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,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  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 __BEGIN_DECLS
  40
  41
  42 void SecOCSPCacheAddResponse(SecOCSPResponseRef response,
  43     CFURLRef localResponderURI);
  44
  45 SecOCSPResponseRef SecOCSPCacheCopyMatching(SecOCSPRequestRef request,
  46     CFURLRef localResponderURI /* may be NULL */);
  47
  48 /* This should be called on a normal non emergency exit. */
  49 void SecOCSPCacheGC(void);
  50
  51 /* Call this periodically or perhaps when we are exiting due to low memory. */
  52 void SecOCSPCacheFlush(void);
  53
  54 __END_DECLS
  55
  56 #endif /* _SECURITY_SECOCSPCACHE_H_ */
  57
  58 #if 0
  59 /*
  60 Experation policy assumptions:
  61 - We never check revocation status of anchors, whether they be system anchors,
  62   passed in anchors or anchors hardcoded in a policy.
  63 - Revocation information is cached for positive reponses for a limited time.
  64 - Revocation information can be cached for negative reponses for an unlimited time.
  65 - 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).
  66 - Revocation information records that are used and still valid should be kept longer.
  67 - We can set an upper limit in number of records (or certificates) in the cache.
  68 - We can set an upper limit on total space consumed by the cache.
  69 Questions:
  70 - 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.
  71
  72 Data needed per type of revocation record to implement this policy.
  73
  74 Caching policy:
  75 - Deleting cache should not be user option.
  76 - Cache should surrvive backups.
  77 - Negative caching as long as possible.
  78
  79 CRL certificate stati:
  80 unspecified, keyCompromise, cACompromise,
  81 affiliationChanged, superseded, cessationOfOperation,
  82 certificateHold, removeFromCRL, privilegeWithdrawn,
  83 aACompromise, the special value UNREVOKED, or the special
  84 value UNDETERMINED.  This variable is initialized to the
  85 special value UNREVOKED.
  86
  87 CRL Timestamp values:
  88 - thisUpdate
  89 - nextUpdate (optional but not really 5280 says CAs must provide it even though ASN.1 is optional)
  90 (no producedAt in CRLs, that's what thisUpdate is by definition it seems).
  91
  92
  93 OCSP Timestamp values:
  94       thisUpdate = May 1, 2005  01:00:00 GMT
  95       nextUpdate = May 3, 2005 01:00:00 GMT (optional abscence means update available any time)
  96       productedAt = May 1, 2005 01:00:00 GMT
  97
  98 PER CERTIFICATE RETURN in INFO
  99
 100 Revocation object used: OCSP Response, mapping from
 101 reasons-> (CRL + most current delta CRL), Error Object (with status code).
 102    -- good
 103    -- revoked
 104    -- unknown
 105
 106 other exceptions (unsigned responses):
 107    -- malformedRequest
 108    -- internalError
 109    -- tryLater
 110    -- sigRequired
 111    -- unauthorized (5019 The response "unauthorized" is returned in cases where the client
 112       is not authorized to make this query to this server or the server
 113       is not capable of responding authoritatively.  (Expired certs might get this answer too))
 114
 115
 116 CRL signer chain rules:
 117 1) Must use same anchor as cert itself.
 118 This implies that we can only cache the validity of a leaf or intermediate certificate for CRL checking based on the mapping:
 119 (certificate, path anchor, use_deltas) -> Revocation_status (unspecified, keyCompromise, cACompromise,
 120 affiliationChanged, superseded, cessationOfOperation,certificateHold, removeFromCRL, privilegeWithdrawn,aACompromise, UNREVOKED, UNDETERMINED).
 121
 122 OCSP signer chain rules:
 123 (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)})
 124
 125 rfc text of the wikipedia: Therefore, a certificate's issuer MUST either sign the OCSP
 126    responses itself or it MUST explicitly designate this authority to
 127    another entity.  OCSP signing delegation SHALL be designated by the
 128    inclusion of id-kp-OCSPSigning in an extendedKeyUsage certificate
 129    extension included in the OCSP response signer's certificate.  This
 130    certificate MUST be issued directly by the CA that issued the
 131    certificate in question.
 132
 133 rfc: If ocsp signing cert has id-pkix-ocsp-nocheck extension we don't check it's revocation status.
