Implement auditor-server protocol (#182)

* Part of #151

protocol/auditlog.go

@@ -16,6 +16,16 @@ type directoryHistory struct {
 	snapshots map[uint64]*DirSTR
 }
 
+// A ConiksAuditLog maintains the histories
+// of all CONIKS directories known to a CONIKS auditor,
+// indexing the histories by the hash of a directory's initial
+// STR (specifically, the hash of the STR's signature).
+// Each history includes the directory's domain addr as a string, its
+// public signing key enabling the auditor to verify the corresponding
+// signed tree roots, and a list with all observed snapshots in
+// chronological order.
+type ConiksAuditLog map[[crypto.HashSizeByte]byte]*directoryHistory
+
 // caller validates that initSTR is for epoch 0.
 func newDirectoryHistory(addr string, signKey sign.PublicKey, initSTR *DirSTR) *directoryHistory {
 	a := NewAuditor(signKey, initSTR)
@@ -28,23 +38,22 @@ func newDirectoryHistory(addr string, signKey sign.PublicKey, initSTR *DirSTR) *
 	return h
 }
 
-// A ConiksAuditLog maintains the histories
-// of all CONIKS directories known to a CONIKS auditor,
-// indexing the histories by the hash of a directory's initial
-// STR (specifically, the hash of the STR's signature).
-// Each history includes the directory's domain addr as a string, its
-// public signing key enabling the auditor to verify the corresponding
-// signed tree roots, and a list with all observed snapshots in
-// chronological order.
-type ConiksAuditLog map[[crypto.HashSizeByte]byte]*directoryHistory
-
 // updateVerifiedSTR inserts the latest verified STR into a directory history;
 // assumes the STRs have been validated by the caller.
 func (h *directoryHistory) updateVerifiedSTR(newVerified *DirSTR) {
 	h.Update(newVerified)
 	h.snapshots[newVerified.Epoch] = newVerified
 }
 
+// insertRange inserts the given range of STRs snaps
+// into the directoryHistory h.
+// insertRange() assumes that snaps has been audited by Audit().
+func (h *directoryHistory) insertRange(snaps []*DirSTR) {
+	for i := 0; i < len(snaps); i++ {
+		h.updateVerifiedSTR(snaps[i])
+	}
+}
+
 // Audit checks that a directory's STR history
 // is linear and updates the auditor's state
 // if the checks pass.
@@ -53,10 +62,28 @@ func (h *directoryHistory) updateVerifiedSTR(newVerified *DirSTR) {
 // and then verifies the remaining STRs in msg, and
 // finally updates the snapshots if the checks pass.
 // Audit() is called when an auditor receives new STRs
-// from a directory.
+// from a specific directory.
 func (h *directoryHistory) Audit(msg *Response) error {
-	// TODO: Implement as part of the auditor-server protocol
-	return CheckPassed
+	if err := msg.validate(); err != nil {
+		return err
+	}
+
+	strs := msg.DirectoryResponse.(*STRHistoryRange)
+
+	// audit the STRs
+	// if strs.STR is somehow malformed or invalid (e.g. strs.STR
+	// contains old STRs), AuditDirectory() will detect this
+	// and throw and error
+	if err := h.AuditDirectory(strs.STR); err != CheckPassed {
+		return err
+	}
+
+	// TODO: we should be storing inconsistent STRs nonetheless
+	// so clients can detect inconsistencies -- or auditors
+	// should blow the whistle and not store the bad STRs
+	h.insertRange(strs.STR)
+
+	return nil
 }
 
 // NewAuditLog constructs a new ConiksAuditLog. It creates an empty
@@ -68,7 +95,8 @@ func NewAuditLog() ConiksAuditLog {
 
 // set associates the given directoryHistory with the directory identifier
 // (i.e. the hash of the initial STR) dirInitHash in the ConiksAuditLog.
-func (l ConiksAuditLog) set(dirInitHash [crypto.HashSizeByte]byte, dirHistory *directoryHistory) {
+func (l ConiksAuditLog) set(dirInitHash [crypto.HashSizeByte]byte,
+	dirHistory *directoryHistory) {
 	l[dirInitHash] = dirHistory
 }
 
@@ -81,24 +109,21 @@ func (l ConiksAuditLog) get(dirInitHash [crypto.HashSizeByte]byte) (*directoryHi
 	return h, ok
 }
 
