optionnally provide an external seed

usage: `PHOENIX_SEED="focus certain canvas rude exist sausage chuckle
forget bronze brown warm comic" ./phoenixd`

src/commonMain/kotlin/fr/acinq/lightning/bin/Main.kt

@@ -18,12 +18,15 @@ import com.github.ajalt.clikt.sources.MapValueSource
 import com.github.ajalt.mordant.rendering.TextColors.*
 import com.github.ajalt.mordant.rendering.TextStyles.bold
 import fr.acinq.bitcoin.Chain
+import fr.acinq.bitcoin.MnemonicCode
 import fr.acinq.lightning.BuildVersions
 import fr.acinq.lightning.Lightning.randomBytes32
 import fr.acinq.lightning.LiquidityEvents
 import fr.acinq.lightning.NodeParams
 import fr.acinq.lightning.PaymentEvents
+import fr.acinq.lightning.bin.conf.EnvVars.PHOENIX_SEED
 import fr.acinq.lightning.bin.conf.LSP
+import fr.acinq.lightning.bin.conf.PhoenixSeed
 import fr.acinq.lightning.bin.conf.getOrGenerateSeed
 import fr.acinq.lightning.bin.conf.readConfFile
 import fr.acinq.lightning.bin.db.SqliteChannelsDb
@@ -47,6 +50,7 @@ import fr.acinq.lightning.payment.LiquidityPolicy
 import fr.acinq.lightning.utils.Connection
 import fr.acinq.lightning.utils.msat
 import fr.acinq.lightning.utils.sat
+import fr.acinq.lightning.utils.toByteVector
 import fr.acinq.phoenix.db.*
 import io.ktor.http.*
 import io.ktor.server.application.*
@@ -69,6 +73,17 @@ fun main(args: Array<String>) = Phoenixd()
 
 class Phoenixd : CliktCommand() {
     private val confFile = datadir / "phoenix.conf"
+    private val seed by option("--seed", help = "Manually provide a 12-words seed", hidden = true, envvar = PHOENIX_SEED)
+        .convert { PhoenixSeed(MnemonicCode.toSeed(it, "").toByteVector(), isNew = false) }
+        .defaultLazy {
+            val value = getOrGenerateSeed(datadir)
+            if (value.isNew) {
+                terminal.print(yellow("Generating new seed..."))
+                runBlocking { delay(500.milliseconds) }
+                terminal.println(white("done"))
+            }
+            value
+        }
     private val chain by option("--chain", help = "Bitcoin chain to use").choice(
         "mainnet" to Chain.Mainnet, "testnet" to Chain.Testnet
     ).default(Chain.Mainnet, defaultForHelp = "mainnet")
@@ -155,13 +170,8 @@ class Phoenixd : CliktCommand() {
     @OptIn(DelicateCoroutinesApi::class)
     override fun run() {
         FileSystem.SYSTEM.createDirectories(datadir)
-        val (seed, new) = getOrGenerateSeed(datadir)
-        if (new) {
+        if (seed.isNew) {
             runBlocking {
-                terminal.print(yellow("Generating new seed..."))
-                delay(500.milliseconds)
-                terminal.println(white("done"))
-                terminal.println()
                 terminal.println(green("Backup"))
                 terminal.println("This software is self-custodial, you have full control and responsibility over your funds.")
                 terminal.println("Your 12-words seed is located in ${FileSystem.SYSTEM.canonicalize(datadir)}, ${bold(red("make sure to do a backup or you risk losing your funds"))}.")
@@ -215,7 +225,7 @@ class Phoenixd : CliktCommand() {
             skipAbsoluteFeeCheck = false,
             maxAllowedCredit = liquidityOptions.maxFeeCredit
         )
-        val keyManager = LocalKeyManager(seed, chain, lsp.swapInXpub)
+        val keyManager = LocalKeyManager(seed.seed, chain, lsp.swapInXpub)
         val nodeParams = NodeParams(chain, loggerFactory, keyManager)
             .copy(
                 zeroConfPeers = setOf(lsp.walletParams.trampolineNode.id),

src/commonMain/kotlin/fr/acinq/lightning/bin/conf/EnvVars.kt

@@ -2,4 +2,5 @@ package fr.acinq.lightning.bin.conf
 
 object EnvVars {
     const val PHOENIX_DATADIR = "PHOENIX_DATADIR"
+    const val PHOENIX_SEED = "PHOENIX_SEED"
 }

src/commonMain/kotlin/fr/acinq/lightning/bin/conf/Seed.kt

@@ -1,18 +1,21 @@
 package fr.acinq.lightning.bin.conf
 
 import fr.acinq.bitcoin.ByteVector
+import fr.acinq.bitcoin.ByteVector32
 import fr.acinq.bitcoin.MnemonicCode
 import fr.acinq.lightning.Lightning.randomBytes
 import fr.acinq.lightning.utils.toByteVector
 import okio.FileSystem
 import okio.Path
 
+data class PhoenixSeed(val seed: ByteVector, val isNew: Boolean)
+
 /**
  * @return a pair with the seed and a boolean indicating whether the seed was newly generated
  */
-fun getOrGenerateSeed(dir: Path): Pair<ByteVector, Boolean> {
+fun getOrGenerateSeed(dir: Path): PhoenixSeed {
     val file = dir / "seed.dat"
-    val (mnemonics, new) = if (FileSystem.SYSTEM.exists(file)) {
+    val (mnemonics, isNew) = if (FileSystem.SYSTEM.exists(file)) {
         FileSystem.SYSTEM.read(file) { readUtf8() } to false
     } else {
         val entropy = randomBytes(16)
@@ -20,5 +23,5 @@ fun getOrGenerateSeed(dir: Path): Pair<ByteVector, Boolean> {
         FileSystem.SYSTEM.write(file) { writeUtf8(mnemonics) }
         mnemonics to true
     }
-    return MnemonicCode.toSeed(mnemonics, "").toByteVector() to new
+    return PhoenixSeed(seed = MnemonicCode.toSeed(mnemonics, "").toByteVector(), isNew = isNew)
 }