192 lines
5.3 KiB
Go
192 lines
5.3 KiB
Go
// Copyright 2010 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 ocsp parses OCSP responses as specified in RFC 2560. OCSP responses
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// are signed messages attesting to the validity of a certificate for a small
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// period of time. This is used to manage revocation for X.509 certificates.
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package ocsp
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import (
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"crypto"
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"crypto/rsa"
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_ "crypto/sha1"
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"crypto/x509"
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"crypto/x509/pkix"
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"encoding/asn1"
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"time"
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)
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var idPKIXOCSPBasic = asn1.ObjectIdentifier([]int{1, 3, 6, 1, 5, 5, 7, 48, 1, 1})
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var idSHA1WithRSA = asn1.ObjectIdentifier([]int{1, 2, 840, 113549, 1, 1, 5})
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// These are internal structures that reflect the ASN.1 structure of an OCSP
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// response. See RFC 2560, section 4.2.
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const (
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ocspSuccess = 0
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ocspMalformed = 1
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ocspInternalError = 2
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ocspTryLater = 3
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ocspSigRequired = 4
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ocspUnauthorized = 5
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)
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type certID struct {
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HashAlgorithm pkix.AlgorithmIdentifier
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NameHash []byte
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IssuerKeyHash []byte
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SerialNumber asn1.RawValue
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}
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type responseASN1 struct {
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Status asn1.Enumerated
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Response responseBytes `asn1:"explicit,tag:0"`
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}
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type responseBytes struct {
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ResponseType asn1.ObjectIdentifier
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Response []byte
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}
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type basicResponse struct {
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TBSResponseData responseData
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SignatureAlgorithm pkix.AlgorithmIdentifier
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Signature asn1.BitString
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Certificates []asn1.RawValue `asn1:"explicit,tag:0,optional"`
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}
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type responseData struct {
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Raw asn1.RawContent
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Version int `asn1:"optional,default:1,explicit,tag:0"`
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RequestorName pkix.RDNSequence `asn1:"optional,explicit,tag:1"`
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KeyHash []byte `asn1:"optional,explicit,tag:2"`
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ProducedAt time.Time
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Responses []singleResponse
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}
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type singleResponse struct {
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CertID certID
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Good asn1.Flag `asn1:"explicit,tag:0,optional"`
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Revoked revokedInfo `asn1:"explicit,tag:1,optional"`
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Unknown asn1.Flag `asn1:"explicit,tag:2,optional"`
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ThisUpdate time.Time
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NextUpdate time.Time `asn1:"explicit,tag:0,optional"`
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}
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type revokedInfo struct {
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RevocationTime time.Time
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Reason int `asn1:"explicit,tag:0,optional"`
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}
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// This is the exposed reflection of the internal OCSP structures.
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const (
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// Good means that the certificate is valid.
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Good = iota
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// Revoked means that the certificate has been deliberately revoked.
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Revoked = iota
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// Unknown means that the OCSP responder doesn't know about the certificate.
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Unknown = iota
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// ServerFailed means that the OCSP responder failed to process the request.
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ServerFailed = iota
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)
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// Response represents an OCSP response. See RFC 2560.
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type Response struct {
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// Status is one of {Good, Revoked, Unknown, ServerFailed}
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Status int
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SerialNumber []byte
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ProducedAt, ThisUpdate, NextUpdate, RevokedAt time.Time
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RevocationReason int
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Certificate *x509.Certificate
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}
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// ParseError results from an invalid OCSP response.
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type ParseError string
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func (p ParseError) Error() string {
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return string(p)
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}
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// ParseResponse parses an OCSP response in DER form. It only supports
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// responses for a single certificate and only those using RSA signatures.
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// Non-RSA responses will result in an x509.UnsupportedAlgorithmError.
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// Signature errors or parse failures will result in a ParseError.
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func ParseResponse(bytes []byte) (*Response, error) {
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var resp responseASN1
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rest, err := asn1.Unmarshal(bytes, &resp)
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if err != nil {
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return nil, err
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}
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if len(rest) > 0 {
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return nil, ParseError("trailing data in OCSP response")
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}
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ret := new(Response)
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if resp.Status != ocspSuccess {
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ret.Status = ServerFailed
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return ret, nil
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}
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if !resp.Response.ResponseType.Equal(idPKIXOCSPBasic) {
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return nil, ParseError("bad OCSP response type")
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}
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var basicResp basicResponse
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rest, err = asn1.Unmarshal(resp.Response.Response, &basicResp)
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if err != nil {
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return nil, err
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}
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if len(basicResp.Certificates) != 1 {
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return nil, ParseError("OCSP response contains bad number of certificates")
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}
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if len(basicResp.TBSResponseData.Responses) != 1 {
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return nil, ParseError("OCSP response contains bad number of responses")
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}
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ret.Certificate, err = x509.ParseCertificate(basicResp.Certificates[0].FullBytes)
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if err != nil {
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return nil, err
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}
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if ret.Certificate.PublicKeyAlgorithm != x509.RSA || !basicResp.SignatureAlgorithm.Algorithm.Equal(idSHA1WithRSA) {
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return nil, x509.UnsupportedAlgorithmError{}
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}
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hashType := crypto.SHA1
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h := hashType.New()
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pub := ret.Certificate.PublicKey.(*rsa.PublicKey)
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h.Write(basicResp.TBSResponseData.Raw)
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digest := h.Sum(nil)
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signature := basicResp.Signature.RightAlign()
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if rsa.VerifyPKCS1v15(pub, hashType, digest, signature) != nil {
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return nil, ParseError("bad OCSP signature")
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}
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r := basicResp.TBSResponseData.Responses[0]
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ret.SerialNumber = r.CertID.SerialNumber.Bytes
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switch {
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case bool(r.Good):
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ret.Status = Good
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case bool(r.Unknown):
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ret.Status = Unknown
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default:
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ret.Status = Revoked
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ret.RevokedAt = r.Revoked.RevocationTime
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ret.RevocationReason = r.Revoked.Reason
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}
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ret.ProducedAt = basicResp.TBSResponseData.ProducedAt
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ret.ThisUpdate = r.ThisUpdate
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ret.NextUpdate = r.NextUpdate
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return ret, nil
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}
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