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| 1 | +// Copyright 2010 The Go Authors. All rights reserved. |
| 2 | +// Use of this source code is governed by a BSD-style |
| 3 | +// license that can be found in the LICENSE file. |
| 4 | + |
| 5 | +// This package parses OCSP responses as specified in RFC 2560. OCSP responses |
| 6 | +// are signed messages attesting to the validity of a certificate for a small |
| 7 | +// period of time. This is used to manage revocation for X.509 certificates. |
| 8 | +package ocsp |
| 9 | + |
| 10 | +import ( |
| 11 | + "asn1" |
| 12 | + "crypto/rsa" |
| 13 | + "crypto/sha1" |
| 14 | + "crypto/x509" |
| 15 | + "os" |
| 16 | + "time" |
| 17 | +) |
| 18 | + |
| 19 | +var idPKIXOCSPBasic = asn1.ObjectIdentifier([]int{1, 3, 6, 1, 5, 5, 7, 48, 1, 1}) |
| 20 | +var idSHA1WithRSA = asn1.ObjectIdentifier([]int{1, 2, 840, 113549, 1, 1, 5}) |
| 21 | + |
| 22 | +// These are internal structures that reflect the ASN.1 structure of an OCSP |
| 23 | +// response. See RFC 2560, section 4.2. |
| 24 | + |
| 25 | +const ( |
| 26 | + ocspSuccess = 0 |
| 27 | + ocspMalformed = 1 |
| 28 | + ocspInternalError = 2 |
| 29 | + ocspTryLater = 3 |
| 30 | + ocspSigRequired = 4 |
| 31 | + ocspUnauthorized = 5 |
| 32 | +) |
| 33 | + |
| 34 | +type rdnSequence []relativeDistinguishedNameSET |
| 35 | + |
| 36 | +type relativeDistinguishedNameSET []attributeTypeAndValue |
| 37 | + |
| 38 | +type attributeTypeAndValue struct { |
| 39 | + Type asn1.ObjectIdentifier |
| 40 | + Value interface{} |
| 41 | +} |
| 42 | + |
| 43 | +type algorithmIdentifier struct { |
| 44 | + Algorithm asn1.ObjectIdentifier |
| 45 | +} |
| 46 | + |
| 47 | +type certID struct { |
| 48 | + HashAlgorithm algorithmIdentifier |
| 49 | + NameHash []byte |
| 50 | + IssuerKeyHash []byte |
| 51 | + SerialNumber asn1.RawValue |
| 52 | +} |
| 53 | + |
| 54 | +type responseASN1 struct { |
| 55 | + Status asn1.Enumerated |
| 56 | + Response responseBytes "explicit,tag:0" |
| 57 | +} |
| 58 | + |
| 59 | +type responseBytes struct { |
| 60 | + ResponseType asn1.ObjectIdentifier |
| 61 | + Response []byte |
| 62 | +} |
| 63 | + |
| 64 | +type basicResponse struct { |
| 65 | + TBSResponseData responseData |
| 66 | + SignatureAlgorithm algorithmIdentifier |
| 67 | + Signature asn1.BitString |
| 68 | + Certificates []asn1.RawValue "explicit,tag:0,optional" |
| 69 | +} |
| 70 | + |
| 71 | +type responseData struct { |
| 72 | + Raw asn1.RawContent |
| 73 | + Version int "optional,default:1,explicit,tag:0" |
| 74 | + RequestorName rdnSequence "optional,explicit,tag:1" |
| 75 | + KeyHash []byte "optional,explicit,tag:2" |
| 76 | + ProducedAt *time.Time |
| 77 | + Responses []singleResponse |
| 78 | +} |
| 79 | + |
| 80 | +type singleResponse struct { |
| 81 | + CertID certID |
| 82 | + Good asn1.Flag "explicit,tag:0,optional" |
| 83 | + Revoked revokedInfo "explicit,tag:1,optional" |
| 84 | + Unknown asn1.Flag "explicit,tag:2,optional" |
| 85 | + ThisUpdate *time.Time |
| 86 | + NextUpdate *time.Time "explicit,tag:0,optional" |
| 87 | +} |
| 88 | + |
| 89 | +type revokedInfo struct { |
| 90 | + RevocationTime *time.Time |
| 91 | + Reason int "explicit,tag:0,optional" |
| 92 | +} |
| 93 | + |
| 94 | +// This is the exposed reflection of the internal OCSP structures. |
| 95 | + |
| 96 | +const ( |
| 97 | + // Good means that the certificate is valid. |
| 98 | + Good = iota |
| 99 | + // Revoked means that the certificate has been deliberately revoked. |
| 100 | + Revoked = iota |
| 101 | + // Unknown means that the OCSP responder doesn't know about the certificate. |
| 102 | + Unknown = iota |
| 103 | + // ServerFailed means that the OCSP responder failed to process the request. |
| 104 | + ServerFailed = iota |
