goutils/certlib/pkcs7/pkcs7.go

package pkcs7

// Originally from CFSSL, and licensed under:

/*
Copyright (c) 2014 CloudFlare Inc.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:

Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.

Redistributions in binary form must reproduce the above copyright notice,
this list of conditions and the following disclaimer in the documentation
and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

// I've modified it for use in my own code e.g. by removing the CFSSL errors
// and replacing them with sane ones.

// Package pkcs7 implements the subset of the CMS PKCS #7 datatype that is typically
// used to package certificates and CRLs.  Using openssl, every certificate converted
// to PKCS #7 format from another encoding such as PEM conforms to this implementation.
// reference: https://www.openssl.org/docs/man1.1.0/apps/crl2pkcs7.html
//
// PKCS #7 Data type, reference: https://tools.ietf.org/html/rfc2315
//
// The full pkcs#7 cryptographic message syntax allows for cryptographic enhancements,
// for example data can be encrypted and signed and then packaged through pkcs#7 to be
// sent over a network and then verified and decrypted.  It is asn1, and the type of
// PKCS #7 ContentInfo, which comprises the PKCS #7 structure, is:
//
//	ContentInfo ::= SEQUENCE {
//		contentType ContentType,
//		content [0] EXPLICIT ANY DEFINED BY contentType OPTIONAL
//	}
//
// There are 6 possible ContentTypes, data, signedData, envelopedData,
// signedAndEnvelopedData, digestedData, and encryptedData.  Here signedData, Data, and encrypted
// Data are implemented, as the degenerate case of signedData without a signature is the typical
// format for transferring certificates and CRLS, and Data and encryptedData are used in PKCS #12
// formats.
// The ContentType signedData has the form:
//
//	signedData ::= SEQUENCE {
//		version Version,
//		digestAlgorithms DigestAlgorithmIdentifiers,
//		contentInfo ContentInfo,
//		certificates [0] IMPLICIT ExtendedCertificatesAndCertificates OPTIONAL
//		crls [1] IMPLICIT CertificateRevocationLists OPTIONAL,
//		signerInfos SignerInfos
//	}
//
// As of yet signerInfos and digestAlgorithms are not parsed, as they are not relevant to
// this system's use of PKCS #7 data.  Version is an integer type, note that PKCS #7 is
// recursive, this second layer of ContentInfo is similar ignored for our degenerate
// usage.  The ExtendedCertificatesAndCertificates type consists of a sequence of choices
// between PKCS #6 extended certificates and x509 certificates.  Any sequence consisting
// of any number of extended certificates is not yet supported in this implementation.
//
// The ContentType Data is simply a raw octet string and is parsed directly into a Go []byte slice.
//
// The ContentType encryptedData is the most complicated and its form can be gathered by
// the go type below.  It essentially contains a raw octet string of encrypted data and an
// algorithm identifier for use in decrypting this data.

import (
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/asn1"
	"errors"

	"git.wntrmute.dev/kyle/goutils/certlib/certerr"
)

// Types used for asn1 Unmarshaling.

type signedData struct {
	Version          int
	DigestAlgorithms asn1.RawValue
	ContentInfo      asn1.RawValue
	Certificates     asn1.RawValue `asn1:"optional" asn1:"tag:0"`
	Crls             asn1.RawValue `asn1:"optional"`
	SignerInfos      asn1.RawValue
}

type initPKCS7 struct {
	Raw         asn1.RawContent
	ContentType asn1.ObjectIdentifier
	Content     asn1.RawValue `asn1:"tag:0,explicit,optional"`
}

// Object identifier strings of the three implemented PKCS7 types.
const (
	ObjIDData          = "1.2.840.113549.1.7.1"
	ObjIDSignedData    = "1.2.840.113549.1.7.2"
	ObjIDEncryptedData = "1.2.840.113549.1.7.6"
)

