OSX/libsecurity_cdsa_utilities/lib/acl_threshold.h

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  23
  24
  25 //
  26 // acl_threshold - Threshold-based group ACL subjects.
  27 //
  28 // This subject type implements threshold (k of n) subjects as per CSSM standard.
  29 // Subsubjects are stored and evaluated in the order received. Any subsubject
  30 // is presented with all subsamples of the corresponding threshold sample, but
  31 // not any other samples possibly present in the credentials. Subsubject evaluation
  32 // stops as soon as the threshold is satisfied, or as soon as it becomes numerically
  33 // impossible to satisfy the threshold with future matches.
  34 // Note that this subject will reject out of hand any threshold sample that
  35 // contains more than <n> subsamples. This defeats "sample stuffing" attacks
  36 // where the attacker provides thousands of samples in the hope that some may
  37 // match by accident. It will however accept threshold samples with fewer than
  38 // <n> subsamples, as long as there are at least <k> subsamples.
  39 //
  40 #ifndef _ACL_THRESHOLD
  41 #define _ACL_THRESHOLD
  42
  43 #include <security_cdsa_utilities/cssmacl.h>
  44 #include <vector>
  45
  46
  47 namespace Security {
  48
  49 class ThresholdAclSubject : public SimpleAclSubject {
  50     typedef ObjectAcl::AclSubjectPointer AclSubjectPointer;
  51     typedef vector<AclSubjectPointer> AclSubjectVector;
  52 public:
  53     bool validate(const AclValidationContext &baseCtx, const TypedList &sample) const;
  54     CssmList toList(Allocator &alloc) const;
  55
  56     ThresholdAclSubject(uint32 n, uint32 k, const AclSubjectVector &subSubjects);
  57
  58     void exportBlob(Writer::Counter &pub, Writer::Counter &priv);
  59     void exportBlob(Writer &pub, Writer &priv);
  60
  61         unsigned count() const { return totalSubjects; }
  62         AclSubject *subject(unsigned n) const { return elements[n]; }
  63         void add(AclSubject *subject, unsigned beforePosition);
  64
  65         IFDUMP(void debugDump() const);
  66
  67     class Maker : public AclSubject::Maker {
  68     public:
  69         Maker() : AclSubject::Maker(CSSM_ACL_SUBJECT_TYPE_THRESHOLD) { }
  70         ThresholdAclSubject *make(const TypedList &list) const;
  71         ThresholdAclSubject *make(Version, Reader &pub, Reader &priv) const;
  72     };
  73
  74 private:
  75     uint32 minimumNeeded;                               // number of matches needed
  76     uint32 totalSubjects;                               // number of subSubjects
  77     AclSubjectVector elements;                  // sub-subject vector
  78
  79     template <class Action>
  80     void exportBlobForm(Action &pub, Action &priv);
  81 };
  82
  83 } // namespace Security
  84
  85
  86 #endif //_ACL_THRESHOLD