358 lines
10 KiB
Go
358 lines
10 KiB
Go
// Copyright (c) 2009 The Go Authors. All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following disclaimer
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// in the documentation and/or other materials provided with the
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// distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived from
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// this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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package constraints
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import (
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"bytes"
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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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"strings"
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)
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func checkNameConstraints(nameType string, name string, parsedName any, permitted, excluded any, match func(name, constraint any) (bool, error)) error {
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excludedValue := reflect.ValueOf(excluded)
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for i := 0; i < excludedValue.Len(); i++ {
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constraint := excludedValue.Index(i).Interface()
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match, err := match(parsedName, constraint)
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if err != nil {
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return err
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}
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if match {
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return fmt.Errorf("%s %q is excluded by constraint %q", nameType, name, constraint)
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}
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}
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var (
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err error
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ok = true
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)
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permittedValue := reflect.ValueOf(permitted)
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for i := 0; i < permittedValue.Len(); i++ {
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constraint := permittedValue.Index(i).Interface()
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if ok, err = match(parsedName, constraint); err != nil {
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return err
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}
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if ok {
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break
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}
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}
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if !ok {
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return fmt.Errorf("%s %q is not permitted by any constraint", nameType, name)
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}
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return nil
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}
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func matchDomainConstraint(domain, constraint string) (bool, error) {
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// The meaning of zero length constraints is not specified, but this
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// code follows NSS and accepts them as matching everything.
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if len(constraint) == 0 {
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return true, nil
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}
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domainLabels, ok := domainToReverseLabels(domain)
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if !ok {
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return false, fmt.Errorf("x509: internal error: cannot parse domain %q", domain)
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}
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// RFC 5280 says that a leading period in a domain name means that at
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// least one label must be prepended, but only for URI and email
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// constraints, not DNS constraints. The code also supports that
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// behaviour for DNS constraints.
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mustHaveSubdomains := false
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if constraint[0] == '.' {
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mustHaveSubdomains = true
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constraint = constraint[1:]
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}
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constraintLabels, ok := domainToReverseLabels(constraint)
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if !ok {
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return false, fmt.Errorf("x509: internal error: cannot parse domain %q", constraint)
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}
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if len(domainLabels) < len(constraintLabels) ||
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(mustHaveSubdomains && len(domainLabels) == len(constraintLabels)) {
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return false, nil
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}
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for i, constraintLabel := range constraintLabels {
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if !strings.EqualFold(constraintLabel, domainLabels[i]) {
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return false, nil
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}
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}
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return true, nil
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}
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func matchIPConstraint(ip net.IP, constraint *net.IPNet) (bool, error) {
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if len(ip) != len(constraint.IP) {
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return false, nil
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}
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for i := range ip {
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if mask := constraint.Mask[i]; ip[i]&mask != constraint.IP[i]&mask {
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return false, nil
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}
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}
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return true, nil
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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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}
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func matchURIConstraint(uri *url.URL, constraint string) (bool, error) {
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// From RFC 5280, 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
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// is specified as an IP address), then the application MUST reject the
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// certificate.”
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host := uri.Host
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if len(host) == 0 {
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return false, fmt.Errorf("URI with empty host (%q) cannot be matched against constraints", uri.String())
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}
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if strings.Contains(host, ":") && !strings.HasSuffix(host, "]") {
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var err error
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host, _, err = net.SplitHostPort(uri.Host)
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if err != nil {
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return false, err
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}
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}
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if strings.HasPrefix(host, "[") && strings.HasSuffix(host, "]") ||
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net.ParseIP(host) != nil {
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return false, fmt.Errorf("URI with IP (%q) cannot be matched against constraints", uri.String())
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}
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return matchDomainConstraint(host, constraint)
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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:])
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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.
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return nil, false
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}
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}
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}
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return reverseLabels, true
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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 RFC 5280,
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// Section 4.2.1.6 that's correct for an rfc822Name from a certificate: “The
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// format of an rfc822Name is a "Mailbox" as defined in RFC 2821, 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 RFC 2822,
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// Section 4. Since it has 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 RFC 2822, 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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// From RFC 3696, 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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