Beispiel #1
0
func parsePublicKey(algo PublicKeyAlgorithm, keyData *publicKeyInfo) (interface{}, os.Error) {
	asn1Data := keyData.PublicKey.RightAlign()
	switch algo {
	case RSA:
		p := new(rsaPublicKey)
		_, err := asn1.Unmarshal(asn1Data, p)
		if err != nil {
			return nil, err
		}

		if !rawValueIsInteger(&p.N) {
			return nil, asn1.StructuralError{"tags don't match"}
		}

		pub := &rsa.PublicKey{
			E: p.E,
			N: new(big.Int).SetBytes(p.N.Bytes),
		}
		return pub, nil
	case DSA:
		p := new(asn1.RawValue)
		_, err := asn1.Unmarshal(asn1Data, p)
		if err != nil {
			return nil, err
		}
		if !rawValueIsInteger(p) {
			return nil, asn1.StructuralError{"tags don't match"}
		}
		paramsData := keyData.Algorithm.Parameters.FullBytes
		params := new(dsaAlgorithmParameters)
		_, err = asn1.Unmarshal(paramsData, params)
		if err != nil {
			return nil, err
		}
		if !rawValueIsInteger(&params.P) ||
			!rawValueIsInteger(&params.Q) ||
			!rawValueIsInteger(&params.G) {
			return nil, asn1.StructuralError{"tags don't match"}
		}
		pub := &dsa.PublicKey{
			Parameters: dsa.Parameters{
				P: new(big.Int).SetBytes(params.P.Bytes),
				Q: new(big.Int).SetBytes(params.Q.Bytes),
				G: new(big.Int).SetBytes(params.G.Bytes),
			},
			Y: new(big.Int).SetBytes(p.Bytes),
		}
		return pub, nil
	default:
		return nil, nil
	}
	panic("unreachable")
}
// ParsePKCS1PrivateKey returns an RSA private key from its ASN.1 PKCS#1 DER encoded form.
func ParsePKCS1PrivateKey(der []byte) (key *rsa.PrivateKey, err os.Error) {
	var priv pkcs1PrivateKey
	rest, err := asn1.Unmarshal(der, &priv)
	if len(rest) > 0 {
		err = asn1.SyntaxError{"trailing data"}
		return
	}
	if err != nil {
		return
	}

	if !rawValueIsInteger(&priv.N) ||
		!rawValueIsInteger(&priv.D) ||
		!rawValueIsInteger(&priv.P) ||
		!rawValueIsInteger(&priv.Q) {
		err = asn1.StructuralError{"tags don't match"}
		return
	}

	key = &rsa.PrivateKey{
		PublicKey: rsa.PublicKey{
			E: priv.E,
			N: new(big.Int).SetBytes(priv.N.Bytes),
		},
		D: new(big.Int).SetBytes(priv.D.Bytes),
		P: new(big.Int).SetBytes(priv.P.Bytes),
		Q: new(big.Int).SetBytes(priv.Q.Bytes),
	}

	err = key.Validate()
	if err != nil {
		return nil, err
	}
	return
}
Beispiel #3
0
// ParseDER parses a DER encoded CRL from the given bytes.
func ParseDER(derBytes []byte) (certList *CertificateList, err os.Error) {
	certList = new(CertificateList)
	_, err = asn1.Unmarshal(derBytes, certList)
	if err != nil {
		certList = nil
	}
	return
}
Beispiel #4
0
// 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
}
Beispiel #5
0
func parsePublicKey(algo PublicKeyAlgorithm, keyData *publicKeyInfo) (interface{}, os.Error) {
	asn1Data := keyData.PublicKey.RightAlign()
	switch algo {
	case RSA:
		p := new(rsaPublicKey)
		_, err := asn1.Unmarshal(asn1Data, p)
		if err != nil {
			return nil, err
		}

