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/rsa"
    14  	"crypto/x509/pkix"
    15  	"encoding/asn1"
    16  	"errors"
    17  	"fmt"
    18  	"internal/godebug"
    19  	"math"
    20  	"math/big"
    21  	"net"
    22  	"net/url"
    23  	"strconv"
    24  	"strings"
    25  	"time"
    26  	"unicode/utf16"
    27  	"unicode/utf8"
    28  
    29  	"golang.org/x/crypto/cryptobyte"
    30  	cryptobyte_asn1 "golang.org/x/crypto/cryptobyte/asn1"
    31  )
    32  
    33  // isPrintable reports whether the given b is in the ASN.1 PrintableString set.
    34  // This is a simplified version of encoding/asn1.isPrintable.
    35  func isPrintable(b byte) bool {
    36  	return 'a' <= b && b <= 'z' ||
    37  		'A' <= b && b <= 'Z' ||
    38  		'0' <= b && b <= '9' ||
    39  		'\'' <= b && b <= ')' ||
    40  		'+' <= b && b <= '/' ||
    41  		b == ' ' ||
    42  		b == ':' ||
    43  		b == '=' ||
    44  		b == '?' ||
    45  		// This is technically not allowed in a PrintableString.
    46  		// However, x509 certificates with wildcard strings don't
    47  		// always use the correct string type so we permit it.
    48  		b == '*' ||
    49  		// This is not technically allowed either. However, not
    50  		// only is it relatively common, but there are also a
    51  		// handful of CA certificates that contain it. At least
    52  		// one of which will not expire until 2027.
    53  		b == '&'
    54  }
    55  
    56  // parseASN1String parses the ASN.1 string types T61String, PrintableString,
    57  // UTF8String, BMPString, IA5String, and NumericString. This is mostly copied
    58  // from the respective encoding/asn1.parse... methods, rather than just
    59  // increasing the API surface of that package.
    60  func parseASN1String(tag cryptobyte_asn1.Tag, value []byte) (string, error) {
    61  	switch tag {
    62  	case cryptobyte_asn1.T61String:
    63  		// T.61 is a defunct ITU 8-bit character encoding which preceded Unicode.
    64  		// T.61 uses a code page layout that _almost_ exactly maps to the code
    65  		// page layout of the ISO 8859-1 (Latin-1) character encoding, with the
    66  		// exception that a number of characters in Latin-1 are not present
    67  		// in T.61.
    68  		//
    69  		// Instead of mapping which characters are present in Latin-1 but not T.61,
    70  		// we just treat these strings as being encoded using Latin-1. This matches
    71  		// what most of the world does, including BoringSSL.
    72  		buf := make([]byte, 0, len(value))
    73  		for _, v := range value {
    74  			// All the 1-byte UTF-8 runes map 1-1 with Latin-1.
    75  			buf = utf8.AppendRune(buf, rune(v))
    76  		}
    77  		return string(buf), nil
    78  	case cryptobyte_asn1.PrintableString:
    79  		for _, b := range value {
    80  			if !isPrintable(b) {
    81  				return "", errors.New("invalid PrintableString")
    82  			}
    83  		}
    84  		return string(value), nil
    85  	case cryptobyte_asn1.UTF8String:
    86  		if !utf8.Valid(value) {
    87  			return "", errors.New("invalid UTF-8 string")
    88  		}
    89  		return string(value), nil
    90  	case cryptobyte_asn1.Tag(asn1.TagBMPString):
    91  		// BMPString uses the defunct UCS-2 16-bit character encoding, which
    92  		// covers the Basic Multilingual Plane (BMP). UTF-16 was an extension of
    93  		// UCS-2, containing all of the same code points, but also including
    94  		// multi-code point characters (by using surrogate code points). We can
    95  		// treat a UCS-2 encoded string as a UTF-16 encoded string, as long as
    96  		// we reject out the UTF-16 specific code points. This matches the
    97  		// BoringSSL behavior.
    98  
    99  		if len(value)%2 != 0 {
   100  			return "", errors.New("invalid BMPString")
   101  		}
   102  
   103  		// Strip terminator if present.
   104  		if l := len(value); l >= 2 && value[l-1] == 0 && value[l-2] == 0 {
   105  			value = value[:l-2]
   106  		}
   107  
   108  		s := make([]uint16, 0, len(value)/2)
   109  		for len(value) > 0 {
   110  			point := uint16(value[0])<<8 + uint16(value[1])
   111  			// Reject UTF-16 code points that are permanently reserved
   112  			// noncharacters (0xfffe, 0xffff, and 0xfdd0-0xfdef) and surrogates
   113  			// (0xd800-0xdfff).
   114  			if point == 0xfffe || point == 0xffff ||
   115  				(point >= 0xfdd0 && point <= 0xfdef) ||
   116  				(point >= 0xd800 && point <= 0xdfff) {
   117  				return "", errors.New("invalid BMPString")
   118  			}
   119  			s = append(s, point)
   120  			value = value[2:]
   121  		}
   122  
   123  		return string(utf16.Decode(s)), nil
   124  	case cryptobyte_asn1.IA5String:
   125  		s := string(value)
   126  		if isIA5String(s) != nil {
   127  			return "", errors.New("invalid IA5String")
   128  		}
   129  		return s, nil
   130  	case cryptobyte_asn1.Tag(asn1.TagNumericString):
   131  		for _, b := range value {
   132  			if !('0' <= b && b <= '9' || b == ' ') {
   133  				return "", errors.New("invalid NumericString")
   134  			}
   135  		}
   136  		return string(value), nil
   137  	}
   138  	return "", fmt.Errorf("unsupported string type: %v", tag)
   139  }
   140  
   141  // parseName parses a DER encoded Name as defined in RFC 5280. We may
   142  // want to export this function in the future for use in crypto/tls.
