mirror of
https://github.com/autc04/Retro68.git
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1018 lines
30 KiB
Go
1018 lines
30 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package x509
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import (
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"bytes"
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"encoding/asn1"
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"errors"
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"fmt"
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"net"
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"net/url"
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"reflect"
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"runtime"
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"strconv"
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"strings"
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"time"
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"unicode/utf8"
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)
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type InvalidReason int
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const (
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// NotAuthorizedToSign results when a certificate is signed by another
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// which isn't marked as a CA certificate.
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NotAuthorizedToSign InvalidReason = iota
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// Expired results when a certificate has expired, based on the time
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// given in the VerifyOptions.
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Expired
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// CANotAuthorizedForThisName results when an intermediate or root
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// certificate has a name constraint which doesn't permit a DNS or
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// other name (including IP address) in the leaf certificate.
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CANotAuthorizedForThisName
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// TooManyIntermediates results when a path length constraint is
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// violated.
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TooManyIntermediates
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// IncompatibleUsage results when the certificate's key usage indicates
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// that it may only be used for a different purpose.
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IncompatibleUsage
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// NameMismatch results when the subject name of a parent certificate
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// does not match the issuer name in the child.
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NameMismatch
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// NameConstraintsWithoutSANs results when a leaf certificate doesn't
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// contain a Subject Alternative Name extension, but a CA certificate
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// contains name constraints.
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NameConstraintsWithoutSANs
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// UnconstrainedName results when a CA certificate contains permitted
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// name constraints, but leaf certificate contains a name of an
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// unsupported or unconstrained type.
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UnconstrainedName
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// TooManyConstraints results when the number of comparision operations
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// needed to check a certificate exceeds the limit set by
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// VerifyOptions.MaxConstraintComparisions. This limit exists to
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// prevent pathological certificates can consuming excessive amounts of
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// CPU time to verify.
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TooManyConstraints
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// CANotAuthorizedForExtKeyUsage results when an intermediate or root
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// certificate does not permit a requested extended key usage.
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CANotAuthorizedForExtKeyUsage
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)
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// CertificateInvalidError results when an odd error occurs. Users of this
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// library probably want to handle all these errors uniformly.
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type CertificateInvalidError struct {
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Cert *Certificate
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Reason InvalidReason
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Detail string
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}
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func (e CertificateInvalidError) Error() string {
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switch e.Reason {
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case NotAuthorizedToSign:
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return "x509: certificate is not authorized to sign other certificates"
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case Expired:
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return "x509: certificate has expired or is not yet valid"
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case CANotAuthorizedForThisName:
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return "x509: a root or intermediate certificate is not authorized to sign for this name: " + e.Detail
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case CANotAuthorizedForExtKeyUsage:
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return "x509: a root or intermediate certificate is not authorized for an extended key usage: " + e.Detail
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case TooManyIntermediates:
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return "x509: too many intermediates for path length constraint"
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case IncompatibleUsage:
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return "x509: certificate specifies an incompatible key usage"
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case NameMismatch:
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return "x509: issuer name does not match subject from issuing certificate"
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case NameConstraintsWithoutSANs:
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return "x509: issuer has name constraints but leaf doesn't have a SAN extension"
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case UnconstrainedName:
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return "x509: issuer has name constraints but leaf contains unknown or unconstrained name: " + e.Detail
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}
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return "x509: unknown error"
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}
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// HostnameError results when the set of authorized names doesn't match the
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// requested name.
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type HostnameError struct {
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Certificate *Certificate
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Host string
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}
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func (h HostnameError) Error() string {
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c := h.Certificate
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var valid string
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if ip := net.ParseIP(h.Host); ip != nil {
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// Trying to validate an IP
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if len(c.IPAddresses) == 0 {
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return "x509: cannot validate certificate for " + h.Host + " because it doesn't contain any IP SANs"
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}
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for _, san := range c.IPAddresses {
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if len(valid) > 0 {
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valid += ", "
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}
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valid += san.String()
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}
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} else {
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if c.hasSANExtension() {
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valid = strings.Join(c.DNSNames, ", ")
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} else {
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valid = c.Subject.CommonName
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}
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}
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if len(valid) == 0 {
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return "x509: certificate is not valid for any names, but wanted to match " + h.Host
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}
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return "x509: certificate is valid for " + valid + ", not " + h.Host
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}
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// UnknownAuthorityError results when the certificate issuer is unknown
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type UnknownAuthorityError struct {
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Cert *Certificate
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// hintErr contains an error that may be helpful in determining why an
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// authority wasn't found.
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hintErr error
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// hintCert contains a possible authority certificate that was rejected
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// because of the error in hintErr.
