pkcs7

package module
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 Go to latest Published: Mar 26, 2026 License: MIT Imports: 24 Imported by: 27

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pkcs7

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pkcs7 implements parsing and creating signed and enveloped messages.

package main

import (
	"bytes"
	"crypto/rsa"
	"crypto/x509"
	"encoding/pem"
	"fmt"
	"os"

    "go.mozilla.org/pkcs7"
)

func SignAndDetach(content []byte, cert *x509.Certificate, privkey *rsa.PrivateKey) (signed []byte, err error) {
	toBeSigned, err := NewSignedData(content)
	if err != nil {
		err = fmt.Errorf("Cannot initialize signed data: %s", err)
		return
	}
	if err = toBeSigned.AddSigner(cert, privkey, SignerInfoConfig{}); err != nil {
		err = fmt.Errorf("Cannot add signer: %s", err)
		return
	}

	// Detach signature, omit if you want an embedded signature
	toBeSigned.Detach()

	signed, err = toBeSigned.Finish()
	if err != nil {
		err = fmt.Errorf("Cannot finish signing data: %s", err)
		return
	}

	// Verify the signature
	pem.Encode(os.Stdout, &pem.Block{Type: "PKCS7", Bytes: signed})
	p7, err := pkcs7.Parse(signed)
	if err != nil {
		err = fmt.Errorf("Cannot parse our signed data: %s", err)
		return
	}

	// since the signature was detached, reattach the content here
	p7.Content = content

	if bytes.Compare(content, p7.Content) != 0 {
		err = fmt.Errorf("Our content was not in the parsed data:\n\tExpected: %s\n\tActual: %s", content, p7.Content)
		return
	}
	if err = p7.Verify(); err != nil {
		err = fmt.Errorf("Cannot verify our signed data: %s", err)
		return
	}

	return signed, nil
}

Credits

This is a fork of fullsailor/pkcs7

Documentation

Overview

Package pkcs7 implements parsing and generation of some PKCS#7 structures.

Index

Examples

Constants

View Source 
const (
	// EncryptionAlgorithmDESCBC is the DES CBC encryption algorithm
	EncryptionAlgorithmDESCBC = iota

	// EncryptionAlgorithmAES128CBC is the AES 128 bits with CBC encryption algorithm
	// Avoid this algorithm unless required for interoperability; use AES GCM instead.
	EncryptionAlgorithmAES128CBC

	// EncryptionAlgorithmAES256CBC is the AES 256 bits with CBC encryption algorithm
	// Avoid this algorithm unless required for interoperability; use AES GCM instead.
	EncryptionAlgorithmAES256CBC

	// EncryptionAlgorithmAES128GCM is the AES 128 bits with GCM encryption algorithm
	EncryptionAlgorithmAES128GCM

	// EncryptionAlgorithmAES256GCM is the AES 256 bits with GCM encryption algorithm
	EncryptionAlgorithmAES256GCM
)

Variables

View Source 
var (
	// Signed Data OIDs
	OIDData                   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 7, 1}
	OIDSignedData             = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 7, 2}
	OIDEnvelopedData          = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 7, 3}
	OIDEncryptedData          = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 7, 6}
	OIDAttributeContentType   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 9, 3}
	OIDAttributeMessageDigest = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 9, 4}
	OIDAttributeSigningTime   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 9, 5}

	// Digest Algorithms
	OIDDigestAlgorithmSHA1   = asn1.ObjectIdentifier{1, 3, 14, 3, 2, 26}
	OIDDigestAlgorithmSHA256 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 1}
	OIDDigestAlgorithmSHA384 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 2}
	OIDDigestAlgorithmSHA512 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 3}

	OIDDigestAlgorithmDSA     = asn1.ObjectIdentifier{1, 2, 840, 10040, 4, 1}
	OIDDigestAlgorithmDSASHA1 = asn1.ObjectIdentifier{1, 2, 840, 10040, 4, 3}

