Source file src/crypto/x509/parser.go

     1  // Copyright 2021 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package x509
     6  
     7  import (
     8  	"bytes"
     9  	"crypto/dsa"
    10  	"crypto/ecdh"
    11  	"crypto/ecdsa"
    12  	"crypto/ed25519"
    13  	"crypto/elliptic"
    14  	"crypto/rsa"
    15  	"crypto/x509/pkix"
    16  	"encoding/asn1"
    17  	"errors"
    18  	"fmt"
    19  	"internal/godebug"
    20  	"math"
    21  	"math/big"
    22  	"net"
    23  	"net/url"
    24  	"strconv"
    25  	"strings"
    26  	"time"
    27  	"unicode/utf16"
    28  	"unicode/utf8"
    29  
    30  	"golang.org/x/crypto/cryptobyte"
    31  	cryptobyte_asn1 "golang.org/x/crypto/cryptobyte/asn1"
    32  )
    33  
    34  // isPrintable reports whether the given b is in the ASN.1 PrintableString set.
    35  // This is a simplified version of encoding/asn1.isPrintable.
    36  func isPrintable(b byte) bool {
    37  	return 'a' <= b && b <= 'z' ||
    38  		'A' <= b && b <= 'Z' ||
    39  		'0' <= b && b <= '9' ||
    40  		'\'' <= b && b <= ')' ||
    41  		'+' <= b && b <= '/' ||
    42  		b == ' ' ||
    43  		b == ':' ||
    44  		b == '=' ||
    45  		b == '?' ||
    46  		// This is technically not allowed in a PrintableString.
    47  		// However, x509 certificates with wildcard strings don't
    48  		// always use the correct string type so we permit it.
    49  		b == '*' ||
    50  		// This is not technically allowed either. However, not
    51  		// only is it relatively common, but there are also a
    52  		// handful of CA certificates that contain it. At least
    53  		// one of which will not expire until 2027.
    54  		b == '&'
    55  }
    56  
    57  // parseASN1String parses the ASN.1 string types T61String, PrintableString,
    58  // UTF8String, BMPString, IA5String, and NumericString. This is mostly copied
    59  // from the respective encoding/asn1.parse... methods, rather than just
    60  // increasing the API surface of that package.
    61  func parseASN1String(tag cryptobyte_asn1.Tag, value []byte) (string, error) {
    62  	switch tag {
    63  	case cryptobyte_asn1.T61String:
    64  		// T.61 is a defunct ITU 8-bit character encoding which preceded Unicode.
    65  		// T.61 uses a code page layout that _almost_ exactly maps to the code
    66  		// page layout of the ISO 8859-1 (Latin-1) character encoding, with the
    67  		// exception that a number of characters in Latin-1 are not present
    68  		// in T.61.
    69  		//
    70  		// Instead of mapping which characters are present in Latin-1 but not T.61,
    71  		// we just treat these strings as being encoded using Latin-1. This matches
    72  		// what most of the world does, including BoringSSL.
    73  		buf := make([]byte, 0, len(value))
    74  		for _, v := range value {
    75  			// All the 1-byte UTF-8 runes map 1-1 with Latin-1.
    76  			buf = utf8.AppendRune(buf, rune(v))
    77  		}
    78  		return string(buf), nil
    79  	case cryptobyte_asn1.PrintableString:
    80  		for _, b := range value {
    81  			if !isPrintable(b) {
    82  				return "", errors.New("invalid PrintableString")
    83  			}
    84  		}
    85  		return string(value), nil
    86  	case cryptobyte_asn1.UTF8String:
    87  		if !utf8.Valid(value) {
    88  			return "", errors.New("invalid UTF-8 string")
    89  		}
    90  		return string(value), nil
    91  	case cryptobyte_asn1.Tag(asn1.TagBMPString):
    92  		// BMPString uses the defunct UCS-2 16-bit character encoding, which
    93  		// covers the Basic Multilingual Plane (BMP). UTF-16 was an extension of
    94  		// UCS-2, containing all of the same code points, but also including
    95  		// multi-code point characters (by using surrogate code points). We can
    96  		// treat a UCS-2 encoded string as a UTF-16 encoded string, as long as
    97  		// we reject out the UTF-16 specific code points. This matches the
    98  		// BoringSSL behavior.
    99  
   100  		if len(value)%2 != 0 {
   101  			return "", errors.New("invalid BMPString")
   102  		}
   103  
   104  		// Strip terminator if present.
   105  		if l := len(value); l >= 2 && value[l-1] == 0 && value[l-2] == 0 {
   106  			value = value[:l-2]
   107  		}
   108  
   109  		s := make([]uint16, 0, len(value)/2)
   110  		for len(value) > 0 {
   111  			point := uint16(value[0])<<8 + uint16(value[1])
   112  			// Reject UTF-16 code points that are permanently reserved
   113  			// noncharacters (0xfffe, 0xffff, and 0xfdd0-0xfdef) and surrogates
   114  			// (0xd800-0xdfff).
   115  			if point == 0xfffe || point == 0xffff ||
   116  				(point >= 0xfdd0 && point <= 0xfdef) ||
   117  				(point >= 0xd800 && point <= 0xdfff) {
   118  				return "", errors.New("invalid BMPString")
   119  			}
   120  			s = append(s, point)
   121  			value = value[2:]
   122  		}
   123  
   124  		return string(utf16.Decode(s)), nil
   125  	case cryptobyte_asn1.IA5String:
   126  		s := string(value)
   127  		if isIA5String(s) != nil {
   128  			return "", errors.New("invalid IA5String")
   129  		}
   130  		return s, nil
   131  	case cryptobyte_asn1.Tag(asn1.TagNumericString):
   132  		for _, b := range value {
   133  			if !('0' <= b && b <= '9' || b == ' ') {
   134  				return "", errors.New("invalid NumericString")
   135  			}
   136  		}
   137  		return string(value), nil
   138  	}
   139  	return "", fmt.Errorf("unsupported string type: %v", tag)
   140  }
   141  
   142  // parseName parses a DER encoded Name as defined in RFC 5280. We may
   143  // want to export this function in the future for use in crypto/tls.
