1 files changed, 62 insertions, 0 deletions

diff --git a/app/src/main/java/org/pacien/tincapp/utils/PemUtils.kt b/app/src/main/java/org/pacien/tincapp/utils/PemUtils.kt
new file mode 100644
index 0000000..3d59476
--- /dev/null
+++ b/app/src/main/java/org/pacien/tincapp/utils/PemUtils.kt
@@ -0,0 +1,62 @@
+package org.pacien.tincapp.utils
+
+import org.bouncycastle.openssl.PEMException
+import org.bouncycastle.openssl.PEMParser
+import org.bouncycastle.openssl.jcajce.JcaPEMWriter
+import org.bouncycastle.openssl.jcajce.JcePEMDecryptorProviderBuilder
+import org.bouncycastle.openssl.jcajce.JcePEMEncryptorBuilder
+import org.bouncycastle.util.encoders.Hex
+import org.bouncycastle.util.io.pem.PemHeader
+import org.bouncycastle.util.io.pem.PemObject
+import java.io.File
+import java.io.FileReader
+import java.io.Writer
+
+/**
+ * @author pacien
+ */
+object PemUtils {
+
+    private val PROVIDER = org.bouncycastle.jce.provider.BouncyCastleProvider()
+    private val ENCRYPTED_PROC_TYPE_HEADER = PemHeader("Proc-Type", "4,ENCRYPTED")
+    private val DEK_INFO_HEADER_KEY = "DEK-Info"
+    private val ALGO = "AES-256-CBC"
+
+    private class DekInfo(val algName: String, val iv: ByteArray)
+
+    private fun dekInfoHeader(iv: ByteArray) = PemHeader(DEK_INFO_HEADER_KEY, "$ALGO,${Hex.toHexString(iv)}")
+    private fun PemObject.getPemHeaders() = headers.map { it as PemHeader }
+
+    fun read(f: File): PemObject = PEMParser(FileReader(f)).readPemObject()
+    fun write(obj: PemObject, out: Writer) = JcaPEMWriter(out).apply { writeObject(obj) }.apply { close() }
+    fun isEncrypted(obj: PemObject) = obj.headers.contains(ENCRYPTED_PROC_TYPE_HEADER)
+
+    fun encrypt(obj: PemObject, passPhrase: String) =
+            JcePEMEncryptorBuilder(ALGO)
+                    .setProvider(PROVIDER)
+                    .build(passPhrase.toCharArray())
+                    .let { PemObject(obj.type, listOf(ENCRYPTED_PROC_TYPE_HEADER, dekInfoHeader(it.iv)), it.encrypt(obj.content)) }
+
+    fun decrypt(obj: PemObject, passPhrase: String?) =
+            if (isEncrypted(obj)) {
+                val dekInfo = try {
+                    obj.getPemHeaders()
+                            .find { it.name == DEK_INFO_HEADER_KEY }!!
+                            .value!!
+                            .split(',')
+                            .let { DekInfo(it[0], Hex.decode(it[1])) }
+                } catch (e: Exception) {
+                    throw PEMException("Malformed DEK-Info header.", e)
+                }
+
+                JcePEMDecryptorProviderBuilder()
+                        .setProvider(PROVIDER)
+                        .build(passPhrase?.toCharArray())
+                        .get(dekInfo.algName)
+                        .decrypt(obj.content, dekInfo.iv)
+                        .let { PemObject(obj.type, it) }
+            } else {
+                obj
+            }
+
+}