Imported Upstream version 1.4upstream/1.4

1 files changed, 1916 insertions, 0 deletions

diff --git a/src/crypto/x509/x509.go b/src/crypto/x509/x509.go
new file mode 100644
index 000000000..7a37b98e3
--- /dev/null
+++ b/src/crypto/x509/x509.go
@@ -0,0 +1,1916 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package x509 parses X.509-encoded keys and certificates.
+package x509
+
+import (
+	"bytes"
+	"crypto"
+	"crypto/dsa"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rsa"
+	"crypto/sha1"
+	_ "crypto/sha256"
+	_ "crypto/sha512"
+	"crypto/x509/pkix"
+	"encoding/asn1"
+	"encoding/pem"
+	"errors"
+	"io"
+	"math/big"
+	"net"
+	"strconv"
+	"time"
+)
+
+// pkixPublicKey reflects a PKIX public key structure. See SubjectPublicKeyInfo
+// in RFC 3280.
+type pkixPublicKey struct {
+	Algo      pkix.AlgorithmIdentifier
+	BitString asn1.BitString
+}
+
+// ParsePKIXPublicKey parses a DER encoded public key. These values are
+// typically found in PEM blocks with "BEGIN PUBLIC KEY".
+func ParsePKIXPublicKey(derBytes []byte) (pub interface{}, err error) {
+	var pki publicKeyInfo
+	if _, err = asn1.Unmarshal(derBytes, &pki); err != nil {
+		return
+	}
+	algo := getPublicKeyAlgorithmFromOID(pki.Algorithm.Algorithm)
+	if algo == UnknownPublicKeyAlgorithm {
+		return nil, errors.New("x509: unknown public key algorithm")
+	}
+	return parsePublicKey(algo, &pki)
+}
+
+func marshalPublicKey(pub interface{}) (publicKeyBytes []byte, publicKeyAlgorithm pkix.AlgorithmIdentifier, err error) {
+	switch pub := pub.(type) {
+	case *rsa.PublicKey:
+		publicKeyBytes, err = asn1.Marshal(rsaPublicKey{
+			N: pub.N,
+			E: pub.E,
+		})
+		publicKeyAlgorithm.Algorithm = oidPublicKeyRSA
+		// This is a NULL parameters value which is technically
+		// superfluous, but most other code includes it and, by
+		// doing this, we match their public key hashes.
+		publicKeyAlgorithm.Parameters = asn1.RawValue{
+			Tag: 5,
+		}
+	case *ecdsa.PublicKey:
+		publicKeyBytes = elliptic.Marshal(pub.Curve, pub.X, pub.Y)
+		oid, ok := oidFromNamedCurve(pub.Curve)
+		if !ok {
+			return nil, pkix.AlgorithmIdentifier{}, errors.New("x509: unsupported elliptic curve")
+		}
+		publicKeyAlgorithm.Algorithm = oidPublicKeyECDSA
+		var paramBytes []byte
+		paramBytes, err = asn1.Marshal(oid)
+		if err != nil {
+			return
+		}
+		publicKeyAlgorithm.Parameters.FullBytes = paramBytes
+	default:
+		return nil, pkix.AlgorithmIdentifier{}, errors.New("x509: only RSA and ECDSA public keys supported")
+	}
+
+	return publicKeyBytes, publicKeyAlgorithm, nil
+}
+
+// MarshalPKIXPublicKey serialises a public key to DER-encoded PKIX format.
+func MarshalPKIXPublicKey(pub interface{}) ([]byte, error) {
+	var publicKeyBytes []byte
+	var publicKeyAlgorithm pkix.AlgorithmIdentifier
+	var err error
+
+	if publicKeyBytes, publicKeyAlgorithm, err = marshalPublicKey(pub); err != nil {
+		return nil, err
+	}
+
+	pkix := pkixPublicKey{
+		Algo: publicKeyAlgorithm,
+		BitString: asn1.BitString{
+			Bytes:     publicKeyBytes,
+			BitLength: 8 * len(publicKeyBytes),
+		},
+	}
+
+	ret, _ := asn1.Marshal(pkix)
+	return ret, nil
+}
+
+// These structures reflect the ASN.1 structure of X.509 certificates.:
+
+type certificate struct {
+	Raw                asn1.RawContent
+	TBSCertificate     tbsCertificate
+	SignatureAlgorithm pkix.AlgorithmIdentifier
+	SignatureValue     asn1.BitString
+}
+
+type tbsCertificate struct {
+	Raw                asn1.RawContent
+	Version            int `asn1:"optional,explicit,default:1,tag:0"`
+	SerialNumber       *big.Int
+	SignatureAlgorithm pkix.AlgorithmIdentifier
+	Issuer             asn1.RawValue
+	Validity           validity
+	Subject            asn1.RawValue
+	PublicKey          publicKeyInfo
+	UniqueId           asn1.BitString   `asn1:"optional,tag:1"`
+	SubjectUniqueId    asn1.BitString   `asn1:"optional,tag:2"`
+	Extensions         []pkix.Extension `asn1:"optional,explicit,tag:3"`
+}
+
+type dsaAlgorithmParameters struct {
+	P, Q, G *big.Int
+}
+
+type dsaSignature struct {
+	R, S *big.Int
+}
+
+type ecdsaSignature dsaSignature
+
+type validity struct {
+	NotBefore, NotAfter time.Time
+}
+
+type publicKeyInfo struct {
+	Raw       asn1.RawContent
+	Algorithm pkix.AlgorithmIdentifier
+	PublicKey asn1.BitString
+}
+
+// RFC 5280,  4.2.1.1
+type authKeyId struct {
+	Id []byte `asn1:"optional,tag:0"`
+}
+
+type SignatureAlgorithm int
+
+const (
+	UnknownSignatureAlgorithm SignatureAlgorithm = iota
+	MD2WithRSA
+	MD5WithRSA
+	SHA1WithRSA
+	SHA256WithRSA
+	SHA384WithRSA
+	SHA512WithRSA
+	DSAWithSHA1
+	DSAWithSHA256
+	ECDSAWithSHA1
+	ECDSAWithSHA256
+	ECDSAWithSHA384
+	ECDSAWithSHA512
+)
+
+type PublicKeyAlgorithm int
+
+const (
+	UnknownPublicKeyAlgorithm PublicKeyAlgorithm = iota
+	RSA
+	DSA
+	ECDSA
+)
+
+// OIDs for signature algorithms
+//
+// pkcs-1 OBJECT IDENTIFIER ::= {
+//    iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) 1 }
+//
+//
+// RFC 3279 2.2.1 RSA Signature Algorithms
+//
+// md2WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 2 }
+//
+// md5WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 4 }
+//
+// sha-1WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 5 }
+//
+// dsaWithSha1 OBJECT IDENTIFIER ::= {
+//    iso(1) member-body(2) us(840) x9-57(10040) x9cm(4) 3 }
+//
+// RFC 3279 2.2.3 ECDSA Signature Algorithm
+//
+// ecdsa-with-SHA1 OBJECT IDENTIFIER ::= {
+// 	  iso(1) member-body(2) us(840) ansi-x962(10045)
+//    signatures(4) ecdsa-with-SHA1(1)}
+//
+//
+// RFC 4055 5 PKCS #1 Version 1.5
+//
+// sha256WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 11 }
+//
+// sha384WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 12 }
+//
+// sha512WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 13 }
+//
+//
+// RFC 5758 3.1 DSA Signature Algorithms
+//
+// dsaWithSha256 OBJECT IDENTIFIER ::= {
+//    joint-iso-ccitt(2) country(16) us(840) organization(1) gov(101)
+//    csor(3) algorithms(4) id-dsa-with-sha2(3) 2}
+//
+// RFC 5758 3.2 ECDSA Signature Algorithm
+//
+// ecdsa-with-SHA256 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
+//    us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 2 }
+//
+// ecdsa-with-SHA384 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
+//    us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 3 }
+//
+// ecdsa-with-SHA512 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
+//    us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 4 }
+
+var (
+	oidSignatureMD2WithRSA      = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 2}
+	oidSignatureMD5WithRSA      = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 4}
+	oidSignatureSHA1WithRSA     = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 5}
+	oidSignatureSHA256WithRSA   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 11}
+	oidSignatureSHA384WithRSA   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 12}
+	oidSignatureSHA512WithRSA   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 13}
+	oidSignatureDSAWithSHA1     = asn1.ObjectIdentifier{1, 2, 840, 10040, 4, 3}
+	oidSignatureDSAWithSHA256   = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 4, 3, 2}
+	oidSignatureECDSAWithSHA1   = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 1}
+	oidSignatureECDSAWithSHA256 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 2}
+	oidSignatureECDSAWithSHA384 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 3}
+	oidSignatureECDSAWithSHA512 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 4}
+)
+
+var signatureAlgorithmDetails = []struct {
+	algo       SignatureAlgorithm
+	oid        asn1.ObjectIdentifier
+	pubKeyAlgo PublicKeyAlgorithm
+	hash       crypto.Hash