   144  func parseName(raw cryptobyte.String) (*pkix.RDNSequence, error) {
   145  	if !raw.ReadASN1(&raw, cryptobyte_asn1.SEQUENCE) {
   146  		return nil, errors.New("x509: invalid RDNSequence")
   147  	}
   148  
   149  	var rdnSeq pkix.RDNSequence
   150  	for !raw.Empty() {
   151  		var rdnSet pkix.RelativeDistinguishedNameSET
   152  		var set cryptobyte.String
   153  		if !raw.ReadASN1(&set, cryptobyte_asn1.SET) {
   154  			return nil, errors.New("x509: invalid RDNSequence")
   155  		}
   156  		for !set.Empty() {
   157  			var atav cryptobyte.String
   158  			if !set.ReadASN1(&atav, cryptobyte_asn1.SEQUENCE) {
   159  				return nil, errors.New("x509: invalid RDNSequence: invalid attribute")
   160  			}
   161  			var attr pkix.AttributeTypeAndValue
   162  			if !atav.ReadASN1ObjectIdentifier(&attr.Type) {
   163  				return nil, errors.New("x509: invalid RDNSequence: invalid attribute type")
   164  			}
   165  			var rawValue cryptobyte.String
   166  			var valueTag cryptobyte_asn1.Tag
   167  			if !atav.ReadAnyASN1(&rawValue, &valueTag) {
   168  				return nil, errors.New("x509: invalid RDNSequence: invalid attribute value")
   169  			}
   170  			var err error
   171  			attr.Value, err = parseASN1String(valueTag, rawValue)
   172  			if err != nil {
   173  				return nil, fmt.Errorf("x509: invalid RDNSequence: invalid attribute value: %s", err)
   174  			}
   175  			rdnSet = append(rdnSet, attr)
   176  		}
   177  
   178  		rdnSeq = append(rdnSeq, rdnSet)
   179  	}
   180  
   181  	return &rdnSeq, nil
   182  }
   183  
   184  func parseAI(der cryptobyte.String) (pkix.AlgorithmIdentifier, error) {
   185  	ai := pkix.AlgorithmIdentifier{}
   186  	if !der.ReadASN1ObjectIdentifier(&ai.Algorithm) {
   187  		return ai, errors.New("x509: malformed OID")
   188  	}
   189  	if der.Empty() {
   190  		return ai, nil
   191  	}
   192  	var params cryptobyte.String
   193  	var tag cryptobyte_asn1.Tag
   194  	if !der.ReadAnyASN1Element(&params, &tag) {
   195  		return ai, errors.New("x509: malformed parameters")
   196  	}
   197  	ai.Parameters.Tag = int(tag)
   198  	ai.Parameters.FullBytes = params
   199  	return ai, nil
   200  }
   201  
   202  func parseTime(der *cryptobyte.String) (time.Time, error) {
   203  	var t time.Time
   204  	switch {
   205  	case der.PeekASN1Tag(cryptobyte_asn1.UTCTime):
   206  		if !der.ReadASN1UTCTime(&t) {
   207  			return t, errors.New("x509: malformed UTCTime")
   208  		}
   209  	case der.PeekASN1Tag(cryptobyte_asn1.GeneralizedTime):
   210  		if !der.ReadASN1GeneralizedTime(&t) {
   211  			return t, errors.New("x509: malformed GeneralizedTime")
   212  		}
   213  	default:
   214  		return t, errors.New("x509: unsupported time format")
   215  	}
   216  	return t, nil
   217  }
   218  
   219  func parseValidity(der cryptobyte.String) (time.Time, time.Time, error) {
   220  	notBefore, err := parseTime(&der)
   221  	if err != nil {
   222  		return time.Time{}, time.Time{}, err
   223  	}
   224  	notAfter, err := parseTime(&der)
   225  	if err != nil {
   226  		return time.Time{}, time.Time{}, err
   227  	}
   228  
   229  	return notBefore, notAfter, nil
   230  }
   231  
   232  func parseExtension(der cryptobyte.String) (pkix.Extension, error) {
   233  	var ext pkix.Extension
   234  	if !der.ReadASN1ObjectIdentifier(&ext.Id) {
   235  		return ext, errors.New("x509: malformed extension OID field")
   236  	}
   237  	if der.PeekASN1Tag(cryptobyte_asn1.BOOLEAN) {
   238  		if !der.ReadASN1Boolean(&ext.Critical) {
   239  			return ext, errors.New("x509: malformed extension critical field")
   240  		}
   241  	}
   242  	var val cryptobyte.String
   243  	if !der.ReadASN1(&val, cryptobyte_asn1.OCTET_STRING) {
   244  		return ext, errors.New("x509: malformed extension value field")
   245  	}
   246  	ext.Value = val
   247  	return ext, nil
   248  }
   249  
   250  func parsePublicKey(keyData *publicKeyInfo) (any, error) {
   251  	oid := keyData.Algorithm.Algorithm
   252  	params := keyData.Algorithm.Parameters
   253  	der := cryptobyte.String(keyData.PublicKey.RightAlign())
   254  	switch {
   255  	case oid.Equal(oidPublicKeyRSA):
   256  		// RSA public keys must have a NULL in the parameters.
   257  		// See RFC 3279, Section 2.3.1.
   258  		if !bytes.Equal(params.FullBytes, asn1.NullBytes) {
   259  			return nil, errors.New("x509: RSA key missing NULL parameters")
   260  		}
   261  
   262  		p := &pkcs1PublicKey{N: new(big.Int)}
   263  		if !der.ReadASN1(&der, cryptobyte_asn1.SEQUENCE) {
   264  			return nil, errors.New("x509: invalid RSA public key")
   265  		}
   266  		if !der.ReadASN1Integer(p.N) {
   267  			return nil, errors.New("x509: invalid RSA modulus")
   268  		}
   269  		if !der.ReadASN1Integer(&p.E) {
   270  			return nil, errors.New("x509: invalid RSA public exponent")
   271  		}
   272  
   273  		if p.N.Sign() <= 0 {
   274  			return nil, errors.New("x509: RSA modulus is not a positive number")
   275  		}
   276  		if p.E <= 0 {
   277  			return nil, errors.New("x509: RSA public exponent is not a positive number")
   278  		}
   279  
   280  		pub := &rsa.PublicKey{
   281  			E: p.E,
   282  			N: p.N,
   283  		}
   284  		return pub, nil
   285  	case oid.Equal(oidPublicKeyECDSA):
   286  		paramsDer := cryptobyte.String(params.FullBytes)
   287  		namedCurveOID := new(asn1.ObjectIdentifier)
   288  		if !paramsDer.ReadASN1ObjectIdentifier(namedCurveOID) {
   289  			return nil, errors.New("x509: invalid ECDSA parameters")
   290  		}
   291  		namedCurve := namedCurveFromOID(*namedCurveOID)
   292  		if namedCurve == nil {
   293  			return nil, errors.New("x509: unsupported elliptic curve")
   294  		}
   295  		x, y := elliptic.Unmarshal(namedCurve, der)
   296  		if x == nil {
   297  			return nil, errors.New("x509: failed to unmarshal elliptic curve point")
   298  		}
   299  		pub := &ecdsa.PublicKey{
   300  			Curve: namedCurve,
   301  			X:     x,
   302  			Y:     y,
   303  		}
   304  		return pub, nil
   305  	case oid.Equal(oidPublicKeyEd25519):
   306  		// RFC 8410, Section 3
   307  		// > For all of the OIDs, the parameters MUST be absent.
   308  		if len(params.FullBytes) != 0 {
   309  			return nil, errors.New("x509: Ed25519 key encoded with illegal parameters")
   310  		}
   311  		if len(der) != ed25519.PublicKeySize {
   312  			return nil, errors.New("x509: wrong Ed25519 public key size")
   313  		}
   314  		return ed25519.PublicKey(der), nil
   315  	case oid.Equal(oidPublicKeyX25519):
   316  		// RFC 8410, Section 3
   317  		// > For all of the OIDs, the parameters MUST be absent.
