Security/sec/securityd/SecOCSPCache.h

   1 /*
   2  * Copyright (c) 2009-2010,2012-2014 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  */
  24
  25 /*!
  26     @header SecOCSPCache
  27     The functions provided in SecOCSPCache.h provide an interface to
  28     an OCSP caching module.
  29 */
  30
  31 #ifndef _SECURITY_SECOCSPCACHE_H_
  32 #define _SECURITY_SECOCSPCACHE_H_
  33
  34 #include <securityd/SecOCSPRequest.h>
  35 #include <securityd/SecOCSPResponse.h>
  36 #include <CoreFoundation/CFURL.h>
  37
  38 __BEGIN_DECLS
  39
  40
  41 void SecOCSPCacheAddResponse(SecOCSPResponseRef response,
  42     CFURLRef localResponderURI);
  43
  44 SecOCSPResponseRef SecOCSPCacheCopyMatching(SecOCSPRequestRef request,
  45     CFURLRef localResponderURI /* may be NULL */);
  46
  47 /* This should be called on a normal non emergency exit. */
  48 void SecOCSPCacheGC(void);
  49
  50 /* Call this periodically or perhaps when we are exiting due to low memory. */
  51 void SecOCSPCacheFlush(void);
  52
  53 __END_DECLS
  54
  55 #endif /* _SECURITY_SECOCSPCACHE_H_ */
  56
  57 #if 0
  58 /*
  59 Experation policy assumptions:
  60 - We never check revocation status of anchors, whether they be system anchors,
  61   passed in anchors or anchors hardcoded in a policy.
  62 - Revocation information is cached for positive reponses for a limited time.
  63 - Revocation information can be cached for negative reponses for an unlimited time.
  64 - 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).
  65 - Revocation information records that are used and still valid should be kept longer.
  66 - We can set an upper limit in number of records (or certificates) in the cache.
  67 - We can set an upper limit on total space consumed by the cache.
  68 Questions:
  69 - 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.
  70
  71 Data needed per type of revocation record to implement this policy.
  72
  73 Caching policy:
  74 - Deleting cache should not be user option.
  75 - Cache should surrvive backups.
  76 - Negative caching as long as possible.
  77
  78 CRL certificate stati:
  79 unspecified, keyCompromise, cACompromise,
  80 affiliationChanged, superseded, cessationOfOperation,
  81 certificateHold, removeFromCRL, privilegeWithdrawn,
  82 aACompromise, the special value UNREVOKED, or the special
  83 value UNDETERMINED.  This variable is initialized to the
  84 special value UNREVOKED.
  85
  86 CRL Timestamp values:
  87 - thisUpdate
  88 - nextUpdate (optional but not really 5280 says CAs must provide it even though ASN.1 is optional)
  89 (no producedAt in CRLs, that's what thisUpdate is by definition it seems).
  90
  91
  92 OCSP Timestamp values:
  93       thisUpdate = May 1, 2005  01:00:00 GMT
  94       nextUpdate = May 3, 2005 01:00:00 GMT (optional abscence means update available any time)
  95       productedAt = May 1, 2005 01:00:00 GMT
  96
  97 PER CERTIFICATE RETURN in INFO
  98
  99 Revocation object used: OCSP Response, mapping from
 100 reasons-> (CRL + most current delta CRL), Error Object (with status code).
 101    -- good
 102    -- revoked
 103    -- unknown
 104
 105 other exceptions (unsigned responses):
 106    -- malformedRequest
 107    -- internalError
 108    -- tryLater
 109    -- sigRequired
 110    -- unauthorized (5019 The response "unauthorized" is returned in cases where the client
 111       is not authorized to make this query to this server or the server
 112       is not capable of responding authoritatively.  (Expired certs might get this answer too))
 113
 114
 115 CRL signer chain rules:
 116 1) Must use same anchor as cert itself.
 117 This implies that we can only cache the validity of a leaf or intermediate certificate for CRL checking based on the mapping:
 118 (certificate, path anchor, use_deltas) -> Revocation_status (unspecified, keyCompromise, cACompromise,
 119 affiliationChanged, superseded, cessationOfOperation,certificateHold, removeFromCRL, privilegeWithdrawn,aACompromise, UNREVOKED, UNDETERMINED).
 120
 121 OCSP signer chain rules:
 122 (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)})
 123
 124 rfc text of the wikipedia: Therefore, a certificate's issuer MUST either sign the OCSP
 125    responses itself or it MUST explicitly designate this authority to
 126    another entity.  OCSP signing delegation SHALL be designated by the
 127    inclusion of id-kp-OCSPSigning in an extendedKeyUsage certificate
 128    extension included in the OCSP response signer's certificate.  This
 129    certificate MUST be issued directly by the CA that issued the
 130    certificate in question.
