cms

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README

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

TODO

  1. verify_test.go: refactor to use other digest algorithms than MD5 and SHA-1
  2. Add support for ~~ECDSA and ~~ CMS with ECC

Supported Algorithms

RSA, ECDSA MD5, SHA1, SHA2, SHA3 DES, AES, ChaCha20Poly1305(TODO: decrypt)

Version

1.3.8

Documentation

Overview

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

Index

Examples

Constants

View Source 
const (
	// DESCBC is the DES CBC encryption algorithm
	DESCBC = EncryptionAlgorithm(iota)

	// DESEDE3CBC is the 3DES CBC encryption algorithm
	DESEDE3CBC

	// AES128CBC is the AES 128 bits with CBC encryption algorithm
	// Avoid this algorithm unless required for interoperability; use AES GCM instead.
	AES128CBC

	// AES192CBC is the AES 192 bits with CBC encryption algorithm
	// Avoid this algorithm unless required for interoperability; use AES GCM instead.
	AES192CBC

	// AES256CBC is the AES 256 bits with CBC encryption algorithm
	// Avoid this algorithm unless required for interoperability; use AES GCM instead.
	AES256CBC

	// AES128GCM is the AES 128 bits with GCM encryption algorithm
	AES128GCM

	// AES192GCM is the AES 192 bits with GCM encryption algorithm
	AES192GCM

	// AES256GCM is the AES 256 bits with GCM encryption algorithm
	AES256GCM

	ChaCha20Poly1305
)

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}
	OIDCompressedData         = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 9, 16, 1, 9}
	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}

	// Compression Algorithms
	OIDCompressionAlgorithmZLIB = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 9, 16, 3, 8}

	// Digest Algorithms
	OIDDigestAlgorithmMD5        = asn1.ObjectIdentifier{1, 2, 840, 113549, 2, 5} // deprecated
	OIDDigestAlgorithmSHA1       = asn1.ObjectIdentifier{1, 3, 14, 3, 2, 26}      // deprecated
	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}
	OIDDigestAlgorithmSHA224     = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 4}
	OIDDigestAlgorithmSHAT224    = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 7}
	OIDDigestAlgorithmSHAT256    = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 8}
	OIDDigestAlgorithmSHAT384    = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 9}
	OIDDigestAlgorithmSHAT512    = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 10}
	OIDDigestAlgorithmBlake2s256 = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 1722, 12, 2, 2, 8}
	OIDDigestAlgorithmBlake2b256 = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 1722, 12, 2, 1, 8}
	OIDDigestAlgorithmBlake2b384 = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 1722, 12, 2, 1, 12}
	OIDDigestAlgorithmBlake2b512 = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 1722, 12, 2, 1, 16}

	// Signature Algorithms
	OIDSignatureAlgorithmRSA       = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 1}
	OIDSignatureAlgorithmRSAPSS    = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 10}
	OIDSignatureAlgorithmRSAMD5    = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 4}
	OIDSignatureAlgorithmRSASHA1   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 5}
	OIDSignatureAlgorithmRSASHA256 = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 11}
	OIDSignatureAlgorithmRSASHA384 = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 12}
	OIDSignatureAlgorithmRSASHA512 = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 13}
	OIDSignatureAlgorithmRSASHA224 = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 14}

	OIDSignatureAlgorithmRSASHAT224 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 3, 13}
	OIDSignatureAlgorithmRSASHAT256 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 3, 14}
	OIDSignatureAlgorithmRSASHAT384 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 3, 15}
	OIDSignatureAlgorithmRSASHAT512 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 3, 16}

	OIDSignatureAlgorithmECDSASHA1   = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 1}
	OIDSignatureAlgorithmECDSASHA256 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 2}
	OIDSignatureAlgorithmECDSASHA384 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 3}
	OIDSignatureAlgorithmECDSASHA512 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 4}
	OIDSignatureAlgorithmECDSASHA224 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 1}

	OIDSignatureAlgorithmECDSASHAT224 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 3, 9}
	OIDSignatureAlgorithmECDSASHAT256 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 3, 10}
	OIDSignatureAlgorithmECDSASHAT384 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 3, 11}
	OIDSignatureAlgorithmECDSASHAT512 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 3, 12}

	OIDSignatureAlgorithmED25519 = asn1.ObjectIdentifier{1, 3, 101, 112}

	OIDEncryptionAlgorithmECDSAP256 = asn1.ObjectIdentifier{1, 2, 840, 10045, 3, 1, 7}
	OIDEncryptionAlgorithmECDSAP384 = asn1.ObjectIdentifier{1, 3, 132, 0, 34}
	OIDEncryptionAlgorithmECDSAP521 = asn1.ObjectIdentifier{1, 3, 132, 0, 35}