   318  		if len(params.FullBytes) != 0 {
   319  			return nil, errors.New("x509: X25519 key encoded with illegal parameters")
   320  		}
   321  		return ecdh.X25519().NewPublicKey(der)
   322  	case oid.Equal(oidPublicKeyDSA):
   323  		y := new(big.Int)
   324  		if !der.ReadASN1Integer(y) {
   325  			return nil, errors.New("x509: invalid DSA public key")
   326  		}
   327  		pub := &dsa.PublicKey{
   328  			Y: y,
   329  			Parameters: dsa.Parameters{
   330  				P: new(big.Int),
   331  				Q: new(big.Int),
   332  				G: new(big.Int),
   333  			},
   334  		}
   335  		paramsDer := cryptobyte.String(params.FullBytes)
   336  		if !paramsDer.ReadASN1(&paramsDer, cryptobyte_asn1.SEQUENCE) ||
   337  			!paramsDer.ReadASN1Integer(pub.Parameters.P) ||
   338  			!paramsDer.ReadASN1Integer(pub.Parameters.Q) ||
   339  			!paramsDer.ReadASN1Integer(pub.Parameters.G) {
   340  			return nil, errors.New("x509: invalid DSA parameters")
   341  		}
   342  		if pub.Y.Sign() <= 0 || pub.Parameters.P.Sign() <= 0 ||
   343  			pub.Parameters.Q.Sign() <= 0 || pub.Parameters.G.Sign() <= 0 {
   344  			return nil, errors.New("x509: zero or negative DSA parameter")
   345  		}
   346  		return pub, nil
   347  	default:
   348  		return nil, errors.New("x509: unknown public key algorithm")
   349  	}
   350  }
   351  
   352  func parseKeyUsageExtension(der cryptobyte.String) (KeyUsage, error) {
   353  	var usageBits asn1.BitString
   354  	if !der.ReadASN1BitString(&usageBits) {
   355  		return 0, errors.New("x509: invalid key usage")
   356  	}
   357  
   358  	var usage int
   359  	for i := 0; i < 9; i++ {
   360  		if usageBits.At(i) != 0 {
   361  			usage |= 1 << uint(i)
   362  		}
   363  	}
   364  	return KeyUsage(usage), nil
   365  }
   366  
   367  func parseBasicConstraintsExtension(der cryptobyte.String) (bool, int, error) {
   368  	var isCA bool
   369  	if !der.ReadASN1(&der, cryptobyte_asn1.SEQUENCE) {
   370  		return false, 0, errors.New("x509: invalid basic constraints")
   371  	}
   372  	if der.PeekASN1Tag(cryptobyte_asn1.BOOLEAN) {
   373  		if !der.ReadASN1Boolean(&isCA) {
   374  			return false, 0, errors.New("x509: invalid basic constraints")
   375  		}
   376  	}
   377  
   378  	maxPathLen := -1
   379  	if der.PeekASN1Tag(cryptobyte_asn1.INTEGER) {
   380  		var mpl uint
   381  		if !der.ReadASN1Integer(&mpl) || mpl > math.MaxInt {
   382  			return false, 0, errors.New("x509: invalid basic constraints")
   383  		}
   384  		maxPathLen = int(mpl)
   385  	}
   386  
   387  	return isCA, maxPathLen, nil
   388  }
   389  
   390  func forEachSAN(der cryptobyte.String, callback func(tag int, data []byte) error) error {
   391  	if !der.ReadASN1(&der, cryptobyte_asn1.SEQUENCE) {
   392  		return errors.New("x509: invalid subject alternative names")
   393  	}
   394  	for !der.Empty() {
   395  		var san cryptobyte.String
   396  		var tag cryptobyte_asn1.Tag
   397  		if !der.ReadAnyASN1(&san, &tag) {
   398  			return errors.New("x509: invalid subject alternative name")
   399  		}
   400  		if err := callback(int(tag^0x80), san); err != nil {
   401  			return err
   402  		}
   403  	}
   404  
   405  	return nil
   406  }
   407  
   408  func parseSANExtension(der cryptobyte.String) (dnsNames, emailAddresses []string, ipAddresses []net.IP, uris []*url.URL, err error) {
   409  	err = forEachSAN(der, func(tag int, data []byte) error {
   410  		switch tag {
   411  		case nameTypeEmail:
   412  			email := string(data)
   413  			if err := isIA5String(email); err != nil {
   414  				return errors.New("x509: SAN rfc822Name is malformed")
   415  			}
   416  			emailAddresses = append(emailAddresses, email)
   417  		case nameTypeDNS:
   418  			name := string(data)
   419  			if err := isIA5String(name); err != nil {
   420  				return errors.New("x509: SAN dNSName is malformed")
   421  			}
   422  			dnsNames = append(dnsNames, string(name))
   423  		case nameTypeURI:
   424  			uriStr := string(data)
   425  			if err := isIA5String(uriStr); err != nil {
   426  				return errors.New("x509: SAN uniformResourceIdentifier is malformed")
   427  			}
   428  			uri, err := url.Parse(uriStr)
   429  			if err != nil {
   430  				return fmt.Errorf("x509: cannot parse URI %q: %s", uriStr, err)
   431  			}
   432  			if len(uri.Host) > 0 {
   433  				if _, ok := domainToReverseLabels(uri.Host); !ok {
   434  					return fmt.Errorf("x509: cannot parse URI %q: invalid domain", uriStr)
   435  				}
   436  			}
   437  			uris = append(uris, uri)
   438  		case nameTypeIP:
   439  			switch len(data) {
   440  			case net.IPv4len, net.IPv6len:
   441  				ipAddresses = append(ipAddresses, data)
   442  			default:
   443  				return errors.New("x509: cannot parse IP address of length " + strconv.Itoa(len(data)))
   444  			}
   445  		}
   446  
   447  		return nil
   448  	})
   449  
   450  	return
   451  }
   452  
   453  func parseAuthorityKeyIdentifier(e pkix.Extension) ([]byte, error) {
   454  	// RFC 5280, Section 4.2.1.1
   455  	if e.Critical {
   456  		// Conforming CAs MUST mark this extension as non-critical
   457  		return nil, errors.New("x509: authority key identifier incorrectly marked critical")
   458  	}
   459  	val := cryptobyte.String(e.Value)
   460  	var akid cryptobyte.String
   461  	if !val.ReadASN1(&akid, cryptobyte_asn1.SEQUENCE) {
   462  		return nil, errors.New("x509: invalid authority key identifier")
   463  	}
   464  	if akid.PeekASN1Tag(cryptobyte_asn1.Tag(0).ContextSpecific()) {
   465  		if !akid.ReadASN1(&akid, cryptobyte_asn1.Tag(0).ContextSpecific()) {
   466  			return nil, errors.New("x509: invalid authority key identifier")
   467  		}
   468  		return akid, nil
   469  	}
   470  	return nil, nil
   471  }
   472  
   473  func parseExtKeyUsageExtension(der cryptobyte.String) ([]ExtKeyUsage, []asn1.ObjectIdentifier, error) {
   474  	var extKeyUsages []ExtKeyUsage
   475  	var unknownUsages []asn1.ObjectIdentifier
   476  	if !der.ReadASN1(&der, cryptobyte_asn1.SEQUENCE) {
   477  		return nil, nil, errors.New("x509: invalid extended key usages")
   478  	}
   479  	for !der.Empty() {
   480  		var eku asn1.ObjectIdentifier
   481  		if !der.ReadASN1ObjectIdentifier(&eku) {
   482  			return nil, nil, errors.New("x509: invalid extended key usages")
   483  		}
   484  		if extKeyUsage, ok := extKeyUsageFromOID(eku); ok {
   485  			extKeyUsages = append(extKeyUsages, extKeyUsage)
   486  		} else {
   487  			unknownUsages = append(unknownUsages, eku)
   488  		}
   489  	}
   490  	return extKeyUsages, unknownUsages, nil
   491  }
   492  
   493  func parseCertificatePoliciesExtension(der cryptobyte.String) ([]OID, error) {
   494  	var oids []OID
   495  	seenOIDs := map[string]bool{}
   496  	if !der.ReadASN1(&der, cryptobyte_asn1.SEQUENCE) {
   497  		return nil, errors.New("x509: invalid certificate policies")
   498  	}
   499  	for !der.Empty() {
   500  		var cp cryptobyte.String
   501  		var OIDBytes cryptobyte.String
   502  		if !der.ReadASN1(&cp, cryptobyte_asn1.SEQUENCE) || !cp.ReadASN1(&OIDBytes, cryptobyte_asn1.OBJECT_IDENTIFIER) {
   503  			return nil, errors.New("x509: invalid certificate policies")
   504  		}
   505  		if seenOIDs[string(OIDBytes)] {
   506  			return nil, errors.New("x509: invalid certificate policies")
   507  		}
   508  		seenOIDs[string(OIDBytes)] = true
   509  		oid, ok := newOIDFromDER(OIDBytes)
   510  		if !ok {
   511  			return nil, errors.New("x509: invalid certificate policies")
   512  		}
   513  		oids = append(oids, oid)
   514  	}
   515  	return oids, nil
   516  }
   517  
   518  // isValidIPMask reports whether mask consists of zero or more 1 bits, followed by zero bits.
