a1766bf · skrepka · git.iko.soy

git.iko.soy/skrepka

Fix SSRF bypass, safeCompare timing, challenge cap, retry backoff, and empty server name

- Block non-standard IP representations (octal, hex prefix, decimal integer) in isBadServerName to prevent SSRF bypass - Add empty string check to isBadServerName as defense-in-depth - Make safeCompareLoop iterate max(len(s1), len(s2)) to prevent timing side-channel on secret length - Add global challenge list cap (maxChallenges=10000) with LRU eviction to prevent memory exhaustion from distinct-pubkey flooding - Add sleep backoff (1s, 2s) between federation retry attempts

commita1766bfc6c39f67c4dfb8e0b0f741f55196a9cf4 authoriko <mail@iko.soy> dateMon 30 Mar 2026, 06:13 (7 months ago) parent3d65e98

1 file changed+73−13

compare with master

unifiedsplit

server.knot+73−13

server.knot+73−13

@@ -22,6 +22,10 @@ maxPresenceEntries = 10000

2222maxMessagesPerRecipient = 500

2323clockSkewTolerance = 5000 -- 5 seconds tolerance for clock skew between federated servers

2424maxForwardsEntries = 10000

25+maxServerNameLen = 128

26+maxMessageIdLen = 128

27+maxTokenLen = 256

28+maxChallenges = 10000

2529

2630-- ============================================

2731-- Types

@@ -174,8 +178,43 @@ containsDoubleColon = \s ->

174178 else if take 1 s == ":" && take 1 (drop 1 s) == ":" then True {}

175179 else containsDoubleColon (drop 1 s)

176180

181+containsColon = \s ->

182+ if s == "" then False {}

183+ else if take 1 s == ":" then True {}

184+ else containsColon (drop 1 s)

185+

186+containsMultipleColons = \s ->

187+ if s == "" then False {}

188+ else if take 1 s == ":" then containsColon (drop 1 s)

189+ else containsMultipleColons (drop 1 s)

190+

191+hasOctalOctet = \s ->

192+ if take 1 s == "0" && isDigitChar (take 1 (drop 1 s)) then True {}

193+ else hasOctalOctetAfterDot s

194+

195+hasOctalOctetAfterDot = \s ->

196+ if s == "" then False {}

197+ else if take 1 s == "." && take 1 (drop 1 s) == "0" && isDigitChar (take 1 (drop 2 s)) then True {}

198+ else hasOctalOctetAfterDot (drop 1 s)

199+

200+hasHexPrefix = \s ->

201+ if take 2 s == "0x" || take 2 s == "0X" then True {}

202+ else hasHexPrefixAfterDot s

203+

204+hasHexPrefixAfterDot = \s ->

205+ if s == "" then False {}

206+ else if take 1 s == "." && (take 2 (drop 1 s) == "0x" || take 2 (drop 1 s) == "0X") then True {}

207+ else hasHexPrefixAfterDot (drop 1 s)

208+

209+isAllDigitsUntilColonOrEnd = \s ->

210+ if s == "" then True {}

211+ else if take 1 s == ":" then True {}

212+ else if isDigitChar (take 1 s) then isAllDigitsUntilColonOrEnd (drop 1 s)

213+ else False {}

214+

177215isBadServerName = \s ->

178− containsBadUrlChar s

216+ s == ""

217+ || containsBadUrlChar s

179218 || s == "localhost" || take 10 s == "localhost:"

180219 || take 4 s == "127." || take 3 s == "10."

181220 || take 8 s == "192.168." || take 7 s == "169.254."

@@ -187,7 +226,10 @@ isBadServerName = \s ->

187226 || take 7 s == "198.18." || take 7 s == "198.19."

188227 || take 2 s == "::"

189228 || isCgnatRange s

190− || containsDoubleColon s

229+ || containsMultipleColons s

230+ || hasOctalOctet s

231+ || hasHexPrefix s

232+ || (isDigitChar (take 1 s) && isAllDigitsUntilColonOrEnd s)

191233

192234lookupSession = \sessions token t ->

193235 single (do

@@ -204,6 +246,7 @@ extractToken = \authHeader ->

204246 && (take 1 (drop 4 authHeader) == "e" || take 1 (drop 4 authHeader) == "E")

205247 && (take 1 (drop 5 authHeader) == "r" || take 1 (drop 5 authHeader) == "R")

206248 && take 1 (drop 6 authHeader) == " "

249+ && not (tooLong (drop 7 authHeader) maxTokenLen)