+}{
+	{MD2WithRSA, oidSignatureMD2WithRSA, RSA, crypto.Hash(0) /* no value for MD2 */},
+	{MD5WithRSA, oidSignatureMD5WithRSA, RSA, crypto.MD5},
+	{SHA1WithRSA, oidSignatureSHA1WithRSA, RSA, crypto.SHA1},
+	{SHA256WithRSA, oidSignatureSHA256WithRSA, RSA, crypto.SHA256},
+	{SHA384WithRSA, oidSignatureSHA384WithRSA, RSA, crypto.SHA384},
+	{SHA512WithRSA, oidSignatureSHA512WithRSA, RSA, crypto.SHA512},
+	{DSAWithSHA1, oidSignatureDSAWithSHA1, DSA, crypto.SHA1},
+	{DSAWithSHA256, oidSignatureDSAWithSHA256, DSA, crypto.SHA256},
+	{ECDSAWithSHA1, oidSignatureECDSAWithSHA1, ECDSA, crypto.SHA1},
+	{ECDSAWithSHA256, oidSignatureECDSAWithSHA256, ECDSA, crypto.SHA256},
+	{ECDSAWithSHA384, oidSignatureECDSAWithSHA384, ECDSA, crypto.SHA384},
+	{ECDSAWithSHA512, oidSignatureECDSAWithSHA512, ECDSA, crypto.SHA512},
+}
+
+func getSignatureAlgorithmFromOID(oid asn1.ObjectIdentifier) SignatureAlgorithm {
+	for _, details := range signatureAlgorithmDetails {
+		if oid.Equal(details.oid) {
+			return details.algo
+		}
+	}
+	return UnknownSignatureAlgorithm
+}
+
+// RFC 3279, 2.3 Public Key Algorithms
+//
+// pkcs-1 OBJECT IDENTIFIER ::== { iso(1) member-body(2) us(840)
+//    rsadsi(113549) pkcs(1) 1 }
+//
+// rsaEncryption OBJECT IDENTIFIER ::== { pkcs1-1 1 }
+//
+// id-dsa OBJECT IDENTIFIER ::== { iso(1) member-body(2) us(840)
+//    x9-57(10040) x9cm(4) 1 }
+//
+// RFC 5480, 2.1.1 Unrestricted Algorithm Identifier and Parameters
+//
+// id-ecPublicKey OBJECT IDENTIFIER ::= {
+//       iso(1) member-body(2) us(840) ansi-X9-62(10045) keyType(2) 1 }
+var (
+	oidPublicKeyRSA   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 1}
+	oidPublicKeyDSA   = asn1.ObjectIdentifier{1, 2, 840, 10040, 4, 1}
+	oidPublicKeyECDSA = asn1.ObjectIdentifier{1, 2, 840, 10045, 2, 1}
+)
+
+func getPublicKeyAlgorithmFromOID(oid asn1.ObjectIdentifier) PublicKeyAlgorithm {
+	switch {
+	case oid.Equal(oidPublicKeyRSA):
+		return RSA
+	case oid.Equal(oidPublicKeyDSA):
+		return DSA
+	case oid.Equal(oidPublicKeyECDSA):
+		return ECDSA
+	}
+	return UnknownPublicKeyAlgorithm
+}
+
+// RFC 5480, 2.1.1.1. Named Curve
+//
+// secp224r1 OBJECT IDENTIFIER ::= {
+//   iso(1) identified-organization(3) certicom(132) curve(0) 33 }
+//
+// secp256r1 OBJECT IDENTIFIER ::= {
+//   iso(1) member-body(2) us(840) ansi-X9-62(10045) curves(3)
+//   prime(1) 7 }
+//
+// secp384r1 OBJECT IDENTIFIER ::= {
+//   iso(1) identified-organization(3) certicom(132) curve(0) 34 }
+//
+// secp521r1 OBJECT IDENTIFIER ::= {
+//   iso(1) identified-organization(3) certicom(132) curve(0) 35 }
+//
+// NB: secp256r1 is equivalent to prime256v1
+var (
+	oidNamedCurveP224 = asn1.ObjectIdentifier{1, 3, 132, 0, 33}
+	oidNamedCurveP256 = asn1.ObjectIdentifier{1, 2, 840, 10045, 3, 1, 7}
+	oidNamedCurveP384 = asn1.ObjectIdentifier{1, 3, 132, 0, 34}
+	oidNamedCurveP521 = asn1.ObjectIdentifier{1, 3, 132, 0, 35}
+)
+
+func namedCurveFromOID(oid asn1.ObjectIdentifier) elliptic.Curve {
+	switch {
+	case oid.Equal(oidNamedCurveP224):
+		return elliptic.P224()
+	case oid.Equal(oidNamedCurveP256):
+		return elliptic.P256()
+	case oid.Equal(oidNamedCurveP384):
+		return elliptic.P384()
+	case oid.Equal(oidNamedCurveP521):
+		return elliptic.P521()
+	}
+	return nil
+}
+
+func oidFromNamedCurve(curve elliptic.Curve) (asn1.ObjectIdentifier, bool) {
+	switch curve {
+	case elliptic.P224():
+		return oidNamedCurveP224, true
+	case elliptic.P256():
+		return oidNamedCurveP256, true
+	case elliptic.P384():
+		return oidNamedCurveP384, true
+	case elliptic.P521():
+		return oidNamedCurveP521, true
+	}
+
+	return nil, false
+}
+
+// KeyUsage represents the set of actions that are valid for a given key. It's
+// a bitmap of the KeyUsage* constants.
+type KeyUsage int
+
+const (
+	KeyUsageDigitalSignature KeyUsage = 1 << iota
+	KeyUsageContentCommitment
+	KeyUsageKeyEncipherment
+	KeyUsageDataEncipherment
+	KeyUsageKeyAgreement
+	KeyUsageCertSign
+	KeyUsageCRLSign
+	KeyUsageEncipherOnly
+	KeyUsageDecipherOnly
+)
+
+// RFC 5280, 4.2.1.12  Extended Key Usage
+//
+// anyExtendedKeyUsage OBJECT IDENTIFIER ::= { id-ce-extKeyUsage 0 }
+//
+// id-kp OBJECT IDENTIFIER ::= { id-pkix 3 }
+//
+// id-kp-serverAuth             OBJECT IDENTIFIER ::= { id-kp 1 }
+// id-kp-clientAuth             OBJECT IDENTIFIER ::= { id-kp 2 }
+// id-kp-codeSigning            OBJECT IDENTIFIER ::= { id-kp 3 }
+// id-kp-emailProtection        OBJECT IDENTIFIER ::= { id-kp 4 }
+// id-kp-timeStamping           OBJECT IDENTIFIER ::= { id-kp 8 }
+// id-kp-OCSPSigning            OBJECT IDENTIFIER ::= { id-kp 9 }
+var (
+	oidExtKeyUsageAny                        = asn1.ObjectIdentifier{2, 5, 29, 37, 0}
+	oidExtKeyUsageServerAuth                 = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 1}
+	oidExtKeyUsageClientAuth                 = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 2}
+	oidExtKeyUsageCodeSigning                = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 3}
+	oidExtKeyUsageEmailProtection            = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 4}
+	oidExtKeyUsageIPSECEndSystem             = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 5}
+	oidExtKeyUsageIPSECTunnel                = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 6}
+	oidExtKeyUsageIPSECUser                  = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 7}
+	oidExtKeyUsageTimeStamping               = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 8}
+	oidExtKeyUsageOCSPSigning                = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 9}
+	oidExtKeyUsageMicrosoftServerGatedCrypto = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 311, 10, 3, 3}
+	oidExtKeyUsageNetscapeServerGatedCrypto  = asn1.ObjectIdentifier{2, 16, 840, 1, 113730, 4, 1}
+)
+
+// ExtKeyUsage represents an extended set of actions that are valid for a given key.
+// Each of the ExtKeyUsage* constants define a unique action.
+type ExtKeyUsage int
+
+const (
+	ExtKeyUsageAny ExtKeyUsage = iota
+	ExtKeyUsageServerAuth
+	ExtKeyUsageClientAuth
+	ExtKeyUsageCodeSigning
+	ExtKeyUsageEmailProtection
+	ExtKeyUsageIPSECEndSystem
+	ExtKeyUsageIPSECTunnel
+	ExtKeyUsageIPSECUser
+	ExtKeyUsageTimeStamping
+	ExtKeyUsageOCSPSigning
+	ExtKeyUsageMicrosoftServerGatedCrypto
+	ExtKeyUsageNetscapeServerGatedCrypto
+)
+
+// extKeyUsageOIDs contains the mapping between an ExtKeyUsage and its OID.
+var extKeyUsageOIDs = []struct {
+	extKeyUsage ExtKeyUsage
+	oid         asn1.ObjectIdentifier
+}{
+	{ExtKeyUsageAny, oidExtKeyUsageAny},
+	{ExtKeyUsageServerAuth, oidExtKeyUsageServerAuth},
+	{ExtKeyUsageClientAuth, oidExtKeyUsageClientAuth},
+	{ExtKeyUsageCodeSigning, oidExtKeyUsageCodeSigning},
+	{ExtKeyUsageEmailProtection, oidExtKeyUsageEmailProtection},
+	{ExtKeyUsageIPSECEndSystem, oidExtKeyUsageIPSECEndSystem},
+	{ExtKeyUsageIPSECTunnel, oidExtKeyUsageIPSECTunnel},
+	{ExtKeyUsageIPSECUser, oidExtKeyUsageIPSECUser},
+	{ExtKeyUsageTimeStamping, oidExtKeyUsageTimeStamping},
+	{ExtKeyUsageOCSPSigning, oidExtKeyUsageOCSPSigning},
+	{ExtKeyUsageMicrosoftServerGatedCrypto, oidExtKeyUsageMicrosoftServerGatedCrypto},
+	{ExtKeyUsageNetscapeServerGatedCrypto, oidExtKeyUsageNetscapeServerGatedCrypto},
+}
+
+func extKeyUsageFromOID(oid asn1.ObjectIdentifier) (eku ExtKeyUsage, ok bool) {
+	for _, pair := range extKeyUsageOIDs {
+		if oid.Equal(pair.oid) {
+			return pair.extKeyUsage, true
+		}
+	}
+	return
+}
+
+func oidFromExtKeyUsage(eku ExtKeyUsage) (oid asn1.ObjectIdentifier, ok bool) {
+	for _, pair := range extKeyUsageOIDs {
+		if eku == pair.extKeyUsage {
+			return pair.oid, true
+		}
+	}
+	return
+}
+
+// A Certificate represents an X.509 certificate.