   519  func isValidIPMask(mask []byte) bool {
   520  	seenZero := false
   521  
   522  	for _, b := range mask {
   523  		if seenZero {
   524  			if b != 0 {
   525  				return false
   526  			}
   527  
   528  			continue
   529  		}
   530  
   531  		switch b {
   532  		case 0x00, 0x80, 0xc0, 0xe0, 0xf0, 0xf8, 0xfc, 0xfe:
   533  			seenZero = true
   534  		case 0xff:
   535  		default:
   536  			return false
   537  		}
   538  	}
   539  
   540  	return true
   541  }
   542  
   543  func parseNameConstraintsExtension(out *Certificate, e pkix.Extension) (unhandled bool, err error) {
   544  	// RFC 5280, 4.2.1.10
   545  
   546  	// NameConstraints ::= SEQUENCE {
   547  	//      permittedSubtrees       [0]     GeneralSubtrees OPTIONAL,
   548  	//      excludedSubtrees        [1]     GeneralSubtrees OPTIONAL }
   549  	//
   550  	// GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree
   551  	//
   552  	// GeneralSubtree ::= SEQUENCE {
   553  	//      base                    GeneralName,
   554  	//      minimum         [0]     BaseDistance DEFAULT 0,
   555  	//      maximum         [1]     BaseDistance OPTIONAL }
   556  	//
   557  	// BaseDistance ::= INTEGER (0..MAX)
   558  
   559  	outer := cryptobyte.String(e.Value)
   560  	var toplevel, permitted, excluded cryptobyte.String
   561  	var havePermitted, haveExcluded bool
   562  	if !outer.ReadASN1(&toplevel, cryptobyte_asn1.SEQUENCE) ||
   563  		!outer.Empty() ||
   564  		!toplevel.ReadOptionalASN1(&permitted, &havePermitted, cryptobyte_asn1.Tag(0).ContextSpecific().Constructed()) ||
   565  		!toplevel.ReadOptionalASN1(&excluded, &haveExcluded, cryptobyte_asn1.Tag(1).ContextSpecific().Constructed()) ||
   566  		!toplevel.Empty() {
   567  		return false, errors.New("x509: invalid NameConstraints extension")
   568  	}
   569  
   570  	if !havePermitted && !haveExcluded || len(permitted) == 0 && len(excluded) == 0 {
   571  		// From RFC 5280, Section 4.2.1.10:
   572  		//   “either the permittedSubtrees field
   573  		//   or the excludedSubtrees MUST be
   574  		//   present”
   575  		return false, errors.New("x509: empty name constraints extension")
   576  	}
   577  
   578  	getValues := func(subtrees cryptobyte.String) (dnsNames []string, ips []*net.IPNet, emails, uriDomains []string, err error) {
   579  		for !subtrees.Empty() {
   580  			var seq, value cryptobyte.String
   581  			var tag cryptobyte_asn1.Tag
   582  			if !subtrees.ReadASN1(&seq, cryptobyte_asn1.SEQUENCE) ||
   583  				!seq.ReadAnyASN1(&value, &tag) {
   584  				return nil, nil, nil, nil, fmt.Errorf("x509: invalid NameConstraints extension")
   585  			}
   586  
   587  			var (
   588  				dnsTag   = cryptobyte_asn1.Tag(2).ContextSpecific()
   589  				emailTag = cryptobyte_asn1.Tag(1).ContextSpecific()
   590  				ipTag    = cryptobyte_asn1.Tag(7).ContextSpecific()
   591  				uriTag   = cryptobyte_asn1.Tag(6).ContextSpecific()
   592  			)
   593  
   594  			switch tag {
   595  			case dnsTag:
   596  				domain := string(value)
   597  				if err := isIA5String(domain); err != nil {
   598  					return nil, nil, nil, nil, errors.New("x509: invalid constraint value: " + err.Error())
   599  				}
   600  
   601  				trimmedDomain := domain
   602  				if len(trimmedDomain) > 0 && trimmedDomain[0] == '.' {
   603  					// constraints can have a leading
   604  					// period to exclude the domain
   605  					// itself, but that's not valid in a
   606  					// normal domain name.
   607  					trimmedDomain = trimmedDomain[1:]
   608  				}
   609  				if _, ok := domainToReverseLabels(trimmedDomain); !ok {
   610  					return nil, nil, nil, nil, fmt.Errorf("x509: failed to parse dnsName constraint %q", domain)
   611  				}
   612  				dnsNames = append(dnsNames, domain)
   613  
   614  			case ipTag:
   615  				l := len(value)
   616  				var ip, mask []byte
   617  
   618  				switch l {
   619  				case 8:
   620  					ip = value[:4]
   621  					mask = value[4:]
   622  
   623  				case 32:
   624  					ip = value[:16]
   625  					mask = value[16:]
   626  
   627  				default:
   628  					return nil, nil, nil, nil, fmt.Errorf("x509: IP constraint contained value of length %d", l)
   629  				}
   630  
   631  				if !isValidIPMask(mask) {
   632  					return nil, nil, nil, nil, fmt.Errorf("x509: IP constraint contained invalid mask %x", mask)
   633  				}
   634  
   635  				ips = append(ips, &net.IPNet{IP: net.IP(ip), Mask: net.IPMask(mask)})
   636  
   637  			case emailTag:
   638  				constraint := string(value)
   639  				if err := isIA5String(constraint); err != nil {
   640  					return nil, nil, nil, nil, errors.New("x509: invalid constraint value: " + err.Error())
   641  				}
   642  
   643  				// If the constraint contains an @ then
   644  				// it specifies an exact mailbox name.
   645  				if strings.Contains(constraint, "@") {
   646  					if _, ok := parseRFC2821Mailbox(constraint); !ok {
   647  						return nil, nil, nil, nil, fmt.Errorf("x509: failed to parse rfc822Name constraint %q", constraint)
   648  					}
   649  				} else {
   650  					// Otherwise it's a domain name.
   651  					domain := constraint
   652  					if len(domain) > 0 && domain[0] == '.' {
   653  						domain = domain[1:]
   654  					}
   655  					if _, ok := domainToReverseLabels(domain); !ok {
   656  						return nil, nil, nil, nil, fmt.Errorf("x509: failed to parse rfc822Name constraint %q", constraint)
   657  					}
   658  				}
   659  				emails = append(emails, constraint)
   660  
   661  			case uriTag:
   662  				domain := string(value)
   663  				if err := isIA5String(domain); err != nil {
   664  					return nil, nil, nil, nil, errors.New("x509: invalid constraint value: " + err.Error())
   665  				}
   666  
   667  				if net.ParseIP(domain) != nil {
   668  					return nil, nil, nil, nil, fmt.Errorf("x509: failed to parse URI constraint %q: cannot be IP address", domain)
   669  				}
   670  
   671  				trimmedDomain := domain
   672  				if len(trimmedDomain) > 0 && trimmedDomain[0] == '.' {
   673  					// constraints can have a leading
   674  					// period to exclude the domain itself,
   675  					// but that's not valid in a normal
   676  					// domain name.