   143  func parseName(raw cryptobyte.String) (*pkix.RDNSequence, error) {
   144  	if !raw.ReadASN1(&raw, cryptobyte_asn1.SEQUENCE) {
   145  		return nil, errors.New("x509: invalid RDNSequence")
   146  	}
   147  
   148  	var rdnSeq pkix.RDNSequence
   149  	for !raw.Empty() {
   150  		var rdnSet pkix.RelativeDistinguishedNameSET
   151  		var set cryptobyte.String
   152  		if !raw.ReadASN1(&set, cryptobyte_asn1.SET) {
   153  			return nil, errors.New("x509: invalid RDNSequence")
   154  		}
   155  		for !set.Empty() {
   156  			var atav cryptobyte.String
   157  			if !set.ReadASN1(&atav, cryptobyte_asn1.SEQUENCE) {
   158  				return nil, errors.New("x509: invalid RDNSequence: invalid attribute")
   159  			}
   160  			var attr pkix.AttributeTypeAndValue
   161  			if !atav.ReadASN1ObjectIdentifier(&attr.Type) {
   162  				return nil, errors.New("x509: invalid RDNSequence: invalid attribute type")
   163  			}
   164  			var rawValue cryptobyte.String
   165  			var valueTag cryptobyte_asn1.Tag
   166  			if !atav.ReadAnyASN1(&rawValue, &valueTag) {
   167  				return nil, errors.New("x509: invalid RDNSequence: invalid attribute value")
   168  			}
   169  			var err error
   170  			attr.Value, err = parseASN1String(valueTag, rawValue)
   171  			if err != nil {
   172  				return nil, fmt.Errorf("x509: invalid RDNSequence: invalid attribute value: %s", err)
   173  			}
   174  			rdnSet = append(rdnSet, attr)
   175  		}
   176  
   177  		rdnSeq = append(rdnSeq, rdnSet)
   178  	}
   179  
   180  	return &rdnSeq, nil
   181  }
   182  
   183  func parseAI(der cryptobyte.String) (pkix.AlgorithmIdentifier, error) {
   184  	ai := pkix.AlgorithmIdentifier{}
   185  	if !der.ReadASN1ObjectIdentifier(&ai.Algorithm) {
   186  		return ai, errors.New("x509: malformed OID")
   187  	}
   188  	if der.Empty() {
   189  		return ai, nil
   190  	}
   191  	var params cryptobyte.String
   192  	var tag cryptobyte_asn1.Tag
   193  	if !der.ReadAnyASN1Element(&params, &tag) {
   194  		return ai, errors.New("x509: malformed parameters")
   195  	}
   196  	ai.Parameters.Tag = int(tag)
   197  	ai.Parameters.FullBytes = params
   198  	return ai, nil
   199  }
   200  
   201  func parseTime(der *cryptobyte.String) (time.Time, error) {
   202  	var t time.Time
   203  	switch {
   204  	case der.PeekASN1Tag(cryptobyte_asn1.UTCTime):
   205  		if !der.ReadASN1UTCTime(&t) {
   206  			return t, errors.New("x509: malformed UTCTime")
   207  		}
   208  	case der.PeekASN1Tag(cryptobyte_asn1.GeneralizedTime):
   209  		if !der.ReadASN1GeneralizedTime(&t) {
   210  			return t, errors.New("x509: malformed GeneralizedTime")
   211  		}
   212  	default:
   213  		return t, errors.New("x509: unsupported time format")
   214  	}
   215  	return t, nil
   216  }
   217  
   218  func parseValidity(der cryptobyte.String) (time.Time, time.Time, error) {
   219  	notBefore, err := parseTime(&der)
   220  	if err != nil {
   221  		return time.Time{}, time.Time{}, err
   222  	}
   223  	notAfter, err := parseTime(&der)
   224  	if err != nil {
   225  		return time.Time{}, time.Time{}, err
   226  	}
   227  
   228  	return notBefore, notAfter, nil
   229  }
   230  
   231  func parseExtension(der cryptobyte.String) (pkix.Extension, error) {
   232  	var ext pkix.Extension
   233  	if !der.ReadASN1ObjectIdentifier(&ext.Id) {
   234  		return ext, errors.New("x509: malformed extension OID field")
   235  	}
   236  	if der.PeekASN1Tag(cryptobyte_asn1.BOOLEAN) {
   237  		if !der.ReadASN1Boolean(&ext.Critical) {
   238  			return ext, errors.New("x509: malformed extension critical field")
   239  		}
   240  	}
   241  	var val cryptobyte.String
   242  	if !der.ReadASN1(&val, cryptobyte_asn1.OCTET_STRING) {
   243  		return ext, errors.New("x509: malformed extension value field")
   244  	}
   245  	ext.Value = val
   246  	return ext, nil
   247  }
   248  
   249  func parsePublicKey(keyData *publicKeyInfo) (any, error) {
   250  	oid := keyData.Algorithm.Algorithm
   251  	params := keyData.Algorithm.Parameters
   252  	data := keyData.PublicKey.RightAlign()
   253  	switch {
   254  	case oid.Equal(oidPublicKeyRSA):
   255  		// RSA public keys must have a NULL in the parameters.
   256  		// See RFC 3279, Section 2.3.1.
   257  		if !bytes.Equal(params.FullBytes, asn1.NullBytes) {
   258  			return nil, errors.New("x509: RSA key missing NULL parameters")
   259  		}
   260  
   261  		der := cryptobyte.String(data)
   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  		return ecdsa.ParseUncompressedPublicKey(namedCurve, data)
   296  	case oid.Equal(oidPublicKeyEd25519):
   297  		// RFC 8410, Section 3
   298  		// > For all of the OIDs, the parameters MUST be absent.
   299  		if len(params.FullBytes) != 0 {
   300  			return nil, errors.New("x509: Ed25519 key encoded with illegal parameters")
   301  		}
   302  		if len(data) != ed25519.PublicKeySize {
   303  			return nil, errors.New("x509: wrong Ed25519 public key size")
   304  		}
   305  		return ed25519.PublicKey(data), nil
   306  	case oid.Equal(oidPublicKeyX25519):
   307  		// RFC 8410, Section 3
   308  		// > For all of the OIDs, the parameters MUST be absent.
   309  		if len(params.FullBytes) != 0 {
   310  			return nil, errors.New("x509: X25519 key encoded with illegal parameters")
   311  		}
   312  		return ecdh.X25519().NewPublicKey(data)
   313  	case oid.Equal(oidPublicKeyDSA):
   314  		der := cryptobyte.String(data)
   315  		y := new(big.Int)
   316  		if !der.ReadASN1Integer(y) {
   317  			return nil, errors.New("x509: invalid DSA public key")
   318  		}
   319  		pub := &dsa.PublicKey{
   320  			Y: y,
   321  			Parameters: dsa.Parameters{
   322  				P: new(big.Int),
   323  				Q: new(big.Int),
   324  				G: new(big.Int),
   325  			},
   326  		}
   327  		paramsDer := cryptobyte.String(params.FullBytes)
   328  		if !paramsDer.ReadASN1(&paramsDer, cryptobyte_asn1.SEQUENCE) ||
   329  			!paramsDer.ReadASN1Integer(pub.Parameters.P) ||
   330  			!paramsDer.ReadASN1Integer(pub.Parameters.Q) ||
   331  			!paramsDer.ReadASN1Integer(pub.Parameters.G) {
   332  			return nil, errors.New("x509: invalid DSA parameters")
   333  		}
   334  		if pub.Y.Sign() <= 0 || pub.Parameters.P.Sign() <= 0 ||
   335  			pub.Parameters.Q.Sign() <= 0 || pub.Parameters.G.Sign() <= 0 {
   336  			return nil, errors.New("x509: zero or negative DSA parameter")
   337  		}
   338  		return pub, nil
   339  	default:
