sec/securityd/SecOCSPCache.h

   1 /*
   2  * Copyright (c) 2009-2010 Apple Inc. All Rights Reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
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  18  * Please see the License for the specific language governing rights and
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  21  * @APPLE_LICENSE_HEADER_END@
  22  *
  23  * Created by Michael Brouwer on 1/15/09.
  24  */
  25
  26 /*!
  27     @header SecOCSPCache
  28     The functions provided in SecOCSPCache.h provide an interface to
  29     an OCSP caching module.
  30 */
  31
  32 #ifndef _SECURITY_SECOCSPCACHE_H_
  33 #define _SECURITY_SECOCSPCACHE_H_
  34
  35 #include <securityd/SecOCSPRequest.h>
  36 #include <securityd/SecOCSPResponse.h>
  37 #include <CoreFoundation/CFURL.h>
  38
  39 #if defined(__cplusplus)
  40 extern "C" {
  41 #endif
  42
  43
  44 void SecOCSPCacheAddResponse(SecOCSPResponseRef response,
  45     CFURLRef localResponderURI);
  46
  47 SecOCSPResponseRef SecOCSPCacheCopyMatching(SecOCSPRequestRef request,
  48     CFURLRef localResponderURI /* may be NULL */);
  49
  50 /* This should be called on a normal non emergency exit. */
  51 void SecOCSPCacheGC(void);
  52
  53 /* Call this periodically or perhaps when we are exiting due to low memory. */
  54 void SecOCSPCacheFlush(void);
  55
  56 #if defined(__cplusplus)
  57 }
  58 #endif
  59
  60 #endif /* _SECURITY_SECOCSPCACHE_H_ */
  61
  62 #if 0
  63 /*
  64 Experation policy assumptions:
  65 - We never check revocation status of anchors, whether they be system anchors,
  66   passed in anchors or anchors hardcoded in a policy.
  67 - Revocation information is cached for positive reponses for a limited time.
  68 - Revocation information can be cached for negative reponses for an unlimited time.
  69 - Revocation information need never be kept around after the certificate has expired (unless we still check after the cert has expired like we were talking about for EERI).
  70 - Revocation information records that are used and still valid should be kept longer.
  71 - We can set an upper limit in number of records (or certificates) in the cache.
  72 - We can set an upper limit on total space consumed by the cache.
  73 Questions:
  74 - Remember bad server responses too?  some ocsp responders required signed requests which we don't support, so we could consider caching the 6 (Not Authorized or something) response.
  75
  76 Data needed per type of revocation record to implement this policy.
  77
  78 Caching policy:
  79 - Deleting cache should not be user option.
  80 - Cache should surrvive backups.
  81 - Negative caching as long as possible.
  82
  83 CRL certificate stati:
  84 unspecified, keyCompromise, cACompromise,
  85 affiliationChanged, superseded, cessationOfOperation,
  86 certificateHold, removeFromCRL, privilegeWithdrawn,
  87 aACompromise, the special value UNREVOKED, or the special
  88 value UNDETERMINED.  This variable is initialized to the
  89 special value UNREVOKED.
  90
  91 CRL Timestamp values:
  92 - thisUpdate
  93 - nextUpdate (optional but not really 5280 says CAs must provide it even though ASN.1 is optional)
  94 (no producedAt in CRLs, that's what thisUpdate is by definition it seems).
  95
  96
  97 OCSP Timestamp values:
  98       thisUpdate = May 1, 2005  01:00:00 GMT
  99       nextUpdate = May 3, 2005 01:00:00 GMT (optional abscence means update available any time)
 100       productedAt = May 1, 2005 01:00:00 GMT
 101
 102 PER CERTIFICATE RETURN in INFO
 103
 104 Revocation object used: OCSP Response, mapping from
 105 reasons-> (CRL + most current delta CRL), Error Object (with status code).
 106    -- good
 107    -- revoked
 108    -- unknown
 109
 110 other exceptions (unsigned responses):
 111    -- malformedRequest
 112    -- internalError
 113    -- tryLater
 114    -- sigRequired
 115    -- unauthorized (5019 The response "unauthorized" is returned in cases where the client
 116       is not authorized to make this query to this server or the server
 117       is not capable of responding authoritatively.  (Expired certs might get this answer too))
 118
 119
 120 CRL signer chain rules:
 121 1) Must use same anchor as cert itself.
 122 This implies that we can only cache the validity of a leaf or intermediate certificate for CRL checking based on the mapping:
 123 (certificate, path anchor, use_deltas) -> Revocation_status (unspecified, keyCompromise, cACompromise,
 124 affiliationChanged, superseded, cessationOfOperation,certificateHold, removeFromCRL, privilegeWithdrawn,aACompromise, UNREVOKED, UNDETERMINED).
 125
 126 OCSP signer chain rules:
 127 (Wikipedia confirmed in rfc): The key that signs a response need not be the same key that signed the certificate. The certificate's issuer may delegate another authority to be the OCSP responder. In this case, the responder's certificate (the one that is used to sign the response) must be issued by the issuer of the certificate in question, and must include a certain extension that marks it as an OCSP signing authority (more precisely, an extended key usage extension with the OID {iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) keyPurpose(3) ocspSigning(9)})
 128
 129 rfc text of the wikipedia: Therefore, a certificate's issuer MUST either sign the OCSP
 130    responses itself or it MUST explicitly designate this authority to
 131    another entity.  OCSP signing delegation SHALL be designated by the
 132    inclusion of id-kp-OCSPSigning in an extendedKeyUsage certificate
 133    extension included in the OCSP response signer's certificate.  This
 134    certificate MUST be issued directly by the CA that issued the
 135    certificate in question.