		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, os.NewError("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
	default:
		return nil, nil
	}
	panic("unreachable")
}
Beispiel #6
0
// 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 os.Error) {
	var pki publicKeyInfo
	if _, err = asn1.Unmarshal(derBytes, &pki); err != nil {
		return
	}
	algo := getPublicKeyAlgorithmFromOID(pki.Algorithm.Algorithm)
	if algo == UnknownPublicKeyAlgorithm {
		return nil, os.NewError("ParsePKIXPublicKey: unknown public key algorithm")
	}
	return parsePublicKey(algo, &pki)
}
// ParseCertificate parses a single certificate from the given ASN.1 DER data.
func ParseCertificate(asn1Data []byte) (*Certificate, os.Error) {
	var cert certificate
	rest, err := asn1.Unmarshal(asn1Data, &cert)
	if err != nil {
		return nil, err
	}
	if len(rest) > 0 {
		return nil, asn1.SyntaxError{"trailing data"}
	}

	return parseCertificate(&cert)
}
Beispiel #8
0
func decode(data []byte) (interface{}, os.Error) {
	m := Message{}
	_, err := asn1.Unmarshal(data, &m)
	if err != nil {
		fmt.Errorf("%#v", data)
		return nil, err
	}
	choice := m.Data.FullBytes[0]
	switch choice {
	case 0xa0, 0xa1, 0xa2:
		// Response
		pdu := new(PDU)
		// hack ANY -> IMPLICIT SEQUENCE
		m.Data.FullBytes[0] = 0x30
		_, err = asn1.Unmarshal(m.Data.FullBytes, pdu)
		if err != nil {
			return nil, fmt.Errorf("%#v, %#v, %s", m.Data.FullBytes, pdu, err)
		}
		return pdu, nil
	}
	return nil, fmt.Errorf("Unknown CHOICE: %x", choice)
}
Beispiel #9
0
// ParsePKCS1PrivateKey returns an RSA private key from its ASN.1 PKCS#1 DER encoded form.
func ParsePKCS1PrivateKey(der []byte) (key *rsa.PrivateKey, err os.Error) {
	var priv pkcs1PrivateKey
	rest, err := asn1.Unmarshal(der, &priv)
	if len(rest) > 0 {
		err = asn1.SyntaxError{"trailing data"}
		return
	}
	if err != nil {
		return
	}

	if priv.Version > 1 {
		return nil, os.ErrorString("x509: unsupported private key version")
	}

	if !rawValueIsInteger(&priv.N) ||
		!rawValueIsInteger(&priv.D) ||
		!rawValueIsInteger(&priv.P) ||
		!rawValueIsInteger(&priv.Q) {
		err = asn1.StructuralError{"tags don't match"}
		return
	}

	key = new(rsa.PrivateKey)
	key.PublicKey = rsa.PublicKey{
		E: priv.E,
		N: new(big.Int).SetBytes(priv.N.Bytes),
	}

	key.D = new(big.Int).SetBytes(priv.D.Bytes)
	key.Primes = make([]*big.Int, 2+len(priv.AdditionalPrimes))
	key.Primes[0] = new(big.Int).SetBytes(priv.P.Bytes)
	key.Primes[1] = new(big.Int).SetBytes(priv.Q.Bytes)
	for i, a := range priv.AdditionalPrimes {
		if !rawValueIsInteger(&a.Prime) {
			return nil, asn1.StructuralError{"tags don't match"}
		}
		key.Primes[i+2] = new(big.Int).SetBytes(a.Prime.Bytes)
		// We ignore the other two values because rsa will calculate
		// them as needed.
	}

	err = key.Validate()
	if err != nil {
		return nil, err
	}
	key.Precompute()

	return
}
Beispiel #10
0
// ParsePKCS1PrivateKey returns an RSA private key from its ASN.1 PKCS#1 DER encoded form.
func ParsePKCS1PrivateKey(der []byte) (key *rsa.PrivateKey, err error) {
	var priv pkcs1PrivateKey
	rest, err := asn1.Unmarshal(der, &priv)
	if len(rest) > 0 {
		err = asn1.SyntaxError{"trailing data"}
		return
	}
	if err != nil {
		return
	}

	if priv.Version > 1 {
		return nil, errors.New("x509: unsupported private key version")
	}

	if priv.N.Sign() <= 0 || priv.D.Sign() <= 0 || priv.P.Sign() <= 0 || priv.Q.Sign() <= 0 {
		return nil, errors.New("private key contains zero or negative value")
	}