 131
 132 rfc: If ocsp signing cert has id-pkix-ocsp-nocheck extension we don't check it's revocation status.
 133
 134 (certificate, direct issuer certificate) -> Revocation_status good (UNREVOKED) revoked revocationTime, CRLReason (unspecified, keyCompromise, cACompromise,affiliationChanged, superseded, cessationOfOperation,certificateHold, removeFromCRL, privilegeWithdrawn,aACompromise) unknown (UNDETERMINED).
 135
 136 ocsp CertID ::= SEQUENCE {
 137        hashAlgorithm       AlgorithmIdentifier,
 138        issuerNameHash      OCTET STRING, -- Hash of Issuer's DN
 139        issuerKeyHash       OCTET STRING, -- Hash of Issuers public key
 140        serialNumber        CertificateSerialNumber }
 141 )
 142
 143 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.
 144
 145 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).
 146
 147 SELECT from ocsp_cache hashAlgorithm WHERE serialNumber = <SERIAL>
 148
 149 for hix = 0 hix < hashAlgorithms.count
 150   ALG(hix).id = hashAlgorithms(hix)
 151
 152 SELECT from ocsp_cache response WHERE serialNumber = <SERIAL> hashAlgorithm = ALG(hix).id issuerNameHash = ALG(hix).hash(issuer) issuerKeyHash = ALG(hix).hash(key)
 153
 154
 155
 156
 157
 158
 159 Notes for Matt:
 160 - ttl in amfi cache (to force recheck when ocsp response is invalid)?
 161 - Periodic check before launch to remove in band waiting for ocsp response?
 162
 163 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
 164
 165 Note on CRL checking and experation and retries of OCSP checking.
 166 Clients MAY attempt to retrieve the CRL if no
 167    OCSPResponse is received from the responder after a locally
 168    configured timeout and number of retries..
 169
 170
 171
 172 CRL/OCSP cache design idea:
 173
 174 revocation status table:
 175
 176 rowid certhash issuer-rowid lastUsed thisUpdate producedAt nextUpdate revocationTime revocationStatus
 177
 178 cacheAddOCSP(path, index_of_cert_resp_is_for, ocspResp)
 179 cacheAddCRLStatus(path, index_of_cert_in_path, nextUpdate, revocationTime, revocationStatus)
 180 (revocationTime, revocationStatus) = cacheLookupStatus(path, ix)
 181
 182 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.
 183
 184 CFArrayRef cacheSuggestParentsHashesFor(cert)
 185
 186 for crl based status root must match root of path.  For ocsp status issuer must match issuer of leaf in path
 187
 188 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.
 189
 190 If a chain isn't properly signed or fails to satisfy the crl policy, it should not be in the cache.
 191
 192 ocsp cache
 193
 194 rowid ocspResponse (responder) lastUsed nextUpdate
 195
 196 hashAlgorithm->(issuerNameHash,issuerKeyHash,serialNumber)->response
 197
 198
 199 crl cache ()
 200
 201 crlDistributionPoint (reasons) crl thisUpdate nextUpdate isDelta
 202
 203
 204 crlEntry cache table
 205 (certHash anchorHash) crlIssuer revocationStatus revocationTime expires lastUsed
 206 crlTable
 207 (crlIssuer anchorHash distributionPointURL?) crl sigVerified expires
 208 ocspEntry cache table
 209 (certHash parentHash ocspReponderID) hashAlg revocationStatus revocationTime expires lastUsed
 210 ocspTable
 211 ((hashAlg, pubKeyHash, issuerHash, serialNum) anchorHash) ocspResponse sigVerified expires
 212
 213 or
 214 cert cache table
 215 (certHash parentHash anchorHash) crlEntryID ocspID
 216
 217 crlEntry cache table
 218 (crlEntryID anchorHash) crlIssuer revocationStatus revocationTime
 219
 220 crlIssuerTable
 221 (crlIssuer anchorHash) crl sigVerified
 222
 223 ocsp table
 224 (ocspID) ocspResponse
 225
 226
 227 but so does caching the raw response as a link to a blob table containing crls
 228 and ocsp-responses
 229 But also cache the revocationStatus for a (cert,parent) or (cert,anchor) via
 230 a link to a cached ocspResponse or revocationStatus and revocationTime entry from crl
 231 */
 232
 233 #endif