forked from TrueCloudLab/certificates
99cd3b74fe
The full contents of the git repository @432b2356ecb... was copied. Only go.mod was removed from it.
429 lines
14 KiB
Go
429 lines
14 KiB
Go
package pkcs7
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import (
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"bytes"
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"crypto"
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"crypto/dsa"
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"crypto/rand"
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"crypto/x509"
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"crypto/x509/pkix"
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"encoding/asn1"
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"errors"
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"fmt"
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"math/big"
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"time"
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)
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// SignedData is an opaque data structure for creating signed data payloads
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type SignedData struct {
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sd signedData
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certs []*x509.Certificate
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data, messageDigest []byte
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digestOid asn1.ObjectIdentifier
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encryptionOid asn1.ObjectIdentifier
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}
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// NewSignedData takes data and initializes a PKCS7 SignedData struct that is
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// ready to be signed via AddSigner. The digest algorithm is set to SHA1 by default
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// and can be changed by calling SetDigestAlgorithm.
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func NewSignedData(data []byte) (*SignedData, error) {
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content, err := asn1.Marshal(data)
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if err != nil {
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return nil, err
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}
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ci := contentInfo{
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ContentType: OIDData,
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Content: asn1.RawValue{Class: 2, Tag: 0, Bytes: content, IsCompound: true},
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}
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sd := signedData{
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ContentInfo: ci,
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Version: 1,
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}
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return &SignedData{sd: sd, data: data, digestOid: OIDDigestAlgorithmSHA1}, nil
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}
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// SignerInfoConfig are optional values to include when adding a signer
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type SignerInfoConfig struct {
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ExtraSignedAttributes []Attribute
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ExtraUnsignedAttributes []Attribute
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}
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type signedData struct {
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Version int `asn1:"default:1"`
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DigestAlgorithmIdentifiers []pkix.AlgorithmIdentifier `asn1:"set"`
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ContentInfo contentInfo
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Certificates rawCertificates `asn1:"optional,tag:0"`
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CRLs []pkix.CertificateList `asn1:"optional,tag:1"`
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SignerInfos []signerInfo `asn1:"set"`
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}
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type signerInfo struct {
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Version int `asn1:"default:1"`
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IssuerAndSerialNumber issuerAndSerial
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DigestAlgorithm pkix.AlgorithmIdentifier
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AuthenticatedAttributes []attribute `asn1:"optional,omitempty,tag:0"`
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DigestEncryptionAlgorithm pkix.AlgorithmIdentifier
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EncryptedDigest []byte
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UnauthenticatedAttributes []attribute `asn1:"optional,omitempty,tag:1"`
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}
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type attribute struct {
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Type asn1.ObjectIdentifier
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Value asn1.RawValue `asn1:"set"`
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}
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func marshalAttributes(attrs []attribute) ([]byte, error) {
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encodedAttributes, err := asn1.Marshal(struct {
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A []attribute `asn1:"set"`
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}{A: attrs})
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if err != nil {
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return nil, err
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}
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// Remove the leading sequence octets
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var raw asn1.RawValue
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asn1.Unmarshal(encodedAttributes, &raw)
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return raw.Bytes, nil
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}
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type rawCertificates struct {
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Raw asn1.RawContent
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}
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type issuerAndSerial struct {
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IssuerName asn1.RawValue
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SerialNumber *big.Int
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}
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// SetDigestAlgorithm sets the digest algorithm to be used in the signing process.
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//
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// This should be called before adding signers
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func (sd *SignedData) SetDigestAlgorithm(d asn1.ObjectIdentifier) {
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sd.digestOid = d
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}
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// SetEncryptionAlgorithm sets the encryption algorithm to be used in the signing process.
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//
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// This should be called before adding signers
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func (sd *SignedData) SetEncryptionAlgorithm(d asn1.ObjectIdentifier) {
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sd.encryptionOid = d
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}
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// AddSigner is a wrapper around AddSignerChain() that adds a signer without any parent.