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hintCert *Certificate
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}
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func (e UnknownAuthorityError) Error() string {
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s := "x509: certificate signed by unknown authority"
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if e.hintErr != nil {
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certName := e.hintCert.Subject.CommonName
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if len(certName) == 0 {
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if len(e.hintCert.Subject.Organization) > 0 {
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certName = e.hintCert.Subject.Organization[0]
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} else {
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certName = "serial:" + e.hintCert.SerialNumber.String()
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}
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}
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s += fmt.Sprintf(" (possibly because of %q while trying to verify candidate authority certificate %q)", e.hintErr, certName)
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}
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return s
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}
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// SystemRootsError results when we fail to load the system root certificates.
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type SystemRootsError struct {
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Err error
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}
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func (se SystemRootsError) Error() string {
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msg := "x509: failed to load system roots and no roots provided"
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if se.Err != nil {
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return msg + "; " + se.Err.Error()
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}
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return msg
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}
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// errNotParsed is returned when a certificate without ASN.1 contents is
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// verified. Platform-specific verification needs the ASN.1 contents.
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var errNotParsed = errors.New("x509: missing ASN.1 contents; use ParseCertificate")
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// VerifyOptions contains parameters for Certificate.Verify. It's a structure
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// because other PKIX verification APIs have ended up needing many options.
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type VerifyOptions struct {
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DNSName string
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Intermediates *CertPool
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Roots *CertPool // if nil, the system roots are used
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CurrentTime time.Time // if zero, the current time is used
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// KeyUsage specifies which Extended Key Usage values are acceptable. A leaf
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// certificate is accepted if it contains any of the listed values. An empty
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// list means ExtKeyUsageServerAuth. To accept any key usage, include
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// ExtKeyUsageAny.
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//
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// Certificate chains are required to nest these extended key usage values.
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// (This matches the Windows CryptoAPI behavior, but not the spec.)
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KeyUsages []ExtKeyUsage
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// MaxConstraintComparisions is the maximum number of comparisons to
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// perform when checking a given certificate's name constraints. If
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// zero, a sensible default is used. This limit prevents pathalogical
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// certificates from consuming excessive amounts of CPU time when
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// validating.
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MaxConstraintComparisions int
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}
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const (
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leafCertificate = iota
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intermediateCertificate
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rootCertificate
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)
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// rfc2821Mailbox represents a “mailbox” (which is an email address to most
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// people) by breaking it into the “local” (i.e. before the '@') and “domain”
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// parts.
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type rfc2821Mailbox struct {
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local, domain string
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}
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// parseRFC2821Mailbox parses an email address into local and domain parts,
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// based on the ABNF for a “Mailbox” from RFC 2821. According to
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// https://tools.ietf.org/html/rfc5280#section-4.2.1.6 that's correct for an
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// rfc822Name from a certificate: “The format of an rfc822Name is a "Mailbox"
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// as defined in https://tools.ietf.org/html/rfc2821#section-4.1.2”.
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func parseRFC2821Mailbox(in string) (mailbox rfc2821Mailbox, ok bool) {
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if len(in) == 0 {
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return mailbox, false
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}
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localPartBytes := make([]byte, 0, len(in)/2)
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if in[0] == '"' {
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// Quoted-string = DQUOTE *qcontent DQUOTE
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// non-whitespace-control = %d1-8 / %d11 / %d12 / %d14-31 / %d127
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// qcontent = qtext / quoted-pair
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// qtext = non-whitespace-control /
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// %d33 / %d35-91 / %d93-126
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// quoted-pair = ("\" text) / obs-qp
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// text = %d1-9 / %d11 / %d12 / %d14-127 / obs-text
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//
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// (Names beginning with “obs-” are the obsolete syntax from
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// https://tools.ietf.org/html/rfc2822#section-4. Since it has
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// been 16 years, we no longer accept that.)
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in = in[1:]
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QuotedString:
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for {
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if len(in) == 0 {
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return mailbox, false
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}
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c := in[0]
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in = in[1:]
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switch {
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case c == '"':
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break QuotedString
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case c == '\\':
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// quoted-pair
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if len(in) == 0 {
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return mailbox, false
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}
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if in[0] == 11 ||
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in[0] == 12 ||
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(1 <= in[0] && in[0] <= 9) ||
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(14 <= in[0] && in[0] <= 127) {
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localPartBytes = append(localPartBytes, in[0])
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in = in[1:]
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} else {
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return mailbox, false
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}
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case c == 11 ||
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c == 12 ||
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// Space (char 32) is not allowed based on the
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// BNF, but RFC 3696 gives an example that
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// assumes that it is. Several “verified”
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// errata continue to argue about this point.
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// We choose to accept it.