-// Insert creates a new directory history for the key directory addr
+// InitHistory creates a new directory history for the key directory addr
 // and inserts it into the audit log l.
+// InitHistory() is called by an auditor when it initializes its state
+// from disk (either first-time startup, or after reboot).
 // The directory history is initialized with the key directory's
-// signing key signKey, and a list of snapshots snaps representing the
-// directory's STR history so far, in chronological order.
-// Insert() returns an ErrAuditLog if the auditor attempts to create
+// signing key signKey, and a list of one or more snapshots snaps
+// containing the pinned initial STR as well as the saved directory's
+// STR history so far, in chronological order.
+// InitHistory() returns an ErrAuditLog if the auditor attempts to create
 // a new history for a known directory, and nil otherwise.
-// Insert() only creates the initial entry in the log for addr. Use Update()
-// to insert newly observed STRs for addr in subsequent epochs.
-// Insert() assumes that the caller
-// has called Audit() on snaps before calling Insert().
-// FIXME: pass Response message as param
-// masomel: will probably want to write a more generic function
-// for "catching up" on a history in case an auditor misses epochs
-func (l ConiksAuditLog) Insert(addr string, signKey sign.PublicKey,
+func (l ConiksAuditLog) InitHistory(addr string, signKey sign.PublicKey,
 	snaps []*DirSTR) error {
 	// make sure we're getting an initial STR at the very least
 	if len(snaps) < 1 || snaps[0].Epoch != 0 {
+		// FIXME: This should be a more generic "malformed error"
 		return ErrMalformedDirectoryMessage
 	}
 
@@ -115,60 +140,17 @@ func (l ConiksAuditLog) Insert(addr string, signKey sign.PublicKey,
 	// create the new directory history
 	h = newDirectoryHistory(addr, signKey, snaps[0])
 
-	// FIXME: remove this check --> caller calls Audit() before
-	// this function
-	// add each STR into the history
-	// start at 1 since we've inserted the initial STR above
-	// This loop automatically catches if snaps is malformed
-	// (i.e. snaps is missing an epoch between 0 and the latest given)
-	for i := 1; i < len(snaps); i++ {
-		str := snaps[i]
-		if str == nil {
-			return ErrMalformedDirectoryMessage
-		}
-
-		// verify the consistency of each new STR before inserting
-		// into the audit log
-		if err := h.verifySTRConsistency(h.VerifiedSTR(), str); err != nil {
-			return err
-		}
-
-		h.updateVerifiedSTR(snaps[i])
-	}
-
+	// TODO: re-verify all snaps although auditor should have
+	// already done so in the past? After all, if we have
+	// more than one snapshot, this means that the auditor is
+	// re-initializing its state from disk, and it wouldn't have
+	// saved those STRs if they didn't pass the Audit() checks.
+	h.insertRange(snaps[1:])
 	l.set(dirInitHash, h)
 
 	return nil
 }
 
-// Update inserts a newly observed STR newSTR into the log entry for the
-// directory history given by dirInitHash (hash of direcotry's initial STR).
-// Update() assumes that Insert() has been called for
-// dirInitHash prior to its first call and thereby expects that an
-// entry for addr exists in the audit log l, and that the caller
-// has called Audit() on newSTR before calling Update().
-// Update() returns ErrAuditLog if the audit log doesn't contain an
-// entry for dirInitHash.
-// FIXME: pass Response message as param
-func (l ConiksAuditLog) Update(dirInitHash [crypto.HashSizeByte]byte, newSTR *DirSTR) error {
-	// error if we want to update the entry for an addr we don't know
-	h, ok := l.get(dirInitHash)
-	if !ok {
-		return ErrAuditLog
-	}
-
-	// FIXME: remove this check --> caller calls Audit() before this
-	// function
-	if err := h.verifySTRConsistency(h.VerifiedSTR(), newSTR); err != nil {
-		return err
-	}
-
-	// update the latest STR
-	// FIXME: use STR slice from Response msg
-	h.updateVerifiedSTR(newSTR)
-	return nil
-}
-
 // GetObservedSTRs gets a range of observed STRs for the CONIKS directory
 // address indicated in the AuditingRequest req received from a
 // CONIKS client, and returns a tuple of the form (response, error).

protocol/auditlog_test.go

@@ -17,10 +17,13 @@ func TestUpdateHistory(t *testing.T) {
 	// update the directory so we can update the audit log
 	dirInitHash := ComputeDirectoryIdentity(hist[0])
 	d.Update()
-	err := aud.Update(dirInitHash, d.LatestSTR())
+	h, _ := aud.get(dirInitHash)
+	resp, _ := NewSTRHistoryRange([]*DirSTR{d.LatestSTR()})
+
+	err := h.Audit(resp)
 
 	if err != nil {
-		t.Fatal("Error updating the server history")
+		t.Fatal("Error auditing and updating the server history")
 	}
 }
 
@@ -35,40 +38,49 @@ func TestInsertExistingHistory(t *testing.T) {
 
 	// let's make sure that we can't re-insert a new server
 	// history into our log
-	err := aud.Insert("test-server", nil, hist)
+	err := aud.InitHistory("test-server", nil, hist)
 	if err != ErrAuditLog {
 		t.Fatal("Expected an ErrAuditLog when inserting an existing server history")
 	}
 }
 