	// Encryption Algorithms
	OIDEncryptionAlgorithmChaCha20Poly1305 = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 9, 16, 3, 18}
	OIDEncryptionAlgorithmDESCBC           = asn1.ObjectIdentifier{1, 3, 14, 3, 2, 7}
	OIDEncryptionAlgorithmDESEDE3CBC       = asn1.ObjectIdentifier{1, 2, 840, 113549, 3, 7}
	OIDEncryptionAlgorithmAES128CBC        = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 1, 2}
	OIDEncryptionAlgorithmAES192CBC        = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 1, 22}
	OIDEncryptionAlgorithmAES256CBC        = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 1, 42}
	OIDEncryptionAlgorithmAES128GCM        = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 1, 6}
	OIDEncryptionAlgorithmAES192GCM        = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 1, 26}
	OIDEncryptionAlgorithmAES256GCM        = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 1, 46}
)
View Source 
var ContentEncryptionAlgorithm = DESCBC

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 ErrNotCompressedContent = errors.New("pkcs7: content data is not a compressed data type")
View Source 
var ErrNotEncryptedContent = errors.New("pkcs7: content data is not 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, AES 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 

func CheckSignature(c *x509.Certificate, algo SignatureAlgorithm, signed, signature []byte) error

CheckSignature verifies that signature is a valid signature over signed from c's public key.

This is a low-level API that performs no validity checks on the certificate.

MD5WithRSA signatures are rejected, while SHA1WithRSA and ECDSAWithSHA1 signatures are currently accepted.

func Compress added in v1.3.0 

func Compress(data []byte) ([]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 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.

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 EncryptionAlgorithm 

type EncryptionAlgorithm int

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
	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) Decompress added in v1.3.2 

func (p7 *PKCS7) Decompress() ([]byte, error)

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 SignatureAlgorithm 

type SignatureAlgorithm int
const (
	UnknownSignatureAlgorithm SignatureAlgorithm = iota

	MD2WithRSA  // Unsupported.
	MD5WithRSA  // Deprecated.
	SHA1WithRSA // Deprecated.
	SHA224WithRSA
	SHA256WithRSA
	SHA384WithRSA
	SHA512WithRSA
	SHAT224WithRSA
	SHAT256WithRSA
	SHAT384WithRSA
	SHAT512WithRSA
	DSAWithSHA1   // Unsupported.
	DSAWithSHA256 // Unsupported.
	ECDSAWithSHA1 // Deprecated.
	ECDSAWithSHA224
	ECDSAWithSHA256
	ECDSAWithSHA384
	ECDSAWithSHA512
	ECDSAWithSHAT224
	ECDSAWithSHAT256
	ECDSAWithSHAT384
	ECDSAWithSHAT512
	SHA224WithRSAPSS
	SHA256WithRSAPSS
	SHA384WithRSAPSS
	SHA512WithRSAPSS
	SHAT224WithRSAPSS
	SHAT256WithRSAPSS
	SHAT384WithRSAPSS
	SHAT512WithRSAPSS
	PureEd25519
)

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([]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, 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})

Output:

func NewSignedData 

func NewSignedData(data []byte) (*SignedData, error)

NewSignedData takes data and initializes a PKCS7 SignedData struct that is ready to be signed via AddSigner. The digest algorithm is set to SHA256 by default and can be changed by calling SetDigestAlgorithm.

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(ee *x509.Certificate, pkey crypto.PrivateKey, config SignerInfoConfig) error

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

func (*SignedData) AddSignerChain 

func (sd *SignedData) AddSignerChain(ee *x509.Certificate, pkey crypto.PrivateKey, 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.

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)

Finish marshals the content and its signers

func (*SignedData) GetSignedData 

func (sd *SignedData) GetSignedData() *signedData

GetSignedData returns the private Signed Data

func (*SignedData) RemoveAuthenticatedAttributes 

func (sd *SignedData) RemoveAuthenticatedAttributes()

RemoveAuthenticatedAttributes removes authenticated attributes from signedData similar to OpenSSL's PKCS7_NOATTR or -noattr flags

func (*SignedData) RemoveUnauthenticatedAttributes 

func (sd *SignedData) RemoveUnauthenticatedAttributes()

RemoveUnauthenticatedAttributes removes unauthenticated attributes from signedData

func (*SignedData) SetDigestAlgorithm 

func (sd *SignedData) SetDigestAlgorithm(d asn1.ObjectIdentifier)

SetDigestAlgorithm sets the digest algorithm to be used in the signing process.

This should be called before adding signers

func (*SignedData) SetEncryptionAlgorithm 

func (sd *SignedData) SetEncryptionAlgorithm(d asn1.ObjectIdentifier)

SetEncryptionAlgorithm sets the encryption algorithm to be used in the signing process.

This should be called before adding signers

func (*SignedData) SignWithoutAttr 

func (sd *SignedData) SignWithoutAttr(ee *x509.Certificate, pkey crypto.PrivateKey, config SignerInfoConfig) error

SignWithoutAttr issues a signature on the content of the pkcs7 SignedData. Unlike AddSigner/AddSignerChain, it calculates the digest on the data alone and does not include any signed attributes like timestamp and so on.

This function is needed to sign old Android APKs, something you probably shouldn't do unless you're maintaining backward compatibility for old applications.

type SignerInfoConfig 

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

SignerInfoConfig are optional values to include when adding a signer

Source Files

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