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c == 32 ||
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c == 33 ||
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c == 127 ||
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(1 <= c && c <= 8) ||
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(14 <= c && c <= 31) ||
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(35 <= c && c <= 91) ||
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(93 <= c && c <= 126):
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// qtext
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localPartBytes = append(localPartBytes, c)
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default:
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return mailbox, false
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}
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}
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} else {
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// Atom ("." Atom)*
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NextChar:
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for len(in) > 0 {
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// atext from https://tools.ietf.org/html/rfc2822#section-3.2.4
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c := in[0]
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switch {
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case c == '\\':
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// Examples given in RFC 3696 suggest that
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// escaped characters can appear outside of a
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// quoted string. Several “verified” errata
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// continue to argue the point. We choose to
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// accept it.
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in = in[1:]
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if len(in) == 0 {
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return mailbox, false
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}
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fallthrough
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case ('0' <= c && c <= '9') ||
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('a' <= c && c <= 'z') ||
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('A' <= c && c <= 'Z') ||
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c == '!' || c == '#' || c == '$' || c == '%' ||
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c == '&' || c == '\'' || c == '*' || c == '+' ||
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c == '-' || c == '/' || c == '=' || c == '?' ||
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c == '^' || c == '_' || c == '`' || c == '{' ||
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c == '|' || c == '}' || c == '~' || c == '.':
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localPartBytes = append(localPartBytes, in[0])
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in = in[1:]
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default:
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break NextChar
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}
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}
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if len(localPartBytes) == 0 {
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return mailbox, false
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}
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// https://tools.ietf.org/html/rfc3696#section-3
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// “period (".") may also appear, but may not be used to start
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// or end the local part, nor may two or more consecutive
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// periods appear.”
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twoDots := []byte{'.', '.'}
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if localPartBytes[0] == '.' ||
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localPartBytes[len(localPartBytes)-1] == '.' ||
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bytes.Contains(localPartBytes, twoDots) {
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return mailbox, false
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}
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}
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if len(in) == 0 || in[0] != '@' {
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return mailbox, false
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}
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in = in[1:]
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// The RFC species a format for domains, but that's known to be
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// violated in practice so we accept that anything after an '@' is the
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// domain part.
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if _, ok := domainToReverseLabels(in); !ok {
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return mailbox, false
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}
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mailbox.local = string(localPartBytes)
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mailbox.domain = in
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return mailbox, true
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}
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// domainToReverseLabels converts a textual domain name like foo.example.com to
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// the list of labels in reverse order, e.g. ["com", "example", "foo"].
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func domainToReverseLabels(domain string) (reverseLabels []string, ok bool) {
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for len(domain) > 0 {
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if i := strings.LastIndexByte(domain, '.'); i == -1 {
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reverseLabels = append(reverseLabels, domain)
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domain = ""
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} else {
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reverseLabels = append(reverseLabels, domain[i+1:len(domain)])
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domain = domain[:i]
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}
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}
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if len(reverseLabels) > 0 && len(reverseLabels[0]) == 0 {
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// An empty label at the end indicates an absolute value.
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return nil, false
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}
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for _, label := range reverseLabels {
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if len(label) == 0 {
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||
// Empty labels are otherwise invalid.
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return nil, false
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}
|
||
|
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for _, c := range label {
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if c < 33 || c > 126 {
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||
// Invalid character.
|
||
return nil, false
|
||
}
|
||
}
|
||
}
|
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|
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return reverseLabels, true
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}
|
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func matchEmailConstraint(mailbox rfc2821Mailbox, constraint string) (bool, error) {
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// If the constraint contains an @, then it specifies an exact mailbox
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// name.
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if strings.Contains(constraint, "@") {
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constraintMailbox, ok := parseRFC2821Mailbox(constraint)
|
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if !ok {
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return false, fmt.Errorf("x509: internal error: cannot parse constraint %q", constraint)
|
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}
|
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return mailbox.local == constraintMailbox.local && strings.EqualFold(mailbox.domain, constraintMailbox.domain), nil
|
||
}
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|
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// Otherwise the constraint is like a DNS constraint of the domain part
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// of the mailbox.
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return matchDomainConstraint(mailbox.domain, constraint)
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||
}
|
||
|
||
func matchURIConstraint(uri *url.URL, constraint string) (bool, error) {
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// https://tools.ietf.org/html/rfc5280#section-4.2.1.10
|
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// “a uniformResourceIdentifier that does not include an authority
|
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// component with a host name specified as a fully qualified domain
|
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// name (e.g., if the URI either does not include an authority
|
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// component or includes an authority component in which the host name
|
||
// is specified as an IP address), then the application MUST reject the
|
||
// certificate.”