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func (sd *SignedData) AddSigner(ee *x509.Certificate, pkey crypto.PrivateKey, config SignerInfoConfig) error {
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var parents []*x509.Certificate
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return sd.AddSignerChain(ee, pkey, parents, config)
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}
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// AddSignerChain signs attributes about the content and adds certificates
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// and signers infos to the Signed Data. The certificate and private key
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// of the end-entity signer are used to issue the signature, and any
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// parent of that end-entity that need to be added to the list of
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// certifications can be specified in the parents slice.
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//
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// The signature algorithm used to hash the data is the one of the end-entity
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// certificate.
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func (sd *SignedData) AddSignerChain(ee *x509.Certificate, pkey crypto.PrivateKey, parents []*x509.Certificate, config SignerInfoConfig) error {
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// Following RFC 2315, 9.2 SignerInfo type, the distinguished name of
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// the issuer of the end-entity signer is stored in the issuerAndSerialNumber
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// section of the SignedData.SignerInfo, alongside the serial number of
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// the end-entity.
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var ias issuerAndSerial
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ias.SerialNumber = ee.SerialNumber
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if len(parents) == 0 {
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// no parent, the issuer is the end-entity cert itself
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ias.IssuerName = asn1.RawValue{FullBytes: ee.RawIssuer}
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} else {
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err := verifyPartialChain(ee, parents)
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if err != nil {
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return err
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}
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// the first parent is the issuer
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ias.IssuerName = asn1.RawValue{FullBytes: parents[0].RawSubject}
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}
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sd.sd.DigestAlgorithmIdentifiers = append(sd.sd.DigestAlgorithmIdentifiers,
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pkix.AlgorithmIdentifier{Algorithm: sd.digestOid},
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)
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hash, err := getHashForOID(sd.digestOid)
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if err != nil {
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return err
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}
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h := hash.New()
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h.Write(sd.data)
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sd.messageDigest = h.Sum(nil)
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encryptionOid, err := getOIDForEncryptionAlgorithm(pkey, sd.digestOid)
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if err != nil {
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return err
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}
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attrs := &attributes{}
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attrs.Add(OIDAttributeContentType, sd.sd.ContentInfo.ContentType)
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attrs.Add(OIDAttributeMessageDigest, sd.messageDigest)
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attrs.Add(OIDAttributeSigningTime, time.Now().UTC())
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for _, attr := range config.ExtraSignedAttributes {
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attrs.Add(attr.Type, attr.Value)
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}
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finalAttrs, err := attrs.ForMarshalling()
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if err != nil {
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return err
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}
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unsignedAttrs := &attributes{}
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for _, attr := range config.ExtraUnsignedAttributes {
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unsignedAttrs.Add(attr.Type, attr.Value)
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}
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finalUnsignedAttrs, err := unsignedAttrs.ForMarshalling()
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if err != nil {
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return err
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}
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// create signature of signed attributes
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signature, err := signAttributes(finalAttrs, pkey, hash)
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if err != nil {
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return err
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}
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signer := signerInfo{
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AuthenticatedAttributes: finalAttrs,
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UnauthenticatedAttributes: finalUnsignedAttrs,
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DigestAlgorithm: pkix.AlgorithmIdentifier{Algorithm: sd.digestOid},
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DigestEncryptionAlgorithm: pkix.AlgorithmIdentifier{Algorithm: encryptionOid},
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IssuerAndSerialNumber: ias,
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EncryptedDigest: signature,
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Version: 1,
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}
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sd.certs = append(sd.certs, ee)
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if len(parents) > 0 {
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sd.certs = append(sd.certs, parents...)
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}
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sd.sd.SignerInfos = append(sd.sd.SignerInfos, signer)
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return nil
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}
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// SignWithoutAttr issues a signature on the content of the pkcs7 SignedData.
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// Unlike AddSigner/AddSignerChain, it calculates the digest on the data alone
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// and does not include any signed attributes like timestamp and so on.
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//
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// This function is needed to sign old Android APKs, something you probably
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// shouldn't do unless you're maintaining backward compatibility for old
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// applications.