+type Certificate struct {
+	Raw                     []byte // Complete ASN.1 DER content (certificate, signature algorithm and signature).
+	RawTBSCertificate       []byte // Certificate part of raw ASN.1 DER content.
+	RawSubjectPublicKeyInfo []byte // DER encoded SubjectPublicKeyInfo.
+	RawSubject              []byte // DER encoded Subject
+	RawIssuer               []byte // DER encoded Issuer
+
+	Signature          []byte
+	SignatureAlgorithm SignatureAlgorithm
+
+	PublicKeyAlgorithm PublicKeyAlgorithm
+	PublicKey          interface{}
+
+	Version             int
+	SerialNumber        *big.Int
+	Issuer              pkix.Name
+	Subject             pkix.Name
+	NotBefore, NotAfter time.Time // Validity bounds.
+	KeyUsage            KeyUsage
+
+	// Extensions contains raw X.509 extensions. When parsing certificates,
+	// this can be used to extract non-critical extensions that are not
+	// parsed by this package. When marshaling certificates, the Extensions
+	// field is ignored, see ExtraExtensions.
+	Extensions []pkix.Extension
+
+	// ExtraExtensions contains extensions to be copied, raw, into any
+	// marshaled certificates. Values override any extensions that would
+	// otherwise be produced based on the other fields. The ExtraExtensions
+	// field is not populated when parsing certificates, see Extensions.
+	ExtraExtensions []pkix.Extension
+
+	ExtKeyUsage        []ExtKeyUsage           // Sequence of extended key usages.
+	UnknownExtKeyUsage []asn1.ObjectIdentifier // Encountered extended key usages unknown to this package.
+
+	BasicConstraintsValid bool // if true then the next two fields are valid.
+	IsCA                  bool
+	MaxPathLen            int
+	// MaxPathLenZero indicates that BasicConstraintsValid==true and
+	// MaxPathLen==0 should be interpreted as an actual maximum path length
+	// of zero. Otherwise, that combination is interpreted as MaxPathLen
+	// not being set.
+	MaxPathLenZero bool
+
+	SubjectKeyId   []byte
+	AuthorityKeyId []byte
+
+	// RFC 5280, 4.2.2.1 (Authority Information Access)
+	OCSPServer            []string
+	IssuingCertificateURL []string
+
+	// Subject Alternate Name values
+	DNSNames       []string
+	EmailAddresses []string
+	IPAddresses    []net.IP
+
+	// Name constraints
+	PermittedDNSDomainsCritical bool // if true then the name constraints are marked critical.
+	PermittedDNSDomains         []string
+
+	// CRL Distribution Points
+	CRLDistributionPoints []string
+
+	PolicyIdentifiers []asn1.ObjectIdentifier
+}
+
+// ErrUnsupportedAlgorithm results from attempting to perform an operation that
+// involves algorithms that are not currently implemented.
+var ErrUnsupportedAlgorithm = errors.New("x509: cannot verify signature: algorithm unimplemented")
+
+// ConstraintViolationError results when a requested usage is not permitted by
+// a certificate. For example: checking a signature when the public key isn't a
+// certificate signing key.
+type ConstraintViolationError struct{}
+
+func (ConstraintViolationError) Error() string {
+	return "x509: invalid signature: parent certificate cannot sign this kind of certificate"
+}
+
+func (c *Certificate) Equal(other *Certificate) bool {
+	return bytes.Equal(c.Raw, other.Raw)
+}
+
+// Entrust have a broken root certificate (CN=Entrust.net Certification
+// Authority (2048)) which isn't marked as a CA certificate and is thus invalid
+// according to PKIX.
+// We recognise this certificate by its SubjectPublicKeyInfo and exempt it
+// from the Basic Constraints requirement.
+// See http://www.entrust.net/knowledge-base/technote.cfm?tn=7869
+//
+// TODO(agl): remove this hack once their reissued root is sufficiently
+// widespread.
+var entrustBrokenSPKI = []byte{
+	0x30, 0x82, 0x01, 0x22, 0x30, 0x0d, 0x06, 0x09,
+	0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01,
+	0x01, 0x05, 0x00, 0x03, 0x82, 0x01, 0x0f, 0x00,
+	0x30, 0x82, 0x01, 0x0a, 0x02, 0x82, 0x01, 0x01,
+	0x00, 0x97, 0xa3, 0x2d, 0x3c, 0x9e, 0xde, 0x05,
+	0xda, 0x13, 0xc2, 0x11, 0x8d, 0x9d, 0x8e, 0xe3,
+	0x7f, 0xc7, 0x4b, 0x7e, 0x5a, 0x9f, 0xb3, 0xff,
+	0x62, 0xab, 0x73, 0xc8, 0x28, 0x6b, 0xba, 0x10,
+	0x64, 0x82, 0x87, 0x13, 0xcd, 0x57, 0x18, 0xff,
+	0x28, 0xce, 0xc0, 0xe6, 0x0e, 0x06, 0x91, 0x50,
+	0x29, 0x83, 0xd1, 0xf2, 0xc3, 0x2a, 0xdb, 0xd8,
+	0xdb, 0x4e, 0x04, 0xcc, 0x00, 0xeb, 0x8b, 0xb6,
+	0x96, 0xdc, 0xbc, 0xaa, 0xfa, 0x52, 0x77, 0x04,
+	0xc1, 0xdb, 0x19, 0xe4, 0xae, 0x9c, 0xfd, 0x3c,
+	0x8b, 0x03, 0xef, 0x4d, 0xbc, 0x1a, 0x03, 0x65,
+	0xf9, 0xc1, 0xb1, 0x3f, 0x72, 0x86, 0xf2, 0x38,
+	0xaa, 0x19, 0xae, 0x10, 0x88, 0x78, 0x28, 0xda,
+	0x75, 0xc3, 0x3d, 0x02, 0x82, 0x02, 0x9c, 0xb9,
+	0xc1, 0x65, 0x77, 0x76, 0x24, 0x4c, 0x98, 0xf7,
+	0x6d, 0x31, 0x38, 0xfb, 0xdb, 0xfe, 0xdb, 0x37,
+	0x02, 0x76, 0xa1, 0x18, 0x97, 0xa6, 0xcc, 0xde,
+	0x20, 0x09, 0x49, 0x36, 0x24, 0x69, 0x42, 0xf6,
+	0xe4, 0x37, 0x62, 0xf1, 0x59, 0x6d, 0xa9, 0x3c,
+	0xed, 0x34, 0x9c, 0xa3, 0x8e, 0xdb, 0xdc, 0x3a,
+	0xd7, 0xf7, 0x0a, 0x6f, 0xef, 0x2e, 0xd8, 0xd5,
+	0x93, 0x5a, 0x7a, 0xed, 0x08, 0x49, 0x68, 0xe2,
+	0x41, 0xe3, 0x5a, 0x90, 0xc1, 0x86, 0x55, 0xfc,
+	0x51, 0x43, 0x9d, 0xe0, 0xb2, 0xc4, 0x67, 0xb4,
+	0xcb, 0x32, 0x31, 0x25, 0xf0, 0x54, 0x9f, 0x4b,
+	0xd1, 0x6f, 0xdb, 0xd4, 0xdd, 0xfc, 0xaf, 0x5e,
+	0x6c, 0x78, 0x90, 0x95, 0xde, 0xca, 0x3a, 0x48,
+	0xb9, 0x79, 0x3c, 0x9b, 0x19, 0xd6, 0x75, 0x05,
+	0xa0, 0xf9, 0x88, 0xd7, 0xc1, 0xe8, 0xa5, 0x09,
+	0xe4, 0x1a, 0x15, 0xdc, 0x87, 0x23, 0xaa, 0xb2,
+	0x75, 0x8c, 0x63, 0x25, 0x87, 0xd8, 0xf8, 0x3d,
+	0xa6, 0xc2, 0xcc, 0x66, 0xff, 0xa5, 0x66, 0x68,
+	0x55, 0x02, 0x03, 0x01, 0x00, 0x01,
+}
+
+// CheckSignatureFrom verifies that the signature on c is a valid signature
+// from parent.
+func (c *Certificate) CheckSignatureFrom(parent *Certificate) (err error) {
+	// RFC 5280, 4.2.1.9:
+	// "If the basic constraints extension is not present in a version 3
+	// certificate, or the extension is present but the cA boolean is not
+	// asserted, then the certified public key MUST NOT be used to verify
+	// certificate signatures."