	OIDDigestAlgorithmECDSASHA1   = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 1}
	OIDDigestAlgorithmECDSASHA256 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 2}
	OIDDigestAlgorithmECDSASHA384 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 3}
	OIDDigestAlgorithmECDSASHA512 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 4}

	// Signature Algorithms
	OIDEncryptionAlgorithmRSA       = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 1}
	OIDEncryptionAlgorithmRSASHA1   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 5}
	OIDEncryptionAlgorithmRSAPSS    = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 10}
	OIDEncryptionAlgorithmRSASHA256 = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 11}
	OIDEncryptionAlgorithmRSASHA384 = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 12}
	OIDEncryptionAlgorithmRSASHA512 = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 13}

	OIDEncryptionAlgorithmECDSAP256   = asn1.ObjectIdentifier{1, 2, 840, 10045, 3, 1, 7} // 256 bit elliptic curve
	OIDEncryptionAlgorithmECDSAP384   = asn1.ObjectIdentifier{1, 3, 132, 0, 34}          // 384-bit elliptic curve
	OIDEncryptionAlgorithmECDSAP521   = asn1.ObjectIdentifier{1, 3, 132, 0, 35}          // 512-bit elliptic curve!
	OIDEncryptionAlgorithmECPUBLICKEY = asn1.ObjectIdentifier{1, 2, 840, 10045, 2, 1}    // ecPublicKey

	OIDEncryptionAlgorithmDESCBC     = asn1.ObjectIdentifier{1, 3, 14, 3, 2, 7}
	OIDEncryptionAlgorithmDESEDE3CBC = asn1.ObjectIdentifier{1, 2, 840, 113549, 3, 7}

	OIDEncryptionAlgorithmAES256CBC = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 1, 42}
	OIDEncryptionAlgorithmAES128GCM = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 1, 6}
	OIDEncryptionAlgorithmAES128CBC = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 1, 2}
	OIDEncryptionAlgorithmAES256GCM = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 1, 46}

	OIDEncryptionAlgorithmECDSAWithSHA256 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 2}
	OIDEncryptionAlgorithmECDSAWithSHA384 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 3}
	OIDEncryptionAlgorithmECDSAWithSHA512 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 4}

	OIDEncryptionAlgorithmEd25519 = asn1.ObjectIdentifier{1, 3, 101, 112}

	// Elliptic curve names
	OIDCurveP256 = asn1.ObjectIdentifier{1, 2, 840, 10045, 3, 1, 7}
	OIDCurveP384 = asn1.ObjectIdentifier{1, 3, 132, 0, 34}
	OIDCurveP521 = asn1.ObjectIdentifier{1, 3, 132, 0, 35}
)
View Source 
var ContentEncryptionAlgorithm = EncryptionAlgorithmDESCBC

ContentEncryptionAlgorithm determines the algorithm used to encrypt the plaintext message. Change the value of this variable to change which algorithm is used in the Encrypt() function.

View Source 
var EC2IdentityDocumentFixture = `` /* 2165-byte string literal not displayed */
View Source 
var ErrNotEncryptedContent = errors.New("pkcs7: content data is a decryptable data type")

ErrNotEncryptedContent is returned when attempting to Decrypt data that is not encrypted data

View Source 
var ErrPSKNotProvided = errors.New("pkcs7: cannot encrypt content: PSK not provided")

ErrPSKNotProvided is returned when attempting to encrypt using a PSK without actually providing the PSK.

