Initial work on name constraints validation

Issue #1060
This commit is contained in:
Mariano Cano 2022-09-19 19:45:13 -07:00
parent fcb9d88223
commit 0263468424
3 changed files with 604 additions and 0 deletions

View File

@ -0,0 +1,106 @@
package constraints
import (
"crypto/x509"
"fmt"
"net"
"net/url"
)
var oidExtensionNameConstraints = []int{2, 5, 29, 30}
type ConstraintError struct {
Type string
Name string
}
func (e ConstraintError) Error() string {
return fmt.Sprintf("%s %q is not allowed", e.Type, e.Name)
}
type service struct {
hasNameConstraints bool
permittedDNSDomains []string
excludedDNSDomains []string
permittedIPRanges []*net.IPNet
excludedIPRanges []*net.IPNet
permittedEmailAddresses []string
excludedEmailAddresses []string
permittedURIDomains []string
excludedURIDomains []string
}
func New(chain ...*x509.Certificate) *service {
s := new(service)
for _, crt := range chain {
s.permittedDNSDomains = append(s.permittedDNSDomains, crt.PermittedDNSDomains...)
s.excludedDNSDomains = append(s.excludedDNSDomains, crt.ExcludedDNSDomains...)
s.permittedIPRanges = append(s.permittedIPRanges, crt.PermittedIPRanges...)
s.excludedIPRanges = append(s.excludedIPRanges, crt.ExcludedIPRanges...)
s.permittedEmailAddresses = append(s.permittedEmailAddresses, crt.PermittedEmailAddresses...)
s.excludedEmailAddresses = append(s.excludedEmailAddresses, crt.ExcludedEmailAddresses...)
s.permittedURIDomains = append(s.permittedURIDomains, crt.PermittedURIDomains...)
s.excludedURIDomains = append(s.excludedURIDomains, crt.ExcludedURIDomains...)
if !s.hasNameConstraints {
for _, ext := range crt.Extensions {
if ext.Id.Equal(oidExtensionNameConstraints) {
s.hasNameConstraints = true
break
}
}
}
}
return s
}
// Validates
func (s *service) Validate(dnsNames []string, ipAddresses []*net.IP, emailAddresses []string, uris []*url.URL) error {
if !s.hasNameConstraints {
return nil
}
for _, name := range dnsNames {
if err := checkNameConstraints("DNS name", name, name, s.permittedDNSDomains, s.excludedDNSDomains,
func(parsedName, constraint any) (bool, error) {
return matchDomainConstraint(parsedName.(string), constraint.(string))
},
); err != nil {
return err
}
}
for _, ip := range ipAddresses {
if err := checkNameConstraints("IP address", ip.String(), ip, s.permittedIPRanges, s.excludedIPRanges,
func(parsedName, constraint any) (bool, error) {
return matchIPConstraint(parsedName.(net.IP), constraint.(*net.IPNet))
}); err != nil {
return err
}
}
for _, email := range emailAddresses {
mailbox, ok := parseRFC2821Mailbox(email)
if !ok {
return fmt.Errorf("cannot parse rfc822Name %q", email)
}
if err := checkNameConstraints("Email address", email, mailbox, s.permittedEmailAddresses, s.excludedEmailAddresses,
func(parsedName, constraint any) (bool, error) {
return matchEmailConstraint(parsedName.(rfc2821Mailbox), constraint.(string))
},
); err != nil {
return err
}
}
for _, uri := range uris {
if err := checkNameConstraints("URI", uri.String(), uri, s.permittedURIDomains, s.excludedURIDomains,
func(parsedName, constraint any) (bool, error) {
return matchURIConstraint(parsedName.(*url.URL), constraint.(string))
}); err != nil {
return err
}
}
return nil
}