+	// (except for Entrust, see comment above entrustBrokenSPKI)
+	if (parent.Version == 3 && !parent.BasicConstraintsValid ||
+		parent.BasicConstraintsValid && !parent.IsCA) &&
+		!bytes.Equal(c.RawSubjectPublicKeyInfo, entrustBrokenSPKI) {
+		return ConstraintViolationError{}
+	}
+
+	if parent.KeyUsage != 0 && parent.KeyUsage&KeyUsageCertSign == 0 {
+		return ConstraintViolationError{}
+	}
+
+	if parent.PublicKeyAlgorithm == UnknownPublicKeyAlgorithm {
+		return ErrUnsupportedAlgorithm
+	}
+
+	// TODO(agl): don't ignore the path length constraint.
+
+	return parent.CheckSignature(c.SignatureAlgorithm, c.RawTBSCertificate, c.Signature)
+}
+
+// CheckSignature verifies that signature is a valid signature over signed from
+// c's public key.
+func (c *Certificate) CheckSignature(algo SignatureAlgorithm, signed, signature []byte) (err error) {
+	var hashType crypto.Hash
+
+	switch algo {
+	case SHA1WithRSA, DSAWithSHA1, ECDSAWithSHA1:
+		hashType = crypto.SHA1
+	case SHA256WithRSA, DSAWithSHA256, ECDSAWithSHA256:
+		hashType = crypto.SHA256
+	case SHA384WithRSA, ECDSAWithSHA384:
+		hashType = crypto.SHA384
+	case SHA512WithRSA, ECDSAWithSHA512:
+		hashType = crypto.SHA512
+	default:
+		return ErrUnsupportedAlgorithm
+	}
+
+	if !hashType.Available() {
+		return ErrUnsupportedAlgorithm
+	}
+	h := hashType.New()
+
+	h.Write(signed)
+	digest := h.Sum(nil)
+
+	switch pub := c.PublicKey.(type) {
+	case *rsa.PublicKey:
+		return rsa.VerifyPKCS1v15(pub, hashType, digest, signature)
+	case *dsa.PublicKey:
+		dsaSig := new(dsaSignature)
+		if _, err := asn1.Unmarshal(signature, dsaSig); err != nil {
+			return err
+		}
+		if dsaSig.R.Sign() <= 0 || dsaSig.S.Sign() <= 0 {
+			return errors.New("x509: DSA signature contained zero or negative values")
+		}
+		if !dsa.Verify(pub, digest, dsaSig.R, dsaSig.S) {
+			return errors.New("x509: DSA verification failure")
+		}
+		return
+	case *ecdsa.PublicKey:
+		ecdsaSig := new(ecdsaSignature)
+		if _, err := asn1.Unmarshal(signature, ecdsaSig); err != nil {
+			return err
+		}
+		if ecdsaSig.R.Sign() <= 0 || ecdsaSig.S.Sign() <= 0 {
+			return errors.New("x509: ECDSA signature contained zero or negative values")
+		}
+		if !ecdsa.Verify(pub, digest, ecdsaSig.R, ecdsaSig.S) {
+			return errors.New("x509: ECDSA verification failure")
+		}
+		return
+	}
+	return ErrUnsupportedAlgorithm
+}
+
+// CheckCRLSignature checks that the signature in crl is from c.
+func (c *Certificate) CheckCRLSignature(crl *pkix.CertificateList) (err error) {
+	algo := getSignatureAlgorithmFromOID(crl.SignatureAlgorithm.Algorithm)
+	return c.CheckSignature(algo, crl.TBSCertList.Raw, crl.SignatureValue.RightAlign())
+}
+
+type UnhandledCriticalExtension struct{}
+
+func (h UnhandledCriticalExtension) Error() string {
+	return "x509: unhandled critical extension"
+}
+
+type basicConstraints struct {
+	IsCA       bool `asn1:"optional"`
+	MaxPathLen int  `asn1:"optional,default:-1"`
+}
+
+// RFC 5280 4.2.1.4
+type policyInformation struct {
+	Policy asn1.ObjectIdentifier
+	// policyQualifiers omitted
+}
+
+// RFC 5280, 4.2.1.10
+type nameConstraints struct {
+	Permitted []generalSubtree `asn1:"optional,tag:0"`
+	Excluded  []generalSubtree `asn1:"optional,tag:1"`
+}
+
+type generalSubtree struct {
+	Name string `asn1:"tag:2,optional,ia5"`
+}
+
+// RFC 5280, 4.2.2.1
+type authorityInfoAccess struct {
+	Method   asn1.ObjectIdentifier
+	Location asn1.RawValue
+}
+
+// RFC 5280, 4.2.1.14
+type distributionPoint struct {
+	DistributionPoint distributionPointName `asn1:"optional,tag:0"`
+	Reason            asn1.BitString        `asn1:"optional,tag:1"`
+	CRLIssuer         asn1.RawValue         `asn1:"optional,tag:2"`
+}
+
+type distributionPointName struct {
+	FullName     asn1.RawValue    `asn1:"optional,tag:0"`
+	RelativeName pkix.RDNSequence `asn1:"optional,tag:1"`
+}
+
+func parsePublicKey(algo PublicKeyAlgorithm, keyData *publicKeyInfo) (interface{}, error) {
+	asn1Data := keyData.PublicKey.RightAlign()
+	switch algo {
+	case RSA:
+		p := new(rsaPublicKey)
+		_, err := asn1.Unmarshal(asn1Data, p)
+		if err != nil {
+			return nil, err
+		}
+
+		if p.N.Sign() <= 0 {
+			return nil, errors.New("x509: RSA modulus is not a positive number")
+		}
+		if p.E <= 0 {
+			return nil, errors.New("x509: RSA public exponent is not a positive number")
+		}
+
+		pub := &rsa.PublicKey{
+			E: p.E,
+			N: p.N,
+		}
+		return pub, nil
+	case DSA:
+		var p *big.Int
+		_, err := asn1.Unmarshal(asn1Data, &p)
+		if err != nil {
+			return nil, err
+		}
+		paramsData := keyData.Algorithm.Parameters.FullBytes
+		params := new(dsaAlgorithmParameters)
+		_, err = asn1.Unmarshal(paramsData, params)
+		if err != nil {
+			return nil, err
+		}
+		if p.Sign() <= 0 || params.P.Sign() <= 0 || params.Q.Sign() <= 0 || params.G.Sign() <= 0 {
+			return nil, errors.New("x509: zero or negative DSA parameter")
+		}
+		pub := &dsa.PublicKey{
+			Parameters: dsa.Parameters{
+				P: params.P,
+				Q: params.Q,
+				G: params.G,
+			},
+			Y: p,
+		}
+		return pub, nil
+	case ECDSA:
+		paramsData := keyData.Algorithm.Parameters.FullBytes
+		namedCurveOID := new(asn1.ObjectIdentifier)
+		_, err := asn1.Unmarshal(paramsData, namedCurveOID)
+		if err != nil {
+			return nil, err
+		}
+		namedCurve := namedCurveFromOID(*namedCurveOID)
+		if namedCurve == nil {
+			return nil, errors.New("x509: unsupported elliptic curve")
+		}
+		x, y := elliptic.Unmarshal(namedCurve, asn1Data)
+		if x == nil {
+			return nil, errors.New("x509: failed to unmarshal elliptic curve point")
+		}
+		pub := &ecdsa.PublicKey{
+			Curve: namedCurve,
+			X:     x,
+			Y:     y,
+		}
+		return pub, nil
+	default:
+		return nil, nil
+	}
+}
+
+func parseSANExtension(value []byte) (dnsNames, emailAddresses []string, ipAddresses []net.IP, err error) {
+	// RFC 5280, 4.2.1.6
+
+	// SubjectAltName ::= GeneralNames
+	//
+	// GeneralNames ::= SEQUENCE SIZE (1..MAX) OF GeneralName
+	//
+	// GeneralName ::= CHOICE {
+	//      otherName                       [0]     OtherName,
+	//      rfc822Name                      [1]     IA5String,
+	//      dNSName                         [2]     IA5String,
+	//      x400Address                     [3]     ORAddress,
+	//      directoryName                   [4]     Name,
+	//      ediPartyName                    [5]     EDIPartyName,
+	//      uniformResourceIdentifier       [6]     IA5String,
+	//      iPAddress                       [7]     OCTET STRING,
+	//      registeredID                    [8]     OBJECT IDENTIFIER }
+	var seq asn1.RawValue
+	if _, err = asn1.Unmarshal(value, &seq); err != nil {
+		return
+	}
+	if !seq.IsCompound || seq.Tag != 16 || seq.Class != 0 {
+		err = asn1.StructuralError{Msg: "bad SAN sequence"}
+		return
+	}
+
+	rest := seq.Bytes
+	for len(rest) > 0 {
+		var v asn1.RawValue
+		rest, err = asn1.Unmarshal(rest, &v)
+		if err != nil {
+			return
+		}
+		switch v.Tag {
+		case 1:
+			emailAddresses = append(emailAddresses, string(v.Bytes))
+		case 2:
+			dnsNames = append(dnsNames, string(v.Bytes))
+		case 7:
+			switch len(v.Bytes) {
+			case net.IPv4len, net.IPv6len:
+				ipAddresses = append(ipAddresses, v.Bytes)
+			default:
+				err = errors.New("x509: certificate contained IP address of length " + strconv.Itoa(len(v.Bytes)))
+				return
+			}
+		}
+	}
+
+	return
+}
+
+func parseCertificate(in *certificate) (*Certificate, error) {
+	out := new(Certificate)
+	out.Raw = in.Raw