   340  		return nil, errors.New("x509: unknown public key algorithm")
   341  	}
   342  }
   343  
   344  func parseKeyUsageExtension(der cryptobyte.String) (KeyUsage, error) {
   345  	var usageBits asn1.BitString
   346  	if !der.ReadASN1BitString(&usageBits) {
   347  		return 0, errors.New("x509: invalid key usage")
   348  	}
   349  
   350  	var usage int
   351  	for i := 0; i < 9; i++ {
   352  		if usageBits.At(i) != 0 {
   353  			usage |= 1 << uint(i)
   354  		}
   355  	}
   356  	return KeyUsage(usage), nil
   357  }
   358  
   359  func parseBasicConstraintsExtension(der cryptobyte.String) (bool, int, error) {
   360  	var isCA bool
   361  	if !der.ReadASN1(&der, cryptobyte_asn1.SEQUENCE) {
   362  		return false, 0, errors.New("x509: invalid basic constraints")
   363  	}
   364  	if der.PeekASN1Tag(cryptobyte_asn1.BOOLEAN) {
   365  		if !der.ReadASN1Boolean(&isCA) {
   366  			return false, 0, errors.New("x509: invalid basic constraints")
   367  		}
   368  	}
   369  
   370  	maxPathLen := -1
   371  	if der.PeekASN1Tag(cryptobyte_asn1.INTEGER) {
   372  		var mpl uint
   373  		if !der.ReadASN1Integer(&mpl) || mpl > math.MaxInt {
   374  			return false, 0, errors.New("x509: invalid basic constraints")
   375  		}
   376  		maxPathLen = int(mpl)
   377  	}
   378  
   379  	return isCA, maxPathLen, nil
   380  }
   381  
   382  func forEachSAN(der cryptobyte.String, callback func(tag int, data []byte) error) error {
   383  	if !der.ReadASN1(&der, cryptobyte_asn1.SEQUENCE) {
   384  		return errors.New("x509: invalid subject alternative names")
   385  	}
   386  	for !der.Empty() {
   387  		var san cryptobyte.String
   388  		var tag cryptobyte_asn1.Tag
   389  		if !der.ReadAnyASN1(&san, &tag) {
   390  			return errors.New("x509: invalid subject alternative name")
   391  		}
   392  		if err := callback(int(tag^0x80), san); err != nil {
   393  			return err
   394  		}
   395  	}
   396  
   397  	return nil
   398  }
   399  
   400  func parseSANExtension(der cryptobyte.String) (dnsNames, emailAddresses []string, ipAddresses []net.IP, uris []*url.URL, err error) {
   401  	err = forEachSAN(der, func(tag int, data []byte) error {
   402  		switch tag {
   403  		case nameTypeEmail:
   404  			email := string(data)
   405  			if err := isIA5String(email); err != nil {
   406  				return errors.New("x509: SAN rfc822Name is malformed")
   407  			}
   408  			emailAddresses = append(emailAddresses, email)
   409  		case nameTypeDNS:
   410  			name := string(data)
   411  			if err := isIA5String(name); err != nil {
   412  				return errors.New("x509: SAN dNSName is malformed")
   413  			}
   414  			dnsNames = append(dnsNames, string(name))
   415  		case nameTypeURI:
   416  			uriStr := string(data)
   417  			if err := isIA5String(uriStr); err != nil {
   418  				return errors.New("x509: SAN uniformResourceIdentifier is malformed")
   419  			}
   420  			uri, err := url.Parse(uriStr)
   421  			if err != nil {
   422  				return fmt.Errorf("x509: cannot parse URI %q: %s", uriStr, err)
   423  			}
   424  			if len(uri.Host) > 0 && !domainNameValid(uri.Host, false) {
   425  				return fmt.Errorf("x509: cannot parse URI %q: invalid domain", uriStr)
   426  			}
   427  			uris = append(uris, uri)
   428  		case nameTypeIP:
   429  			switch len(data) {
   430  			case net.IPv4len, net.IPv6len:
   431  				ipAddresses = append(ipAddresses, data)
   432  			default:
   433  				return errors.New("x509: cannot parse IP address of length " + strconv.Itoa(len(data)))
   434  			}
   435  		}
   436  
   437  		return nil
   438  	})
   439  
   440  	return
   441  }
   442  
   443  func parseAuthorityKeyIdentifier(e pkix.Extension) ([]byte, error) {
   444  	// RFC 5280, Section 4.2.1.1
   445  	if e.Critical {
   446  		// Conforming CAs MUST mark this extension as non-critical
   447  		return nil, errors.New("x509: authority key identifier incorrectly marked critical")
   448  	}
   449  	val := cryptobyte.String(e.Value)
   450  	var akid cryptobyte.String
   451  	if !val.ReadASN1(&akid, cryptobyte_asn1.SEQUENCE) {
   452  		return nil, errors.New("x509: invalid authority key identifier")
   453  	}
   454  	if akid.PeekASN1Tag(cryptobyte_asn1.Tag(0).ContextSpecific()) {
   455  		if !akid.ReadASN1(&akid, cryptobyte_asn1.Tag(0).ContextSpecific()) {
   456  			return nil, errors.New("x509: invalid authority key identifier")
   457  		}
   458  		return akid, nil
   459  	}
   460  	return nil, nil
   461  }
   462  
   463  func parseExtKeyUsageExtension(der cryptobyte.String) ([]ExtKeyUsage, []asn1.ObjectIdentifier, error) {
   464  	var extKeyUsages []ExtKeyUsage
   465  	var unknownUsages []asn1.ObjectIdentifier
   466  	if !der.ReadASN1(&der, cryptobyte_asn1.SEQUENCE) {
   467  		return nil, nil, errors.New("x509: invalid extended key usages")
   468  	}
   469  	for !der.Empty() {
   470  		var eku asn1.ObjectIdentifier
   471  		if !der.ReadASN1ObjectIdentifier(&eku) {
   472  			return nil, nil, errors.New("x509: invalid extended key usages")
   473  		}
   474  		if extKeyUsage, ok := extKeyUsageFromOID(eku); ok {
   475  			extKeyUsages = append(extKeyUsages, extKeyUsage)
   476  		} else {
   477  			unknownUsages = append(unknownUsages, eku)
   478  		}
   479  	}
   480  	return extKeyUsages, unknownUsages, nil
   481  }
   482  
   483  func parseCertificatePoliciesExtension(der cryptobyte.String) ([]OID, error) {
   484  	var oids []OID
   485  	seenOIDs := map[string]bool{}
   486  	if !der.ReadASN1(&der, cryptobyte_asn1.SEQUENCE) {
   487  		return nil, errors.New("x509: invalid certificate policies")
   488  	}
   489  	for !der.Empty() {
   490  		var cp cryptobyte.String
   491  		var OIDBytes cryptobyte.String
   492  		if !der.ReadASN1(&cp, cryptobyte_asn1.SEQUENCE) || !cp.ReadASN1(&OIDBytes, cryptobyte_asn1.OBJECT_IDENTIFIER) {
   493  			return nil, errors.New("x509: invalid certificate policies")
   494  		}
   495  		if seenOIDs[string(OIDBytes)] {
   496  			return nil, errors.New("x509: invalid certificate policies")
   497  		}
   498  		seenOIDs[string(OIDBytes)] = true
   499  		oid, ok := newOIDFromDER(OIDBytes)
   500  		if !ok {
   501  			return nil, errors.New("x509: invalid certificate policies")
   502  		}
   503  		oids = append(oids, oid)
   504  	}
   505  	return oids, nil
   506  }
   507  
   508  // isValidIPMask reports whether mask consists of zero or more 1 bits, followed by zero bits.