-func TestUpdateUnknownHistory(t *testing.T) {
+func TestAuditLogBadEpochRange(t *testing.T) {
 	// create basic test directory and audit log with 1 STR
-	d, aud, _ := NewTestAuditLog(t, 0)
+	d, aud, hist := NewTestAuditLog(t, 0)
 
-	// let's make sure that we can't update a history for an unknown
-	// directory in our log
-	var unknown [crypto.HashSizeByte]byte
-	err := aud.Update(unknown, d.LatestSTR())
-	if err != ErrAuditLog {
-		t.Fatal("Expected an ErrAuditLog when updating an unknown server history")
+	d.Update()
+
+	resp, err := d.GetSTRHistory(&STRHistoryRequest{
+		StartEpoch: uint64(0),
+		EndEpoch:   uint64(1)})
+
+	if err != ReqSuccess {
+		t.Fatalf("Error occurred while fetching STR history: %s", err.Error())
 	}
-}
 
-func TestUpdateBadNewSTR(t *testing.T) {
-	// create basic test directory and audit log with 11 STRs
-	d, aud, hist := NewTestAuditLog(t, 10)
+	strs := resp.DirectoryResponse.(*STRHistoryRange)
+	if len(strs.STR) != 2 {
+		t.Fatalf("Expect 2 STRs from directory, got %d", len(strs.STR))
+	}
+
+	if strs.STR[0].Epoch != 0 || strs.STR[1].Epoch != 1 {
+		t.Fatalf("Expect latest epoch of 1, got %d", strs.STR[1].Epoch)
+	}
 
 	// compute the hash of the initial STR for later lookups
 	dirInitHash := ComputeDirectoryIdentity(hist[0])
+	h, _ := aud.get(dirInitHash)
 
-	// update the directory a few more times and then try
-	// to update
-	d.Update()
-	d.Update()
+	err1 := h.Audit(resp)
+	if err1 != nil {
+		t.Fatalf("Error occurred while auditing STR history: %s", err1.Error())
+	}
 
-	err := aud.Update(dirInitHash, d.LatestSTR())
-	if err != CheckBadSTR {
-		t.Fatal("Expected a CheckBadSTR when attempting update a server history with a bad STR")
+	// now try to audit the same range again: should fail because the
+	// verified epoch is at 1
+	err1 = h.Audit(resp)
+	if err1 != CheckBadSTR {
+		t.Fatalf("Expecting CheckBadSTR, got %s", err1.Error())
 	}
 }
 
@@ -138,7 +150,7 @@ func TestGetObservedSTRMultipleEpochs(t *testing.T) {
 		EndEpoch:       d.LatestSTR().Epoch})
 
 	if err != ReqSuccess {
-		t.Fatal("Unable to get latest range of STRs")
+		t.Fatalf("Unable to get latest range of STRs, got %s", err.Error())
 	}
 
 	obs := res.DirectoryResponse.(*STRHistoryRange)
@@ -154,7 +166,10 @@ func TestGetObservedSTRMultipleEpochs(t *testing.T) {
 
 	// go to next epoch
 	d.Update()
-	err1 := aud.Update(dirInitHash, d.LatestSTR())
+	h, _ := aud.get(dirInitHash)
+	resp, _ := NewSTRHistoryRange([]*DirSTR{d.LatestSTR()})
+
+	err1 := h.Audit(resp)
 	if err1 != nil {
 		t.Fatal("Error occurred updating audit log after auditing request")
 	}

protocol/auditor.go

@@ -51,6 +51,7 @@ func (a *AudState) compareWithVerified(str *DirSTR) error {
 	if reflect.DeepEqual(a.verifiedSTR, str) {
 		return nil
 	}
+
 	return CheckBadSTR
 }
 
@@ -105,7 +106,7 @@ func (a *AudState) checkSTRAgainstVerified(str *DirSTR) error {
 		return CheckBadSTR
 	}
 
-	return nil
+	return CheckPassed
 }
 
 // verifySTRRange checks the consistency of a range
@@ -146,7 +147,7 @@ func (a *AudState) AuditDirectory(strs []*DirSTR) error {
 	}
 
 	// check STR against the latest verified STR
-	if err := a.checkSTRAgainstVerified(strs[0]); err != nil {
+	if err := a.checkSTRAgainstVerified(strs[0]); err != CheckPassed {
 		return err
 	}
 
@@ -157,7 +158,7 @@ func (a *AudState) AuditDirectory(strs []*DirSTR) error {
 		}
 	}
 
-	return nil
+	return CheckPassed
 }
 
 // ComputeDirectoryIdentity returns the hash of