+	out.RawTBSCertificate = in.TBSCertificate.Raw
+	out.RawSubjectPublicKeyInfo = in.TBSCertificate.PublicKey.Raw
+	out.RawSubject = in.TBSCertificate.Subject.FullBytes
+	out.RawIssuer = in.TBSCertificate.Issuer.FullBytes
+
+	out.Signature = in.SignatureValue.RightAlign()
+	out.SignatureAlgorithm =
+		getSignatureAlgorithmFromOID(in.TBSCertificate.SignatureAlgorithm.Algorithm)
+
+	out.PublicKeyAlgorithm =
+		getPublicKeyAlgorithmFromOID(in.TBSCertificate.PublicKey.Algorithm.Algorithm)
+	var err error
+	out.PublicKey, err = parsePublicKey(out.PublicKeyAlgorithm, &in.TBSCertificate.PublicKey)
+	if err != nil {
+		return nil, err
+	}
+
+	if in.TBSCertificate.SerialNumber.Sign() < 0 {
+		return nil, errors.New("x509: negative serial number")
+	}
+
+	out.Version = in.TBSCertificate.Version + 1
+	out.SerialNumber = in.TBSCertificate.SerialNumber
+
+	var issuer, subject pkix.RDNSequence
+	if _, err := asn1.Unmarshal(in.TBSCertificate.Subject.FullBytes, &subject); err != nil {
+		return nil, err
+	}
+	if _, err := asn1.Unmarshal(in.TBSCertificate.Issuer.FullBytes, &issuer); err != nil {
+		return nil, err
+	}
+
+	out.Issuer.FillFromRDNSequence(&issuer)
+	out.Subject.FillFromRDNSequence(&subject)
+
+	out.NotBefore = in.TBSCertificate.Validity.NotBefore
+	out.NotAfter = in.TBSCertificate.Validity.NotAfter
+
+	for _, e := range in.TBSCertificate.Extensions {
+		out.Extensions = append(out.Extensions, e)
+
+		if len(e.Id) == 4 && e.Id[0] == 2 && e.Id[1] == 5 && e.Id[2] == 29 {
+			switch e.Id[3] {
+			case 15:
+				// RFC 5280, 4.2.1.3
+				var usageBits asn1.BitString
+				_, err := asn1.Unmarshal(e.Value, &usageBits)
+
+				if err == nil {
+					var usage int
+					for i := 0; i < 9; i++ {
+						if usageBits.At(i) != 0 {
+							usage |= 1 << uint(i)
+						}
+					}
+					out.KeyUsage = KeyUsage(usage)
+					continue
+				}
+			case 19:
+				// RFC 5280, 4.2.1.9
+				var constraints basicConstraints
+				_, err := asn1.Unmarshal(e.Value, &constraints)
+
+				if err == nil {
+					out.BasicConstraintsValid = true
+					out.IsCA = constraints.IsCA
+					out.MaxPathLen = constraints.MaxPathLen
+					out.MaxPathLenZero = out.MaxPathLen == 0
+					continue
+				}
+			case 17:
+				out.DNSNames, out.EmailAddresses, out.IPAddresses, err = parseSANExtension(e.Value)
+				if err != nil {
+					return nil, err
+				}
+
+				if len(out.DNSNames) > 0 || len(out.EmailAddresses) > 0 || len(out.IPAddresses) > 0 {
+					continue
+				}
+				// If we didn't parse any of the names then we
+				// fall through to the critical check below.
+
+			case 30:
+				// RFC 5280, 4.2.1.10
+
+				// NameConstraints ::= SEQUENCE {
+				//      permittedSubtrees       [0]     GeneralSubtrees OPTIONAL,
+				//      excludedSubtrees        [1]     GeneralSubtrees OPTIONAL }
+				//
+				// GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree
+				//
+				// GeneralSubtree ::= SEQUENCE {
+				//      base                    GeneralName,
+				//      minimum         [0]     BaseDistance DEFAULT 0,
+				//      maximum         [1]     BaseDistance OPTIONAL }
+				//
+				// BaseDistance ::= INTEGER (0..MAX)
+
+				var constraints nameConstraints
+				_, err := asn1.Unmarshal(e.Value, &constraints)
+				if err != nil {
+					return nil, err
+				}
+
+				if len(constraints.Excluded) > 0 && e.Critical {
+					return out, UnhandledCriticalExtension{}
+				}
+
+				for _, subtree := range constraints.Permitted {
+					if len(subtree.Name) == 0 {
+						if e.Critical {
+							return out, UnhandledCriticalExtension{}
+						}
+						continue
+					}
+					out.PermittedDNSDomains = append(out.PermittedDNSDomains, subtree.Name)
+				}
+				continue
+
+			case 31:
+				// RFC 5280, 4.2.1.14
+
+				// CRLDistributionPoints ::= SEQUENCE SIZE (1..MAX) OF DistributionPoint
+				//
+				// DistributionPoint ::= SEQUENCE {
+				//     distributionPoint       [0]     DistributionPointName OPTIONAL,
+				//     reasons                 [1]     ReasonFlags OPTIONAL,
+				//     cRLIssuer               [2]     GeneralNames OPTIONAL }
+				//
+				// DistributionPointName ::= CHOICE {
+				//     fullName                [0]     GeneralNames,
+				//     nameRelativeToCRLIssuer [1]     RelativeDistinguishedName }
+
+				var cdp []distributionPoint
+				_, err := asn1.Unmarshal(e.Value, &cdp)
+				if err != nil {
+					return nil, err
+				}
+
+				for _, dp := range cdp {
+					var n asn1.RawValue
+					_, err = asn1.Unmarshal(dp.DistributionPoint.FullName.Bytes, &n)
+					if err != nil {
+						return nil, err
+					}
+
+					if n.Tag == 6 {
+						out.CRLDistributionPoints = append(out.CRLDistributionPoints, string(n.Bytes))
+					}
+				}
+				continue
+
+			case 35:
+				// RFC 5280, 4.2.1.1
+				var a authKeyId
+				_, err = asn1.Unmarshal(e.Value, &a)
+				if err != nil {
+					return nil, err
+				}
+				out.AuthorityKeyId = a.Id
+				continue
+
+			case 37:
+				// RFC 5280, 4.2.1.12.  Extended Key Usage
+
+				// id-ce-extKeyUsage OBJECT IDENTIFIER ::= { id-ce 37 }
+				//
+				// ExtKeyUsageSyntax ::= SEQUENCE SIZE (1..MAX) OF KeyPurposeId
+				//
+				// KeyPurposeId ::= OBJECT IDENTIFIER
+
+				var keyUsage []asn1.ObjectIdentifier
+				_, err = asn1.Unmarshal(e.Value, &keyUsage)
+				if err != nil {
+					return nil, err
+				}
+
+				for _, u := range keyUsage {
+					if extKeyUsage, ok := extKeyUsageFromOID(u); ok {
+						out.ExtKeyUsage = append(out.ExtKeyUsage, extKeyUsage)
+					} else {
+						out.UnknownExtKeyUsage = append(out.UnknownExtKeyUsage, u)
+					}
+				}
+
+				continue
+
+			case 14:
+				// RFC 5280, 4.2.1.2
+				var keyid []byte
+				_, err = asn1.Unmarshal(e.Value, &keyid)
+				if err != nil {
+					return nil, err
+				}
+				out.SubjectKeyId = keyid
+				continue
+
+			case 32:
+				// RFC 5280 4.2.1.4: Certificate Policies
+				var policies []policyInformation
+				if _, err = asn1.Unmarshal(e.Value, &policies); err != nil {
+					return nil, err
+				}
+				out.PolicyIdentifiers = make([]asn1.ObjectIdentifier, len(policies))
+				for i, policy := range policies {
+					out.PolicyIdentifiers[i] = policy.Policy
+				}
+			}
+		} else if e.Id.Equal(oidExtensionAuthorityInfoAccess) {
+			// RFC 5280 4.2.2.1: Authority Information Access
+			var aia []authorityInfoAccess
+			if _, err = asn1.Unmarshal(e.Value, &aia); err != nil {
+				return nil, err
+			}
+
+			for _, v := range aia {
+				// GeneralName: uniformResourceIdentifier [6] IA5String
+				if v.Location.Tag != 6 {
+					continue
+				}
+				if v.Method.Equal(oidAuthorityInfoAccessOcsp) {
+					out.OCSPServer = append(out.OCSPServer, string(v.Location.Bytes))
+				} else if v.Method.Equal(oidAuthorityInfoAccessIssuers) {
+					out.IssuingCertificateURL = append(out.IssuingCertificateURL, string(v.Location.Bytes))
+				}
+			}
+		}
+
+		if e.Critical {
+			return out, UnhandledCriticalExtension{}
+		}
+	}
+
+	return out, nil
+}
+
+// ParseCertificate parses a single certificate from the given ASN.1 DER data.
+func ParseCertificate(asn1Data []byte) (*Certificate, error) {
+	var cert certificate
+	rest, err := asn1.Unmarshal(asn1Data, &cert)
+	if err != nil {
+		return nil, err
+	}
+	if len(rest) > 0 {
+		return nil, asn1.SyntaxError{Msg: "trailing data"}
+	}
+
+	return parseCertificate(&cert)
+}
+
+// ParseCertificates parses one or more certificates from the given ASN.1 DER
+// data. The certificates must be concatenated with no intermediate padding.