	key = new(rsa.PrivateKey)
	key.PublicKey = rsa.PublicKey{
		E: priv.E,
		N: priv.N,
	}

	key.D = priv.D
	key.Primes = make([]*big.Int, 2+len(priv.AdditionalPrimes))
	key.Primes[0] = priv.P
	key.Primes[1] = priv.Q
	for i, a := range priv.AdditionalPrimes {
		if a.Prime.Sign() <= 0 {
			return nil, errors.New("private key contains zero or negative prime")
		}
		key.Primes[i+2] = a.Prime
		// We ignore the other two values because rsa will calculate
		// them as needed.
	}

	err = key.Validate()
	if err != nil {
		return nil, err
	}
	key.Precompute()

	return
}
Beispiel #11
0
// 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 os.Error) {
	var hashType crypto.Hash

	switch algo {
	case SHA1WithRSA, DSAWithSHA1:
		hashType = crypto.SHA1
	case SHA256WithRSA, DSAWithSHA256:
		hashType = crypto.SHA256
	case SHA384WithRSA:
		hashType = crypto.SHA384
	case SHA512WithRSA:
		hashType = crypto.SHA512
	default:
		return UnsupportedAlgorithmError{}
	}

	h := hashType.New()
	if h == nil {
		return UnsupportedAlgorithmError{}
	}

	h.Write(signed)
	digest := h.Sum()

	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 !rawValueIsInteger(&dsaSig.R) || !rawValueIsInteger(&dsaSig.S) {
			return asn1.StructuralError{"tags don't match"}
		}
		r := new(big.Int).SetBytes(dsaSig.R.Bytes)
		s := new(big.Int).SetBytes(dsaSig.S.Bytes)
		if !dsa.Verify(pub, digest, r, s) {
			return os.ErrorString("DSA verification failure")
		}
		return
	}
	return UnsupportedAlgorithmError{}
}
Beispiel #12
0
// 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 os.Error) {
	var hashType crypto.Hash

	switch algo {
	case SHA1WithRSA, DSAWithSHA1:
		hashType = crypto.SHA1
	case SHA256WithRSA, DSAWithSHA256:
		hashType = crypto.SHA256
	case SHA384WithRSA:
		hashType = crypto.SHA384
	case SHA512WithRSA:
		hashType = crypto.SHA512
	default:
		return UnsupportedAlgorithmError{}
	}

	h := hashType.New()
	if h == nil {
		return UnsupportedAlgorithmError{}
	}

	h.Write(signed)
	digest := h.Sum()

	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 os.NewError("DSA signature contained zero or negative values")
		}
		if !dsa.Verify(pub, digest, dsaSig.R, dsaSig.S) {
			return os.NewError("DSA verification failure")
		}
		return
	}
	return UnsupportedAlgorithmError{}
}
func parsePublicKey(algo PublicKeyAlgorithm, asn1Data []byte) (interface{}, os.Error) {
	switch algo {
	case RSA:
		p := new(rsaPublicKey)
		_, err := asn1.Unmarshal(asn1Data, p)
		if err != nil {
			return nil, err
		}

		if !rawValueIsInteger(&p.N) {
			return nil, asn1.StructuralError{"tags don't match"}
		}

		pub := &rsa.PublicKey{
			E: p.E,
			N: new(big.Int).SetBytes(p.N.Bytes),
		}
		return pub, nil
	default:
		return nil, nil
	}

	panic("unreachable")
}
Beispiel #14
0
// 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, os.Error) {
	var v []*certificate

	for len(asn1Data) > 0 {
		cert := new(certificate)
		var err os.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
}
// 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, os.Error) {
	v := new(vector.Vector)

	for len(asn1Data) > 0 {
		cert := new(certificate)
		var err os.Error
		asn1Data, err = asn1.Unmarshal(asn1Data, cert)
		if err != nil {
			return nil, err
		}
		v.Push(cert)
	}

	ret := make([]*Certificate, v.Len())
	for i := 0; i < v.Len(); i++ {
		cert, err := parseCertificate(v.At(i).(*certificate))
		if err != nil {
			return nil, err
		}
		ret[i] = cert
	}

