certificates/scep/pkcs7/sign.go
Herman Slatman 99cd3b74fe Add full copy of mozilla/pkcs7 module as internal dependency
The full contents of the git repository @432b2356ecb...
was copied. Only go.mod was removed from it.
2021-05-26 16:01:20 -07:00

429 lines
14 KiB
Go

package pkcs7
import (
"bytes"
"crypto"
"crypto/dsa"
"crypto/rand"
"crypto/x509"
"crypto/x509/pkix"
"encoding/asn1"
"errors"
"fmt"
"math/big"
"time"
)
// SignedData is an opaque data structure for creating signed data payloads
type SignedData struct {
sd signedData
certs []*x509.Certificate
data, messageDigest []byte
digestOid asn1.ObjectIdentifier
encryptionOid asn1.ObjectIdentifier
}
// NewSignedData takes data and initializes a PKCS7 SignedData struct that is
// ready to be signed via AddSigner. The digest algorithm is set to SHA1 by default
// and can be changed by calling SetDigestAlgorithm.
func NewSignedData(data []byte) (*SignedData, error) {
content, err := asn1.Marshal(data)
if err != nil {
return nil, err
}
ci := contentInfo{
ContentType: OIDData,
Content: asn1.RawValue{Class: 2, Tag: 0, Bytes: content, IsCompound: true},
}
sd := signedData{
ContentInfo: ci,
Version: 1,
}
return &SignedData{sd: sd, data: data, digestOid: OIDDigestAlgorithmSHA1}, nil
}
// SignerInfoConfig are optional values to include when adding a signer
type SignerInfoConfig struct {
ExtraSignedAttributes []Attribute
ExtraUnsignedAttributes []Attribute
}
type signedData struct {
Version int `asn1:"default:1"`
DigestAlgorithmIdentifiers []pkix.AlgorithmIdentifier `asn1:"set"`
ContentInfo contentInfo
Certificates rawCertificates `asn1:"optional,tag:0"`
CRLs []pkix.CertificateList `asn1:"optional,tag:1"`
SignerInfos []signerInfo `asn1:"set"`
}
type signerInfo struct {
Version int `asn1:"default:1"`
IssuerAndSerialNumber issuerAndSerial
DigestAlgorithm pkix.AlgorithmIdentifier
AuthenticatedAttributes []attribute `asn1:"optional,omitempty,tag:0"`
DigestEncryptionAlgorithm pkix.AlgorithmIdentifier
EncryptedDigest []byte
UnauthenticatedAttributes []attribute `asn1:"optional,omitempty,tag:1"`
}
type attribute struct {
Type asn1.ObjectIdentifier
Value asn1.RawValue `asn1:"set"`
}
func marshalAttributes(attrs []attribute) ([]byte, error) {
encodedAttributes, err := asn1.Marshal(struct {
A []attribute `asn1:"set"`
}{A: attrs})
if err != nil {
return nil, err
}
// Remove the leading sequence octets
var raw asn1.RawValue
asn1.Unmarshal(encodedAttributes, &raw)
return raw.Bytes, nil
}
type rawCertificates struct {
Raw asn1.RawContent
}
type issuerAndSerial struct {
IssuerName asn1.RawValue
SerialNumber *big.Int
}
// SetDigestAlgorithm sets the digest algorithm to be used in the signing process.
//
// This should be called before adding signers
func (sd *SignedData) SetDigestAlgorithm(d asn1.ObjectIdentifier) {
sd.digestOid = d
}
// SetEncryptionAlgorithm sets the encryption algorithm to be used in the signing process.
//
// This should be called before adding signers
func (sd *SignedData) SetEncryptionAlgorithm(d asn1.ObjectIdentifier) {
sd.encryptionOid = d
}
// AddSigner is a wrapper around AddSignerChain() that adds a signer without any parent.
func (sd *SignedData) AddSigner(ee *x509.Certificate, pkey crypto.PrivateKey, config SignerInfoConfig) error {
var parents []*x509.Certificate
return sd.AddSignerChain(ee, pkey, parents, config)
}
// 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 (sd *SignedData) AddSignerChain(ee *x509.Certificate, pkey crypto.PrivateKey, parents []*x509.Certificate, config SignerInfoConfig) error {
// Following RFC 2315, 9.2 SignerInfo type, the distinguished name of
// the issuer of the end-entity signer is stored in the issuerAndSerialNumber
// section of the SignedData.SignerInfo, alongside the serial number of
// the end-entity.