+func ParseCertificates(asn1Data []byte) ([]*Certificate, error) {
+	var v []*certificate
+
+	for len(asn1Data) > 0 {
+		cert := new(certificate)
+		var err error
+		asn1Data, err = asn1.Unmarshal(asn1Data, cert)
+		if err != nil {
+			return nil, err
+		}
+		v = append(v, cert)
+	}
+
+	ret := make([]*Certificate, len(v))
+	for i, ci := range v {
+		cert, err := parseCertificate(ci)
+		if err != nil {
+			return nil, err
+		}
+		ret[i] = cert
+	}
+
+	return ret, nil
+}
+
+func reverseBitsInAByte(in byte) byte {
+	b1 := in>>4 | in<<4
+	b2 := b1>>2&0x33 | b1<<2&0xcc
+	b3 := b2>>1&0x55 | b2<<1&0xaa
+	return b3
+}
+
+var (
+	oidExtensionSubjectKeyId          = []int{2, 5, 29, 14}
+	oidExtensionKeyUsage              = []int{2, 5, 29, 15}
+	oidExtensionExtendedKeyUsage      = []int{2, 5, 29, 37}
+	oidExtensionAuthorityKeyId        = []int{2, 5, 29, 35}
+	oidExtensionBasicConstraints      = []int{2, 5, 29, 19}
+	oidExtensionSubjectAltName        = []int{2, 5, 29, 17}
+	oidExtensionCertificatePolicies   = []int{2, 5, 29, 32}
+	oidExtensionNameConstraints       = []int{2, 5, 29, 30}
+	oidExtensionCRLDistributionPoints = []int{2, 5, 29, 31}
+	oidExtensionAuthorityInfoAccess   = []int{1, 3, 6, 1, 5, 5, 7, 1, 1}
+)
+
+var (
+	oidAuthorityInfoAccessOcsp    = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 48, 1}
+	oidAuthorityInfoAccessIssuers = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 48, 2}
+)
+
+// oidNotInExtensions returns whether an extension with the given oid exists in
+// extensions.
+func oidInExtensions(oid asn1.ObjectIdentifier, extensions []pkix.Extension) bool {
+	for _, e := range extensions {
+		if e.Id.Equal(oid) {
+			return true
+		}
+	}
+	return false
+}
+
+// marshalSANs marshals a list of addresses into a the contents of an X.509
+// SubjectAlternativeName extension.
+func marshalSANs(dnsNames, emailAddresses []string, ipAddresses []net.IP) (derBytes []byte, err error) {
+	var rawValues []asn1.RawValue
+	for _, name := range dnsNames {
+		rawValues = append(rawValues, asn1.RawValue{Tag: 2, Class: 2, Bytes: []byte(name)})
+	}
+	for _, email := range emailAddresses {
+		rawValues = append(rawValues, asn1.RawValue{Tag: 1, Class: 2, Bytes: []byte(email)})
+	}
+	for _, rawIP := range ipAddresses {
+		// If possible, we always want to encode IPv4 addresses in 4 bytes.
+		ip := rawIP.To4()
+		if ip == nil {
+			ip = rawIP
+		}
+		rawValues = append(rawValues, asn1.RawValue{Tag: 7, Class: 2, Bytes: ip})
+	}
+	return asn1.Marshal(rawValues)
+}
+
+func buildExtensions(template *Certificate) (ret []pkix.Extension, err error) {
+	ret = make([]pkix.Extension, 10 /* maximum number of elements. */)
+	n := 0
+
+	if template.KeyUsage != 0 &&
+		!oidInExtensions(oidExtensionKeyUsage, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionKeyUsage
+		ret[n].Critical = true
+
+		var a [2]byte
+		a[0] = reverseBitsInAByte(byte(template.KeyUsage))
+		a[1] = reverseBitsInAByte(byte(template.KeyUsage >> 8))
+
+		l := 1
+		if a[1] != 0 {
+			l = 2
+		}
+
+		ret[n].Value, err = asn1.Marshal(asn1.BitString{Bytes: a[0:l], BitLength: l * 8})
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	if (len(template.ExtKeyUsage) > 0 || len(template.UnknownExtKeyUsage) > 0) &&
+		!oidInExtensions(oidExtensionExtendedKeyUsage, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionExtendedKeyUsage
+
+		var oids []asn1.ObjectIdentifier
+		for _, u := range template.ExtKeyUsage {
+			if oid, ok := oidFromExtKeyUsage(u); ok {
+				oids = append(oids, oid)
+			} else {
+				panic("internal error")
+			}
+		}
+
+		oids = append(oids, template.UnknownExtKeyUsage...)
+
+		ret[n].Value, err = asn1.Marshal(oids)
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	if template.BasicConstraintsValid && !oidInExtensions(oidExtensionBasicConstraints, template.ExtraExtensions) {
+		// Leaving MaxPathLen as zero indicates that no maximum path
+		// length is desired, unless MaxPathLenZero is set. A value of
+		// -1 causes encoding/asn1 to omit the value as desired.
+		maxPathLen := template.MaxPathLen
+		if maxPathLen == 0 && !template.MaxPathLenZero {
+			maxPathLen = -1
+		}
+		ret[n].Id = oidExtensionBasicConstraints
+		ret[n].Value, err = asn1.Marshal(basicConstraints{template.IsCA, maxPathLen})
+		ret[n].Critical = true
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	if len(template.SubjectKeyId) > 0 && !oidInExtensions(oidExtensionSubjectKeyId, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionSubjectKeyId
+		ret[n].Value, err = asn1.Marshal(template.SubjectKeyId)
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	if len(template.AuthorityKeyId) > 0 && !oidInExtensions(oidExtensionAuthorityKeyId, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionAuthorityKeyId
+		ret[n].Value, err = asn1.Marshal(authKeyId{template.AuthorityKeyId})
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	if (len(template.OCSPServer) > 0 || len(template.IssuingCertificateURL) > 0) &&
+		!oidInExtensions(oidExtensionAuthorityInfoAccess, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionAuthorityInfoAccess
+		var aiaValues []authorityInfoAccess
+		for _, name := range template.OCSPServer {
+			aiaValues = append(aiaValues, authorityInfoAccess{
+				Method:   oidAuthorityInfoAccessOcsp,
+				Location: asn1.RawValue{Tag: 6, Class: 2, Bytes: []byte(name)},
+			})
+		}
+		for _, name := range template.IssuingCertificateURL {
+			aiaValues = append(aiaValues, authorityInfoAccess{
+				Method:   oidAuthorityInfoAccessIssuers,
+				Location: asn1.RawValue{Tag: 6, Class: 2, Bytes: []byte(name)},
+			})
+		}
+		ret[n].Value, err = asn1.Marshal(aiaValues)
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	if (len(template.DNSNames) > 0 || len(template.EmailAddresses) > 0 || len(template.IPAddresses) > 0) &&
+		!oidInExtensions(oidExtensionSubjectAltName, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionSubjectAltName
+		ret[n].Value, err = marshalSANs(template.DNSNames, template.EmailAddresses, template.IPAddresses)
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	if len(template.PolicyIdentifiers) > 0 &&
+		!oidInExtensions(oidExtensionCertificatePolicies, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionCertificatePolicies
+		policies := make([]policyInformation, len(template.PolicyIdentifiers))
+		for i, policy := range template.PolicyIdentifiers {
+			policies[i].Policy = policy
+		}
+		ret[n].Value, err = asn1.Marshal(policies)
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	if len(template.PermittedDNSDomains) > 0 &&
+		!oidInExtensions(oidExtensionNameConstraints, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionNameConstraints
+		ret[n].Critical = template.PermittedDNSDomainsCritical
+
+		var out nameConstraints
+		out.Permitted = make([]generalSubtree, len(template.PermittedDNSDomains))
+		for i, permitted := range template.PermittedDNSDomains {
+			out.Permitted[i] = generalSubtree{Name: permitted}
+		}
+		ret[n].Value, err = asn1.Marshal(out)
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	if len(template.CRLDistributionPoints) > 0 &&
+		!oidInExtensions(oidExtensionCRLDistributionPoints, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionCRLDistributionPoints
+
+		var crlDp []distributionPoint
+		for _, name := range template.CRLDistributionPoints {
+			rawFullName, _ := asn1.Marshal(asn1.RawValue{Tag: 6, Class: 2, Bytes: []byte(name)})
+
+			dp := distributionPoint{
+				DistributionPoint: distributionPointName{
+					FullName: asn1.RawValue{Tag: 0, Class: 2, IsCompound: true, Bytes: rawFullName},
+				},
+			}
+			crlDp = append(crlDp, dp)
+		}
+
+		ret[n].Value, err = asn1.Marshal(crlDp)
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	// Adding another extension here? Remember to update the maximum number
+	// of elements in the make() at the top of the function.
+
+	return append(ret[:n], template.ExtraExtensions...), nil
+}
+
+func subjectBytes(cert *Certificate) ([]byte, error) {
+	if len(cert.RawSubject) > 0 {
+		return cert.RawSubject, nil
+	}
+
+	return asn1.Marshal(cert.Subject.ToRDNSequence())
+}
+
+// signingParamsForPrivateKey returns the parameters to use for signing with
+// priv. If requestedSigAlgo is not zero then it overrides the default
+// signature algorithm.