| 105 | +) |
| 106 | + |
| 107 | +// Response represents an OCSP response. See RFC 2560. |
| 108 | +type Response struct { |
| 109 | + // Status is one of {Good, Revoked, Unknown, ServerFailed} |
| 110 | + Status int |
| 111 | + SerialNumber []byte |
| 112 | + ProducedAt, ThisUpdate, NextUpdate, RevokedAt *time.Time |
| 113 | + RevocationReason int |
| 114 | + Certificate *x509.Certificate |
| 115 | +} |
| 116 | + |
| 117 | +// ParseError results from an invalid OCSP response. |
| 118 | +type ParseError string |
| 119 | + |
| 120 | +func (p ParseError) String() string { |
| 121 | + return string(p) |
| 122 | +} |
| 123 | + |
| 124 | +// ParseResponse parses an OCSP response in DER form. It only supports |
| 125 | +// responses for a single certificate and only those using RSA signatures. |
| 126 | +// Non-RSA responses will result in an x509.UnsupportedAlgorithmError. |
| 127 | +// Signature errors or parse failures will result in a ParseError. |
| 128 | +func ParseResponse(bytes []byte) (*Response, os.Error) { |
| 129 | + var resp responseASN1 |
| 130 | + rest, err := asn1.Unmarshal(&resp, bytes) |
| 131 | + if err != nil { |
| 132 | + return nil, err |
| 133 | + } |
| 134 | + if len(rest) > 0 { |
| 135 | + return nil, ParseError("trailing data in OCSP response") |
| 136 | + } |
| 137 | + |
| 138 | + ret := new(Response) |
| 139 | + if resp.Status != ocspSuccess { |
| 140 | + ret.Status = ServerFailed |
| 141 | + return ret, nil |
| 142 | + } |
| 143 | + |
| 144 | + if !resp.Response.ResponseType.Equal(idPKIXOCSPBasic) { |
| 145 | + return nil, ParseError("bad OCSP response type") |
| 146 | + } |
| 147 | + |
| 148 | + var basicResp basicResponse |
| 149 | + rest, err = asn1.Unmarshal(&basicResp, resp.Response.Response) |
| 150 | + if err != nil { |
| 151 | + return nil, err |
| 152 | + } |
| 153 | + |
| 154 | + if len(basicResp.Certificates) != 1 { |
| 155 | + return nil, ParseError("OCSP response contains bad number of certificates") |
| 156 | + } |
| 157 | + |
| 158 | + if len(basicResp.TBSResponseData.Responses) != 1 { |
| 159 | + return nil, ParseError("OCSP response contains bad number of responses") |
| 160 | + } |
| 161 | + |
| 162 | + ret.Certificate, err = x509.ParseCertificate(basicResp.Certificates[0].FullBytes) |
| 163 | + if err != nil { |
| 164 | + return nil, err |
| 165 | + } |
| 166 | + |
| 167 | + if ret.Certificate.PublicKeyAlgorithm != x509.RSA || !basicResp.SignatureAlgorithm.Algorithm.Equal(idSHA1WithRSA) { |
| 168 | + return nil, x509.UnsupportedAlgorithmError{} |
| 169 | + } |
| 170 | + |
| 171 | + h := sha1.New() |
| 172 | + hashType := rsa.HashSHA1 |
| 173 | + |
| 174 | + pub := ret.Certificate.PublicKey.(*rsa.PublicKey) |
| 175 | + h.Write(basicResp.TBSResponseData.Raw) |
| 176 | + digest := h.Sum() |
| 177 | + signature := basicResp.Signature.RightAlign() |
| 178 | + |
| 179 | + if rsa.VerifyPKCS1v15(pub, hashType, digest, signature) != nil { |
| 180 | + return nil, ParseError("bad OCSP signature") |
| 181 | + } |
| 182 | + |
| 183 | + r := basicResp.TBSResponseData.Responses[0] |
| 184 | + |
| 185 | + ret.SerialNumber = r.CertID.SerialNumber.Bytes |
| 186 | + |
| 187 | + switch { |
| 188 | + case bool(r.Good): |
| 189 | + ret.Status = Good |
| 190 | + case bool(r.Unknown): |
| 191 | + ret.Status = Unknown |
| 192 | + default: |
| 193 | + ret.Status = Revoked |
| 194 | + ret.RevokedAt = r.Revoked.RevocationTime |
| 195 | + ret.RevocationReason = r.Revoked.Reason |
| 196 | + } |
| 197 | + |
| 198 | + ret.ProducedAt = basicResp.TBSResponseData.ProducedAt |
| 199 | + ret.ThisUpdate = r.ThisUpdate |
| 200 | + ret.NextUpdate = r.NextUpdate |
| 201 | + |
| 202 | + return ret, nil |
| 203 | +} |
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