View File

@ -0,0 +1,140 @@
package constraints
import (
"crypto/x509"
"net"
"net/url"
"reflect"
"testing"
"go.step.sm/crypto/minica"
)
func TestNew(t *testing.T) {
ca1, err := minica.New()
if err != nil {
t.Fatal(err)
}
ca2, err := minica.New(
minica.WithIntermediateTemplate(`{
"subject": {{ toJson .Subject }},
"keyUsage": ["certSign", "crlSign"],
"basicConstraints": {
"isCA": true,
"maxPathLen": 0
},
"nameConstraints": {
"critical": true,
"permittedDNSDomains": ["internal.example.org"],
"excludedDNSDomains": ["internal.example.com"],
"permittedIPRanges": ["192.168.1.0/24", "192.168.2.1/32"],
"excludedIPRanges": ["192.168.3.0/24", "192.168.4.0/28"],
"permittedEmailAddresses": ["root@example.org", "example.org", ".acme.org"],
"excludedEmailAddresses": ["root@example.com", "example.com", ".acme.com"],
"permittedURIDomains": ["host.example.org", ".acme.org"],
"excludedURIDomains": ["host.example.com", ".acme.com"]
}
}`),
)
if err != nil {
t.Fatal(err)
}
type args struct {
chain []*x509.Certificate
}
tests := []struct {
name string
args args
want *service
}{
{"ok", args{[]*x509.Certificate{ca1.Intermediate, ca1.Root}}, &service{
hasNameConstraints: false,
}},
{"ok with constraints", args{[]*x509.Certificate{ca2.Intermediate, ca2.Root}}, &service{
hasNameConstraints: true,
permittedDNSDomains: []string{"internal.example.org"},
excludedDNSDomains: []string{"internal.example.com"},
permittedIPRanges: []*net.IPNet{
{IP: net.ParseIP("192.168.1.0").To4(), Mask: net.IPMask{255, 255, 255, 0}},
{IP: net.ParseIP("192.168.2.1").To4(), Mask: net.IPMask{255, 255, 255, 255}},
},
excludedIPRanges: []*net.IPNet{
{IP: net.ParseIP("192.168.3.0").To4(), Mask: net.IPMask{255, 255, 255, 0}},
{IP: net.ParseIP("192.168.4.0").To4(), Mask: net.IPMask{255, 255, 255, 240}},
},
permittedEmailAddresses: []string{"root@example.org", "example.org", ".acme.org"},
excludedEmailAddresses: []string{"root@example.com", "example.com", ".acme.com"},
permittedURIDomains: []string{"host.example.org", ".acme.org"},
excludedURIDomains: []string{"host.example.com", ".acme.com"},
}},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
if got := New(tt.args.chain...); !reflect.DeepEqual(got, tt.want) {
t.Errorf("New() = %v, want %v", got, tt.want)
}
})
}
}
func Test_service_Validate(t *testing.T) {
type fields struct {
hasNameConstraints bool
permittedDNSDomains []string
excludedDNSDomains []string
permittedIPRanges []*net.IPNet
excludedIPRanges []*net.IPNet
permittedEmailAddresses []string
excludedEmailAddresses []string
permittedURIDomains []string
excludedURIDomains []string
}
type args struct {
dnsNames []string
ipAddresses []*net.IP
emailAddresses []string
uris []*url.URL
}
tests := []struct {
name string
fields fields
args args
wantErr bool
}{
{"ok", fields{hasNameConstraints: false}, args{
dnsNames: []string{"example.com", "host.example.com"},
ipAddresses: []*net.IP{{192, 168, 1, 1}, {0x26, 0x00, 0x1f, 0x1c, 0x47, 0x1, 0x9d, 0x00, 0xc3, 0xa7, 0x66, 0x94, 0x87, 0x0f, 0x20, 0x72}},
emailAddresses: []string{"root@example.com"},
uris: []*url.URL{{Scheme: "https", Host: "example.com", Path: "/uuid/c6d1a755-0c12-431e-9136-b64cb3173ec7"}},
}, false},
// {"ok dns", fields{}, args{}, false},
// {"ok ip", fields{}, args{}, false},
// {"ok email", fields{}, args{}, false},
// {"ok uri", fields{}, args{}, false},
// {"fail dns", fields{}, args{}, true},
// {"fail ip", fields{}, args{}, true},
// {"fail email", fields{}, args{}, true},
// {"fail uri", fields{}, args{}, true},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
s := &service{
hasNameConstraints: tt.fields.hasNameConstraints,
permittedDNSDomains: tt.fields.permittedDNSDomains,
excludedDNSDomains: tt.fields.excludedDNSDomains,
permittedIPRanges: tt.fields.permittedIPRanges,
excludedIPRanges: tt.fields.excludedIPRanges,
permittedEmailAddresses: tt.fields.permittedEmailAddresses,
excludedEmailAddresses: tt.fields.excludedEmailAddresses,
permittedURIDomains: tt.fields.permittedURIDomains,
excludedURIDomains: tt.fields.excludedURIDomains,
}
if err := s.Validate(tt.args.dnsNames, tt.args.ipAddresses, tt.args.emailAddresses, tt.args.uris); (err != nil) != tt.wantErr {
t.Errorf("service.Validate() error = %v, wantErr %v", err, tt.wantErr)
}
})
}
}