var ias issuerAndSerial
ias.SerialNumber = ee.SerialNumber
if len(parents) == 0 {
// no parent, the issuer is the end-entity cert itself
ias.IssuerName = asn1.RawValue{FullBytes: ee.RawIssuer}
} else {
err := verifyPartialChain(ee, parents)
if err != nil {
return err
}
// the first parent is the issuer
ias.IssuerName = asn1.RawValue{FullBytes: parents[0].RawSubject}
}
sd.sd.DigestAlgorithmIdentifiers = append(sd.sd.DigestAlgorithmIdentifiers,
pkix.AlgorithmIdentifier{Algorithm: sd.digestOid},
)
hash, err := getHashForOID(sd.digestOid)
if err != nil {
return err
}
h := hash.New()
h.Write(sd.data)
sd.messageDigest = h.Sum(nil)
encryptionOid, err := getOIDForEncryptionAlgorithm(pkey, sd.digestOid)
if err != nil {
return err
}
attrs := &attributes{}
attrs.Add(OIDAttributeContentType, sd.sd.ContentInfo.ContentType)
attrs.Add(OIDAttributeMessageDigest, sd.messageDigest)
attrs.Add(OIDAttributeSigningTime, time.Now().UTC())
for _, attr := range config.ExtraSignedAttributes {
attrs.Add(attr.Type, attr.Value)
}
finalAttrs, err := attrs.ForMarshalling()
if err != nil {
return err
}
unsignedAttrs := &attributes{}
for _, attr := range config.ExtraUnsignedAttributes {
unsignedAttrs.Add(attr.Type, attr.Value)
}
finalUnsignedAttrs, err := unsignedAttrs.ForMarshalling()
if err != nil {
return err
}
// create signature of signed attributes
signature, err := signAttributes(finalAttrs, pkey, hash)
if err != nil {
return err
}
signer := signerInfo{
AuthenticatedAttributes: finalAttrs,
UnauthenticatedAttributes: finalUnsignedAttrs,
DigestAlgorithm: pkix.AlgorithmIdentifier{Algorithm: sd.digestOid},
DigestEncryptionAlgorithm: pkix.AlgorithmIdentifier{Algorithm: encryptionOid},
IssuerAndSerialNumber: ias,
EncryptedDigest: signature,
Version: 1,
}
sd.certs = append(sd.certs, ee)
if len(parents) > 0 {
sd.certs = append(sd.certs, parents...)
}
sd.sd.SignerInfos = append(sd.sd.SignerInfos, signer)
return nil
}
// 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.
func (sd *SignedData) SignWithoutAttr(ee *x509.Certificate, pkey crypto.PrivateKey, config SignerInfoConfig) error {
var signature []byte
sd.sd.DigestAlgorithmIdentifiers = append(sd.sd.DigestAlgorithmIdentifiers, pkix.AlgorithmIdentifier{Algorithm: sd.digestOid})
hash, err := getHashForOID(sd.digestOid)
if err != nil {
return err
}
h := hash.New()
h.Write(sd.data)
sd.messageDigest = h.Sum(nil)
switch pkey := pkey.(type) {
case *dsa.PrivateKey:
// dsa doesn't implement crypto.Signer so we make a special case
// https://github.com/golang/go/issues/27889
r, s, err := dsa.Sign(rand.Reader, pkey, sd.messageDigest)
if err != nil {
return err
}
signature, err = asn1.Marshal(dsaSignature{r, s})
if err != nil {
return err
}
default:
key, ok := pkey.(crypto.Signer)
if !ok {
return errors.New("pkcs7: private key does not implement crypto.Signer")
}
signature, err = key.Sign(rand.Reader, sd.messageDigest, hash)
if err != nil {
return err
}
}
var ias issuerAndSerial
ias.SerialNumber = ee.SerialNumber
// no parent, the issue is the end-entity cert itself
ias.IssuerName = asn1.RawValue{FullBytes: ee.RawIssuer}
if sd.encryptionOid == nil {
// if the encryption algorithm wasn't set by SetEncryptionAlgorithm,
// infer it from the digest algorithm
sd.encryptionOid, err = getOIDForEncryptionAlgorithm(pkey, sd.digestOid)
}
if err != nil {
return err
}
signer := signerInfo{
DigestAlgorithm: pkix.AlgorithmIdentifier{Algorithm: sd.digestOid},
DigestEncryptionAlgorithm: pkix.AlgorithmIdentifier{Algorithm: sd.encryptionOid},
IssuerAndSerialNumber: ias,
EncryptedDigest: signature,
Version: 1,
}
// create signature of signed attributes
sd.certs = append(sd.certs, ee)
sd.sd.SignerInfos = append(sd.sd.SignerInfos, signer)
return nil
}
func (si *signerInfo) SetUnauthenticatedAttributes(extraUnsignedAttrs []Attribute) error {
unsignedAttrs := &attributes{}
for _, attr := range extraUnsignedAttrs {
unsignedAttrs.Add(attr.Type, attr.Value)
}
finalUnsignedAttrs, err := unsignedAttrs.ForMarshalling()
if err != nil {
return err
}
si.UnauthenticatedAttributes = finalUnsignedAttrs
return nil
}
// AddCertificate adds the certificate to the payload. Useful for parent certificates
func (sd *SignedData) AddCertificate(cert *x509.Certificate) {
sd.certs = append(sd.certs, cert)
}
// Detach removes content from the signed data struct to make it a detached signature.