View Source 
var ErrUnsupportedAlgorithm = errors.New("pkcs7: cannot decrypt data: only RSA, DES, DES-EDE3, AES-256-CBC and AES-128-GCM supported")

ErrUnsupportedAlgorithm tells you when our quick dev assumptions have failed

View Source 
var ErrUnsupportedContentType = errors.New("pkcs7: cannot parse data: unimplemented content type")

ErrUnsupportedContentType is returned when a PKCS7 content is not supported. Currently only Data (1.2.840.113549.1.7.1), Signed Data (1.2.840.113549.1.7.2), and Enveloped Data are supported (1.2.840.113549.1.7.3)

View Source 
var ErrUnsupportedEncryptionAlgorithm = errors.New("pkcs7: cannot encrypt content: only DES-CBC, AES-CBC, and AES-GCM supported")

ErrUnsupportedEncryptionAlgorithm is returned when attempting to encrypt content with an unsupported algorithm.

Functions

func CheckSignature added in v0.2.0 

func CheckSignature(cert *x509.Certificate, signer SignerInfo, content []byte) error

func DegenerateCertificate 

func DegenerateCertificate(cert []byte) ([]byte, error)

DegenerateCertificate creates a signed data structure containing only the provided certificate or certificate chain.

func DigestOIDForSignatureAlgorithm added in v0.2.1 

func DigestOIDForSignatureAlgorithm(digestAlg x509.SignatureAlgorithm) (asn1.ObjectIdentifier, error)

DigestOIDForSignatureAlgorithm takes an x509.SignatureAlgorithm and returns the corresponding OID digest algorithm

func Encrypt 

func Encrypt(content []byte, recipients []*x509.Certificate) ([]byte, error)

Encrypt creates and returns an envelope data PKCS7 structure with encrypted recipient keys for each recipient public key.

The algorithm used to perform encryption is determined by the current value of the global ContentEncryptionAlgorithm package variable. By default, the value is EncryptionAlgorithmDESCBC. To use a different algorithm, change the value before calling Encrypt(). For example: 

ContentEncryptionAlgorithm = EncryptionAlgorithmAES128GCM

TODO(fullsailor): Add support for encrypting content with other algorithms

func EncryptUsingPSK 

func EncryptUsingPSK(content []byte, key []byte) ([]byte, error)

EncryptUsingPSK creates and returns an encrypted data PKCS7 structure, encrypted using caller provided pre-shared secret.

func GetCertFromCertsByIssuerAndSerial added in v0.2.0 

func GetCertFromCertsByIssuerAndSerial(certs []*x509.Certificate, ias issuerAndSerial) *x509.Certificate

func HashForOID added in v0.2.1 

func HashForOID(oid asn1.ObjectIdentifier) (crypto.Hash, error)

func OIDForEncryptionAlgorithm added in v0.2.1 

func OIDForEncryptionAlgorithm(pkey crypto.PrivateKey, OIDDigestAlg asn1.ObjectIdentifier) (asn1.ObjectIdentifier, error)

OIDForEncryptionAlgorithm takes the private key type of the signer and the OID of a digest algorithm to return the appropriate signerInfo.DigestEncryptionAlgorithm

func TestDSASignWithOpenSSLAndVerify 

func TestDSASignWithOpenSSLAndVerify(t *testing.T)

func TestVerifyEC2 

func TestVerifyEC2(t *testing.T)

func VerifyCertChain added in v0.2.0 

func VerifyCertChain(ee *x509.Certificate, certs []*x509.Certificate, truststore *x509.CertPool, currentTime time.Time) (chains [][]*x509.Certificate, err error)

verifyCertChain takes an end-entity certs, a list of potential intermediates and a truststore, and built all potential chains between the EE and a trusted root.

When verifying chains that may have expired, currentTime can be set to a past date to allow the verification to pass. If unset, currentTime is set to the current UTC time.

func VerifyMessageDigestDetached added in v0.2.0 

func VerifyMessageDigestDetached(signer SignerInfo, signedData []byte) error

func VerifyMessageDigestEmbedded added in v0.2.0 

func VerifyMessageDigestEmbedded(digest, signedData []byte) error

func VerifyMessageDigestTSToken added in v0.2.0 

func VerifyMessageDigestTSToken(oidHashAlg asn1.ObjectIdentifier, digest, signedData []byte) error