   509  func isValidIPMask(mask []byte) bool {
   510  	seenZero := false
   511  
   512  	for _, b := range mask {
   513  		if seenZero {
   514  			if b != 0 {
   515  				return false
   516  			}
   517  
   518  			continue
   519  		}
   520  
   521  		switch b {
   522  		case 0x00, 0x80, 0xc0, 0xe0, 0xf0, 0xf8, 0xfc, 0xfe:
   523  			seenZero = true
   524  		case 0xff:
   525  		default:
   526  			return false
   527  		}
   528  	}
   529  
   530  	return true
   531  }
   532  
   533  func parseNameConstraintsExtension(out *Certificate, e pkix.Extension) (unhandled bool, err error) {
   534  	// RFC 5280, 4.2.1.10
   535  
   536  	// NameConstraints ::= SEQUENCE {
   537  	//      permittedSubtrees       [0]     GeneralSubtrees OPTIONAL,
   538  	//      excludedSubtrees        [1]     GeneralSubtrees OPTIONAL }
   539  	//
   540  	// GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree
   541  	//
   542  	// GeneralSubtree ::= SEQUENCE {
   543  	//      base                    GeneralName,
   544  	//      minimum         [0]     BaseDistance DEFAULT 0,
   545  	//      maximum         [1]     BaseDistance OPTIONAL }
   546  	//
   547  	// BaseDistance ::= INTEGER (0..MAX)
   548  
   549  	outer := cryptobyte.String(e.Value)
   550  	var toplevel, permitted, excluded cryptobyte.String
   551  	var havePermitted, haveExcluded bool
   552  	if !outer.ReadASN1(&toplevel, cryptobyte_asn1.SEQUENCE) ||
   553  		!outer.Empty() ||
   554  		!toplevel.ReadOptionalASN1(&permitted, &havePermitted, cryptobyte_asn1.Tag(0).ContextSpecific().Constructed()) ||
   555  		!toplevel.ReadOptionalASN1(&excluded, &haveExcluded, cryptobyte_asn1.Tag(1).ContextSpecific().Constructed()) ||
   556  		!toplevel.Empty() {
   557  		return false, errors.New("x509: invalid NameConstraints extension")
   558  	}
   559  
   560  	if !havePermitted && !haveExcluded || len(permitted) == 0 && len(excluded) == 0 {
   561  		// From RFC 5280, Section 4.2.1.10:
   562  		//   “either the permittedSubtrees field
   563  		//   or the excludedSubtrees MUST be
   564  		//   present”
   565  		return false, errors.New("x509: empty name constraints extension")
   566  	}
   567  
   568  	getValues := func(subtrees cryptobyte.String) (dnsNames []string, ips []*net.IPNet, emails, uriDomains []string, err error) {
   569  		for !subtrees.Empty() {
   570  			var seq, value cryptobyte.String
   571  			var tag cryptobyte_asn1.Tag
   572  			if !subtrees.ReadASN1(&seq, cryptobyte_asn1.SEQUENCE) ||
   573  				!seq.ReadAnyASN1(&value, &tag) {
   574  				return nil, nil, nil, nil, fmt.Errorf("x509: invalid NameConstraints extension")
   575  			}
   576  
   577  			var (
   578  				dnsTag   = cryptobyte_asn1.Tag(2).ContextSpecific()
   579  				emailTag = cryptobyte_asn1.Tag(1).ContextSpecific()
   580  				ipTag    = cryptobyte_asn1.Tag(7).ContextSpecific()
   581  				uriTag   = cryptobyte_asn1.Tag(6).ContextSpecific()
   582  			)
   583  
   584  			switch tag {
   585  			case dnsTag:
   586  				domain := string(value)
   587  				if err := isIA5String(domain); err != nil {
   588  					return nil, nil, nil, nil, errors.New("x509: invalid constraint value: " + err.Error())
   589  				}
   590  
   591  				if !domainNameValid(domain, true) {
   592  					return nil, nil, nil, nil, fmt.Errorf("x509: failed to parse dnsName constraint %q", domain)
   593  				}
   594  				dnsNames = append(dnsNames, domain)
   595  
   596  			case ipTag:
   597  				l := len(value)
   598  				var ip, mask []byte
   599  
   600  				switch l {
   601  				case 8:
   602  					ip = value[:4]
   603  					mask = value[4:]
   604  
   605  				case 32:
   606  					ip = value[:16]
   607  					mask = value[16:]
   608  
   609  				default:
   610  					return nil, nil, nil, nil, fmt.Errorf("x509: IP constraint contained value of length %d", l)
   611  				}
   612  
   613  				if !isValidIPMask(mask) {
   614  					return nil, nil, nil, nil, fmt.Errorf("x509: IP constraint contained invalid mask %x", mask)
   615  				}
   616  
   617  				ips = append(ips, &net.IPNet{IP: net.IP(ip), Mask: net.IPMask(mask)})
   618  
   619  			case emailTag:
   620  				constraint := string(value)
   621  				if err := isIA5String(constraint); err != nil {
   622  					return nil, nil, nil, nil, errors.New("x509: invalid constraint value: " + err.Error())
   623  				}
   624  
   625  				// If the constraint contains an @ then
   626  				// it specifies an exact mailbox name.
   627  				if strings.Contains(constraint, "@") {
   628  					if _, ok := parseRFC2821Mailbox(constraint); !ok {
   629  						return nil, nil, nil, nil, fmt.Errorf("x509: failed to parse rfc822Name constraint %q", constraint)
   630  					}
   631  				} else {
   632  					if !domainNameValid(constraint, true) {
   633  						return nil, nil, nil, nil, fmt.Errorf("x509: failed to parse rfc822Name constraint %q", constraint)
   634  					}
   635  				}
   636  				emails = append(emails, constraint)
   637  
   638  			case uriTag:
   639  				domain := string(value)
   640  				if err := isIA5String(domain); err != nil {
   641  					return nil, nil, nil, nil, errors.New("x509: invalid constraint value: " + err.Error())
   642  				}
   643  
   644  				if net.ParseIP(domain) != nil {
   645  					return nil, nil, nil, nil, fmt.Errorf("x509: failed to parse URI constraint %q: cannot be IP address", domain)
   646  				}
   647  
   648  				if !domainNameValid(domain, true) {
   649  					return nil, nil, nil, nil, fmt.Errorf("x509: failed to parse URI constraint %q", domain)
   650  				}
   651  				uriDomains = append(uriDomains, domain)
   652  
   653  			default:
   654  				unhandled = true
   655  			}
   656  		}
   657  
   658  		return dnsNames, ips, emails, uriDomains, nil
   659  	}
   660  
   661  	if out.PermittedDNSDomains, out.PermittedIPRanges, out.PermittedEmailAddresses, out.PermittedURIDomains, err = getValues(permitted); err != nil {
   662  		return false, err
   663  	}
   664  	if out.ExcludedDNSDomains, out.ExcludedIPRanges, out.ExcludedEmailAddresses, out.ExcludedURIDomains, err = getValues(excluded); err != nil {
   665  		return false, err
   666  	}
   667  	out.PermittedDNSDomainsCritical = e.Critical
   668  
   669  	return unhandled, nil
   670  }
   671  
   672  func processExtensions(out *Certificate) error {
   673  	var err error
   674  	for _, e := range out.Extensions {
   675  		unhandled := false
   676  
   677  		if len(e.Id) == 4 && e.Id[0] == 2 && e.Id[1] == 5 && e.Id[2] == 29 {
   678  			switch e.Id[3] {
   679  			case 15:
   680  				out.KeyUsage, err = parseKeyUsageExtension(e.Value)
   681  				if err != nil {
   682  					return err
   683  				}
   684  			case 19:
   685  				out.IsCA, out.MaxPathLen, err = parseBasicConstraintsExtension(e.Value)
   686  				if err != nil {
   687  					return err
   688  				}
   689  				out.BasicConstraintsValid = true
   690  				out.MaxPathLenZero = out.MaxPathLen == 0
   691  			case 17:
   692  				out.DNSNames, out.EmailAddresses, out.IPAddresses, out.URIs, err = parseSANExtension(e.Value)
   693  				if err != nil {
   694  					return err
   695  				}
   696  
   697  				if len(out.DNSNames) == 0 && len(out.EmailAddresses) == 0 && len(out.IPAddresses) == 0 && len(out.URIs) == 0 {
   698  					// If we didn't parse anything then we do the critical check, below.
