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Add file-level locking to prevent race conditions in key persistence

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Per-key ReentrantLock prevents concurrent writes to same key file
This commit is contained in:
Enginex0
2026-02-07 00:47:36 +01:00
parent c99a2ab302
commit ff88543c98
1 changed files with 64 additions and 40 deletions
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app/src/main/java/org/matrix/TEESimulator/interception/keystore/shim/GeneratedKeyPersistence.kt
+64 -40
View File
@@ -7,9 +7,12 @@ import java.io.DataOutputStream
import java.io.File import java.io.File
import java.io.FileInputStream import java.io.FileInputStream
import java.io.FileOutputStream import java.io.FileOutputStream
import java.io.IOException
import java.security.KeyPair import java.security.KeyPair
import java.security.MessageDigest import java.security.MessageDigest
import java.security.cert.Certificate import java.security.cert.Certificate
import java.util.concurrent.ConcurrentHashMap
import java.util.concurrent.locks.ReentrantLock
import org.matrix.TEESimulator.config.ConfigurationManager.CONFIG_PATH import org.matrix.TEESimulator.config.ConfigurationManager.CONFIG_PATH
import org.matrix.TEESimulator.interception.keystore.KeyIdentifier import org.matrix.TEESimulator.interception.keystore.KeyIdentifier
import org.matrix.TEESimulator.logging.SystemLogger import org.matrix.TEESimulator.logging.SystemLogger
@@ -35,6 +38,13 @@ object GeneratedKeyPersistence {
private const val FORMAT_VERSION = 1 private const val FORMAT_VERSION = 1
private val PERSISTENCE_DIR = File(CONFIG_PATH, "persistent_keys") private val PERSISTENCE_DIR = File(CONFIG_PATH, "persistent_keys")
// Per-filename locks to prevent concurrent writes to the same key file
private val fileLocks = ConcurrentHashMap<String, ReentrantLock>()
private fun getLockForKey(filename: String): ReentrantLock {
return fileLocks.computeIfAbsent(filename) { ReentrantLock() }
}
fun save( fun save(
keyId: KeyIdentifier, keyId: KeyIdentifier,
keyPair: KeyPair, keyPair: KeyPair,
@@ -48,55 +58,69 @@ object GeneratedKeyPersistence {
digests: List<Int>, digests: List<Int>,
isAttestationKey: Boolean, isAttestationKey: Boolean,
) { ) {
runCatching { val filename = keyFileName(keyId.uid, keyId.alias)
PERSISTENCE_DIR.mkdirs() val lock = getLockForKey(filename)
val filename = keyFileName(keyId.uid, keyId.alias) SystemLogger.debug("[Persistence] Acquiring lock for $filename")
val finalFile = File(PERSISTENCE_DIR, filename) lock.lock()
val tmpFile = File(PERSISTENCE_DIR, "$filename.tmp") try {
SystemLogger.debug("[Persistence] Lock acquired for $filename")
runCatching {
PERSISTENCE_DIR.mkdirs()
val finalFile = File(PERSISTENCE_DIR, filename)
val tmpFile = File(PERSISTENCE_DIR, "$filename.tmp")
try { try {
DataOutputStream(BufferedOutputStream(FileOutputStream(tmpFile))).use { out -> DataOutputStream(BufferedOutputStream(FileOutputStream(tmpFile))).use { out ->
out.writeInt(FORMAT_VERSION) out.writeInt(FORMAT_VERSION)
out.writeInt(securityLevel) out.writeInt(securityLevel)
out.writeInt(keyId.uid) out.writeInt(keyId.uid)
out.writeUTF(keyId.alias) out.writeUTF(keyId.alias)
out.writeLong(nspace) out.writeLong(nspace)
out.writeBoolean(isAttestationKey) out.writeBoolean(isAttestationKey)
out.writeInt(algorithm) out.writeInt(algorithm)
out.writeInt(keySize) out.writeInt(keySize)
out.writeInt(ecCurve) out.writeInt(ecCurve)
out.writeInt(purposes.size) out.writeInt(purposes.size)
purposes.forEach { out.writeInt(it) } purposes.forEach { out.writeInt(it) }
out.writeInt(digests.size) out.writeInt(digests.size)
digests.forEach { out.writeInt(it) } digests.forEach { out.writeInt(it) }
val pkBytes = keyPair.private.encoded val pkBytes = keyPair.private.encoded
out.writeInt(pkBytes.size) out.writeInt(pkBytes.size)
out.write(pkBytes) out.write(pkBytes)
out.writeInt(certChain.size) out.writeInt(certChain.size)
certChain.forEach { cert -> certChain.forEach { cert ->
val encoded = cert.encoded val encoded = cert.encoded
out.writeInt(encoded.size) out.writeInt(encoded.size)
out.write(encoded) out.write(encoded)
}
} }
} catch (e: Exception) {
tmpFile.delete()
throw e
} }
} catch (e: Exception) {
tmpFile.delete()
throw e
}
// Atomic rename — if this fails the tmp is left behind and cleaned on next deleteAll // Atomic rename — if this fails the tmp is left behind and cleaned on next deleteAll
if (!tmpFile.renameTo(finalFile)) { if (!tmpFile.renameTo(finalFile)) {
tmpFile.delete() tmpFile.delete()
throw IllegalStateException("Failed to atomically rename $tmpFile -> $finalFile") throw IllegalStateException("Failed to atomically rename $tmpFile -> $finalFile")
} }
SystemLogger.debug("Persisted key: $keyId") // Verify write succeeded - catches disk-full or filesystem errors
}.onFailure { e -> if (!finalFile.exists() || finalFile.length() < 20) {
SystemLogger.error("Failed to persist key $keyId", e) throw IOException("File write verification failed - possible disk full")
}
SystemLogger.debug("Persisted key: $keyId")
}.onFailure { e ->
SystemLogger.error("Failed to persist key $keyId", e)
}
} finally {
lock.unlock()
SystemLogger.debug("[Persistence] Lock released for $filename")
} }
} }