 134
 135 (certificate, direct issuer certificate) -> Revocation_status good (UNREVOKED) revoked revocationTime, CRLReason (unspecified, keyCompromise, cACompromise,affiliationChanged, superseded, cessationOfOperation,certificateHold, removeFromCRL, privilegeWithdrawn,aACompromise) unknown (UNDETERMINED).
 136
 137 ocsp CertID ::= SEQUENCE {
 138        hashAlgorithm       AlgorithmIdentifier,
 139        issuerNameHash      OCTET STRING, -- Hash of Issuer's DN
 140        issuerKeyHash       OCTET STRING, -- Hash of Issuers public key
 141        serialNumber        CertificateSerialNumber }
 142 )
 143
 144 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.
 145
 146 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).
 147
 148 SELECT from ocsp_cache hashAlgorithm WHERE serialNumber = <SERIAL>
 149
 150 for hix = 0 hix < hashAlgorithms.count
 151   ALG(hix).id = hashAlgorithms(hix)
 152
 153 SELECT from ocsp_cache response WHERE serialNumber = <SERIAL> hashAlgorithm = ALG(hix).id issuerNameHash = ALG(hix).hash(issuer) issuerKeyHash = ALG(hix).hash(key)
 154
 155
 156
 157
 158
 159
 160 Notes for Matt:
 161 - ttl in amfi cache (to force recheck when ocsp response is invalid)?
 162 - Periodic check before launch to remove in band waiting for ocsp response?
 163
 164 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
 165
 166 Note on CRL checking and experation and retries of OCSP checking.
 167 Clients MAY attempt to retrieve the CRL if no
 168    OCSPResponse is received from the responder after a locally
 169    configured timeout and number of retries..
 170
 171
 172
 173 CRL/OCSP cache design idea:
 174
 175 revocation status table:
 176
 177 rowid certhash issuer-rowid lastUsed thisUpdate producedAt nextUpdate revocationTime revocationStatus
 178
 179 cacheAddOCSP(path, index_of_cert_resp_is_for, ocspResp)
 180 cacheAddCRLStatus(path, index_of_cert_in_path, nextUpdate, revocationTime, revocationStatus)
 181 (revocationTime, revocationStatus) = cacheLookupStatus(path, ix)
 182
 183 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.
 184
 185 CFArrayRef cacheSuggestParentsHashesFor(cert)
 186
 187 for crl based status root must match root of path.  For ocsp status issuer must match issuer of leaf in path
 188
 189 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.
 190
 191 If a chain isn't properly signed or fails to satisfy the crl policy, it should not be in the cache.
 192
 193 ocsp cache
 194
 195 rowid ocspResponse (responder) lastUsed nextUpdate
 196
 197 hashAlgorithm->(issuerNameHash,issuerKeyHash,serialNumber)->response
 198
 199
 200 crl cache ()
 201
 202 crlDistributionPoint (reasons) crl thisUpdate nextUpdate isDelta
 203
 204
 205 crlEntry cache table
 206 (certHash anchorHash) crlIssuer revocationStatus revocationTime expires lastUsed
 207 crlTable
 208 (crlIssuer anchorHash distributionPointURL?) crl sigVerified expires
 209 ocspEntry cache table
 210 (certHash parentHash ocspReponderID) hashAlg revocationStatus revocationTime expires lastUsed
 211 ocspTable
 212 ((hashAlg, pubKeyHash, issuerHash, serialNum) anchorHash) ocspResponse sigVerified expires
 213
 214 or
 215 cert cache table
 216 (certHash parentHash anchorHash) crlEntryID ocspID
 217
 218 crlEntry cache table
 219 (crlEntryID anchorHash) crlIssuer revocationStatus revocationTime
 220
 221 crlIssuerTable
 222 (crlIssuer anchorHash) crl sigVerified
 223
 224 ocsp table
 225 (ocspID) ocspResponse
 226
 227
 228 but so does caching the raw response as a link to a blob table containing crls
 229 and ocsp-responses
 230 But also cache the revocationStatus for a (cert,parent) or (cert,anchor) via
 231 a link to a cached ocspResponse or revocationStatus and revocationTime entry from crl
 232 */
 233
 234 #endif