	return ret, nil
}
Beispiel #16
0
// ParseResponse parses an OCSP response in DER form. It only supports
// responses for a single certificate and only those using RSA signatures.
// Non-RSA responses will result in an x509.UnsupportedAlgorithmError.
// Signature errors or parse failures will result in a ParseError.
func ParseResponse(bytes []byte) (*Response, error) {
	var resp responseASN1
	rest, err := asn1.Unmarshal(bytes, &resp)
	if err != nil {
		return nil, err
	}
	if len(rest) > 0 {
		return nil, ParseError("trailing data in OCSP response")
	}

	ret := new(Response)
	if resp.Status != ocspSuccess {
		ret.Status = ServerFailed
		return ret, nil
	}

	if !resp.Response.ResponseType.Equal(idPKIXOCSPBasic) {
		return nil, ParseError("bad OCSP response type")
	}

	var basicResp basicResponse
	rest, err = asn1.Unmarshal(resp.Response.Response, &basicResp)
	if err != nil {
		return nil, err
	}

	if len(basicResp.Certificates) != 1 {
		return nil, ParseError("OCSP response contains bad number of certificates")
	}

	if len(basicResp.TBSResponseData.Responses) != 1 {
		return nil, ParseError("OCSP response contains bad number of responses")
	}

	ret.Certificate, err = x509.ParseCertificate(basicResp.Certificates[0].FullBytes)
	if err != nil {
		return nil, err
	}

	if ret.Certificate.PublicKeyAlgorithm != x509.RSA || !basicResp.SignatureAlgorithm.Algorithm.Equal(idSHA1WithRSA) {
		return nil, x509.UnsupportedAlgorithmError{}
	}

	hashType := crypto.SHA1
	h := hashType.New()

	pub := ret.Certificate.PublicKey.(*rsa.PublicKey)
	h.Write(basicResp.TBSResponseData.Raw)
	digest := h.Sum()
	signature := basicResp.Signature.RightAlign()

	if rsa.VerifyPKCS1v15(pub, hashType, digest, signature) != nil {
		return nil, ParseError("bad OCSP signature")
	}

	r := basicResp.TBSResponseData.Responses[0]

	ret.SerialNumber = r.CertID.SerialNumber.Bytes

	switch {
	case bool(r.Good):
		ret.Status = Good
	case bool(r.Unknown):
		ret.Status = Unknown
	default:
		ret.Status = Revoked
		ret.RevokedAt = r.Revoked.RevocationTime
		ret.RevocationReason = r.Revoked.Reason
	}

	ret.ProducedAt = basicResp.TBSResponseData.ProducedAt
	ret.ThisUpdate = r.ThisUpdate
	ret.NextUpdate = r.NextUpdate

	return ret, nil
}
Beispiel #17
0
func parseCertificate(in *certificate) (*Certificate, os.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 os.Error
	out.PublicKey, err = parsePublicKey(out.PublicKeyAlgorithm, &in.TBSCertificate.PublicKey)
	if err != nil {
		return nil, err
	}

	if in.TBSCertificate.SerialNumber.Sign() < 0 {
		return nil, os.NewError("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 {
		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
					continue
				}
			case 17:
				// 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
				_, err := asn1.Unmarshal(e.Value, &seq)
				if err != nil {
					return nil, err
				}
				if !seq.IsCompound || seq.Tag != 16 || seq.Class != 0 {
					return nil, asn1.StructuralError{"bad SAN sequence"}
				}

				parsedName := false

				rest := seq.Bytes
				for len(rest) > 0 {
					var v asn1.RawValue
					rest, err = asn1.Unmarshal(rest, &v)
					if err != nil {
						return nil, err
					}
					switch v.Tag {
					case 1:
						out.EmailAddresses = append(out.EmailAddresses, string(v.Bytes))
						parsedName = true
					case 2:
						out.DNSNames = append(out.DNSNames, string(v.Bytes))
						parsedName = true
					}
				}