   699  					unhandled = true
   700  				}
   701  
   702  			case 30:
   703  				unhandled, err = parseNameConstraintsExtension(out, e)
   704  				if err != nil {
   705  					return err
   706  				}
   707  
   708  			case 31:
   709  				// RFC 5280, 4.2.1.13
   710  
   711  				// CRLDistributionPoints ::= SEQUENCE SIZE (1..MAX) OF DistributionPoint
   712  				//
   713  				// DistributionPoint ::= SEQUENCE {
   714  				//     distributionPoint       [0]     DistributionPointName OPTIONAL,
   715  				//     reasons                 [1]     ReasonFlags OPTIONAL,
   716  				//     cRLIssuer               [2]     GeneralNames OPTIONAL }
   717  				//
   718  				// DistributionPointName ::= CHOICE {
   719  				//     fullName                [0]     GeneralNames,
   720  				//     nameRelativeToCRLIssuer [1]     RelativeDistinguishedName }
   721  				val := cryptobyte.String(e.Value)
   722  				if !val.ReadASN1(&val, cryptobyte_asn1.SEQUENCE) {
   723  					return errors.New("x509: invalid CRL distribution points")
   724  				}
   725  				for !val.Empty() {
   726  					var dpDER cryptobyte.String
   727  					if !val.ReadASN1(&dpDER, cryptobyte_asn1.SEQUENCE) {
   728  						return errors.New("x509: invalid CRL distribution point")
   729  					}
   730  					var dpNameDER cryptobyte.String
   731  					var dpNamePresent bool
   732  					if !dpDER.ReadOptionalASN1(&dpNameDER, &dpNamePresent, cryptobyte_asn1.Tag(0).Constructed().ContextSpecific()) {
   733  						return errors.New("x509: invalid CRL distribution point")
   734  					}
   735  					if !dpNamePresent {
   736  						continue
   737  					}
   738  					if !dpNameDER.ReadASN1(&dpNameDER, cryptobyte_asn1.Tag(0).Constructed().ContextSpecific()) {
   739  						return errors.New("x509: invalid CRL distribution point")
   740  					}
   741  					for !dpNameDER.Empty() {
   742  						if !dpNameDER.PeekASN1Tag(cryptobyte_asn1.Tag(6).ContextSpecific()) {
   743  							break
   744  						}
   745  						var uri cryptobyte.String
   746  						if !dpNameDER.ReadASN1(&uri, cryptobyte_asn1.Tag(6).ContextSpecific()) {
   747  							return errors.New("x509: invalid CRL distribution point")
   748  						}
   749  						out.CRLDistributionPoints = append(out.CRLDistributionPoints, string(uri))
   750  					}
   751  				}
   752  
   753  			case 35:
   754  				out.AuthorityKeyId, err = parseAuthorityKeyIdentifier(e)
   755  				if err != nil {
   756  					return err
   757  				}
   758  			case 36:
   759  				val := cryptobyte.String(e.Value)
   760  				if !val.ReadASN1(&val, cryptobyte_asn1.SEQUENCE) {
   761  					return errors.New("x509: invalid policy constraints extension")
   762  				}
   763  				if val.PeekASN1Tag(cryptobyte_asn1.Tag(0).ContextSpecific()) {
   764  					var v int64
   765  					if !val.ReadASN1Int64WithTag(&v, cryptobyte_asn1.Tag(0).ContextSpecific()) {
   766  						return errors.New("x509: invalid policy constraints extension")
   767  					}
   768  					out.RequireExplicitPolicy = int(v)
   769  					// Check for overflow.
   770  					if int64(out.RequireExplicitPolicy) != v {
   771  						return errors.New("x509: policy constraints requireExplicitPolicy field overflows int")
   772  					}
   773  					out.RequireExplicitPolicyZero = out.RequireExplicitPolicy == 0
   774  				}
   775  				if val.PeekASN1Tag(cryptobyte_asn1.Tag(1).ContextSpecific()) {
   776  					var v int64
   777  					if !val.ReadASN1Int64WithTag(&v, cryptobyte_asn1.Tag(1).ContextSpecific()) {
   778  						return errors.New("x509: invalid policy constraints extension")
   779  					}
   780  					out.InhibitPolicyMapping = int(v)
   781  					// Check for overflow.
   782  					if int64(out.InhibitPolicyMapping) != v {
   783  						return errors.New("x509: policy constraints inhibitPolicyMapping field overflows int")
   784  					}
   785  					out.InhibitPolicyMappingZero = out.InhibitPolicyMapping == 0
   786  				}
   787  			case 37:
   788  				out.ExtKeyUsage, out.UnknownExtKeyUsage, err = parseExtKeyUsageExtension(e.Value)
   789  				if err != nil {
   790  					return err
   791  				}
   792  			case 14: // RFC 5280, 4.2.1.2
   793  				if e.Critical {
   794  					// Conforming CAs MUST mark this extension as non-critical
   795  					return errors.New("x509: subject key identifier incorrectly marked critical")
   796  				}
   797  				val := cryptobyte.String(e.Value)
   798  				var skid cryptobyte.String
   799  				if !val.ReadASN1(&skid, cryptobyte_asn1.OCTET_STRING) {
   800  					return errors.New("x509: invalid subject key identifier")
   801  				}
   802  				out.SubjectKeyId = skid
   803  			case 32:
   804  				out.Policies, err = parseCertificatePoliciesExtension(e.Value)
   805  				if err != nil {
   806  					return err
   807  				}
   808  				out.PolicyIdentifiers = make([]asn1.ObjectIdentifier, 0, len(out.Policies))
   809  				for _, oid := range out.Policies {
   810  					if oid, ok := oid.toASN1OID(); ok {
   811  						out.PolicyIdentifiers = append(out.PolicyIdentifiers, oid)
   812  					}
   813  				}
   814  			case 33:
   815  				val := cryptobyte.String(e.Value)
   816  				if !val.ReadASN1(&val, cryptobyte_asn1.SEQUENCE) {
   817  					return errors.New("x509: invalid policy mappings extension")
   818  				}
   819  				for !val.Empty() {
   820  					var s cryptobyte.String
   821  					var issuer, subject cryptobyte.String
   822  					if !val.ReadASN1(&s, cryptobyte_asn1.SEQUENCE) ||
   823  						!s.ReadASN1(&issuer, cryptobyte_asn1.OBJECT_IDENTIFIER) ||
   824  						!s.ReadASN1(&subject, cryptobyte_asn1.OBJECT_IDENTIFIER) {
   825  						return errors.New("x509: invalid policy mappings extension")
   826  					}
   827  					out.PolicyMappings = append(out.PolicyMappings, PolicyMapping{OID{issuer}, OID{subject}})
   828  				}
   829  			case 54:
   830  				val := cryptobyte.String(e.Value)
   831  				if !val.ReadASN1Integer(&out.InhibitAnyPolicy) {
   832  					return errors.New("x509: invalid inhibit any policy extension")
   833  				}
   834  				out.InhibitAnyPolicyZero = out.InhibitAnyPolicy == 0
   835  			default:
   836  				// Unknown extensions are recorded if critical.
   837  				unhandled = true
   838  			}
   839  		} else if e.Id.Equal(oidExtensionAuthorityInfoAccess) {
   840  			// RFC 5280 4.2.2.1: Authority Information Access
   841  			if e.Critical {
   842  				// Conforming CAs MUST mark this extension as non-critical
   843  				return errors.New("x509: authority info access incorrectly marked critical")
   844  			}
   845  			val := cryptobyte.String(e.Value)
   846  			if !val.ReadASN1(&val, cryptobyte_asn1.SEQUENCE) {
   847  				return errors.New("x509: invalid authority info access")
   848  			}
   849  			for !val.Empty() {
   850  				var aiaDER cryptobyte.String
   851  				if !val.ReadASN1(&aiaDER, cryptobyte_asn1.SEQUENCE) {
   852  					return errors.New("x509: invalid authority info access")
   853  				}
   854  				var method asn1.ObjectIdentifier
   855  				if !aiaDER.ReadASN1ObjectIdentifier(&method) {
   856  					return errors.New("x509: invalid authority info access")
   857  				}
   858  				if !aiaDER.PeekASN1Tag(cryptobyte_asn1.Tag(6).ContextSpecific()) {
   859  					continue
   860  				}
   861  				if !aiaDER.ReadASN1(&aiaDER, cryptobyte_asn1.Tag(6).ContextSpecific()) {
   862  					return errors.New("x509: invalid authority info access")
   863  				}
   864  				switch {
   865  				case method.Equal(oidAuthorityInfoAccessOcsp):
   866  					out.OCSPServer = append(out.OCSPServer, string(aiaDER))
   867  				case method.Equal(oidAuthorityInfoAccessIssuers):
   868  					out.IssuingCertificateURL = append(out.IssuingCertificateURL, string(aiaDER))
   869  				}
   870  			}
   871  		} else {
   872  			// Unknown extensions are recorded if critical.