// PKCS7 represents the ASN1 PKCS #7 Content type.  It contains one of three
// possible types of Content objects, as denoted by the object identifier in
// the ContentInfo field, the other two being nil.  SignedData
// is the degenerate SignedData Content info without signature used
// to hold certificates and crls.  Data is raw bytes, and EncryptedData
// is as defined in PKCS #7 standard.
type PKCS7 struct {
	Raw         asn1.RawContent
	ContentInfo string
	Content     Content
}

// Content implements three of the six possible PKCS7 data types.  Only one is non-nil.
type Content struct {
	Data          []byte
	SignedData    SignedData
	EncryptedData EncryptedData
}

// SignedData defines the typical carrier of certificates and crls.
type SignedData struct {
	Raw          asn1.RawContent
	Version      int
	Certificates []*x509.Certificate
	Crl          *x509.RevocationList
}

// Data contains raw bytes.  Used as a subtype in PKCS12.
type Data struct {
	Bytes []byte
}

// EncryptedData contains encrypted data.  Used as a subtype in PKCS12.
type EncryptedData struct {
	Raw                  asn1.RawContent
	Version              int
	EncryptedContentInfo EncryptedContentInfo
}

// EncryptedContentInfo is a subtype of PKCS7EncryptedData.
type EncryptedContentInfo struct {
	Raw                        asn1.RawContent
	ContentType                asn1.ObjectIdentifier
	ContentEncryptionAlgorithm pkix.AlgorithmIdentifier
	EncryptedContent           []byte `asn1:"tag:0,optional"`
}

// ParsePKCS7 attempts to parse the DER encoded bytes of a
// PKCS7 structure.
func ParsePKCS7(raw []byte) (msg *PKCS7, err error) {

	var pkcs7 initPKCS7
	_, err = asn1.Unmarshal(raw, &pkcs7)
	if err != nil {
		return nil, certerr.ParsingError(certerr.ErrorSourceCertificate, err)
	}

	msg = new(PKCS7)
	msg.Raw = pkcs7.Raw
	msg.ContentInfo = pkcs7.ContentType.String()
	switch {
	case msg.ContentInfo == ObjIDData:
		msg.ContentInfo = "Data"
		_, err = asn1.Unmarshal(pkcs7.Content.Bytes, &msg.Content.Data)
		if err != nil {
			return nil, certerr.ParsingError(certerr.ErrorSourceCertificate, err)
		}
	case msg.ContentInfo == ObjIDSignedData:
		msg.ContentInfo = "SignedData"
		var signedData signedData
		_, err = asn1.Unmarshal(pkcs7.Content.Bytes, &signedData)
		if err != nil {
			return nil, certerr.ParsingError(certerr.ErrorSourceCertificate, err)
		}
		if len(signedData.Certificates.Bytes) != 0 {
			msg.Content.SignedData.Certificates, err = x509.ParseCertificates(signedData.Certificates.Bytes)
			if err != nil {
				return nil, certerr.ParsingError(certerr.ErrorSourceCertificate, err)
			}
		}
		if len(signedData.Crls.Bytes) != 0 {
			msg.Content.SignedData.Crl, err = x509.ParseRevocationList(signedData.Crls.Bytes)
			if err != nil {
				return nil, certerr.ParsingError(certerr.ErrorSourceCertificate, err)
			}
		}
		msg.Content.SignedData.Version = signedData.Version
		msg.Content.SignedData.Raw = pkcs7.Content.Bytes
	case msg.ContentInfo == ObjIDEncryptedData:
		msg.ContentInfo = "EncryptedData"
		var encryptedData EncryptedData
		_, err = asn1.Unmarshal(pkcs7.Content.Bytes, &encryptedData)
		if err != nil {
			return nil, certerr.ParsingError(certerr.ErrorSourceCertificate, err)
		}
		if encryptedData.Version != 0 {
			return nil, certerr.ParsingError(certerr.ErrorSourceCertificate, errors.New("only PKCS #7 encryptedData version 0 is supported"))
		}
		msg.Content.EncryptedData = encryptedData

	default:
		return nil, certerr.ParsingError(certerr.ErrorSourceCertificate, errors.New("only PKCS# 7 content of type data, signed data or encrypted data can be parsed"))
	}

	return msg, nil

}