   677  					trimmedDomain = trimmedDomain[1:]
   678  				}
   679  				if _, ok := domainToReverseLabels(trimmedDomain); !ok {
   680  					return nil, nil, nil, nil, fmt.Errorf("x509: failed to parse URI constraint %q", domain)
   681  				}
   682  				uriDomains = append(uriDomains, domain)
   683  
   684  			default:
   685  				unhandled = true
   686  			}
   687  		}
   688  
   689  		return dnsNames, ips, emails, uriDomains, nil
   690  	}
   691  
   692  	if out.PermittedDNSDomains, out.PermittedIPRanges, out.PermittedEmailAddresses, out.PermittedURIDomains, err = getValues(permitted); err != nil {
   693  		return false, err
   694  	}
   695  	if out.ExcludedDNSDomains, out.ExcludedIPRanges, out.ExcludedEmailAddresses, out.ExcludedURIDomains, err = getValues(excluded); err != nil {
   696  		return false, err
   697  	}
   698  	out.PermittedDNSDomainsCritical = e.Critical
   699  
   700  	return unhandled, nil
   701  }
   702  
   703  func processExtensions(out *Certificate) error {
   704  	var err error
   705  	for _, e := range out.Extensions {
   706  		unhandled := false
   707  
   708  		if len(e.Id) == 4 && e.Id[0] == 2 && e.Id[1] == 5 && e.Id[2] == 29 {
   709  			switch e.Id[3] {
   710  			case 15:
   711  				out.KeyUsage, err = parseKeyUsageExtension(e.Value)
   712  				if err != nil {
   713  					return err
   714  				}
   715  			case 19:
   716  				out.IsCA, out.MaxPathLen, err = parseBasicConstraintsExtension(e.Value)
   717  				if err != nil {
   718  					return err
   719  				}
   720  				out.BasicConstraintsValid = true
   721  				out.MaxPathLenZero = out.MaxPathLen == 0
   722  			case 17:
   723  				out.DNSNames, out.EmailAddresses, out.IPAddresses, out.URIs, err = parseSANExtension(e.Value)
   724  				if err != nil {
   725  					return err
   726  				}
   727  
   728  				if len(out.DNSNames) == 0 && len(out.EmailAddresses) == 0 && len(out.IPAddresses) == 0 && len(out.URIs) == 0 {
   729  					// If we didn't parse anything then we do the critical check, below.
   730  					unhandled = true
   731  				}
   732  
   733  			case 30:
   734  				unhandled, err = parseNameConstraintsExtension(out, e)
   735  				if err != nil {
   736  					return err
   737  				}
   738  
   739  			case 31:
   740  				// RFC 5280, 4.2.1.13
   741  
   742  				// CRLDistributionPoints ::= SEQUENCE SIZE (1..MAX) OF DistributionPoint
   743  				//
   744  				// DistributionPoint ::= SEQUENCE {
   745  				//     distributionPoint       [0]     DistributionPointName OPTIONAL,
   746  				//     reasons                 [1]     ReasonFlags OPTIONAL,
   747  				//     cRLIssuer               [2]     GeneralNames OPTIONAL }
   748  				//
   749  				// DistributionPointName ::= CHOICE {
   750  				//     fullName                [0]     GeneralNames,
   751  				//     nameRelativeToCRLIssuer [1]     RelativeDistinguishedName }
   752  				val := cryptobyte.String(e.Value)
   753  				if !val.ReadASN1(&val, cryptobyte_asn1.SEQUENCE) {
   754  					return errors.New("x509: invalid CRL distribution points")
   755  				}
   756  				for !val.Empty() {
   757  					var dpDER cryptobyte.String
   758  					if !val.ReadASN1(&dpDER, cryptobyte_asn1.SEQUENCE) {
   759  						return errors.New("x509: invalid CRL distribution point")
   760  					}
   761  					var dpNameDER cryptobyte.String
   762  					var dpNamePresent bool
   763  					if !dpDER.ReadOptionalASN1(&dpNameDER, &dpNamePresent, cryptobyte_asn1.Tag(0).Constructed().ContextSpecific()) {
   764  						return errors.New("x509: invalid CRL distribution point")
   765  					}
   766  					if !dpNamePresent {
   767  						continue
   768  					}
   769  					if !dpNameDER.ReadASN1(&dpNameDER, cryptobyte_asn1.Tag(0).Constructed().ContextSpecific()) {
   770  						return errors.New("x509: invalid CRL distribution point")
   771  					}
   772  					for !dpNameDER.Empty() {
   773  						if !dpNameDER.PeekASN1Tag(cryptobyte_asn1.Tag(6).ContextSpecific()) {
   774  							break
   775  						}
   776  						var uri cryptobyte.String
   777  						if !dpNameDER.ReadASN1(&uri, cryptobyte_asn1.Tag(6).ContextSpecific()) {
   778  							return errors.New("x509: invalid CRL distribution point")
   779  						}
   780  						out.CRLDistributionPoints = append(out.CRLDistributionPoints, string(uri))
   781  					}
   782  				}
   783  
   784  			case 35:
   785  				out.AuthorityKeyId, err = parseAuthorityKeyIdentifier(e)
   786  				if err != nil {
   787  					return err
   788  				}
   789  			case 36:
   790  				val := cryptobyte.String(e.Value)
   791  				if !val.ReadASN1(&val, cryptobyte_asn1.SEQUENCE) {
   792  					return errors.New("x509: invalid policy constraints extension")
   793  				}
   794  				if val.PeekASN1Tag(cryptobyte_asn1.Tag(0).ContextSpecific()) {
   795  					var v int64
   796  					if !val.ReadASN1Int64WithTag(&v, cryptobyte_asn1.Tag(0).ContextSpecific()) {
   797  						return errors.New("x509: invalid policy constraints extension")
   798  					}
   799  					out.RequireExplicitPolicy = int(v)
   800  					// Check for overflow.
   801  					if int64(out.RequireExplicitPolicy) != v {
   802  						return errors.New("x509: policy constraints requireExplicitPolicy field overflows int")
   803  					}
   804  					out.RequireExplicitPolicyZero = out.RequireExplicitPolicy == 0
   805  				}
   806  				if val.PeekASN1Tag(cryptobyte_asn1.Tag(1).ContextSpecific()) {
   807  					var v int64
   808  					if !val.ReadASN1Int64WithTag(&v, cryptobyte_asn1.Tag(1).ContextSpecific()) {
   809  						return errors.New("x509: invalid policy constraints extension")
   810  					}
   811  					out.InhibitPolicyMapping = int(v)
   812  					// Check for overflow.