|
||
|
||
host := uri.Host
|
||
if len(host) == 0 {
|
||
return false, fmt.Errorf("URI with empty host (%q) cannot be matched against constraints", uri.String())
|
||
}
|
||
|
||
if strings.Contains(host, ":") && !strings.HasSuffix(host, "]") {
|
||
var err error
|
||
host, _, err = net.SplitHostPort(uri.Host)
|
||
if err != nil {
|
||
return false, err
|
||
}
|
||
}
|
||
|
||
if strings.HasPrefix(host, "[") && strings.HasSuffix(host, "]") ||
|
||
net.ParseIP(host) != nil {
|
||
return false, fmt.Errorf("URI with IP (%q) cannot be matched against constraints", uri.String())
|
||
}
|
||
|
||
return matchDomainConstraint(host, constraint)
|
||
}
|
||
|
||
func matchIPConstraint(ip net.IP, constraint *net.IPNet) (bool, error) {
|
||
if len(ip) != len(constraint.IP) {
|
||
return false, nil
|
||
}
|
||
|
||
for i := range ip {
|
||
if mask := constraint.Mask[i]; ip[i]&mask != constraint.IP[i]&mask {
|
||
return false, nil
|
||
}
|
||
}
|
||
|
||
return true, nil
|
||
}
|
||
|
||
func matchDomainConstraint(domain, constraint string) (bool, error) {
|
||
// The meaning of zero length constraints is not specified, but this
|
||
// code follows NSS and accepts them as matching everything.
|
||
if len(constraint) == 0 {
|
||
return true, nil
|
||
}
|
||
|
||
domainLabels, ok := domainToReverseLabels(domain)
|
||
if !ok {
|
||
return false, fmt.Errorf("x509: internal error: cannot parse domain %q", domain)
|
||
}
|
||
|
||
// RFC 5280 says that a leading period in a domain name means that at
|
||
// least one label must be prepended, but only for URI and email
|
||
// constraints, not DNS constraints. The code also supports that
|
||
// behaviour for DNS constraints.
|
||
|
||
mustHaveSubdomains := false
|
||
if constraint[0] == '.' {
|
||
mustHaveSubdomains = true
|
||
constraint = constraint[1:]
|
||
}
|
||
|
||
constraintLabels, ok := domainToReverseLabels(constraint)
|
||
if !ok {
|
||
return false, fmt.Errorf("x509: internal error: cannot parse domain %q", constraint)
|
||
}
|
||
|
||
if len(domainLabels) < len(constraintLabels) ||
|
||
(mustHaveSubdomains && len(domainLabels) == len(constraintLabels)) {
|
||
return false, nil
|
||
}
|
||
|
||
for i, constraintLabel := range constraintLabels {
|
||
if !strings.EqualFold(constraintLabel, domainLabels[i]) {
|
||
return false, nil
|
||
}
|
||
}
|
||
|
||
return true, nil
|
||
}
|
||
|
||
// checkNameConstraints checks that c permits a child certificate to claim the
|
||
// given name, of type nameType. The argument parsedName contains the parsed
|
||
// form of name, suitable for passing to the match function. The total number
|
||
// of comparisons is tracked in the given count and should not exceed the given
|
||
// limit.
|
||
func (c *Certificate) checkNameConstraints(count *int,
|
||
maxConstraintComparisons int,
|
||
nameType string,
|
||
name string,
|
||
parsedName interface{},
|
||
match func(parsedName, constraint interface{}) (match bool, err error),
|
||
permitted, excluded interface{}) error {
|
||
|
||
excludedValue := reflect.ValueOf(excluded)
|
||
|
||
*count += excludedValue.Len()
|
||
if *count > maxConstraintComparisons {
|
||
return CertificateInvalidError{c, TooManyConstraints, ""}
|
||
}
|
||
|
||
for i := 0; i < excludedValue.Len(); i++ {
|
||
constraint := excludedValue.Index(i).Interface()
|
||
match, err := match(parsedName, constraint)
|
||
if err != nil {
|
||
return CertificateInvalidError{c, CANotAuthorizedForThisName, err.Error()}
|
||
}
|
||
|
||
if match {
|
||
return CertificateInvalidError{c, CANotAuthorizedForThisName, fmt.Sprintf("%s %q is excluded by constraint %q", nameType, name, constraint)}
|
||
}
|
||
}
|
||
|
||
permittedValue := reflect.ValueOf(permitted)
|
||
|
||
*count += permittedValue.Len()
|
||
if *count > maxConstraintComparisons {
|
||
return CertificateInvalidError{c, TooManyConstraints, ""}
|
||
}
|
||
|
||
ok := true
|
||
for i := 0; i < permittedValue.Len(); i++ {
|
||
constraint := permittedValue.Index(i).Interface()
|
||
|
||
var err error
|
||
if ok, err = match(parsedName, constraint); err != nil {
|
||
return CertificateInvalidError{c, CANotAuthorizedForThisName, err.Error()}
|
||
}
|
||
|
||
if ok {
|
||
break
|
||
}
|
||
}
|
||
|
||
if !ok {
|
||
return CertificateInvalidError{c, CANotAuthorizedForThisName, fmt.Sprintf("%s %q is not permitted by any constraint", nameType, name)}
|
||
}
|
||
|
||
return nil
|
||
}
|
||
|
||
// isValid performs validity checks on c given that it is a candidate to append
|
||
// to the chain in currentChain.