+func signingParamsForPrivateKey(priv interface{}, requestedSigAlgo SignatureAlgorithm) (hashFunc crypto.Hash, sigAlgo pkix.AlgorithmIdentifier, err error) {
+	var pubType PublicKeyAlgorithm
+
+	switch priv := priv.(type) {
+	case *rsa.PrivateKey:
+		pubType = RSA
+		sigAlgo.Algorithm = oidSignatureSHA256WithRSA
+		hashFunc = crypto.SHA256
+
+	case *ecdsa.PrivateKey:
+		pubType = ECDSA
+
+		switch priv.Curve {
+		case elliptic.P224(), elliptic.P256():
+			hashFunc = crypto.SHA256
+			sigAlgo.Algorithm = oidSignatureECDSAWithSHA256
+		case elliptic.P384():
+			hashFunc = crypto.SHA384
+			sigAlgo.Algorithm = oidSignatureECDSAWithSHA384
+		case elliptic.P521():
+			hashFunc = crypto.SHA512
+			sigAlgo.Algorithm = oidSignatureECDSAWithSHA512
+		default:
+			err = errors.New("x509: unknown elliptic curve")
+		}
+
+	default:
+		err = errors.New("x509: only RSA and ECDSA private keys supported")
+	}
+
+	if err != nil {
+		return
+	}
+
+	if requestedSigAlgo == 0 {
+		return
+	}
+
+	found := false
+	for _, details := range signatureAlgorithmDetails {
+		if details.algo == requestedSigAlgo {
+			if details.pubKeyAlgo != pubType {
+				err = errors.New("x509: requested SignatureAlgorithm does not match private key type")
+				return
+			}
+			sigAlgo.Algorithm, hashFunc = details.oid, details.hash
+			if hashFunc == 0 {
+				err = errors.New("x509: cannot sign with hash function requested")
+				return
+			}
+			found = true
+			break
+		}
+	}
+
+	if !found {
+		err = errors.New("x509: unknown SignatureAlgorithm")
+	}
+
+	return
+}
+
+// CreateCertificate creates a new certificate based on a template. The
+// following members of template are used: SerialNumber, Subject, NotBefore,
+// NotAfter, KeyUsage, ExtKeyUsage, UnknownExtKeyUsage, BasicConstraintsValid,
+// IsCA, MaxPathLen, SubjectKeyId, DNSNames, PermittedDNSDomainsCritical,
+// PermittedDNSDomains, SignatureAlgorithm.
+//
+// The certificate is signed by parent. If parent is equal to template then the
+// certificate is self-signed. The parameter pub is the public key of the
+// signee and priv is the private key of the signer.
+//
+// The returned slice is the certificate in DER encoding.
+//
+// The only supported key types are RSA and ECDSA (*rsa.PublicKey or
+// *ecdsa.PublicKey for pub, *rsa.PrivateKey or *ecdsa.PrivateKey for priv).
+func CreateCertificate(rand io.Reader, template, parent *Certificate, pub interface{}, priv interface{}) (cert []byte, err error) {
+	hashFunc, signatureAlgorithm, err := signingParamsForPrivateKey(priv, template.SignatureAlgorithm)
+	if err != nil {
+		return nil, err
+	}
+
+	publicKeyBytes, publicKeyAlgorithm, err := marshalPublicKey(pub)
+	if err != nil {
+		return nil, err
+	}
+
+	if err != nil {
+		return
+	}
+
+	if len(parent.SubjectKeyId) > 0 {
+		template.AuthorityKeyId = parent.SubjectKeyId
+	}
+
+	extensions, err := buildExtensions(template)
+	if err != nil {
+		return
+	}
+
+	asn1Issuer, err := subjectBytes(parent)
+	if err != nil {
+		return
+	}
+
+	asn1Subject, err := subjectBytes(template)
+	if err != nil {
+		return
+	}
+
+	encodedPublicKey := asn1.BitString{BitLength: len(publicKeyBytes) * 8, Bytes: publicKeyBytes}
+	c := tbsCertificate{
+		Version:            2,
+		SerialNumber:       template.SerialNumber,
+		SignatureAlgorithm: signatureAlgorithm,
+		Issuer:             asn1.RawValue{FullBytes: asn1Issuer},
+		Validity:           validity{template.NotBefore.UTC(), template.NotAfter.UTC()},
+		Subject:            asn1.RawValue{FullBytes: asn1Subject},
+		PublicKey:          publicKeyInfo{nil, publicKeyAlgorithm, encodedPublicKey},
+		Extensions:         extensions,
+	}
+
+	tbsCertContents, err := asn1.Marshal(c)
+	if err != nil {
+		return
+	}
+
+	c.Raw = tbsCertContents
+
+	h := hashFunc.New()
+	h.Write(tbsCertContents)
+	digest := h.Sum(nil)
+
+	var signature []byte
+
+	switch priv := priv.(type) {
+	case *rsa.PrivateKey:
+		signature, err = rsa.SignPKCS1v15(rand, priv, hashFunc, digest)
+	case *ecdsa.PrivateKey:
+		var r, s *big.Int
+		if r, s, err = ecdsa.Sign(rand, priv, digest); err == nil {
+			signature, err = asn1.Marshal(ecdsaSignature{r, s})
+		}
+	default:
+		panic("internal error")
+	}
+
+	if err != nil {
+		return
+	}
+
+	cert, err = asn1.Marshal(certificate{
+		nil,
+		c,
+		signatureAlgorithm,
+		asn1.BitString{Bytes: signature, BitLength: len(signature) * 8},
+	})
+	return
+}
+
+// pemCRLPrefix is the magic string that indicates that we have a PEM encoded
+// CRL.
+var pemCRLPrefix = []byte("-----BEGIN X509 CRL")
+
+// pemType is the type of a PEM encoded CRL.
+var pemType = "X509 CRL"
+
+// ParseCRL parses a CRL from the given bytes. It's often the case that PEM
+// encoded CRLs will appear where they should be DER encoded, so this function
+// will transparently handle PEM encoding as long as there isn't any leading
+// garbage.
+func ParseCRL(crlBytes []byte) (certList *pkix.CertificateList, err error) {
+	if bytes.HasPrefix(crlBytes, pemCRLPrefix) {
+		block, _ := pem.Decode(crlBytes)
+		if block != nil && block.Type == pemType {
+			crlBytes = block.Bytes
+		}
+	}
+	return ParseDERCRL(crlBytes)
+}
+
+// ParseDERCRL parses a DER encoded CRL from the given bytes.
+func ParseDERCRL(derBytes []byte) (certList *pkix.CertificateList, err error) {
+	certList = new(pkix.CertificateList)
+	_, err = asn1.Unmarshal(derBytes, certList)
+	if err != nil {
+		certList = nil
+	}
+	return
+}
+
+// CreateCRL returns a DER encoded CRL, signed by this Certificate, that
+// contains the given list of revoked certificates.
+//
+// The only supported key type is RSA (*rsa.PrivateKey for priv).
+func (c *Certificate) CreateCRL(rand io.Reader, priv interface{}, revokedCerts []pkix.RevokedCertificate, now, expiry time.Time) (crlBytes []byte, err error) {
+	rsaPriv, ok := priv.(*rsa.PrivateKey)
+	if !ok {
+		return nil, errors.New("x509: non-RSA private keys not supported")
+	}
+	tbsCertList := pkix.TBSCertificateList{
+		Version: 2,
+		Signature: pkix.AlgorithmIdentifier{
+			Algorithm: oidSignatureSHA1WithRSA,
+		},
+		Issuer:              c.Subject.ToRDNSequence(),
+		ThisUpdate:          now.UTC(),
+		NextUpdate:          expiry.UTC(),
+		RevokedCertificates: revokedCerts,
+	}
+
+	tbsCertListContents, err := asn1.Marshal(tbsCertList)
+	if err != nil {
+		return
+	}
+
+	h := sha1.New()
+	h.Write(tbsCertListContents)
+	digest := h.Sum(nil)
+
+	signature, err := rsa.SignPKCS1v15(rand, rsaPriv, crypto.SHA1, digest)
+	if err != nil {
+		return
+	}
+
+	return asn1.Marshal(pkix.CertificateList{
+		TBSCertList: tbsCertList,
+		SignatureAlgorithm: pkix.AlgorithmIdentifier{
+			Algorithm: oidSignatureSHA1WithRSA,
+		},
+		SignatureValue: asn1.BitString{Bytes: signature, BitLength: len(signature) * 8},
+	})
+}
+
+// CertificateRequest represents a PKCS #10, certificate signature request.
+type CertificateRequest struct {
+	Raw                      []byte // Complete ASN.1 DER content (CSR, signature algorithm and signature).
+	RawTBSCertificateRequest []byte // Certificate request info part of raw ASN.1 DER content.
+	RawSubjectPublicKeyInfo  []byte // DER encoded SubjectPublicKeyInfo.
+	RawSubject               []byte // DER encoded Subject.
+
+	Version            int
+	Signature          []byte
+	SignatureAlgorithm SignatureAlgorithm
+
+	PublicKeyAlgorithm PublicKeyAlgorithm
+	PublicKey          interface{}
+
+	Subject pkix.Name
+
+	// Attributes is a collection of attributes providing
+	// additional information about the subject of the certificate.
+	// See RFC 2986 section 4.1.
+	Attributes []pkix.AttributeTypeAndValueSET
+
+	// Extensions contains raw X.509 extensions. When parsing CSRs, this
+	// can be used to extract extensions that are not parsed by this
+	// package.
+	Extensions []pkix.Extension
+
+	// ExtraExtensions contains extensions to be copied, raw, into any
+	// marshaled CSR. Values override any extensions that would otherwise
+	// be produced based on the other fields but are overridden by any
+	// extensions specified in Attributes.
+	//
+	// The ExtraExtensions field is not populated when parsing CSRs, see
+	// Extensions.
+	ExtraExtensions []pkix.Extension
+
+	// Subject Alternate Name values.