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func (sd *SignedData) SignWithoutAttr(ee *x509.Certificate, pkey crypto.PrivateKey, config SignerInfoConfig) error {
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var signature []byte
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sd.sd.DigestAlgorithmIdentifiers = append(sd.sd.DigestAlgorithmIdentifiers, pkix.AlgorithmIdentifier{Algorithm: sd.digestOid})
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hash, err := getHashForOID(sd.digestOid)
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if err != nil {
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return err
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}
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h := hash.New()
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h.Write(sd.data)
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sd.messageDigest = h.Sum(nil)
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switch pkey := pkey.(type) {
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case *dsa.PrivateKey:
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// dsa doesn't implement crypto.Signer so we make a special case
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// https://github.com/golang/go/issues/27889
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r, s, err := dsa.Sign(rand.Reader, pkey, sd.messageDigest)
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if err != nil {
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return err
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}
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signature, err = asn1.Marshal(dsaSignature{r, s})
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if err != nil {
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return err
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}
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default:
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key, ok := pkey.(crypto.Signer)
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if !ok {
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return errors.New("pkcs7: private key does not implement crypto.Signer")
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}
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signature, err = key.Sign(rand.Reader, sd.messageDigest, hash)
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if err != nil {
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return err
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}
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}
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var ias issuerAndSerial
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ias.SerialNumber = ee.SerialNumber
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// no parent, the issue is the end-entity cert itself
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ias.IssuerName = asn1.RawValue{FullBytes: ee.RawIssuer}
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if sd.encryptionOid == nil {
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// if the encryption algorithm wasn't set by SetEncryptionAlgorithm,
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// infer it from the digest algorithm
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sd.encryptionOid, err = getOIDForEncryptionAlgorithm(pkey, sd.digestOid)
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}
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if err != nil {
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return err
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}
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signer := signerInfo{
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DigestAlgorithm: pkix.AlgorithmIdentifier{Algorithm: sd.digestOid},
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DigestEncryptionAlgorithm: pkix.AlgorithmIdentifier{Algorithm: sd.encryptionOid},
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IssuerAndSerialNumber: ias,
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EncryptedDigest: signature,
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Version: 1,
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}
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// create signature of signed attributes
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sd.certs = append(sd.certs, ee)
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sd.sd.SignerInfos = append(sd.sd.SignerInfos, signer)
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return nil
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}
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func (si *signerInfo) SetUnauthenticatedAttributes(extraUnsignedAttrs []Attribute) error {
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unsignedAttrs := &attributes{}
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for _, attr := range extraUnsignedAttrs {
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unsignedAttrs.Add(attr.Type, attr.Value)
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}
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finalUnsignedAttrs, err := unsignedAttrs.ForMarshalling()
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if err != nil {
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return err
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}
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si.UnauthenticatedAttributes = finalUnsignedAttrs
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return nil
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}
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// AddCertificate adds the certificate to the payload. Useful for parent certificates
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func (sd *SignedData) AddCertificate(cert *x509.Certificate) {
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sd.certs = append(sd.certs, cert)
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}
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// Detach removes content from the signed data struct to make it a detached signature.
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// This must be called right before Finish()
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func (sd *SignedData) Detach() {
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sd.sd.ContentInfo = contentInfo{ContentType: OIDData}
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}
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// GetSignedData returns the private Signed Data
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func (sd *SignedData) GetSignedData() *signedData {
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return &sd.sd
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}
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// Finish marshals the content and its signers
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func (sd *SignedData) Finish() ([]byte, error) {
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sd.sd.Certificates = marshalCertificates(sd.certs)
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inner, err := asn1.Marshal(sd.sd)
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if err != nil {
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return nil, err
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}
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outer := contentInfo{
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ContentType: OIDSignedData,
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Content: asn1.RawValue{Class: 2, Tag: 0, Bytes: inner, IsCompound: true},
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}
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return asn1.Marshal(outer)
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}
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// RemoveAuthenticatedAttributes removes authenticated attributes from signedData
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// similar to OpenSSL's PKCS7_NOATTR or -noattr flags
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func (sd *SignedData) RemoveAuthenticatedAttributes() {
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for i := range sd.sd.SignerInfos {
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sd.sd.SignerInfos[i].AuthenticatedAttributes = nil
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}
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}
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// RemoveUnauthenticatedAttributes removes unauthenticated attributes from signedData
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func (sd *SignedData) RemoveUnauthenticatedAttributes() {
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for i := range sd.sd.SignerInfos {
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sd.sd.SignerInfos[i].UnauthenticatedAttributes = nil
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}
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}
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// verifyPartialChain checks that a given cert is issued by the first parent in the list,
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// then continue down the path. It doesn't require the last parent to be a root CA,
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// or to be trusted in any truststore. It simply verifies that the chain provided, albeit
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// partial, makes sense.