|
||
func (c *Certificate) isValid(certType int, currentChain []*Certificate, opts *VerifyOptions) error {
|
||
if len(c.UnhandledCriticalExtensions) > 0 {
|
||
return UnhandledCriticalExtension{}
|
||
}
|
||
|
||
if len(currentChain) > 0 {
|
||
child := currentChain[len(currentChain)-1]
|
||
if !bytes.Equal(child.RawIssuer, c.RawSubject) {
|
||
return CertificateInvalidError{c, NameMismatch, ""}
|
||
}
|
||
}
|
||
|
||
now := opts.CurrentTime
|
||
if now.IsZero() {
|
||
now = time.Now()
|
||
}
|
||
if now.Before(c.NotBefore) || now.After(c.NotAfter) {
|
||
return CertificateInvalidError{c, Expired, ""}
|
||
}
|
||
|
||
maxConstraintComparisons := opts.MaxConstraintComparisions
|
||
if maxConstraintComparisons == 0 {
|
||
maxConstraintComparisons = 250000
|
||
}
|
||
comparisonCount := 0
|
||
|
||
var leaf *Certificate
|
||
if certType == intermediateCertificate || certType == rootCertificate {
|
||
if len(currentChain) == 0 {
|
||
return errors.New("x509: internal error: empty chain when appending CA cert")
|
||
}
|
||
leaf = currentChain[0]
|
||
}
|
||
|
||
if (certType == intermediateCertificate || certType == rootCertificate) && c.hasNameConstraints() {
|
||
sanExtension, ok := leaf.getSANExtension()
|
||
if !ok {
|
||
// This is the deprecated, legacy case of depending on
|
||
// the CN as a hostname. Chains modern enough to be
|
||
// using name constraints should not be depending on
|
||
// CNs.
|
||
return CertificateInvalidError{c, NameConstraintsWithoutSANs, ""}
|
||
}
|
||
|
||
err := forEachSAN(sanExtension, func(tag int, data []byte) error {
|
||
switch tag {
|
||
case nameTypeEmail:
|
||
name := string(data)
|
||
mailbox, ok := parseRFC2821Mailbox(name)
|
||
if !ok {
|
||
return fmt.Errorf("x509: cannot parse rfc822Name %q", mailbox)
|
||
}
|
||
|
||
if err := c.checkNameConstraints(&comparisonCount, maxConstraintComparisons, "email address", name, mailbox,
|
||
func(parsedName, constraint interface{}) (bool, error) {
|
||
return matchEmailConstraint(parsedName.(rfc2821Mailbox), constraint.(string))
|
||
}, c.PermittedEmailAddresses, c.ExcludedEmailAddresses); err != nil {
|
||
return err
|
||
}
|
||
|
||
case nameTypeDNS:
|
||
name := string(data)
|
||
if _, ok := domainToReverseLabels(name); !ok {
|
||
return fmt.Errorf("x509: cannot parse dnsName %q", name)
|
||
}
|
||
|
||
if err := c.checkNameConstraints(&comparisonCount, maxConstraintComparisons, "DNS name", name, name,
|
||
func(parsedName, constraint interface{}) (bool, error) {
|
||
return matchDomainConstraint(parsedName.(string), constraint.(string))
|
||
}, c.PermittedDNSDomains, c.ExcludedDNSDomains); err != nil {
|
||
return err
|
||
}
|
||
|
||
case nameTypeURI:
|
||
name := string(data)
|
||
uri, err := url.Parse(name)
|
||
if err != nil {
|
||
return fmt.Errorf("x509: internal error: URI SAN %q failed to parse", name)
|
||
}
|
||
|
||
if err := c.checkNameConstraints(&comparisonCount, maxConstraintComparisons, "URI", name, uri,
|
||
func(parsedName, constraint interface{}) (bool, error) {
|
||
return matchURIConstraint(parsedName.(*url.URL), constraint.(string))
|
||
}, c.PermittedURIDomains, c.ExcludedURIDomains); err != nil {
|
||
return err
|
||
}
|
||
|
||
case nameTypeIP:
|
||
ip := net.IP(data)
|
||
if l := len(ip); l != net.IPv4len && l != net.IPv6len {
|
||
return fmt.Errorf("x509: internal error: IP SAN %x failed to parse", data)
|
||
}
|
||
|
||
if err := c.checkNameConstraints(&comparisonCount, maxConstraintComparisons, "IP address", ip.String(), ip,
|
||
func(parsedName, constraint interface{}) (bool, error) {
|
||
return matchIPConstraint(parsedName.(net.IP), constraint.(*net.IPNet))
|
||
}, c.PermittedIPRanges, c.ExcludedIPRanges); err != nil {
|
||
return err
|
||
}
|
||
|
||
default:
|
||
// Unknown SAN types are ignored.