				if parsedName {
					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 subtree.Min > 0 || subtree.Max > 0 || len(subtree.Name) == 0 {
						if e.Critical {
							return out, UnhandledCriticalExtension{}
						}
						continue
					}
					out.PermittedDNSDomains = append(out.PermittedDNSDomains, subtree.Name)
				}
				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 {
					switch {
					case u.Equal(oidExtKeyUsageAny):
						out.ExtKeyUsage = append(out.ExtKeyUsage, ExtKeyUsageAny)
					case u.Equal(oidExtKeyUsageServerAuth):
						out.ExtKeyUsage = append(out.ExtKeyUsage, ExtKeyUsageServerAuth)
					case u.Equal(oidExtKeyUsageClientAuth):
						out.ExtKeyUsage = append(out.ExtKeyUsage, ExtKeyUsageClientAuth)
					case u.Equal(oidExtKeyUsageCodeSigning):
						out.ExtKeyUsage = append(out.ExtKeyUsage, ExtKeyUsageCodeSigning)
					case u.Equal(oidExtKeyUsageEmailProtection):
						out.ExtKeyUsage = append(out.ExtKeyUsage, ExtKeyUsageEmailProtection)
					case u.Equal(oidExtKeyUsageTimeStamping):
						out.ExtKeyUsage = append(out.ExtKeyUsage, ExtKeyUsageTimeStamping)
					case u.Equal(oidExtKeyUsageOCSPSigning):
						out.ExtKeyUsage = append(out.ExtKeyUsage, ExtKeyUsageOCSPSigning)
					default:
						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
				}
			}
		}

		if e.Critical {
			return out, UnhandledCriticalExtension{}
		}
	}

	return out, nil
}
func parseCertificate(in *certificate) (*Certificate, os.Error) {
	out := new(Certificate)
	out.Raw = in.TBSCertificate.Raw

	out.Signature = in.SignatureValue.RightAlign()
	out.SignatureAlgorithm =
		getSignatureAlgorithmFromOID(in.TBSCertificate.SignatureAlgorithm.Algorithm)

	out.PublicKeyAlgorithm =
		getPublicKeyAlgorithmFromOID(in.TBSCertificate.PublicKey.Algorithm.Algorithm)
	var err os.Error
	out.PublicKey, err = parsePublicKey(out.PublicKeyAlgorithm, in.TBSCertificate.PublicKey.PublicKey.RightAlign())
	if err != nil {
		return nil, err
	}

	out.Version = in.TBSCertificate.Version + 1
	out.SerialNumber = in.TBSCertificate.SerialNumber.Bytes
	out.Issuer.fillFromRDNSequence(&in.TBSCertificate.Issuer)
	out.Subject.fillFromRDNSequence(&in.TBSCertificate.Subject)
	out.NotBefore = in.TBSCertificate.Validity.NotBefore
	out.NotAfter = in.TBSCertificate.Validity.NotAfter

	for _, e := range in.TBSCertificate.Extensions {
		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 constriants basicConstraints
				_, err := asn1.Unmarshal(e.Value, &constriants)

				if err == nil {
					out.BasicConstraintsValid = true
					out.IsCA = constriants.IsCA
					out.MaxPathLen = constriants.MaxPathLen
					continue
				}
			case 17:
				// 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
				_, err := asn1.Unmarshal(e.Value, &seq)
				if err != nil {
					return nil, err
				}
				if !seq.IsCompound || seq.Tag != 16 || seq.Class != 0 {
					return nil, asn1.StructuralError{"bad SAN sequence"}
				}

				parsedName := false

				rest := seq.Bytes
				for len(rest) > 0 {
					var v asn1.RawValue
					rest, err = asn1.Unmarshal(rest, &v)
					if err != nil {
						return nil, err
					}
					switch v.Tag {
					case 1:
						out.EmailAddresses = append(out.EmailAddresses, string(v.Bytes))
						parsedName = true
					case 2:
						out.DNSNames = append(out.DNSNames, string(v.Bytes))
						parsedName = true
					}
				}

				if parsedName {
					continue
				}
				// If we didn't parse any of the names then we
				// fall through to the critical check below.

			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 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
				}
			}
		}

		if e.Critical {
			return out, UnhandledCriticalExtension{}
		}
	}

	return out, nil
}