OSX/sec/securityd/SecOCSPCache.h

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  77 affiliationChanged, superseded, cessationOfOperation,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