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https://github.com/logos-storage/logos-storage-nim-dht.git
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a9d0d0d69b
Since key exchange can be started both ways simultaneously, and these might not get finalised with UDP transport, we can't be sure what encryption key will be used by the other side: - the one derived in the key-exchange started by us, - the one derived in the key-exchange started by the other node. To alleviate this issue, we store two decryption keys in each session. Signed-off-by: Csaba Kiraly <csaba.kiraly@gmail.com>
89 lines
3.1 KiB
Nim
89 lines
3.1 KiB
Nim
# codex-dht - Codex DHT
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# Copyright (c) 2022 Status Research & Development GmbH
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# Licensed and distributed under either of
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# * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
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# * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
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# at your option. This file may not be copied, modified, or distributed except according to those terms.
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#
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## Session cache as mentioned at
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## https://github.com/ethereum/devp2p/blob/master/discv5/discv5-theory.md#session-cache
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##
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## A session stores encryption and decryption keys for P2P encryption.
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## Since key exchange can be started both ways, and these might not get finalised with
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## UDP transport, we can't be sure what encryption key will be used by the other side:
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## - the one derived in the key-exchange started by us,
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## - the one derived in the key-exchange started by the other node.
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## To alleviate this issue, we store two decryption keys in each session.
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{.push raises: [Defect].}
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import
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std/options,
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stint, stew/endians2, stew/shims/net,
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node, lru
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export lru
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const
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aesKeySize* = 128 div 8
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keySize = sizeof(NodeId) +
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16 + # max size of ip address (ipv6)
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2 # Sizeof port
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type
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AesKey* = array[aesKeySize, byte]
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SessionKey* = array[keySize, byte]
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SessionValue* = array[3 * sizeof(AesKey), byte]
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Sessions* = LRUCache[SessionKey, SessionValue]
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func makeKey(id: NodeId, address: Address): SessionKey =
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var pos = 0
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result[pos ..< pos+sizeof(id)] = toBytes(id)
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pos.inc(sizeof(id))
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case address.ip.family
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of IpAddressFamily.IpV4:
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result[pos ..< pos+sizeof(address.ip.address_v4)] = address.ip.address_v4
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of IpAddressFamily.IpV6:
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result[pos ..< pos+sizeof(address.ip.address_v6)] = address.ip.address_v6
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pos.inc(sizeof(address.ip.address_v6))
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result[pos ..< pos+sizeof(address.port)] = toBytes(address.port.uint16)
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func swapr*(s: var Sessions, id: NodeId, address: Address) =
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var value: array[3 * sizeof(AesKey), byte]
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let
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key = makeKey(id, address)
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entry = s.get(key)
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if entry.isSome():
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let val = entry.get()
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copyMem(addr value[0], unsafeAddr val[16], sizeof(AesKey))
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copyMem(addr value[16], unsafeAddr val[0], sizeof(AesKey))
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copyMem(addr value[32], unsafeAddr val[32], sizeof(AesKey))
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s.put(key, value)
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func store*(s: var Sessions, id: NodeId, address: Address, r, w: AesKey) =
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var value: array[3 * sizeof(AesKey), byte]
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let
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key = makeKey(id, address)
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entry = s.get(key)
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if entry.isSome():
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let val = entry.get()
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copyMem(addr value[0], unsafeAddr val[16], sizeof(r))
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value[16 .. 31] = r
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value[32 .. ^1] = w
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s.put(key, value)
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func load*(s: var Sessions, id: NodeId, address: Address, r1, r2, w: var AesKey): bool =
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let res = s.get(makeKey(id, address))
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if res.isSome():
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let val = res.get()
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copyMem(addr r1[0], unsafeAddr val[0], sizeof(r1))
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copyMem(addr r2[0], unsafeAddr val[sizeof(r1)], sizeof(r2))
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copyMem(addr w[0], unsafeAddr val[sizeof(r1) + sizeof(r2)], sizeof(w))
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return true
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else:
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return false
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func del*(s: var Sessions, id: NodeId, address: Address) =
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s.del(makeKey(id, address))
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