207250 then drop 7 authHeader

208251 else ""

209252

@@ -234,8 +277,10 @@ sendToEach = \servers action ->

234277 else do

235278 catch (action server) (\err -> do

236279 println ("federation: error reaching " ++ server ++ ", retrying (1/2): " ++ show err)

280+ sleep 1000

237281 catch (action server) (\err2 -> do

238282 println ("federation: retry 1 failed for " ++ server ++ ", retrying (2/2): " ++ show err2)

283+ sleep 2000

239284 catch (action server) (\err3 -> do

240285 println ("federation: all retries exhausted for " ++ server ++ ": " ++ show err3)

241286 yield {})))

@@ -336,8 +381,17 @@ serve = \req -> case req of

336381 then {removed: True {}, items: acc.items}

337382 else {removed: acc.removed, items: union acc.items [c]}) {removed: False {}, items: []} challenges

338383 else {removed: False {}, items: challenges}

384+ let globalOldestExpiry = if count cappedChallenges.items >= maxChallenges

385+ then fold (\acc c -> if acc == -1 || c.expiresAt < acc then c.expiresAt else acc) -1 cappedChallenges.items

386+ else -1

387+ let globalCapped = if globalOldestExpiry >= 0

388+ then (fold (\acc c ->

389+ if not acc.removed && c.expiresAt == globalOldestExpiry

390+ then {removed: True {}, items: acc.items}

391+ else {removed: acc.removed, items: union acc.items [c]}) {removed: False {}, items: []} cappedChallenges.items).items

392+ else cappedChallenges.items

339393 set *challenges = union

340− cappedChallenges.items

394+ globalCapped

341395 [{pubkey: pubkey, challenge: challenge, expiresAt: t + 60000}]

342396 yield pr

343397 respond {challenge: challenge}

@@ -546,7 +600,7 @@ serve = \req -> case req of

546600 let dedupedIds = fold (\acc mid ->

547601 if mid == "" then acc

548602 else if count acc >= maxMessageIds then acc

549− else if tooLong mid maxPubkeyLen then acc

603+ else if tooLong mid maxMessageIdLen then acc

550604 else if not (isValidHex mid) then acc

551605 else if count (do a <- acc; where a == normalizeHex mid; yield a) > 0 then acc

552606 else union acc [normalizeHex mid]) [] messageIds

@@ -566,10 +620,15 @@ serve = \req -> case req of

566620 set *messages = case session of

567621 Nothing {} -> messages

568622 Just {value: _} -> diff messages ackedMessages

623+ presence <- *presence

624+ let knownPeers = fold (\acc p ->

625+ if p.server == serverHost then acc

626+ else if count (do a <- acc; where a == p.server; yield a) > 0 then acc

627+ else union acc [p.server]) [] presence

569628 let ok = case session of

570629 Nothing {} -> False {}

571630 _ -> True {}

572− yield {ok: ok, ackedMessages: ackedMessages, expiredLocal: pr.expiredLocal, peerServers: pr.peerServers}

631+ yield {ok: ok, ackedMessages: ackedMessages, expiredLocal: pr.expiredLocal, peerServers: pr.peerServers, knownPeers: knownPeers}

573632 let fedMessages = do

574633 m <- result.ackedMessages

575634 where not (m.originServer == "")

@@ -577,6 +636,7 @@ serve = \req -> case req of

577636 yield m

578637 let originServers = fold (\acc m ->

579638 if count (do a <- acc; where a == m.originServer; yield a) > 0 then acc

639+ else if count (do k <- result.knownPeers; where k == m.originServer; yield k) == 0 then acc

580640 else union acc [m.originServer]) [] fedMessages

581641 respond {ok: result.ok}

582642 if result.ok && count originServers > 0 && not (federationSecret == "")

@@ -624,7 +684,7 @@ serve = \req -> case req of

624684 t <- now

625685 let authorized = verifyFederationAuth authorization

626686 let cappedHops = if hopsRemaining > 5 then 5 else hopsRemaining

627− let validRequest = authorized && cappedHops >= 1 && not (fromServer == "") && not (fromServer == serverHost) && not (tooLong fromServer maxPubkeyLen) && not (isBadServerName fromServer) && count events <= maxGossipEvents

687+ let validRequest = authorized && cappedHops >= 1 && not (fromServer == "") && not (fromServer == serverHost) && not (tooLong fromServer maxServerNameLen) && not (isBadServerName fromServer) && count events <= maxGossipEvents