// This must be called right before Finish()
func (sd *SignedData) Detach() {
sd.sd.ContentInfo = contentInfo{ContentType: OIDData}
}
// GetSignedData returns the private Signed Data
func (sd *SignedData) GetSignedData() *signedData {
return &sd.sd
}
// Finish marshals the content and its signers
func (sd *SignedData) Finish() ([]byte, error) {
sd.sd.Certificates = marshalCertificates(sd.certs)
inner, err := asn1.Marshal(sd.sd)
if err != nil {
return nil, err
}
outer := contentInfo{
ContentType: OIDSignedData,
Content: asn1.RawValue{Class: 2, Tag: 0, Bytes: inner, IsCompound: true},
}
return asn1.Marshal(outer)
}
// RemoveAuthenticatedAttributes removes authenticated attributes from signedData
// similar to OpenSSL's PKCS7_NOATTR or -noattr flags
func (sd *SignedData) RemoveAuthenticatedAttributes() {
for i := range sd.sd.SignerInfos {
sd.sd.SignerInfos[i].AuthenticatedAttributes = nil
}
}
// RemoveUnauthenticatedAttributes removes unauthenticated attributes from signedData
func (sd *SignedData) RemoveUnauthenticatedAttributes() {
for i := range sd.sd.SignerInfos {
sd.sd.SignerInfos[i].UnauthenticatedAttributes = nil
}
}
// verifyPartialChain checks that a given cert is issued by the first parent in the list,
// then continue down the path. It doesn't require the last parent to be a root CA,
// or to be trusted in any truststore. It simply verifies that the chain provided, albeit
// partial, makes sense.
func verifyPartialChain(cert *x509.Certificate, parents []*x509.Certificate) error {
if len(parents) == 0 {
return fmt.Errorf("pkcs7: zero parents provided to verify the signature of certificate %q", cert.Subject.CommonName)
}
err := cert.CheckSignatureFrom(parents[0])
if err != nil {
return fmt.Errorf("pkcs7: certificate signature from parent is invalid: %v", err)
}
if len(parents) == 1 {
// there is no more parent to check, return
return nil
}
return verifyPartialChain(parents[0], parents[1:])
}
func cert2issuerAndSerial(cert *x509.Certificate) (issuerAndSerial, error) {
var ias issuerAndSerial
// The issuer RDNSequence has to match exactly the sequence in the certificate
// We cannot use cert.Issuer.ToRDNSequence() here since it mangles the sequence
ias.IssuerName = asn1.RawValue{FullBytes: cert.RawIssuer}
ias.SerialNumber = cert.SerialNumber
return ias, nil
}
// signs the DER encoded form of the attributes with the private key
func signAttributes(attrs []attribute, pkey crypto.PrivateKey, digestAlg crypto.Hash) ([]byte, error) {
attrBytes, err := marshalAttributes(attrs)
if err != nil {
return nil, err
}
h := digestAlg.New()
h.Write(attrBytes)
hash := h.Sum(nil)
// dsa doesn't implement crypto.Signer so we make a special case
// https://github.com/golang/go/issues/27889
switch pkey := pkey.(type) {
case *dsa.PrivateKey:
r, s, err := dsa.Sign(rand.Reader, pkey, hash)
if err != nil {
return nil, err
}
return asn1.Marshal(dsaSignature{r, s})
}
key, ok := pkey.(crypto.Signer)
if !ok {
return nil, errors.New("pkcs7: private key does not implement crypto.Signer")
}
return key.Sign(rand.Reader, hash, digestAlg)
}
type dsaSignature struct {
R, S *big.Int
}
// concats and wraps the certificates in the RawValue structure
func marshalCertificates(certs []*x509.Certificate) rawCertificates {
var buf bytes.Buffer
for _, cert := range certs {
buf.Write(cert.Raw)
}
rawCerts, _ := marshalCertificateBytes(buf.Bytes())
return rawCerts
}
// Even though, the tag & length are stripped out during marshalling the
// RawContent, we have to encode it into the RawContent. If its missing,
// then `asn1.Marshal()` will strip out the certificate wrapper instead.
func marshalCertificateBytes(certs []byte) (rawCertificates, error) {
var val = asn1.RawValue{Bytes: certs, Class: 2, Tag: 0, IsCompound: true}
b, err := asn1.Marshal(val)
if err != nil {
return rawCertificates{}, err
}
return rawCertificates{Raw: b}, nil
}
// DegenerateCertificate creates a signed data structure containing only the
// provided certificate or certificate chain.
func DegenerateCertificate(cert []byte) ([]byte, error) {
rawCert, err := marshalCertificateBytes(cert)
if err != nil {
return nil, err
}
emptyContent := contentInfo{ContentType: OIDData}
sd := signedData{
Version: 1,
ContentInfo: emptyContent,
Certificates: rawCert,
CRLs: []pkix.CertificateList{},
}
content, err := asn1.Marshal(sd)
if err != nil {
return nil, err
}
signedContent := contentInfo{
ContentType: OIDSignedData,
Content: asn1.RawValue{Class: 2, Tag: 0, Bytes: content, IsCompound: true},
}
return asn1.Marshal(signedContent)
}