OSX/sec/securityd/SecOCSPCache.h

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  74 affiliationChanged, superseded, cessationOfOperation,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