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Fix symmetric v6 message encryption #1931

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vanitasvitae wants to merge 2 commits into from
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Fix symmetric v6 message encryption #1931

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b28dba4
Fix symmetric v6 message encryption
vanitasvitae Dec 3, 2024
a78f344
Do not emit v5 SKESKs if no AEAD is configured
vanitasvitae Dec 3, 2024
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9 changes: 6 additions & 3 deletions pg/src/main/java/org/bouncycastle/openpgp/PGPEncryptedDataGenerator.java
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Original file line number Diff line number Diff line change
Expand Up @@ -224,10 +224,13 @@ private OutputStream open(

boolean directS2K = !forceSessionKey && methods.size() == 1 &&
methods.get(0) instanceof PBEKeyEncryptionMethodGenerator; // not public key
boolean isV5StyleAEAD = dataEncryptorBuilder.isV5StyleAEAD(); //v5
if (dataEncryptorBuilder.getAeadAlgorithm() != -1 && !isV5StyleAEAD)

boolean isAEAD = dataEncryptorBuilder.getAeadAlgorithm() != -1;
boolean isV5StyleAEAD = isAEAD && dataEncryptorBuilder.isV5StyleAEAD(); //v5
if (isAEAD && !isV5StyleAEAD) // v6
{
sessionKey = PGPUtil.makeRandomKey(defAlgorithm, rand);
sessionInfo = createSessionInfo(defAlgorithm, sessionKey);
// In OpenPGP v6, we need an additional step to derive a message key and IV from the session info.
// Since we cannot inject the IV into the data encryptor, we append it to the message key.
byte[] info = SymmetricEncIntegrityPacket.createAAData(
Expand Down Expand Up @@ -271,7 +274,7 @@ else if (directS2K)
{
//https://www.rfc-editor.org/rfc/rfc9580.html#section-3.7.2.1 Table 2
//AEAD(HKDF(S2K(passphrase), info), secrets, packetprefix)
writeOpenPGPv6ESKPacket(method, aeadDataEncryptor.getAEADAlgorithm(), sessionKey);
writeOpenPGPv6ESKPacket(method, aeadDataEncryptor.getAEADAlgorithm(), sessionInfo);
}
}
// OpenPGP v4
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3 changes: 2 additions & 1 deletion pg/src/main/java/org/bouncycastle/openpgp/operator/PBEKeyEncryptionMethodGenerator.java
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Expand Up @@ -201,7 +201,7 @@ private ContainedPacket generateV5ESK(int kekAlgorithm, int aeadAlgorithm, byte[
return SymmetricKeyEncSessionPacket.createV5Packet(kekAlgorithm, aeadAlgorithm, iv, s2k, esk, tag);
}

private ContainedPacket generateV6ESK(int kekAlgorithm, int aeadAlgorithm, byte[] sessionKey)
private ContainedPacket generateV6ESK(int kekAlgorithm, int aeadAlgorithm, byte[] sessionInfo)
throws PGPException
{
byte[] ikm = getKey(kekAlgorithm);
Expand All @@ -217,6 +217,7 @@ private ContainedPacket generateV6ESK(int kekAlgorithm, int aeadAlgorithm, byte[
random.nextBytes(iv);

int tagLen = AEADUtils.getAuthTagLength(aeadAlgorithm);
byte[] sessionKey = getSessionKey(sessionInfo);
byte[] eskAndTag = getEskAndTag(kekAlgorithm, aeadAlgorithm, sessionKey, kek, iv, info);
byte[] esk = Arrays.copyOfRange(eskAndTag, 0, eskAndTag.length - tagLen);
byte[] tag = Arrays.copyOfRange(eskAndTag, esk.length, eskAndTag.length);
Expand Down