View File

@ -0,0 +1,358 @@
// Copyright (c) 2009 The Go Authors. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
package constraints
import (
"bytes"
"fmt"
"net"
"net/url"
"reflect"
"strings"
)
func checkNameConstraints(nameType string, name string, parsedName any, permitted, excluded any, match func(name, constraint any) (bool, error)) error {
excludedValue := reflect.ValueOf(excluded)
for i := 0; i < excludedValue.Len(); i++ {
constraint := excludedValue.Index(i).Interface()
match, err := match(parsedName, constraint)
if err != nil {
return err
}
if match {
return fmt.Errorf("%s %q is excluded by constraint %q", nameType, name, constraint)
}
}
var (
err error
ok = true
)
permittedValue := reflect.ValueOf(permitted)
for i := 0; i < permittedValue.Len(); i++ {
constraint := permittedValue.Index(i).Interface()
if ok, err = match(parsedName, constraint); err != nil {
return err
}
if ok {
break
}
}
if !ok {
return fmt.Errorf("%s %q is not permitted by any constraint", nameType, name)
}
return 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
}
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 matchEmailConstraint(mailbox rfc2821Mailbox, constraint string) (bool, error) {
// If the constraint contains an @, then it specifies an exact mailbox
// name.
if strings.Contains(constraint, "@") {
constraintMailbox, ok := parseRFC2821Mailbox(constraint)
if !ok {
return false, fmt.Errorf("x509: internal error: cannot parse constraint %q", constraint)
}
return mailbox.local == constraintMailbox.local && strings.EqualFold(mailbox.domain, constraintMailbox.domain), nil
}
// Otherwise the constraint is like a DNS constraint of the domain part
// of the mailbox.
return matchDomainConstraint(mailbox.domain, constraint)
}
func matchURIConstraint(uri *url.URL, constraint string) (bool, error) {
// From RFC 5280, Section 4.2.1.10:
// “a uniformResourceIdentifier that does not include an authority
// component with a host name specified as a fully qualified domain
// name (e.g., if the URI either does not include an authority
// 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)
}
// domainToReverseLabels converts a textual domain name like foo.example.com to
// the list of labels in reverse order, e.g. ["com", "example", "foo"].
func domainToReverseLabels(domain string) (reverseLabels []string, ok bool) {
for len(domain) > 0 {
if i := strings.LastIndexByte(domain, '.'); i == -1 {
reverseLabels = append(reverseLabels, domain)
domain = ""
} else {
reverseLabels = append(reverseLabels, domain[i+1:])
domain = domain[:i]
}
}
if len(reverseLabels) > 0 && len(reverseLabels[0]) == 0 {
// An empty label at the end indicates an absolute value.
return nil, false
}
for _, label := range reverseLabels {
if len(label) == 0 {
// Empty labels are otherwise invalid.
return nil, false
}
for _, c := range label {
if c < 33 || c > 126 {
// Invalid character.
return nil, false
}
}
}
return reverseLabels, true
}
// rfc2821Mailbox represents a “mailbox” (which is an email address to most
// people) by breaking it into the “local” (i.e. before the '@') and “domain”
// parts.
type rfc2821Mailbox struct {
local, domain string
}
// parseRFC2821Mailbox parses an email address into local and domain parts,
