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package constraints
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import (
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"crypto/x509"
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"fmt"
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"net"
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"net/http"
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"net/url"
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)
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var oidExtensionNameConstraints = []int{2, 5, 29, 30}
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// ConstraintError is the typed error that will be returned if a constraint
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// error is found.
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type ConstraintError struct {
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Type string
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Name string
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Detail string
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}
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// Error implements the error interface.
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func (e ConstraintError) Error() string {
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return e.Detail
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}
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// StatusCode implements an status coder interface.
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func (e ConstraintError) StatusCode() int {
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return http.StatusForbidden
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}
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// Engine implements a constraint validator for DNS names, IP addresses, Email
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// addresses and URIs.
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type Engine struct {
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hasNameConstraints bool
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permittedDNSDomains []string
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excludedDNSDomains []string
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permittedIPRanges []*net.IPNet
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excludedIPRanges []*net.IPNet
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permittedEmailAddresses []string
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excludedEmailAddresses []string
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permittedURIDomains []string
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excludedURIDomains []string
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}
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// New creates a constraint validation engine that contains the given chain of
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// certificates.
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func New(chain ...*x509.Certificate) *Engine {
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e := new(Engine)
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for _, crt := range chain {
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e.permittedDNSDomains = append(e.permittedDNSDomains, crt.PermittedDNSDomains...)
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e.excludedDNSDomains = append(e.excludedDNSDomains, crt.ExcludedDNSDomains...)
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e.permittedIPRanges = append(e.permittedIPRanges, crt.PermittedIPRanges...)
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e.excludedIPRanges = append(e.excludedIPRanges, crt.ExcludedIPRanges...)
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e.permittedEmailAddresses = append(e.permittedEmailAddresses, crt.PermittedEmailAddresses...)
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e.excludedEmailAddresses = append(e.excludedEmailAddresses, crt.ExcludedEmailAddresses...)
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e.permittedURIDomains = append(e.permittedURIDomains, crt.PermittedURIDomains...)
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e.excludedURIDomains = append(e.excludedURIDomains, crt.ExcludedURIDomains...)
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if !e.hasNameConstraints {
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for _, ext := range crt.Extensions {
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if ext.Id.Equal(oidExtensionNameConstraints) {
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e.hasNameConstraints = true
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break
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}
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}
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}
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}
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return e
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}
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// Validate checks the given names with the name constraints defined in the
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// service.
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func (e *Engine) Validate(dnsNames []string, ipAddresses []net.IP, emailAddresses []string, uris []*url.URL) error {
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if e == nil || !e.hasNameConstraints {
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return nil
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}
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for _, name := range dnsNames {
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if err := checkNameConstraints("DNS name", name, name, e.permittedDNSDomains, e.excludedDNSDomains,
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func(parsedName, constraint any) (bool, error) {
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return matchDomainConstraint(parsedName.(string), constraint.(string))
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},
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); err != nil {
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return err
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}
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}
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for _, ip := range ipAddresses {
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if err := checkNameConstraints("IP address", ip.String(), ip, e.permittedIPRanges, e.excludedIPRanges,
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func(parsedName, constraint any) (bool, error) {
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return matchIPConstraint(parsedName.(net.IP), constraint.(*net.IPNet))
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},
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); err != nil {
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return err
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}
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}
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for _, email := range emailAddresses {
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mailbox, ok := parseRFC2821Mailbox(email)
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if !ok {
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return fmt.Errorf("cannot parse rfc822Name %q", email)
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}
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if err := checkNameConstraints("Email address", email, mailbox, e.permittedEmailAddresses, e.excludedEmailAddresses,
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func(parsedName, constraint any) (bool, error) {
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return matchEmailConstraint(parsedName.(rfc2821Mailbox), constraint.(string))
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},
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); err != nil {
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return err
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}
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}
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for _, uri := range uris {
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if err := checkNameConstraints("URI", uri.String(), uri, e.permittedURIDomains, e.excludedURIDomains,
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func(parsedName, constraint any) (bool, error) {
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return matchURIConstraint(parsedName.(*url.URL), constraint.(string))
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},
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); err != nil {
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return err
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}
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}
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return nil
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}
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// ValidateCertificate validates the DNS names, IP addresses, Email address and
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// URIs present in the given certificate.
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func (e *Engine) ValidateCertificate(cert *x509.Certificate) error {
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return e.Validate(cert.DNSNames, cert.IPAddresses, cert.EmailAddresses, cert.URIs)
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}
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