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func verifyPartialChain(cert *x509.Certificate, parents []*x509.Certificate) error {
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if len(parents) == 0 {
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return fmt.Errorf("pkcs7: zero parents provided to verify the signature of certificate %q", cert.Subject.CommonName)
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}
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err := cert.CheckSignatureFrom(parents[0])
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if err != nil {
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return fmt.Errorf("pkcs7: certificate signature from parent is invalid: %v", err)
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}
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if len(parents) == 1 {
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// there is no more parent to check, return
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return nil
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}
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return verifyPartialChain(parents[0], parents[1:])
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}
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func cert2issuerAndSerial(cert *x509.Certificate) (issuerAndSerial, error) {
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var ias issuerAndSerial
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// The issuer RDNSequence has to match exactly the sequence in the certificate
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// We cannot use cert.Issuer.ToRDNSequence() here since it mangles the sequence
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ias.IssuerName = asn1.RawValue{FullBytes: cert.RawIssuer}
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ias.SerialNumber = cert.SerialNumber
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return ias, nil
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}
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// signs the DER encoded form of the attributes with the private key
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func signAttributes(attrs []attribute, pkey crypto.PrivateKey, digestAlg crypto.Hash) ([]byte, error) {
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attrBytes, err := marshalAttributes(attrs)
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if err != nil {
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return nil, err
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}
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h := digestAlg.New()
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h.Write(attrBytes)
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hash := h.Sum(nil)
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// dsa doesn't implement crypto.Signer so we make a special case
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// https://github.com/golang/go/issues/27889
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switch pkey := pkey.(type) {
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case *dsa.PrivateKey:
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r, s, err := dsa.Sign(rand.Reader, pkey, hash)
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if err != nil {
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return nil, err
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}
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return asn1.Marshal(dsaSignature{r, s})
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}
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key, ok := pkey.(crypto.Signer)
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if !ok {
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return nil, errors.New("pkcs7: private key does not implement crypto.Signer")
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}
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return key.Sign(rand.Reader, hash, digestAlg)
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}
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type dsaSignature struct {
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R, S *big.Int
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}
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// concats and wraps the certificates in the RawValue structure
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func marshalCertificates(certs []*x509.Certificate) rawCertificates {
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var buf bytes.Buffer
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for _, cert := range certs {
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buf.Write(cert.Raw)
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}
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rawCerts, _ := marshalCertificateBytes(buf.Bytes())
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return rawCerts
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}
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// Even though, the tag & length are stripped out during marshalling the
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// RawContent, we have to encode it into the RawContent. If its missing,
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// then `asn1.Marshal()` will strip out the certificate wrapper instead.
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func marshalCertificateBytes(certs []byte) (rawCertificates, error) {
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var val = asn1.RawValue{Bytes: certs, Class: 2, Tag: 0, IsCompound: true}
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b, err := asn1.Marshal(val)
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if err != nil {
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return rawCertificates{}, err
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}
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return rawCertificates{Raw: b}, nil
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}
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// DegenerateCertificate creates a signed data structure containing only the
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// provided certificate or certificate chain.
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func DegenerateCertificate(cert []byte) ([]byte, error) {
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rawCert, err := marshalCertificateBytes(cert)
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if err != nil {
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return nil, err
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}
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emptyContent := contentInfo{ContentType: OIDData}
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sd := signedData{
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Version: 1,
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ContentInfo: emptyContent,
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Certificates: rawCert,
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CRLs: []pkix.CertificateList{},
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}
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content, err := asn1.Marshal(sd)
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if err != nil {
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return nil, err
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}
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signedContent := contentInfo{
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ContentType: OIDSignedData,
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Content: asn1.RawValue{Class: 2, Tag: 0, Bytes: content, IsCompound: true},
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}
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return asn1.Marshal(signedContent)
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}
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