// based on the ABNF for a “Mailbox” from RFC 2821. According to RFC 5280,
// Section 4.2.1.6 that's correct for an rfc822Name from a certificate: “The
// format of an rfc822Name is a "Mailbox" as defined in RFC 2821, Section 4.1.2”.
func parseRFC2821Mailbox(in string) (mailbox rfc2821Mailbox, ok bool) {
if len(in) == 0 {
return mailbox, false
}
localPartBytes := make([]byte, 0, len(in)/2)
if in[0] == '"' {
// Quoted-string = DQUOTE *qcontent DQUOTE
// non-whitespace-control = %d1-8 / %d11 / %d12 / %d14-31 / %d127
// qcontent = qtext / quoted-pair
// qtext = non-whitespace-control /
// %d33 / %d35-91 / %d93-126
// quoted-pair = ("\" text) / obs-qp
// text = %d1-9 / %d11 / %d12 / %d14-127 / obs-text
//
// (Names beginning with “obs-” are the obsolete syntax from RFC 2822,
// Section 4. Since it has been 16 years, we no longer accept that.)
in = in[1:]
QuotedString:
for {
if len(in) == 0 {
return mailbox, false
}
c := in[0]
in = in[1:]
switch {
case c == '"':
break QuotedString
case c == '\\':
// quoted-pair
if len(in) == 0 {
return mailbox, false
}
if in[0] == 11 ||
in[0] == 12 ||
(1 <= in[0] && in[0] <= 9) ||
(14 <= in[0] && in[0] <= 127) {
localPartBytes = append(localPartBytes, in[0])
in = in[1:]
} else {
return mailbox, false
}
case c == 11 ||
c == 12 ||
// Space (char 32) is not allowed based on the
// BNF, but RFC 3696 gives an example that
// assumes that it is. Several “verified”
// errata continue to argue about this point.
// We choose to accept it.
c == 32 ||
c == 33 ||
c == 127 ||
(1 <= c && c <= 8) ||
(14 <= c && c <= 31) ||
(35 <= c && c <= 91) ||
(93 <= c && c <= 126):
// qtext
localPartBytes = append(localPartBytes, c)
default:
return mailbox, false
}
}
} else {
// Atom ("." Atom)*
NextChar:
for len(in) > 0 {
// atext from RFC 2822, Section 3.2.4
c := in[0]
switch {
case c == '\\':
// Examples given in RFC 3696 suggest that
// escaped characters can appear outside of a
// quoted string. Several “verified” errata
// continue to argue the point. We choose to
// accept it.
in = in[1:]
if len(in) == 0 {
return mailbox, false
}
fallthrough
case ('0' <= c && c <= '9') ||
('a' <= c && c <= 'z') ||
('A' <= c && c <= 'Z') ||
c == '!' || c == '#' || c == '$' || c == '%' ||
c == '&' || c == '\'' || c == '*' || c == '+' ||
c == '-' || c == '/' || c == '=' || c == '?' ||
c == '^' || c == '_' || c == '`' || c == '{' ||
c == '|' || c == '}' || c == '~' || c == '.':
localPartBytes = append(localPartBytes, in[0])
in = in[1:]
default:
break NextChar
}
}
if len(localPartBytes) == 0 {
return mailbox, false
}
// From RFC 3696, Section 3:
// “period (".") may also appear, but may not be used to start
// or end the local part, nor may two or more consecutive
// periods appear.”
twoDots := []byte{'.', '.'}
if localPartBytes[0] == '.' ||
localPartBytes[len(localPartBytes)-1] == '.' ||
bytes.Contains(localPartBytes, twoDots) {
return mailbox, false
}
}
if len(in) == 0 || in[0] != '@' {
return mailbox, false
}
in = in[1:]
// The RFC species a format for domains, but that's known to be
// violated in practice so we accept that anything after an '@' is the
// domain part.
if _, ok := domainToReverseLabels(in); !ok {
return mailbox, false
}
mailbox.local = string(localPartBytes)
mailbox.domain = in
return mailbox, true
}