   813  					if int64(out.InhibitPolicyMapping) != v {
   814  						return errors.New("x509: policy constraints inhibitPolicyMapping field overflows int")
   815  					}
   816  					out.InhibitPolicyMappingZero = out.InhibitPolicyMapping == 0
   817  				}
   818  			case 37:
   819  				out.ExtKeyUsage, out.UnknownExtKeyUsage, err = parseExtKeyUsageExtension(e.Value)
   820  				if err != nil {
   821  					return err
   822  				}
   823  			case 14: // RFC 5280, 4.2.1.2
   824  				if e.Critical {
   825  					// Conforming CAs MUST mark this extension as non-critical
   826  					return errors.New("x509: subject key identifier incorrectly marked critical")
   827  				}
   828  				val := cryptobyte.String(e.Value)
   829  				var skid cryptobyte.String
   830  				if !val.ReadASN1(&skid, cryptobyte_asn1.OCTET_STRING) {
   831  					return errors.New("x509: invalid subject key identifier")
   832  				}
   833  				out.SubjectKeyId = skid
   834  			case 32:
   835  				out.Policies, err = parseCertificatePoliciesExtension(e.Value)
   836  				if err != nil {
   837  					return err
   838  				}
   839  				out.PolicyIdentifiers = make([]asn1.ObjectIdentifier, 0, len(out.Policies))
   840  				for _, oid := range out.Policies {
   841  					if oid, ok := oid.toASN1OID(); ok {
   842  						out.PolicyIdentifiers = append(out.PolicyIdentifiers, oid)
   843  					}
   844  				}
   845  			case 33:
   846  				val := cryptobyte.String(e.Value)
   847  				if !val.ReadASN1(&val, cryptobyte_asn1.SEQUENCE) {
   848  					return errors.New("x509: invalid policy mappings extension")
   849  				}
   850  				for !val.Empty() {
   851  					var s cryptobyte.String
   852  					var issuer, subject cryptobyte.String
   853  					if !val.ReadASN1(&s, cryptobyte_asn1.SEQUENCE) ||
   854  						!s.ReadASN1(&issuer, cryptobyte_asn1.OBJECT_IDENTIFIER) ||
   855  						!s.ReadASN1(&subject, cryptobyte_asn1.OBJECT_IDENTIFIER) {
   856  						return errors.New("x509: invalid policy mappings extension")
   857  					}
   858  					out.PolicyMappings = append(out.PolicyMappings, PolicyMapping{OID{issuer}, OID{subject}})
   859  				}
   860  			case 54:
   861  				val := cryptobyte.String(e.Value)
   862  				if !val.ReadASN1Integer(&out.InhibitAnyPolicy) {
   863  					return errors.New("x509: invalid inhibit any policy extension")
   864  				}
   865  				out.InhibitAnyPolicyZero = out.InhibitAnyPolicy == 0
   866  			default:
   867  				// Unknown extensions are recorded if critical.
   868  				unhandled = true
   869  			}
   870  		} else if e.Id.Equal(oidExtensionAuthorityInfoAccess) {
   871  			// RFC 5280 4.2.2.1: Authority Information Access
   872  			if e.Critical {
   873  				// Conforming CAs MUST mark this extension as non-critical
   874  				return errors.New("x509: authority info access incorrectly marked critical")
   875  			}
   876  			val := cryptobyte.String(e.Value)
   877  			if !val.ReadASN1(&val, cryptobyte_asn1.SEQUENCE) {
   878  				return errors.New("x509: invalid authority info access")
   879  			}
   880  			for !val.Empty() {
   881  				var aiaDER cryptobyte.String
   882  				if !val.ReadASN1(&aiaDER, cryptobyte_asn1.SEQUENCE) {
   883  					return errors.New("x509: invalid authority info access")
   884  				}
   885  				var method asn1.ObjectIdentifier
   886  				if !aiaDER.ReadASN1ObjectIdentifier(&method) {
   887  					return errors.New("x509: invalid authority info access")
   888  				}
   889  				if !aiaDER.PeekASN1Tag(cryptobyte_asn1.Tag(6).ContextSpecific()) {
   890  					continue
   891  				}
   892  				if !aiaDER.ReadASN1(&aiaDER, cryptobyte_asn1.Tag(6).ContextSpecific()) {
   893  					return errors.New("x509: invalid authority info access")
   894  				}
   895  				switch {
   896  				case method.Equal(oidAuthorityInfoAccessOcsp):
   897  					out.OCSPServer = append(out.OCSPServer, string(aiaDER))
   898  				case method.Equal(oidAuthorityInfoAccessIssuers):
   899  					out.IssuingCertificateURL = append(out.IssuingCertificateURL, string(aiaDER))
   900  				}
   901  			}
   902  		} else {
   903  			// Unknown extensions are recorded if critical.
   904  			unhandled = true
   905  		}
   906  
   907  		if e.Critical && unhandled {
   908  			out.UnhandledCriticalExtensions = append(out.UnhandledCriticalExtensions, e.Id)
   909  		}
   910  	}
   911  
   912  	return nil
   913  }
   914  
   915  var x509negativeserial = godebug.New("x509negativeserial")
   916  
   917  func parseCertificate(der []byte) (*Certificate, error) {
   918  	cert := &Certificate{}
   919  
   920  	input := cryptobyte.String(der)
   921  	// we read the SEQUENCE including length and tag bytes so that
   922  	// we can populate Certificate.Raw, before unwrapping the
   923  	// SEQUENCE so it can be operated on
   924  	if !input.ReadASN1Element(&input, cryptobyte_asn1.SEQUENCE) {
   925  		return nil, errors.New("x509: malformed certificate")
   926  	}
   927  	cert.Raw = input
   928  	if !input.ReadASN1(&input, cryptobyte_asn1.SEQUENCE) {
   929  		return nil, errors.New("x509: malformed certificate")
   930  	}
   931  
   932  	var tbs cryptobyte.String
   933  	// do the same trick again as above to extract the raw
   934  	// bytes for Certificate.RawTBSCertificate
   935  	if !input.ReadASN1Element(&tbs, cryptobyte_asn1.SEQUENCE) {
   936  		return nil, errors.New("x509: malformed tbs certificate")
   937  	}
   938  	cert.RawTBSCertificate = tbs
   939  	if !tbs.ReadASN1(&tbs, cryptobyte_asn1.SEQUENCE) {
   940  		return nil, errors.New("x509: malformed tbs certificate")
   941  	}
   942  
   943  	if !tbs.ReadOptionalASN1Integer(&cert.Version, cryptobyte_asn1.Tag(0).Constructed().ContextSpecific(), 0) {
   944  		return nil, errors.New("x509: malformed version")
   945  	}
   946  	if cert.Version < 0 {
   947  		return nil, errors.New("x509: malformed version")
   948  	}
   949  	// for backwards compat reasons Version is one-indexed,
   950  	// rather than zero-indexed as defined in 5280
   951  	cert.Version++
   952  	if cert.Version > 3 {
   953  		return nil, errors.New("x509: invalid version")
   954  	}
   955  
   956  	serial := new(big.Int)
   957  	if !tbs.ReadASN1Integer(serial) {
   958  		return nil, errors.New("x509: malformed serial number")
   959  	}
   960  	if serial.Sign() == -1 {
   961  		if x509negativeserial.Value() != "1" {
   962  			return nil, errors.New("x509: negative serial number")
   963  		} else {
   964  			x509negativeserial.IncNonDefault()
   965  		}
   966  	}
   967  	cert.SerialNumber = serial
   968  
   969  	var sigAISeq cryptobyte.String
   970  	if !tbs.ReadASN1(&sigAISeq, cryptobyte_asn1.SEQUENCE) {
   971  		return nil, errors.New("x509: malformed signature algorithm identifier")
   972  	}
   973  	// Before parsing the inner algorithm identifier, extract
   974  	// the outer algorithm identifier and make sure that they
   975  	// match.