+	DNSNames       []string
+	EmailAddresses []string
+	IPAddresses    []net.IP
+}
+
+// These structures reflect the ASN.1 structure of X.509 certificate
+// signature requests (see RFC 2986):
+
+type tbsCertificateRequest struct {
+	Raw        asn1.RawContent
+	Version    int
+	Subject    asn1.RawValue
+	PublicKey  publicKeyInfo
+	Attributes []pkix.AttributeTypeAndValueSET `asn1:"tag:0"`
+}
+
+type certificateRequest struct {
+	Raw                asn1.RawContent
+	TBSCSR             tbsCertificateRequest
+	SignatureAlgorithm pkix.AlgorithmIdentifier
+	SignatureValue     asn1.BitString
+}
+
+// oidExtensionRequest is a PKCS#9 OBJECT IDENTIFIER that indicates requested
+// extensions in a CSR.
+var oidExtensionRequest = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 9, 14}
+
+// CreateCertificateRequest creates a new certificate based on a template. The
+// following members of template are used: Subject, Attributes,
+// SignatureAlgorithm, Extensions, DNSNames, EmailAddresses, and IPAddresses.
+// The private key is the private key of the signer.
+//
+// The returned slice is the certificate request in DER encoding.
+//
+// The only supported key types are RSA (*rsa.PrivateKey) and ECDSA
+// (*ecdsa.PrivateKey).
+func CreateCertificateRequest(rand io.Reader, template *CertificateRequest, priv interface{}) (csr []byte, err error) {
+	hashFunc, sigAlgo, err := signingParamsForPrivateKey(priv, template.SignatureAlgorithm)
+	if err != nil {
+		return nil, err
+	}
+
+	var publicKeyBytes []byte
+	var publicKeyAlgorithm pkix.AlgorithmIdentifier
+
+	switch priv := priv.(type) {
+	case *rsa.PrivateKey:
+		publicKeyBytes, publicKeyAlgorithm, err = marshalPublicKey(&priv.PublicKey)
+	case *ecdsa.PrivateKey:
+		publicKeyBytes, publicKeyAlgorithm, err = marshalPublicKey(&priv.PublicKey)
+	default:
+		panic("internal error")
+	}
+
+	if err != nil {
+		return nil, err
+	}
+
+	var extensions []pkix.Extension
+
+	if (len(template.DNSNames) > 0 || len(template.EmailAddresses) > 0 || len(template.IPAddresses) > 0) &&
+		!oidInExtensions(oidExtensionSubjectAltName, template.ExtraExtensions) {
+		sanBytes, err := marshalSANs(template.DNSNames, template.EmailAddresses, template.IPAddresses)
+		if err != nil {
+			return nil, err
+		}
+
+		extensions = append(extensions, pkix.Extension{
+			Id:    oidExtensionSubjectAltName,
+			Value: sanBytes,
+		})
+	}
+
+	extensions = append(extensions, template.ExtraExtensions...)
+
+	var attributes []pkix.AttributeTypeAndValueSET
+	attributes = append(attributes, template.Attributes...)
+
+	if len(extensions) > 0 {
+		// specifiedExtensions contains all the extensions that we
+		// found specified via template.Attributes.
+		specifiedExtensions := make(map[string]bool)
+
+		for _, atvSet := range template.Attributes {
+			if !atvSet.Type.Equal(oidExtensionRequest) {
+				continue
+			}
+
+			for _, atvs := range atvSet.Value {
+				for _, atv := range atvs {
+					specifiedExtensions[atv.Type.String()] = true
+				}
+			}
+		}
+
+		atvs := make([]pkix.AttributeTypeAndValue, 0, len(extensions))
+		for _, e := range extensions {
+			if specifiedExtensions[e.Id.String()] {
+				// Attributes already contained a value for
+				// this extension and it takes priority.
+				continue
+			}
+
+			atvs = append(atvs, pkix.AttributeTypeAndValue{
+				// There is no place for the critical flag in a CSR.
+				Type:  e.Id,
+				Value: e.Value,
+			})
+		}
+
+		// Append the extensions to an existing attribute if possible.
+		appended := false
+		for _, atvSet := range attributes {
+			if !atvSet.Type.Equal(oidExtensionRequest) || len(atvSet.Value) == 0 {
+				continue
+			}
+
+			atvSet.Value[0] = append(atvSet.Value[0], atvs...)
+			appended = true
+			break
+		}
+
+		// Otherwise, add a new attribute for the extensions.
+		if !appended {
+			attributes = append(attributes, pkix.AttributeTypeAndValueSET{
+				Type: oidExtensionRequest,
+				Value: [][]pkix.AttributeTypeAndValue{
+					atvs,
+				},
+			})
+		}
+	}
+
+	asn1Subject := template.RawSubject
+	if len(asn1Subject) == 0 {
+		asn1Subject, err = asn1.Marshal(template.Subject.ToRDNSequence())
+		if err != nil {
+			return
+		}
+	}
+
+	tbsCSR := tbsCertificateRequest{
+		Version: 0, // PKCS #10, RFC 2986
+		Subject: asn1.RawValue{FullBytes: asn1Subject},
+		PublicKey: publicKeyInfo{
+			Algorithm: publicKeyAlgorithm,
+			PublicKey: asn1.BitString{
+				Bytes:     publicKeyBytes,
+				BitLength: len(publicKeyBytes) * 8,
+			},
+		},
+		Attributes: attributes,
+	}
+
+	tbsCSRContents, err := asn1.Marshal(tbsCSR)
+	if err != nil {
+		return
+	}
+	tbsCSR.Raw = tbsCSRContents
+
+	h := hashFunc.New()
+	h.Write(tbsCSRContents)
+	digest := h.Sum(nil)
+
+	var signature []byte
+	switch priv := priv.(type) {
+	case *rsa.PrivateKey:
+		signature, err = rsa.SignPKCS1v15(rand, priv, hashFunc, digest)
+	case *ecdsa.PrivateKey:
+		var r, s *big.Int
+		if r, s, err = ecdsa.Sign(rand, priv, digest); err == nil {
+			signature, err = asn1.Marshal(ecdsaSignature{r, s})
+		}
+	default:
+		panic("internal error")
+	}
+
+	if err != nil {
+		return
+	}
+
+	return asn1.Marshal(certificateRequest{
+		TBSCSR:             tbsCSR,
+		SignatureAlgorithm: sigAlgo,
+		SignatureValue: asn1.BitString{
+			Bytes:     signature,
+			BitLength: len(signature) * 8,
+		},
+	})
+}
+
+// ParseCertificateRequest parses a single certificate request from the
+// given ASN.1 DER data.
+func ParseCertificateRequest(asn1Data []byte) (*CertificateRequest, error) {
+	var csr certificateRequest
+
+	rest, err := asn1.Unmarshal(asn1Data, &csr)
+	if err != nil {
+		return nil, err
+	} else if len(rest) != 0 {
+		return nil, asn1.SyntaxError{Msg: "trailing data"}
+	}
+
+	return parseCertificateRequest(&csr)
+}
+
+func parseCertificateRequest(in *certificateRequest) (*CertificateRequest, error) {
+	out := &CertificateRequest{
+		Raw: in.Raw,
+		RawTBSCertificateRequest: in.TBSCSR.Raw,
+		RawSubjectPublicKeyInfo:  in.TBSCSR.PublicKey.Raw,
+		RawSubject:               in.TBSCSR.Subject.FullBytes,
+
+		Signature:          in.SignatureValue.RightAlign(),
+		SignatureAlgorithm: getSignatureAlgorithmFromOID(in.SignatureAlgorithm.Algorithm),
+
+		PublicKeyAlgorithm: getPublicKeyAlgorithmFromOID(in.TBSCSR.PublicKey.Algorithm.Algorithm),
+
+		Version:    in.TBSCSR.Version,
+		Attributes: in.TBSCSR.Attributes,
+	}
+
+	var err error
+	out.PublicKey, err = parsePublicKey(out.PublicKeyAlgorithm, &in.TBSCSR.PublicKey)
+	if err != nil {
+		return nil, err
+	}
+
+	var subject pkix.RDNSequence
+	if _, err := asn1.Unmarshal(in.TBSCSR.Subject.FullBytes, &subject); err != nil {
+		return nil, err
+	}
+
+	out.Subject.FillFromRDNSequence(&subject)
+
+	var extensions []pkix.AttributeTypeAndValue
+
+	for _, atvSet := range in.TBSCSR.Attributes {
+		if !atvSet.Type.Equal(oidExtensionRequest) {
+			continue
+		}
+
+		for _, atvs := range atvSet.Value {
+			extensions = append(extensions, atvs...)
+		}
+	}
+
+	out.Extensions = make([]pkix.Extension, 0, len(extensions))
+
+	for _, e := range extensions {
+		value, ok := e.Value.([]byte)
+		if !ok {
+			return nil, errors.New("x509: extension attribute contained non-OCTET STRING data")
+		}
+
+		out.Extensions = append(out.Extensions, pkix.Extension{
+			Id:    e.Type,
+			Value: value,
+		})
+
+		if len(e.Type) == 4 && e.Type[0] == 2 && e.Type[1] == 5 && e.Type[2] == 29 {
+			switch e.Type[3] {
+			case 17:
+				out.DNSNames, out.EmailAddresses, out.IPAddresses, err = parseSANExtension(value)
+				if err != nil {
+					return nil, err
+				}
+			}
+		}
+	}
+
+	return out, nil
+}