|
||
}
|
||
|
||
return nil
|
||
})
|
||
|
||
if err != nil {
|
||
return err
|
||
}
|
||
}
|
||
|
||
// KeyUsage status flags are ignored. From Engineering Security, Peter
|
||
// Gutmann: A European government CA marked its signing certificates as
|
||
// being valid for encryption only, but no-one noticed. Another
|
||
// European CA marked its signature keys as not being valid for
|
||
// signatures. A different CA marked its own trusted root certificate
|
||
// as being invalid for certificate signing. Another national CA
|
||
// distributed a certificate to be used to encrypt data for the
|
||
// country’s tax authority that was marked as only being usable for
|
||
// digital signatures but not for encryption. Yet another CA reversed
|
||
// the order of the bit flags in the keyUsage due to confusion over
|
||
// encoding endianness, essentially setting a random keyUsage in
|
||
// certificates that it issued. Another CA created a self-invalidating
|
||
// certificate by adding a certificate policy statement stipulating
|
||
// that the certificate had to be used strictly as specified in the
|
||
// keyUsage, and a keyUsage containing a flag indicating that the RSA
|
||
// encryption key could only be used for Diffie-Hellman key agreement.
|
||
|
||
if certType == intermediateCertificate && (!c.BasicConstraintsValid || !c.IsCA) {
|
||
return CertificateInvalidError{c, NotAuthorizedToSign, ""}
|
||
}
|
||
|
||
if c.BasicConstraintsValid && c.MaxPathLen >= 0 {
|
||
numIntermediates := len(currentChain) - 1
|
||
if numIntermediates > c.MaxPathLen {
|
||
return CertificateInvalidError{c, TooManyIntermediates, ""}
|
||
}
|
||
}
|
||
|
||
return nil
|
||
}
|
||
|
||
// formatOID formats an ASN.1 OBJECT IDENTIFER in the common, dotted style.
|
||
func formatOID(oid asn1.ObjectIdentifier) string {
|
||
ret := ""
|
||
for i, v := range oid {
|
||
if i > 0 {
|
||
ret += "."
|
||
}
|
||
ret += strconv.Itoa(v)
|
||
}
|
||
return ret
|
||
}
|
||
|
||
// Verify attempts to verify c by building one or more chains from c to a
|
||
// certificate in opts.Roots, using certificates in opts.Intermediates if
|
||
// needed. If successful, it returns one or more chains where the first
|
||
// element of the chain is c and the last element is from opts.Roots.
|
||
//
|
||
// If opts.Roots is nil and system roots are unavailable the returned error
|
||
// will be of type SystemRootsError.
|
||
//
|
||
// Name constraints in the intermediates will be applied to all names claimed
|
||
// in the chain, not just opts.DNSName. Thus it is invalid for a leaf to claim
|
||
// example.com if an intermediate doesn't permit it, even if example.com is not
|
||
// the name being validated. Note that DirectoryName constraints are not
|
||
// supported.
|
||
//
|
||
// Extended Key Usage values are enforced down a chain, so an intermediate or
|
||
// root that enumerates EKUs prevents a leaf from asserting an EKU not in that
|
||
// list.
|
||
//
|
||
// WARNING: this function doesn't do any revocation checking.
|
||
func (c *Certificate) Verify(opts VerifyOptions) (chains [][]*Certificate, err error) {
|
||
// Platform-specific verification needs the ASN.1 contents so
|
||
// this makes the behavior consistent across platforms.
|
||
if len(c.Raw) == 0 {
|
||
return nil, errNotParsed
|
||
}
|
||
if opts.Intermediates != nil {
|
||
for _, intermediate := range opts.Intermediates.certs {
|
||
if len(intermediate.Raw) == 0 {
|
||
return nil, errNotParsed
|
||
}
|
||
}
|
||
}
|
||
|
||
// Use Windows's own verification and chain building.