   873  			unhandled = true
   874  		}
   875  
   876  		if e.Critical && unhandled {
   877  			out.UnhandledCriticalExtensions = append(out.UnhandledCriticalExtensions, e.Id)
   878  		}
   879  	}
   880  
   881  	return nil
   882  }
   883  
   884  var x509negativeserial = godebug.New("x509negativeserial")
   885  
   886  func parseCertificate(der []byte) (*Certificate, error) {
   887  	cert := &Certificate{}
   888  
   889  	input := cryptobyte.String(der)
   890  	// we read the SEQUENCE including length and tag bytes so that
   891  	// we can populate Certificate.Raw, before unwrapping the
   892  	// SEQUENCE so it can be operated on
   893  	if !input.ReadASN1Element(&input, cryptobyte_asn1.SEQUENCE) {
   894  		return nil, errors.New("x509: malformed certificate")
   895  	}
   896  	cert.Raw = input
   897  	if !input.ReadASN1(&input, cryptobyte_asn1.SEQUENCE) {
   898  		return nil, errors.New("x509: malformed certificate")
   899  	}
   900  
   901  	var tbs cryptobyte.String
   902  	// do the same trick again as above to extract the raw
   903  	// bytes for Certificate.RawTBSCertificate
   904  	if !input.ReadASN1Element(&tbs, cryptobyte_asn1.SEQUENCE) {
   905  		return nil, errors.New("x509: malformed tbs certificate")
   906  	}
   907  	cert.RawTBSCertificate = tbs
   908  	if !tbs.ReadASN1(&tbs, cryptobyte_asn1.SEQUENCE) {
   909  		return nil, errors.New("x509: malformed tbs certificate")
   910  	}
   911  
   912  	if !tbs.ReadOptionalASN1Integer(&cert.Version, cryptobyte_asn1.Tag(0).Constructed().ContextSpecific(), 0) {
   913  		return nil, errors.New("x509: malformed version")
   914  	}
   915  	if cert.Version < 0 {
   916  		return nil, errors.New("x509: malformed version")
   917  	}
   918  	// for backwards compat reasons Version is one-indexed,
   919  	// rather than zero-indexed as defined in 5280
   920  	cert.Version++
   921  	if cert.Version > 3 {
   922  		return nil, errors.New("x509: invalid version")
   923  	}
   924  
   925  	serial := new(big.Int)
   926  	if !tbs.ReadASN1Integer(serial) {
   927  		return nil, errors.New("x509: malformed serial number")
   928  	}
   929  	if serial.Sign() == -1 {
   930  		if x509negativeserial.Value() != "1" {
   931  			return nil, errors.New("x509: negative serial number")
   932  		} else {
   933  			x509negativeserial.IncNonDefault()
   934  		}
   935  	}
   936  	cert.SerialNumber = serial
   937  
   938  	var sigAISeq cryptobyte.String
   939  	if !tbs.ReadASN1(&sigAISeq, cryptobyte_asn1.SEQUENCE) {
   940  		return nil, errors.New("x509: malformed signature algorithm identifier")
   941  	}
   942  	// Before parsing the inner algorithm identifier, extract
   943  	// the outer algorithm identifier and make sure that they
   944  	// match.
   945  	var outerSigAISeq cryptobyte.String
   946  	if !input.ReadASN1(&outerSigAISeq, cryptobyte_asn1.SEQUENCE) {
   947  		return nil, errors.New("x509: malformed algorithm identifier")
   948  	}
   949  	if !bytes.Equal(outerSigAISeq, sigAISeq) {
   950  		return nil, errors.New("x509: inner and outer signature algorithm identifiers don't match")
   951  	}
   952  	sigAI, err := parseAI(sigAISeq)
   953  	if err != nil {
   954  		return nil, err
   955  	}
   956  	cert.SignatureAlgorithm = getSignatureAlgorithmFromAI(sigAI)
   957  
   958  	var issuerSeq cryptobyte.String
   959  	if !tbs.ReadASN1Element(&issuerSeq, cryptobyte_asn1.SEQUENCE) {
   960  		return nil, errors.New("x509: malformed issuer")
   961  	}
   962  	cert.RawIssuer = issuerSeq
   963  	issuerRDNs, err := parseName(issuerSeq)
   964  	if err != nil {
   965  		return nil, err
   966  	}
   967  	cert.Issuer.FillFromRDNSequence(issuerRDNs)
   968  
   969  	var validity cryptobyte.String
   970  	if !tbs.ReadASN1(&validity, cryptobyte_asn1.SEQUENCE) {
   971  		return nil, errors.New("x509: malformed validity")
   972  	}
   973  	cert.NotBefore, cert.NotAfter, err = parseValidity(validity)
   974  	if err != nil {
   975  		return nil, err
   976  	}
   977  
   978  	var subjectSeq cryptobyte.String
   979  	if !tbs.ReadASN1Element(&subjectSeq, cryptobyte_asn1.SEQUENCE) {
   980  		return nil, errors.New("x509: malformed issuer")
   981  	}
   982  	cert.RawSubject = subjectSeq
   983  	subjectRDNs, err := parseName(subjectSeq)
   984  	if err != nil {
   985  		return nil, err
   986  	}
   987  	cert.Subject.FillFromRDNSequence(subjectRDNs)
   988  
   989  	var spki cryptobyte.String
   990  	if !tbs.ReadASN1Element(&spki, cryptobyte_asn1.SEQUENCE) {
   991  		return nil, errors.New("x509: malformed spki")
   992  	}
   993  	cert.RawSubjectPublicKeyInfo = spki
   994  	if !spki.ReadASN1(&spki, cryptobyte_asn1.SEQUENCE) {
   995  		return nil, errors.New("x509: malformed spki")
   996  	}
   997  	var pkAISeq cryptobyte.String
   998  	if !spki.ReadASN1(&pkAISeq, cryptobyte_asn1.SEQUENCE) {
   999  		return nil, errors.New("x509: malformed public key algorithm identifier")
  1000  	}
  1001  	pkAI, err := parseAI(pkAISeq)
  1002  	if err != nil {
  1003  		return nil, err
  1004  	}
  1005  	cert.PublicKeyAlgorithm = getPublicKeyAlgorithmFromOID(pkAI.Algorithm)
  1006  	var spk asn1.BitString
  1007  	if !spki.ReadASN1BitString(&spk) {
  1008  		return nil, errors.New("x509: malformed subjectPublicKey")
  1009  	}
  1010  	if cert.PublicKeyAlgorithm != UnknownPublicKeyAlgorithm {
  1011  		cert.PublicKey, err = parsePublicKey(&publicKeyInfo{
  1012  			Algorithm: pkAI,
