pkcs7

Documentation

Overview

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/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.

Index

• Constants
• type Content
• type Data
• type EncryptedContentInfo
• type EncryptedData
• type PKCS7
  • func ParsePKCS7(raw []byte) (msg *PKCS7, err error)
• type SignedData

Constants

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"
)

Object identifier strings of the three implemented PKCS7 types.

Types

type Content

type Content struct {
	Data          []byte
	SignedData    SignedData
	EncryptedData EncryptedData
}

Content implements three of the six possible PKCS7 data types. Only one is non-nil.

type Data

type Data struct {
	Bytes []byte
}

Data contains raw bytes. Used as a subtype in PKCS12.

type EncryptedContentInfo

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

EncryptedContentInfo is a subtype of PKCS7EncryptedData.

type EncryptedData

type EncryptedData struct {
	Raw                  asn1.RawContent
	Version              int
	EncryptedContentInfo EncryptedContentInfo
}

EncryptedData contains encrypted data. Used as a subtype in PKCS12.

type PKCS7

type PKCS7 struct {
	Raw         asn1.RawContent
	ContentInfo string
	Content     Content
}

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.

func ParsePKCS7

func ParsePKCS7(raw []byte) (msg *PKCS7, err error)

ParsePKCS7 attempts to parse the DER encoded bytes of a PKCS7 structure.

type SignedData

type SignedData struct {
	Raw          asn1.RawContent
	Version      int
	Certificates []*x509.Certificate
	Crl          *pkix.CertificateList
}

SignedData defines the typical carrier of certificates and crls.