|
||
if opts.Roots == nil && runtime.GOOS == "windows" {
|
||
return c.systemVerify(&opts)
|
||
}
|
||
|
||
if opts.Roots == nil {
|
||
opts.Roots = systemRootsPool()
|
||
if opts.Roots == nil {
|
||
return nil, SystemRootsError{systemRootsErr}
|
||
}
|
||
}
|
||
|
||
err = c.isValid(leafCertificate, nil, &opts)
|
||
if err != nil {
|
||
return
|
||
}
|
||
|
||
if len(opts.DNSName) > 0 {
|
||
err = c.VerifyHostname(opts.DNSName)
|
||
if err != nil {
|
||
return
|
||
}
|
||
}
|
||
|
||
var candidateChains [][]*Certificate
|
||
if opts.Roots.contains(c) {
|
||
candidateChains = append(candidateChains, []*Certificate{c})
|
||
} else {
|
||
if candidateChains, err = c.buildChains(make(map[int][][]*Certificate), []*Certificate{c}, &opts); err != nil {
|
||
return nil, err
|
||
}
|
||
}
|
||
|
||
keyUsages := opts.KeyUsages
|
||
if len(keyUsages) == 0 {
|
||
keyUsages = []ExtKeyUsage{ExtKeyUsageServerAuth}
|
||
}
|
||
|
||
// If any key usage is acceptable then we're done.
|
||
for _, usage := range keyUsages {
|
||
if usage == ExtKeyUsageAny {
|
||
return candidateChains, nil
|
||
}
|
||
}
|
||
|
||
for _, candidate := range candidateChains {
|
||
if checkChainForKeyUsage(candidate, keyUsages) {
|
||
chains = append(chains, candidate)
|
||
}
|
||
}
|
||
|
||
if len(chains) == 0 {
|
||
return nil, CertificateInvalidError{c, IncompatibleUsage, ""}
|
||
}
|
||
|
||
return chains, nil
|
||
}
|
||
|
||
func appendToFreshChain(chain []*Certificate, cert *Certificate) []*Certificate {
|
||
n := make([]*Certificate, len(chain)+1)
|
||
copy(n, chain)
|
||
n[len(chain)] = cert
|
||
return n
|
||
}
|
||
|
||
func (c *Certificate) buildChains(cache map[int][][]*Certificate, currentChain []*Certificate, opts *VerifyOptions) (chains [][]*Certificate, err error) {
|
||
possibleRoots, failedRoot, rootErr := opts.Roots.findVerifiedParents(c)
|
||
nextRoot:
|
||
for _, rootNum := range possibleRoots {
|
||
root := opts.Roots.certs[rootNum]
|
||
|
||
for _, cert := range currentChain {
|
||
if cert.Equal(root) {
|
||
continue nextRoot
|
||
}
|
||
}
|
||
|
||
err = root.isValid(rootCertificate, currentChain, opts)
|
||
if err != nil {
|
||
continue
|
||
}
|
||
chains = append(chains, appendToFreshChain(currentChain, root))
|
||
}
|
||
|
||
possibleIntermediates, failedIntermediate, intermediateErr := opts.Intermediates.findVerifiedParents(c)
|
||
nextIntermediate:
|
||
for _, intermediateNum := range possibleIntermediates {
|
||
intermediate := opts.Intermediates.certs[intermediateNum]
|
||
for _, cert := range currentChain {
|
||
if cert.Equal(intermediate) {
|
||
continue nextIntermediate
|
||
}
|
||
}
|
||
err = intermediate.isValid(intermediateCertificate, currentChain, opts)
|
||
if err != nil {
|
||
continue
|
||
}
|
||
var childChains [][]*Certificate
|
||
childChains, ok := cache[intermediateNum]
|
||
if !ok {
|
||
childChains, err = intermediate.buildChains(cache, appendToFreshChain(currentChain, intermediate), opts)
|
||
cache[intermediateNum] = childChains
|
||
}
|
||
chains = append(chains, childChains...)
|
||
}
|
||
|
||
if len(chains) > 0 {
|
||
err = nil
|
||
}
|
||
|
||
if len(chains) == 0 && err == nil {
|
||
hintErr := rootErr
|
||
hintCert := failedRoot
|
||
if hintErr == nil {
|
||
hintErr = intermediateErr
|
||
hintCert = failedIntermediate
|
||
}
|
||
err = UnknownAuthorityError{c, hintErr, hintCert}
|
||
}
|
||
|
||
return
|
||
}
|
||
|
||
func matchHostnames(pattern, host string) bool {
|
||
host = strings.TrimSuffix(host, ".")
|
||
pattern = strings.TrimSuffix(pattern, ".")
|
||
|
||
if len(pattern) == 0 || len(host) == 0 {
|
||
return false
|
||
}
|
||
|
||
patternParts := strings.Split(pattern, ".")
|
||
hostParts := strings.Split(host, ".")
|
||
|
||
if len(patternParts) != len(hostParts) {
|
||
return false
|
||
}
|
||
|
||
for i, patternPart := range patternParts {
|
||
if i == 0 && patternPart == "*" {
|
||
continue
|
||
}
|
||
if patternPart != hostParts[i] {
|
||
return false
|
||
}
|
||
}
|
||
|
||
return true
|
||
}
|
||
|
||
// toLowerCaseASCII returns a lower-case version of in. See RFC 6125 6.4.1. We use
|
||
// an explicitly ASCII function to avoid any sharp corners resulting from
|
||
// performing Unicode operations on DNS labels.