   976  	var outerSigAISeq cryptobyte.String
   977  	if !input.ReadASN1(&outerSigAISeq, cryptobyte_asn1.SEQUENCE) {
   978  		return nil, errors.New("x509: malformed algorithm identifier")
   979  	}
   980  	if !bytes.Equal(outerSigAISeq, sigAISeq) {
   981  		return nil, errors.New("x509: inner and outer signature algorithm identifiers don't match")
   982  	}
   983  	sigAI, err := parseAI(sigAISeq)
   984  	if err != nil {
   985  		return nil, err
   986  	}
   987  	cert.SignatureAlgorithm = getSignatureAlgorithmFromAI(sigAI)
   988  
   989  	var issuerSeq cryptobyte.String
   990  	if !tbs.ReadASN1Element(&issuerSeq, cryptobyte_asn1.SEQUENCE) {
   991  		return nil, errors.New("x509: malformed issuer")
   992  	}
   993  	cert.RawIssuer = issuerSeq
   994  	issuerRDNs, err := parseName(issuerSeq)
   995  	if err != nil {
   996  		return nil, err
   997  	}
   998  	cert.Issuer.FillFromRDNSequence(issuerRDNs)
   999  
  1000  	var validity cryptobyte.String
  1001  	if !tbs.ReadASN1(&validity, cryptobyte_asn1.SEQUENCE) {
  1002  		return nil, errors.New("x509: malformed validity")
  1003  	}
  1004  	cert.NotBefore, cert.NotAfter, err = parseValidity(validity)
  1005  	if err != nil {
  1006  		return nil, err
  1007  	}
  1008  
  1009  	var subjectSeq cryptobyte.String
  1010  	if !tbs.ReadASN1Element(&subjectSeq, cryptobyte_asn1.SEQUENCE) {
  1011  		return nil, errors.New("x509: malformed issuer")
  1012  	}
  1013  	cert.RawSubject = subjectSeq
  1014  	subjectRDNs, err := parseName(subjectSeq)
  1015  	if err != nil {
  1016  		return nil, err
  1017  	}
  1018  	cert.Subject.FillFromRDNSequence(subjectRDNs)
  1019  
  1020  	var spki cryptobyte.String
  1021  	if !tbs.ReadASN1Element(&spki, cryptobyte_asn1.SEQUENCE) {
  1022  		return nil, errors.New("x509: malformed spki")
  1023  	}
  1024  	cert.RawSubjectPublicKeyInfo = spki
  1025  	if !spki.ReadASN1(&spki, cryptobyte_asn1.SEQUENCE) {
  1026  		return nil, errors.New("x509: malformed spki")
  1027  	}
  1028  	var pkAISeq cryptobyte.String
  1029  	if !spki.ReadASN1(&pkAISeq, cryptobyte_asn1.SEQUENCE) {
  1030  		return nil, errors.New("x509: malformed public key algorithm identifier")
  1031  	}
  1032  	pkAI, err := parseAI(pkAISeq)
  1033  	if err != nil {
  1034  		return nil, err
  1035  	}
  1036  	cert.PublicKeyAlgorithm = getPublicKeyAlgorithmFromOID(pkAI.Algorithm)
  1037  	var spk asn1.BitString
  1038  	if !spki.ReadASN1BitString(&spk) {
  1039  		return nil, errors.New("x509: malformed subjectPublicKey")
  1040  	}
  1041  	if cert.PublicKeyAlgorithm != UnknownPublicKeyAlgorithm {
  1042  		cert.PublicKey, err = parsePublicKey(&publicKeyInfo{
  1043  			Algorithm: pkAI,
  1044  			PublicKey: spk,
  1045  		})
  1046  		if err != nil {
  1047  			return nil, err
  1048  		}
  1049  	}
  1050  
  1051  	if cert.Version > 1 {
  1052  		if !tbs.SkipOptionalASN1(cryptobyte_asn1.Tag(1).ContextSpecific()) {
  1053  			return nil, errors.New("x509: malformed issuerUniqueID")
  1054  		}
  1055  		if !tbs.SkipOptionalASN1(cryptobyte_asn1.Tag(2).ContextSpecific()) {
  1056  			return nil, errors.New("x509: malformed subjectUniqueID")
  1057  		}
  1058  		if cert.Version == 3 {
  1059  			var extensions cryptobyte.String
  1060  			var present bool
  1061  			if !tbs.ReadOptionalASN1(&extensions, &present, cryptobyte_asn1.Tag(3).Constructed().ContextSpecific()) {
  1062  				return nil, errors.New("x509: malformed extensions")
  1063  			}
  1064  			if present {
  1065  				seenExts := make(map[string]bool)
  1066  				if !extensions.ReadASN1(&extensions, cryptobyte_asn1.SEQUENCE) {
  1067  					return nil, errors.New("x509: malformed extensions")
  1068  				}
  1069  				for !extensions.Empty() {
  1070  					var extension cryptobyte.String
  1071  					if !extensions.ReadASN1(&extension, cryptobyte_asn1.SEQUENCE) {
  1072  						return nil, errors.New("x509: malformed extension")
  1073  					}
  1074  					ext, err := parseExtension(extension)
  1075  					if err != nil {
  1076  						return nil, err
  1077  					}
  1078  					oidStr := ext.Id.String()
  1079  					if seenExts[oidStr] {
  1080  						return nil, fmt.Errorf("x509: certificate contains duplicate extension with OID %q", oidStr)
  1081  					}
  1082  					seenExts[oidStr] = true
  1083  					cert.Extensions = append(cert.Extensions, ext)
  1084  				}
  1085  				err = processExtensions(cert)
  1086  				if err != nil {
  1087  					return nil, err
  1088  				}
  1089  			}
  1090  		}
  1091  	}
  1092  
  1093  	var signature asn1.BitString
  1094  	if !input.ReadASN1BitString(&signature) {
  1095  		return nil, errors.New("x509: malformed signature")
  1096  	}
  1097  	cert.Signature = signature.RightAlign()
  1098  
  1099  	return cert, nil
  1100  }
  1101  
  1102  // ParseCertificate parses a single certificate from the given ASN.1 DER data.
  1103  //
  1104  // Before Go 1.23, ParseCertificate accepted certificates with negative serial
  1105  // numbers. This behavior can be restored by including "x509negativeserial=1" in
  1106  // the GODEBUG environment variable.
  1107  func ParseCertificate(der []byte) (*Certificate, error) {
  1108  	cert, err := parseCertificate(der)
  1109  	if err != nil {
  1110  		return nil, err
  1111  	}
  1112  	if len(der) != len(cert.Raw) {
  1113  		return nil, errors.New("x509: trailing data")
  1114  	}
  1115  	return cert, nil
  1116  }
  1117  
  1118  // ParseCertificates parses one or more certificates from the given ASN.1 DER
  1119  // data. The certificates must be concatenated with no intermediate padding.
  1120  func ParseCertificates(der []byte) ([]*Certificate, error) {
  1121  	var certs []*Certificate
  1122  	for len(der) > 0 {
  1123  		cert, err := parseCertificate(der)
  1124  		if err != nil {
  1125  			return nil, err
  1126  		}
  1127  		certs = append(certs, cert)
  1128  		der = der[len(cert.Raw):]
  1129  	}
  1130  	return certs, nil
  1131  }
  1132  
  1133  // The X.509 standards confusingly 1-indexed the version names, but 0-indexed
  1134  // the actual encoded version, so the version for X.509v2 is 1.
  1135  const x509v2Version = 1
  1136  
  1137  // ParseRevocationList parses a X509 v2 [Certificate] Revocation List from the given
  1138  // ASN.1 DER data.
  1139  func ParseRevocationList(der []byte) (*RevocationList, error) {
  1140  	rl := &RevocationList{}
  1141  
  1142  	input := cryptobyte.String(der)
  1143  	// we read the SEQUENCE including length and tag bytes so that
  1144  	// we can populate RevocationList.Raw, before unwrapping the
  1145  	// SEQUENCE so it can be operated on
  1146  	if !input.ReadASN1Element(&input, cryptobyte_asn1.SEQUENCE) {
  1147  		return nil, errors.New("x509: malformed crl")
  1148  	}
  1149  	rl.Raw = input
  1150  	if !input.ReadASN1(&input, cryptobyte_asn1.SEQUENCE) {
  1151  		return nil, errors.New("x509: malformed crl")
  1152  	}
  1153  
  1154  	var tbs cryptobyte.String
  1155  	// do the same trick again as above to extract the raw
  1156  	// bytes for Certificate.RawTBSCertificate
  1157  	if !input.ReadASN1Element(&tbs, cryptobyte_asn1.SEQUENCE) {
  1158  		return nil, errors.New("x509: malformed tbs crl")
  1159  	}
  1160  	rl.RawTBSRevocationList = tbs
  1161  	if !tbs.ReadASN1(&tbs, cryptobyte_asn1.SEQUENCE) {
  1162  		return nil, errors.New("x509: malformed tbs crl")
  1163  	}
  1164  
  1165  	var version int
  1166  	if !tbs.PeekASN1Tag(cryptobyte_asn1.INTEGER) {
  1167  		return nil, errors.New("x509: unsupported crl version")
  1168  	}
  1169  	if !tbs.ReadASN1Integer(&version) {
  1170  		return nil, errors.New("x509: malformed crl")
  1171  	}
  1172  	if version != x509v2Version {
  1173  		return nil, fmt.Errorf("x509: unsupported crl version: %d", version)
  1174  	}
  1175  
  1176  	var sigAISeq cryptobyte.String
  1177  	if !tbs.ReadASN1(&sigAISeq, cryptobyte_asn1.SEQUENCE) {
  1178  		return nil, errors.New("x509: malformed signature algorithm identifier")
  1179  	}
  1180  	// Before parsing the inner algorithm identifier, extract
  1181  	// the outer algorithm identifier and make sure that they
  1182  	// match.
