nim-libp2p/libp2p/nameresolving/nameresolver.nim

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# Nim-LibP2P
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# Copyright (c) 2023 Status Research & Development GmbH
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# Licensed under either of
# * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
# * MIT license ([LICENSE-MIT](LICENSE-MIT))
# at your option.
# This file may not be copied, modified, or distributed except according to
# those terms.
when (NimMajor, NimMinor) < (1, 4):
{.push raises: [Defect].}
else:
{.push raises: [].}
import std/[sugar, sets, sequtils, strutils]
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import
chronos,
chronicles,
stew/[endians2, byteutils]
import ".."/[multiaddress, multicodec]
logScope:
topics = "libp2p nameresolver"
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type
NameResolver* = ref object of RootObj
method resolveTxt*(
self: NameResolver,
address: string): Future[seq[string]] {.async, base.} =
## Get TXT record
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##
doAssert(false, "Not implemented!")
method resolveIp*(
self: NameResolver,
address: string,
port: Port,
domain: Domain = Domain.AF_UNSPEC): Future[seq[TransportAddress]] {.async, base.} =
## Resolve the specified address
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##
doAssert(false, "Not implemented!")
proc getHostname*(ma: MultiAddress): string =
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let
firstPart = ma[0].valueOr: return ""
fpSplitted = ($firstPart).split('/', 2)
if fpSplitted.len > 2: fpSplitted[2]
else: ""
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proc resolveOneAddress(
self: NameResolver,
ma: MultiAddress,
domain: Domain = Domain.AF_UNSPEC,
prefix = ""): Future[seq[MultiAddress]]
{.async, raises: [Defect, MaError, TransportAddressError].} =
#Resolve a single address
var pbuf: array[2, byte]
var dnsval = getHostname(ma)
if ma[1].tryGet().protoArgument(pbuf).tryGet() == 0:
raise newException(MaError, "Incorrect port number")
let
port = Port(fromBytesBE(uint16, pbuf))
resolvedAddresses = await self.resolveIp(prefix & dnsval, port, domain)
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return collect(newSeqOfCap(4)):
for address in resolvedAddresses:
var createdAddress = MultiAddress.init(address).tryGet()[0].tryGet()
for part in ma:
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if DNS.match(part.tryGet()): continue
createdAddress &= part.tryGet()
createdAddress
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proc resolveDnsAddr*(
self: NameResolver,
ma: MultiAddress,
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depth: int = 0): Future[seq[MultiAddress]] {.async.} =
if not DNSADDR.matchPartial(ma):
return @[ma]
trace "Resolving dnsaddr", ma
if depth > 6:
info "Stopping DNSADDR recursion, probably malicious", ma
return @[]
var dnsval = getHostname(ma)
let txt = await self.resolveTxt("_dnsaddr." & dnsval)
trace "txt entries", txt
var result: seq[MultiAddress]
for entry in txt:
if not entry.startsWith("dnsaddr="): continue
let entryValue = MultiAddress.init(entry[8..^1]).tryGet()
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if entryValue.contains(multiCodec("p2p")).tryGet() and ma.contains(multiCodec("p2p")).tryGet():
if entryValue[multiCodec("p2p")] != ma[multiCodec("p2p")]:
continue
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let resolved = await self.resolveDnsAddr(entryValue, depth + 1)
for r in resolved:
result.add(r)
if result.len == 0:
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debug "Failed to resolve a DNSADDR", ma
return @[]
return result
proc resolveMAddress*(
self: NameResolver,
address: MultiAddress): Future[seq[MultiAddress]] {.async.} =
var res = initOrderedSet[MultiAddress]()
if not DNS.matchPartial(address):
res.incl(address)
else:
let code = address[0].get().protoCode().get()
let seq = case code:
of multiCodec("dns"):
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await self.resolveOneAddress(address)
of multiCodec("dns4"):
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await self.resolveOneAddress(address, Domain.AF_INET)
of multiCodec("dns6"):
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await self.resolveOneAddress(address, Domain.AF_INET6)
of multiCodec("dnsaddr"):
await self.resolveDnsAddr(address)
else:
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doAssert false
@[address]
for ad in seq:
res.incl(ad)
return res.toSeq