is used to represent the content of a CMS message,
+// which can be encrypted, signed, or both.
+//
+// References: RFC 5652 3 ContentInfo Type
+//
+//	ContentInfo ::= SEQUENCE {
+//	  contentType ContentType,
+//	  content [0] EXPLICIT ANY DEFINED BY contentType }
+type ContentInfo struct {
+	// ContentType field specifies the type of the content, which can be one of
+	// several predefined types, such as data, signedData, envelopedData, or
+	// encryptedData. Only signedData is supported currently.
+	ContentType asn1.ObjectIdentifier
+
+	// Content field contains the actual content of the message.
+	Content asn1.RawValue `asn1:"explicit,tag:0"`
+}
+
+// SignedData struct is used to represent a signed CMS message, which contains
+// one or more signatures that are used to verify the authenticity and integrity
+// of the message.
+//
+// Reference: RFC 5652 5.1 SignedData
+//
+//	SignedData ::= SEQUENCE {
+//	 version             CMSVersion,
+//	 digestAlgorithms    DigestAlgorithmIdentifiers,
+//	 encapContentInfo    EncapsulatedContentInfo,
+//	 certificates        [0] IMPLICIT CertificateSet             OPTIONAL,
+//	 crls                [1] IMPLICIT CertificateRevocationLists OPTIONAL,
+//	 signerInfos         SignerInfos }
+type SignedData struct {
+	// Version field specifies the syntax version number of the SignedData.
+	Version int
+
+	// DigestAlgorithmIdentifiers field specifies the digest algorithms used
+	// by one or more signatures in SignerInfos.
+	DigestAlgorithmIdentifiers []pkix.AlgorithmIdentifier `asn1:"set"`
+
+	// EncapsulatedContentInfo field specifies the content that is signed.
+	EncapsulatedContentInfo EncapsulatedContentInfo
+
+	// Certificates field contains the certificates that are used to verify the
+	// signatures in SignerInfos.
+	Certificates asn1.RawValue `asn1:"optional,tag:0"`
+
+	// CRLs field contains the Certificate Revocation Lists that are used to
+	// verify the signatures in SignerInfos.
+	CRLs []x509.RevocationList `asn1:"optional,tag:1"`
+
+	// SignerInfos field contains one or more signatures.
+	SignerInfos []SignerInfo `asn1:"set"`
+}
+
+// EncapsulatedContentInfo struct is used to represent the content of a CMS
+// message.
+//
+// References: RFC 5652 5.2 EncapsulatedContentInfo
+//
+//	EncapsulatedContentInfo ::= SEQUENCE {
+//	 eContentType    ContentType,
+//	 eContent        [0] EXPLICIT OCTET STRING   OPTIONAL }
+type EncapsulatedContentInfo struct {
+	// ContentType is an object identifier. The object identifier uniquely
+	// specifies the content type.
+	ContentType asn1.ObjectIdentifier
+
+	// Content field contains the actual content of the message.
+	Content []byte `asn1:"explicit,optional,tag:0"`
+}
+
+// SignerInfo struct is used to represent a signature and related information
+// that is needed to verify the signature.
+//
+// Reference: RFC 5652 5.3 SignerInfo
+//
+//	SignerInfo ::= SEQUENCE {
+//	 version             CMSVersion,
+//	 sid                 SignerIdentifier,
+//	 digestAlgorithm     DigestAlgorithmIdentifier,
+//	 signedAttrs         [0] IMPLICIT SignedAttributes   OPTIONAL,
+//	 signatureAlgorithm  SignatureAlgorithmIdentifier,
+//	 signature           SignatureValue,
+//	 unsignedAttrs       [1] IMPLICIT UnsignedAttributes OPTIONAL }
+//
+// Only version 1 is supported. As defined in RFC 5652 5.3, SignerIdentifier
+// is IssuerAndSerialNumber when version is 1.
+type SignerInfo struct {
+	// Version field specifies the syntax version number of the SignerInfo.
+	Version int
+
+	// SignerIdentifier field specifies the signer's certificate. Only IssuerAndSerialNumber
+	// is supported currently.
+	SignerIdentifier IssuerAndSerialNumber
+
+	// DigestAlgorithm field specifies the digest algorithm used by the signer.
+	DigestAlgorithm pkix.AlgorithmIdentifier
+
+	// SignedAttributes field contains a collection of attributes that are
+	// signed.
+	SignedAttributes Attributes `asn1:"optional,tag:0"`
+
+	// SignatureAlgorithm field specifies the signature algorithm used by the
+	// signer.
+	SignatureAlgorithm pkix.AlgorithmIdentifier
+
+	// Signature field contains the actual signature.
+	Signature []byte
+
+	// UnsignedAttributes field contains a collection of attributes that are
+	// not signed.
+	UnsignedAttributes Attributes `asn1:"optional,tag:1"`
+}
+
+// IssuerAndSerialNumber struct is used to identify a certificate.
+//
+// Reference: RFC 5652 5.3 SignerIdentifier
+//
+//	IssuerAndSerialNumber ::= SEQUENCE {
+//	 issuer          Name,
+//	 serialNumber    CertificateSerialNumber }
+type IssuerAndSerialNumber struct {
+	// Issuer field identifies the certificate issuer.
+	Issuer asn1.RawValue
+
+	// SerialNumber field identifies the certificate.
+	SerialNumber *big.Int
+}
+
+// Attributes struct is used to represent a collection of attributes.
+//
+// Reference: RFC 5652 5.3 SignerInfo
+//
+//	Attribute ::= SEQUENCE {
+//	  attrType    OBJECT IDENTIFIER,
+//	  attrValues  SET OF AttributeValue }
+type Attribute struct {
+	// Type field specifies the type of the attribute.
+	Type asn1.ObjectIdentifier
+
+	// Values field contains the actual value of the attribute.
+	Values asn1.RawValue `asn1:"set"`
+}
+
+// Attribute ::= SET SIZE (1..MAX) OF Attribute
+type Attributes []Attribute
+
+// TryGet tries to find the attribute by the given identifier, parse and store
+// the result in the value pointed to by out.
+func (a *Attributes) TryGet(identifier asn1.ObjectIdentifier, out interface{}) error {
+	for _, attribute := range *a {
+		if identifier.Equal(attribute.Type) {
+			_, err := asn1.Unmarshal(attribute.Values.Bytes, out)
+			return err
+		}
+	}
+	return ErrAttributeNotFound
+}