  1183  	var outerSigAISeq cryptobyte.String
  1184  	if !input.ReadASN1(&outerSigAISeq, cryptobyte_asn1.SEQUENCE) {
  1185  		return nil, errors.New("x509: malformed algorithm identifier")
  1186  	}
  1187  	if !bytes.Equal(outerSigAISeq, sigAISeq) {
  1188  		return nil, errors.New("x509: inner and outer signature algorithm identifiers don't match")
  1189  	}
  1190  	sigAI, err := parseAI(sigAISeq)
  1191  	if err != nil {
  1192  		return nil, err
  1193  	}
  1194  	rl.SignatureAlgorithm = getSignatureAlgorithmFromAI(sigAI)
  1195  
  1196  	var signature asn1.BitString
  1197  	if !input.ReadASN1BitString(&signature) {
  1198  		return nil, errors.New("x509: malformed signature")
  1199  	}
  1200  	rl.Signature = signature.RightAlign()
  1201  
  1202  	var issuerSeq cryptobyte.String
  1203  	if !tbs.ReadASN1Element(&issuerSeq, cryptobyte_asn1.SEQUENCE) {
  1204  		return nil, errors.New("x509: malformed issuer")
  1205  	}
  1206  	rl.RawIssuer = issuerSeq
  1207  	issuerRDNs, err := parseName(issuerSeq)
  1208  	if err != nil {
  1209  		return nil, err
  1210  	}
  1211  	rl.Issuer.FillFromRDNSequence(issuerRDNs)
  1212  
  1213  	rl.ThisUpdate, err = parseTime(&tbs)
  1214  	if err != nil {
  1215  		return nil, err
  1216  	}
  1217  	if tbs.PeekASN1Tag(cryptobyte_asn1.GeneralizedTime) || tbs.PeekASN1Tag(cryptobyte_asn1.UTCTime) {
  1218  		rl.NextUpdate, err = parseTime(&tbs)
  1219  		if err != nil {
  1220  			return nil, err
  1221  		}
  1222  	}
  1223  
  1224  	if tbs.PeekASN1Tag(cryptobyte_asn1.SEQUENCE) {
  1225  		var revokedSeq cryptobyte.String
  1226  		if !tbs.ReadASN1(&revokedSeq, cryptobyte_asn1.SEQUENCE) {
  1227  			return nil, errors.New("x509: malformed crl")
  1228  		}
  1229  		for !revokedSeq.Empty() {
  1230  			rce := RevocationListEntry{}
  1231  
  1232  			var certSeq cryptobyte.String
  1233  			if !revokedSeq.ReadASN1Element(&certSeq, cryptobyte_asn1.SEQUENCE) {
  1234  				return nil, errors.New("x509: malformed crl")
  1235  			}
  1236  			rce.Raw = certSeq
  1237  			if !certSeq.ReadASN1(&certSeq, cryptobyte_asn1.SEQUENCE) {
  1238  				return nil, errors.New("x509: malformed crl")
  1239  			}
  1240  
  1241  			rce.SerialNumber = new(big.Int)
  1242  			if !certSeq.ReadASN1Integer(rce.SerialNumber) {
  1243  				return nil, errors.New("x509: malformed serial number")
  1244  			}
  1245  			rce.RevocationTime, err = parseTime(&certSeq)
  1246  			if err != nil {
  1247  				return nil, err
  1248  			}
  1249  			var extensions cryptobyte.String
  1250  			var present bool
  1251  			if !certSeq.ReadOptionalASN1(&extensions, &present, cryptobyte_asn1.SEQUENCE) {
  1252  				return nil, errors.New("x509: malformed extensions")
  1253  			}
  1254  			if present {
  1255  				for !extensions.Empty() {
  1256  					var extension cryptobyte.String
  1257  					if !extensions.ReadASN1(&extension, cryptobyte_asn1.SEQUENCE) {
  1258  						return nil, errors.New("x509: malformed extension")
  1259  					}
  1260  					ext, err := parseExtension(extension)
  1261  					if err != nil {
  1262  						return nil, err
  1263  					}
  1264  					if ext.Id.Equal(oidExtensionReasonCode) {
  1265  						val := cryptobyte.String(ext.Value)
  1266  						if !val.ReadASN1Enum(&rce.ReasonCode) {
  1267  							return nil, fmt.Errorf("x509: malformed reasonCode extension")
  1268  						}
  1269  					}
  1270  					rce.Extensions = append(rce.Extensions, ext)
  1271  				}
  1272  			}
  1273  
  1274  			rl.RevokedCertificateEntries = append(rl.RevokedCertificateEntries, rce)
  1275  			rcDeprecated := pkix.RevokedCertificate{
  1276  				SerialNumber:   rce.SerialNumber,
  1277  				RevocationTime: rce.RevocationTime,
  1278  				Extensions:     rce.Extensions,
  1279  			}
  1280  			rl.RevokedCertificates = append(rl.RevokedCertificates, rcDeprecated)
  1281  		}
  1282  	}
  1283  
  1284  	var extensions cryptobyte.String
  1285  	var present bool
  1286  	if !tbs.ReadOptionalASN1(&extensions, &present, cryptobyte_asn1.Tag(0).Constructed().ContextSpecific()) {
  1287  		return nil, errors.New("x509: malformed extensions")
  1288  	}
  1289  	if present {
  1290  		if !extensions.ReadASN1(&extensions, cryptobyte_asn1.SEQUENCE) {
  1291  			return nil, errors.New("x509: malformed extensions")
  1292  		}
  1293  		for !extensions.Empty() {
  1294  			var extension cryptobyte.String
  1295  			if !extensions.ReadASN1(&extension, cryptobyte_asn1.SEQUENCE) {
  1296  				return nil, errors.New("x509: malformed extension")
  1297  			}
  1298  			ext, err := parseExtension(extension)
  1299  			if err != nil {
  1300  				return nil, err
  1301  			}
  1302  			if ext.Id.Equal(oidExtensionAuthorityKeyId) {
  1303  				rl.AuthorityKeyId, err = parseAuthorityKeyIdentifier(ext)
  1304  				if err != nil {
  1305  					return nil, err
  1306  				}
  1307  			} else if ext.Id.Equal(oidExtensionCRLNumber) {
  1308  				value := cryptobyte.String(ext.Value)
  1309  				rl.Number = new(big.Int)
  1310  				if !value.ReadASN1Integer(rl.Number) {
  1311  					return nil, errors.New("x509: malformed crl number")
  1312  				}
  1313  			}
  1314  			rl.Extensions = append(rl.Extensions, ext)
  1315  		}
  1316  	}
  1317  
  1318  	return rl, nil
  1319  }
  1320  

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