628688 let onlineEntries = do

629689 e <- events

630690 where validRequest

@@ -632,7 +692,7 @@ serve = \req -> case req of

632692 where not (e.server == "")

633693 where not (e.pubkey == "")

634694 where not (tooLong e.pubkey maxPubkeyLen)

635− where not (tooLong e.server maxPubkeyLen)

695+ where not (tooLong e.server maxServerNameLen)

636696 where not (isBadServerName e.server)

637697 where isValidHex e.pubkey

638698 where not (e.server == serverHost)

@@ -646,7 +706,7 @@ serve = \req -> case req of

646706 where not (e.server == "")

647707 where not (e.pubkey == "")

648708 where not (tooLong e.pubkey maxPubkeyLen)

649− where not (tooLong e.server maxPubkeyLen)

709+ where not (tooLong e.server maxServerNameLen)

650710 where not (isBadServerName e.server)

651711 where isValidHex e.pubkey

652712 where not (e.server == serverHost)

@@ -823,7 +883,7 @@ serve = \req -> case req of

823883 where not (e.server == "")

824884 where not (e.pubkey == "")

825885 where not (tooLong e.pubkey maxPubkeyLen)

826− where not (tooLong e.server maxPubkeyLen)

886+ where not (tooLong e.server maxServerNameLen)

827887 where not (isBadServerName e.server)

828888 where isValidHex e.pubkey

829889 where not (e.server == serverHost)

@@ -861,14 +921,14 @@ serve = \req -> case req of

861921 broadcastOfflineGossip t gossipResult.peerServers gossipResult.expiredLocal

862922

863923 ForwardMessage {toKey, fromKey, encryptedBlob, timestamp, originServer, messageId, authorization, respond} -> do

864− let validFields = not (toKey == "") && not (fromKey == "") && not (encryptedBlob == "") && not (messageId == "") && not (tooLong toKey maxPubkeyLen) && not (tooLong fromKey maxPubkeyLen) && not (tooLong encryptedBlob maxBlobLen) && not (tooLong messageId maxPubkeyLen) && isValidHex toKey && isValidHex fromKey && isValidHex encryptedBlob && isValidHex messageId

924+ let validFields = not (toKey == "") && not (fromKey == "") && not (encryptedBlob == "") && not (messageId == "") && not (tooLong toKey maxPubkeyLen) && not (tooLong fromKey maxPubkeyLen) && not (tooLong encryptedBlob maxBlobLen) && not (tooLong messageId maxMessageIdLen) && isValidHex toKey && isValidHex fromKey && isValidHex encryptedBlob && isValidHex messageId

865925 let toKey = if isValidHex toKey then normalizeHex toKey else toKey

866926 let fromKey = if isValidHex fromKey then normalizeHex fromKey else fromKey

867927 let encryptedBlob = if isValidHex encryptedBlob then normalizeHex encryptedBlob else encryptedBlob

868928 let messageId = if isValidHex messageId then normalizeHex messageId else messageId

869929 t <- now

870930 let authorized = verifyFederationAuth authorization

871− let validOrigin = not (originServer == "") && not (originServer == serverHost) && not (tooLong originServer maxPubkeyLen) && not (isBadServerName originServer)

931+ let validOrigin = not (originServer == "") && not (originServer == serverHost) && not (tooLong originServer maxServerNameLen) && not (isBadServerName originServer)

872932 let clampedTs = if timestamp > t then t else if timestamp < t - messageMaxAge then t else timestamp

873933 result <- atomic do

874934 pr <- pruneExpired t

@@ -903,11 +963,11 @@ serve = \req -> case req of

903963 let dedupedIds = fold (\acc mid ->

904964 if mid == "" then acc

905965 else if count acc >= maxMessageIds then acc

906− else if tooLong mid maxPubkeyLen then acc

966+ else if tooLong mid maxMessageIdLen then acc

907967 else if not (isValidHex mid) then acc

908968 else if count (do a <- acc; where a == normalizeHex mid; yield a) > 0 then acc

909969 else union acc [normalizeHex mid]) [] messageIds

910− let validAckFields = authorized && originServer == serverHost && not (fromServer == "") && not (fromServer == serverHost) && not (tooLong fromServer maxPubkeyLen) && not (isBadServerName fromServer)

970+ let validAckFields = authorized && originServer == serverHost && not (fromServer == "") && not (fromServer == serverHost) && not (tooLong fromServer maxServerNameLen) && not (isBadServerName fromServer)

911971 pruneResult <- atomic do

912972 pr <- pruneExpired t

913973 forwards <- *forwards