|
||
func toLowerCaseASCII(in string) string {
|
||
// If the string is already lower-case then there's nothing to do.
|
||
isAlreadyLowerCase := true
|
||
for _, c := range in {
|
||
if c == utf8.RuneError {
|
||
// If we get a UTF-8 error then there might be
|
||
// upper-case ASCII bytes in the invalid sequence.
|
||
isAlreadyLowerCase = false
|
||
break
|
||
}
|
||
if 'A' <= c && c <= 'Z' {
|
||
isAlreadyLowerCase = false
|
||
break
|
||
}
|
||
}
|
||
|
||
if isAlreadyLowerCase {
|
||
return in
|
||
}
|
||
|
||
out := []byte(in)
|
||
for i, c := range out {
|
||
if 'A' <= c && c <= 'Z' {
|
||
out[i] += 'a' - 'A'
|
||
}
|
||
}
|
||
return string(out)
|
||
}
|
||
|
||
// VerifyHostname returns nil if c is a valid certificate for the named host.
|
||
// Otherwise it returns an error describing the mismatch.
|
||
func (c *Certificate) VerifyHostname(h string) error {
|
||
// IP addresses may be written in [ ].
|
||
candidateIP := h
|
||
if len(h) >= 3 && h[0] == '[' && h[len(h)-1] == ']' {
|
||
candidateIP = h[1 : len(h)-1]
|
||
}
|
||
if ip := net.ParseIP(candidateIP); ip != nil {
|
||
// We only match IP addresses against IP SANs.
|
||
// https://tools.ietf.org/html/rfc6125#appendix-B.2
|
||
for _, candidate := range c.IPAddresses {
|
||
if ip.Equal(candidate) {
|
||
return nil
|
||
}
|
||
}
|
||
return HostnameError{c, candidateIP}
|
||
}
|
||
|
||
lowered := toLowerCaseASCII(h)
|
||
|
||
if c.hasSANExtension() {
|
||
for _, match := range c.DNSNames {
|
||
if matchHostnames(toLowerCaseASCII(match), lowered) {
|
||
return nil
|
||
}
|
||
}
|
||
// If Subject Alt Name is given, we ignore the common name.
|
||
} else if matchHostnames(toLowerCaseASCII(c.Subject.CommonName), lowered) {
|
||
return nil
|
||
}
|
||
|
||
return HostnameError{c, h}
|
||
}
|
||
|
||
func checkChainForKeyUsage(chain []*Certificate, keyUsages []ExtKeyUsage) bool {
|
||
usages := make([]ExtKeyUsage, len(keyUsages))
|
||
copy(usages, keyUsages)
|
||
|
||
if len(chain) == 0 {
|
||
return false
|
||
}
|
||
|
||
usagesRemaining := len(usages)
|
||
|
||
// We walk down the list and cross out any usages that aren't supported
|
||
// by each certificate. If we cross out all the usages, then the chain
|
||
// is unacceptable.
|
||
|
||
NextCert:
|
||
for i := len(chain) - 1; i >= 0; i-- {
|
||
cert := chain[i]
|
||
if len(cert.ExtKeyUsage) == 0 && len(cert.UnknownExtKeyUsage) == 0 {
|
||
// The certificate doesn't have any extended key usage specified.
|
||
continue
|
||
}
|
||
|
||
for _, usage := range cert.ExtKeyUsage {
|
||
if usage == ExtKeyUsageAny {
|
||
// The certificate is explicitly good for any usage.
|
||
continue NextCert
|
||
}
|
||
}
|
||
|
||
const invalidUsage ExtKeyUsage = -1
|
||
|
||
NextRequestedUsage:
|
||
for i, requestedUsage := range usages {
|
||
if requestedUsage == invalidUsage {
|
||
continue
|
||
}
|
||
|
||
for _, usage := range cert.ExtKeyUsage {
|
||
if requestedUsage == usage {
|
||
continue NextRequestedUsage
|
||
} else if requestedUsage == ExtKeyUsageServerAuth &&
|
||
(usage == ExtKeyUsageNetscapeServerGatedCrypto ||
|
||
usage == ExtKeyUsageMicrosoftServerGatedCrypto) {
|
||
// In order to support COMODO
|
||
// certificate chains, we have to
|
||
// accept Netscape or Microsoft SGC
|
||
// usages as equal to ServerAuth.
|
||
continue NextRequestedUsage
|
||
}
|
||
}
|
||
|
||
usages[i] = invalidUsage
|
||
usagesRemaining--
|
||
if usagesRemaining == 0 {
|
||
return false
|
||
}
|
||
}
|
||
}
|
||
|
||
return true
|
||
}
|