  1013  			PublicKey: spk,
  1014  		})
  1015  		if err != nil {
  1016  			return nil, err
  1017  		}
  1018  	}
  1019  
  1020  	if cert.Version > 1 {
  1021  		if !tbs.SkipOptionalASN1(cryptobyte_asn1.Tag(1).ContextSpecific()) {
  1022  			return nil, errors.New("x509: malformed issuerUniqueID")
  1023  		}
  1024  		if !tbs.SkipOptionalASN1(cryptobyte_asn1.Tag(2).ContextSpecific()) {
  1025  			return nil, errors.New("x509: malformed subjectUniqueID")
  1026  		}
  1027  		if cert.Version == 3 {
  1028  			var extensions cryptobyte.String
  1029  			var present bool
  1030  			if !tbs.ReadOptionalASN1(&extensions, &present, cryptobyte_asn1.Tag(3).Constructed().ContextSpecific()) {
  1031  				return nil, errors.New("x509: malformed extensions")
  1032  			}
  1033  			if present {
  1034  				seenExts := make(map[string]bool)
  1035  				if !extensions.ReadASN1(&extensions, cryptobyte_asn1.SEQUENCE) {
  1036  					return nil, errors.New("x509: malformed extensions")
  1037  				}
  1038  				for !extensions.Empty() {
  1039  					var extension cryptobyte.String
  1040  					if !extensions.ReadASN1(&extension, cryptobyte_asn1.SEQUENCE) {
  1041  						return nil, errors.New("x509: malformed extension")
  1042  					}
  1043  					ext, err := parseExtension(extension)
  1044  					if err != nil {
  1045  						return nil, err
  1046  					}
  1047  					oidStr := ext.Id.String()
  1048  					if seenExts[oidStr] {
  1049  						return nil, fmt.Errorf("x509: certificate contains duplicate extension with OID %q", oidStr)
  1050  					}
  1051  					seenExts[oidStr] = true
  1052  					cert.Extensions = append(cert.Extensions, ext)
  1053  				}
  1054  				err = processExtensions(cert)
  1055  				if err != nil {
  1056  					return nil, err
  1057  				}
  1058  			}
  1059  		}
  1060  	}
  1061  
  1062  	var signature asn1.BitString
  1063  	if !input.ReadASN1BitString(&signature) {
  1064  		return nil, errors.New("x509: malformed signature")
  1065  	}
  1066  	cert.Signature = signature.RightAlign()
  1067  
  1068  	return cert, nil
  1069  }
  1070  
  1071  // ParseCertificate parses a single certificate from the given ASN.1 DER data.
  1072  //
  1073  // Before Go 1.23, ParseCertificate accepted certificates with negative serial
  1074  // numbers. This behavior can be restored by including "x509negativeserial=1" in
  1075  // the GODEBUG environment variable.
  1076  func ParseCertificate(der []byte) (*Certificate, error) {
  1077  	cert, err := parseCertificate(der)
  1078  	if err != nil {
  1079  		return nil, err
  1080  	}
  1081  	if len(der) != len(cert.Raw) {
  1082  		return nil, errors.New("x509: trailing data")
  1083  	}
  1084  	return cert, nil
  1085  }
  1086  
  1087  // ParseCertificates parses one or more certificates from the given ASN.1 DER
  1088  // data. The certificates must be concatenated with no intermediate padding.
  1089  func ParseCertificates(der []byte) ([]*Certificate, error) {
  1090  	var certs []*Certificate
  1091  	for len(der) > 0 {
  1092  		cert, err := parseCertificate(der)
  1093  		if err != nil {
  1094  			return nil, err
  1095  		}
  1096  		certs = append(certs, cert)
  1097  		der = der[len(cert.Raw):]
  1098  	}
  1099  	return certs, nil
  1100  }
  1101  
  1102  // The X.509 standards confusingly 1-indexed the version names, but 0-indexed
  1103  // the actual encoded version, so the version for X.509v2 is 1.
  1104  const x509v2Version = 1
  1105  
  1106  // ParseRevocationList parses a X509 v2 [Certificate] Revocation List from the given
  1107  // ASN.1 DER data.
  1108  func ParseRevocationList(der []byte) (*RevocationList, error) {
  1109  	rl := &RevocationList{}
  1110  
  1111  	input := cryptobyte.String(der)
  1112  	// we read the SEQUENCE including length and tag bytes so that
  1113  	// we can populate RevocationList.Raw, before unwrapping the
  1114  	// SEQUENCE so it can be operated on
  1115  	if !input.ReadASN1Element(&input, cryptobyte_asn1.SEQUENCE) {
  1116  		return nil, errors.New("x509: malformed crl")
  1117  	}
  1118  	rl.Raw = input
  1119  	if !input.ReadASN1(&input, cryptobyte_asn1.SEQUENCE) {
  1120  		return nil, errors.New("x509: malformed crl")
  1121  	}
  1122  
  1123  	var tbs cryptobyte.String
  1124  	// do the same trick again as above to extract the raw
  1125  	// bytes for Certificate.RawTBSCertificate
  1126  	if !input.ReadASN1Element(&tbs, cryptobyte_asn1.SEQUENCE) {
  1127  		return nil, errors.New("x509: malformed tbs crl")
  1128  	}
  1129  	rl.RawTBSRevocationList = tbs
  1130  	if !tbs.ReadASN1(&tbs, cryptobyte_asn1.SEQUENCE) {
  1131  		return nil, errors.New("x509: malformed tbs crl")
  1132  	}
  1133  
  1134  	var version int
  1135  	if !tbs.PeekASN1Tag(cryptobyte_asn1.INTEGER) {
  1136  		return nil, errors.New("x509: unsupported crl version")
  1137  	}
  1138  	if !tbs.ReadASN1Integer(&version) {
  1139  		return nil, errors.New("x509: malformed crl")
  1140  	}
  1141  	if version != x509v2Version {
  1142  		return nil, fmt.Errorf("x509: unsupported crl version: %d", version)
  1143  	}
  1144  
  1145  	var sigAISeq cryptobyte.String
  1146  	if !tbs.ReadASN1(&sigAISeq, cryptobyte_asn1.SEQUENCE) {
  1147  		return nil, errors.New("x509: malformed signature algorithm identifier")
  1148  	}
  1149  	// Before parsing the inner algorithm identifier, extract
  1150  	// the outer algorithm identifier and make sure that they
  1151  	// match.