 136
 137 rfc: If ocsp signing cert has id-pkix-ocsp-nocheck extension we don't check it's revocation status.
 138
 139 (certificate, direct issuer certificate) -> Revocation_status good (UNREVOKED) revoked revocationTime, CRLReason (unspecified, keyCompromise, cACompromise,affiliationChanged, superseded, cessationOfOperation,certificateHold, removeFromCRL, privilegeWithdrawn,aACompromise) unknown (UNDETERMINED).
 140
 141 ocsp CertID ::= SEQUENCE {
 142        hashAlgorithm       AlgorithmIdentifier,
 143        issuerNameHash      OCTET STRING, -- Hash of Issuer's DN
 144        issuerKeyHash       OCTET STRING, -- Hash of Issuers public key
 145        serialNumber        CertificateSerialNumber }
 146 )
 147
 148 In order to accomadate the responder using a different hashAlgorithm than we used in the request we need to recalc these from the cert itself.
 149
 150 If all we have is a list of ocspresponses without knowing where they came from, we have to calculate the hashes of our issuerName and issuerKey for each hashAlgorithm we have cached ocsp responses for (optionally after limiting our candidates to those with matching serialNumbers first).
 151
 152 SELECT from ocsp_cache hashAlgorithm WHERE serialNumber = <SERIAL>
 153
 154 for hix = 0 hix < hashAlgorithms.count
 155   ALG(hix).id = hashAlgorithms(hix)
 156
 157 SELECT from ocsp_cache response WHERE serialNumber = <SERIAL> hashAlgorithm = ALG(hix).id issuerNameHash = ALG(hix).hash(issuer) issuerKeyHash = ALG(hix).hash(key)
 158
 159
 160
 161
 162
 163
 164 Notes for Matt:
 165 - ttl in amfi cache (to force recheck when ocsp response is invalid)?
 166 - Periodic check before launch to remove in band waiting for ocsp response?
 167
 168 Notes on Nonces in ocsp request and responses.  Only ask for nonce if we think server supports it (no way to know today). Fall back on time based validity checking if reponse has no nonce, even if we asked for one
 169
 170 Note on CRL checking and experation and retries of OCSP checking.
 171 Clients MAY attempt to retrieve the CRL if no
 172    OCSPResponse is received from the responder after a locally
 173    configured timeout and number of retries..
 174
 175
 176
 177 CRL/OCSP cache design idea:
 178
 179 revocation status table:
 180
 181 rowid certhash issuer-rowid lastUsed thisUpdate producedAt nextUpdate revocationTime revocationStatus
 182
 183 cacheAddOCSP(path, index_of_cert_resp_is_for, ocspResp)
 184 cacheAddCRLStatus(path, index_of_cert_in_path, nextUpdate, revocationTime, revocationStatus)
 185 (revocationTime, revocationStatus) = cacheLookupStatus(path, ix)
 186
 187 Return a list of parent certificate hashes for the current leaf.  If a result is returned, we have a candiate path leading up to an anchor, for which we already trust the signature in the chain and revocation information has been checked.
 188
 189 CFArrayRef cacheSuggestParentsHashesFor(cert)
 190
 191 for crl based status root must match root of path.  For ocsp status issuer must match issuer of leaf in path
 192
 193 presence in the cache means cert chain leading to an anchor is valid, and signed properly and trusted by the ocsp or crl policy, revocation status for cert is valid until the time indicated by nextUpdate.  Cert chain itself may or may not be valid but that's checked by the policy engine.
 194
 195 If a chain isn't properly signed or fails to satisfy the crl policy, it should not be in the cache.
 196
 197 ocsp cache
 198
 199 rowid ocspResponse (responder) lastUsed nextUpdate
 200
 201 hashAlgorithm->(issuerNameHash,issuerKeyHash,serialNumber)->response
 202
 203
 204 crl cache ()
 205
 206 crlDistributionPoint (reasons) crl thisUpdate nextUpdate isDelta
 207
 208
 209 crlEntry cache table
 210 (certHash anchorHash) crlIssuer revocationStatus revocationTime expires lastUsed
 211 crlTable
 212 (crlIssuer anchorHash distributionPointURL?) crl sigVerified expires
 213 ocspEntry cache table
 214 (certHash parentHash ocspReponderID) hashAlg revocationStatus revocationTime expires lastUsed
 215 ocspTable
 216 ((hashAlg, pubKeyHash, issuerHash, serialNum) anchorHash) ocspResponse sigVerified expires
 217
 218 or
 219 cert cache table
 220 (certHash parentHash anchorHash) crlEntryID ocspID
 221
 222 crlEntry cache table
 223 (crlEntryID anchorHash) crlIssuer revocationStatus revocationTime
 224
 225 crlIssuerTable
 226 (crlIssuer anchorHash) crl sigVerified
 227
 228 ocsp table
 229 (ocspID) ocspResponse
 230
 231
 232 but so does caching the raw response as a link to a blob table containing crls
 233 and ocsp-responses
 234 But also cache the revocationStatus for a (cert,parent) or (cert,anchor) via
 235 a link to a cached ocspResponse or revocationStatus and revocationTime entry from crl
 236 */
 237
 238 #endif