Types

type Attribute 

type Attribute struct {
	Type  asn1.ObjectIdentifier
	Value interface{}
}

Attribute represents a key value pair attribute. Value must be marshalable byte `encoding/asn1`

type DSATestFixture 

type DSATestFixture struct {
	Input       []byte
	Certificate *x509.Certificate
}

func UnmarshalDSATestFixture 

func UnmarshalDSATestFixture(testPEMBlock string) DSATestFixture

type ESSCertID added in v0.2.1 

type ESSCertID struct {
	CertHash              []byte
	IssuerAndSerialNumber issuerAndSerial `asn1:"optional"`
}

type ESSCertIDv2 added in v0.2.1 

type ESSCertIDv2 struct {
	HashAlgorithm         pkix.AlgorithmIdentifier `asn1:"optional"` // DEFAULT sha256
	CertHash              []byte
	IssuerAndSerialNumber issuerAndSerial `asn1:"optional"`
}

type MessageDigestMismatchError 

type MessageDigestMismatchError struct {
	ExpectedDigest []byte
	ActualDigest   []byte
}

MessageDigestMismatchError is returned when the signer data digest does not match the computed digest for the contained content

func (*MessageDigestMismatchError) Error 

func (err *MessageDigestMismatchError) Error() string

type PKCS7 

type PKCS7 struct {
	Content      []byte
	ContentType  asn1.ObjectIdentifier
	Certificates []*x509.Certificate
	CRLs         []*x509.RevocationList
	Signers      []SignerInfo
	// contains filtered or unexported fields
}

PKCS7 Represents a PKCS7 structure

func Parse 

func Parse(data []byte) (p7 *PKCS7, err error)

Parse decodes a DER encoded PKCS7 package

func (*PKCS7) Decrypt 

func (p7 *PKCS7) Decrypt(cert *x509.Certificate, pkey crypto.PrivateKey) ([]byte, error)

Decrypt decrypts encrypted content info for recipient cert and private key

func (*PKCS7) DecryptUsingPSK 

func (p7 *PKCS7) DecryptUsingPSK(key []byte) ([]byte, error)

DecryptUsingPSK decrypts encrypted data using caller provided pre-shared secret

func (*PKCS7) GetOnlySigner 

func (p7 *PKCS7) GetOnlySigner() *x509.Certificate

GetOnlySigner returns an x509.Certificate for the first signer of the signed data payload. If there are more or less than one signer, nil is returned

func (*PKCS7) UnmarshalSignedAttribute 

func (p7 *PKCS7) UnmarshalSignedAttribute(attributeType asn1.ObjectIdentifier, out interface{}) error

UnmarshalSignedAttribute decodes a single attribute from the signer info

func (*PKCS7) Verify 

func (p7 *PKCS7) Verify() (err error)

Verify is a wrapper around VerifyWithChain() that initializes an empty trust store, effectively disabling certificate verification when validating a signature.

func (*PKCS7) VerifyWithChain 

func (p7 *PKCS7) VerifyWithChain(truststore *x509.CertPool) (err error)

VerifyWithChain checks the signatures of a PKCS7 object.

If truststore is not nil, it also verifies the chain of trust of the end-entity signer cert to one of the roots in the truststore. When the PKCS7 object includes the signing time authenticated attr verifies the chain at that time and UTC now otherwise.

func (*PKCS7) VerifyWithChainAtTime 

func (p7 *PKCS7) VerifyWithChainAtTime(truststore *x509.CertPool, currentTime time.Time) (err error)

VerifyWithChainAtTime checks the signatures of a PKCS7 object.