  1152  	var outerSigAISeq cryptobyte.String
  1153  	if !input.ReadASN1(&outerSigAISeq, cryptobyte_asn1.SEQUENCE) {
  1154  		return nil, errors.New("x509: malformed algorithm identifier")
  1155  	}
  1156  	if !bytes.Equal(outerSigAISeq, sigAISeq) {
  1157  		return nil, errors.New("x509: inner and outer signature algorithm identifiers don't match")
  1158  	}
  1159  	sigAI, err := parseAI(sigAISeq)
  1160  	if err != nil {
  1161  		return nil, err
  1162  	}
  1163  	rl.SignatureAlgorithm = getSignatureAlgorithmFromAI(sigAI)
  1164  
  1165  	var signature asn1.BitString
  1166  	if !input.ReadASN1BitString(&signature) {
  1167  		return nil, errors.New("x509: malformed signature")
  1168  	}
  1169  	rl.Signature = signature.RightAlign()
  1170  
  1171  	var issuerSeq cryptobyte.String
  1172  	if !tbs.ReadASN1Element(&issuerSeq, cryptobyte_asn1.SEQUENCE) {
  1173  		return nil, errors.New("x509: malformed issuer")
  1174  	}
  1175  	rl.RawIssuer = issuerSeq
  1176  	issuerRDNs, err := parseName(issuerSeq)
  1177  	if err != nil {
  1178  		return nil, err
  1179  	}
  1180  	rl.Issuer.FillFromRDNSequence(issuerRDNs)
  1181  
  1182  	rl.ThisUpdate, err = parseTime(&tbs)
  1183  	if err != nil {
  1184  		return nil, err
  1185  	}
  1186  	if tbs.PeekASN1Tag(cryptobyte_asn1.GeneralizedTime) || tbs.PeekASN1Tag(cryptobyte_asn1.UTCTime) {
  1187  		rl.NextUpdate, err = parseTime(&tbs)
  1188  		if err != nil {
  1189  			return nil, err
  1190  		}
  1191  	}
  1192  
  1193  	if tbs.PeekASN1Tag(cryptobyte_asn1.SEQUENCE) {
  1194  		var revokedSeq cryptobyte.String
  1195  		if !tbs.ReadASN1(&revokedSeq, cryptobyte_asn1.SEQUENCE) {
  1196  			return nil, errors.New("x509: malformed crl")
  1197  		}
  1198  		for !revokedSeq.Empty() {
  1199  			rce := RevocationListEntry{}
  1200  
  1201  			var certSeq cryptobyte.String
  1202  			if !revokedSeq.ReadASN1Element(&certSeq, cryptobyte_asn1.SEQUENCE) {
  1203  				return nil, errors.New("x509: malformed crl")
  1204  			}
  1205  			rce.Raw = certSeq
  1206  			if !certSeq.ReadASN1(&certSeq, cryptobyte_asn1.SEQUENCE) {
  1207  				return nil, errors.New("x509: malformed crl")
  1208  			}
  1209  
  1210  			rce.SerialNumber = new(big.Int)
  1211  			if !certSeq.ReadASN1Integer(rce.SerialNumber) {
  1212  				return nil, errors.New("x509: malformed serial number")
  1213  			}
  1214  			rce.RevocationTime, err = parseTime(&certSeq)
  1215  			if err != nil {
  1216  				return nil, err
  1217  			}
  1218  			var extensions cryptobyte.String
  1219  			var present bool
  1220  			if !certSeq.ReadOptionalASN1(&extensions, &present, cryptobyte_asn1.SEQUENCE) {
  1221  				return nil, errors.New("x509: malformed extensions")
  1222  			}
  1223  			if present {
  1224  				for !extensions.Empty() {
  1225  					var extension cryptobyte.String
  1226  					if !extensions.ReadASN1(&extension, cryptobyte_asn1.SEQUENCE) {
  1227  						return nil, errors.New("x509: malformed extension")
  1228  					}
  1229  					ext, err := parseExtension(extension)
  1230  					if err != nil {
  1231  						return nil, err
  1232  					}
  1233  					if ext.Id.Equal(oidExtensionReasonCode) {
  1234  						val := cryptobyte.String(ext.Value)
  1235  						if !val.ReadASN1Enum(&rce.ReasonCode) {
  1236  							return nil, fmt.Errorf("x509: malformed reasonCode extension")
  1237  						}
  1238  					}
  1239  					rce.Extensions = append(rce.Extensions, ext)
  1240  				}
  1241  			}
  1242  
  1243  			rl.RevokedCertificateEntries = append(rl.RevokedCertificateEntries, rce)
  1244  			rcDeprecated := pkix.RevokedCertificate{
  1245  				SerialNumber:   rce.SerialNumber,
  1246  				RevocationTime: rce.RevocationTime,
  1247  				Extensions:     rce.Extensions,
  1248  			}
  1249  			rl.RevokedCertificates = append(rl.RevokedCertificates, rcDeprecated)
  1250  		}
  1251  	}
  1252  
  1253  	var extensions cryptobyte.String
  1254  	var present bool
  1255  	if !tbs.ReadOptionalASN1(&extensions, &present, cryptobyte_asn1.Tag(0).Constructed().ContextSpecific()) {
  1256  		return nil, errors.New("x509: malformed extensions")
  1257  	}
  1258  	if present {
  1259  		if !extensions.ReadASN1(&extensions, cryptobyte_asn1.SEQUENCE) {
  1260  			return nil, errors.New("x509: malformed extensions")
  1261  		}
  1262  		for !extensions.Empty() {
  1263  			var extension cryptobyte.String
  1264  			if !extensions.ReadASN1(&extension, cryptobyte_asn1.SEQUENCE) {
  1265  				return nil, errors.New("x509: malformed extension")
  1266  			}
  1267  			ext, err := parseExtension(extension)
  1268  			if err != nil {
  1269  				return nil, err
  1270  			}
  1271  			if ext.Id.Equal(oidExtensionAuthorityKeyId) {
  1272  				rl.AuthorityKeyId, err = parseAuthorityKeyIdentifier(ext)
  1273  				if err != nil {
  1274  					return nil, err
  1275  				}
  1276  			} else if ext.Id.Equal(oidExtensionCRLNumber) {
  1277  				value := cryptobyte.String(ext.Value)
  1278  				rl.Number = new(big.Int)
  1279  				if !value.ReadASN1Integer(rl.Number) {
  1280  					return nil, errors.New("x509: malformed crl number")
  1281  				}
  1282  			}
  1283  			rl.Extensions = append(rl.Extensions, ext)
  1284  		}
  1285  	}
  1286  
  1287  	return rl, nil
  1288  }
  1289  
  1290  // domainNameValid is an alloc-less version of the checks that
  1291  // domainToReverseLabels does.
  1292  func domainNameValid(s string, constraint bool) bool {
  1293  	// TODO(#75835): This function omits a number of checks which we
  1294  	// really should be doing to enforce that domain names are valid names per
  1295  	// RFC 1034. We previously enabled these checks, but this broke a
  1296  	// significant number of certificates we previously considered valid, and we
  1297  	// happily create via CreateCertificate (et al). We should enable these
  1298  	// checks, but will need to gate them behind a GODEBUG.
  1299  	//
  1300  	// I have left the checks we previously enabled, noted with "TODO(#75835)" so
  1301  	// that we can easily re-enable them once we unbreak everyone.
  1302  
  1303  	// TODO(#75835): this should only be true for constraints.
  1304  	if len(s) == 0 {
  1305  		return true
  1306  	}
  1307  
  1308  	// Do not allow trailing period (FQDN format is not allowed in SANs or
  1309  	// constraints).
  1310  	if s[len(s)-1] == '.' {
  1311  		return false
  1312  	}
  1313  
  1314  	// TODO(#75835): domains must have at least one label, cannot have
  1315  	// a leading empty label, and cannot be longer than 253 characters.
  1316  	// if len(s) == 0 || (!constraint && s[0] == '.') || len(s) > 253 {
  1317  	// 	return false
  1318  	// }
  1319  
  1320  	lastDot := -1
  1321  	if constraint && s[0] == '.' {
  1322  		s = s[1:]
  1323  	}
  1324  
  1325  	for i := 0; i <= len(s); i++ {
  1326  		if i < len(s) && (s[i] < 33 || s[i] > 126) {
  1327  			// Invalid character.
  1328  			return false
  1329  		}
  1330  		if i == len(s) || s[i] == '.' {
  1331  			labelLen := i
  1332  			if lastDot >= 0 {
  1333  				labelLen -= lastDot + 1
  1334  			}
  1335  			if labelLen == 0 {
  1336  				return false
  1337  			}
  1338  			// TODO(#75835): labels cannot be longer than 63 characters.
  1339  			// if labelLen > 63 {
  1340  			// 	return false
  1341  			// }
  1342  			lastDot = i
  1343  		}
  1344  	}
  1345  
  1346  	return true
  1347  }
  1348  

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