If truststore is not nil, it also verifies the chain of trust of the end-entity signer cert to a root in the truststore at currentTime. It does not use the signing time authenticated attribute.

type SignedData 

type SignedData struct {
	// contains filtered or unexported fields
}

SignedData is an opaque data structure for creating signed data payloads

Example 
// generate a signing cert or load a key pair
cert, err := createTestCertificate(x509.SHA256WithRSA)
if err != nil {
	fmt.Printf("Cannot create test certificates: %s", err)
}

// Initialize a SignedData struct with content to be signed
signedData, err := NewSignedData()
//signedData, err := NewSignedData([]byte("Example data to be signed"))
if err != nil {
	fmt.Printf("Cannot initialize signed data: %s", err)
}

// Add the signing cert and private key
if err := signedData.AddSigner(cert.Certificate, cert.PrivateKey, nil, nil, SignerInfoConfig{}); err != nil {
	fmt.Printf("Cannot add signer: %s", err)
}

// Call Detach() is you want to remove content from the signature
// and generate an S/MIME detached signature
//signedData.Detach()

// Finish() to obtain the signature bytes
detachedSignature, err := signedData.Finish()
if err != nil {
	fmt.Printf("Cannot finish signing data: %s", err)
}
pem.Encode(os.Stdout, &pem.Block{Type: "PKCS7", Bytes: detachedSignature})

func NewSignedData 

func NewSignedData() (*SignedData, error)

NewSignedData initializes a PKCS7 SignedData struct that is ready to be signed via AddSigner.

func (*SignedData) AddCertificate 

func (sd *SignedData) AddCertificate(cert *x509.Certificate)

AddCertificate adds the certificate to the payload. Useful for parent certificates

func (*SignedData) AddSigner 

func (sd *SignedData) AddSigner(cert *x509.Certificate, pkey crypto.PrivateKey, messageDigest []byte, digestOid asn1.ObjectIdentifier, config SignerInfoConfig) error

AddSigner is a wrapper around AddSignerChain() that adds a signer without any parent.

func (*SignedData) AddSignerChain 

func (sd *SignedData) AddSignerChain(cert *x509.Certificate, pkey crypto.PrivateKey, messageDigest []byte, digestOid asn1.ObjectIdentifier, parents []*x509.Certificate, config SignerInfoConfig) error

AddSignerChain signs attributes about the content and adds certificates and signers infos to the Signed Data. The certificate and private key of the end-entity signer are used to issue the signature, and any parent of that end-entity that need to be added to the list of certifications can be specified in the parents slice.

The signature algorithm used to hash the data is the one of the end-entity certificate aka the cert.

func (*SignedData) Detach 

func (sd *SignedData) Detach()

Detach removes content from the signed data struct to make it a detached signature. This must be called right before Finish()

func (*SignedData) Finish 

func (sd *SignedData) Finish() ([]byte, error)

func (*SignedData) GetSignedData 

func (sd *SignedData) GetSignedData() *signedData

GetSignedData returns the private Signed Data

type SignerInfo added in v0.2.0 

type SignerInfo struct {
	Version                   int `asn1:"default:1"`
	IssuerAndSerialNumber     issuerAndSerial
	DigestAlgorithm           pkix.AlgorithmIdentifier
	AuthenticatedAttributes   []attribute `asn1:"optional,omitempty,tag:0"` // RFC5652: signedAttrs [0] IMPLICIT SignedAttributes OPTIONAL
	DigestEncryptionAlgorithm pkix.AlgorithmIdentifier
	EncryptedDigest           []byte      `asn1:"octet"`
	UnauthenticatedAttributes []attribute `asn1:"optional,omitempty,tag:1"` // RFC5652: unsignedAttrs [1] IMPLICIT UnsignedAttributes OPTIONAL
}

type SignerInfoConfig 

type SignerInfoConfig struct {
	ExtraSignedAttributes   []Attribute
	ExtraUnsignedAttributes []Attribute
}

SignerInfoConfig are optional values to include when adding a signer

type SigningCertificate added in v0.2.1 

type SigningCertificate struct {
	Certs []ESSCertID `asn1:"sequence"`
}

type SigningCertificateV2 added in v0.2.1 

type SigningCertificateV2 struct {
	Certs []ESSCertIDv2
}

Source Files

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