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Add configurable RSA-OAEP support (selectable OAEP & MGF1 digests) #244

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Add configurable RSA-OAEP support (selectable OAEP & MGF1 digests) #244

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118 changes: 118 additions & 0 deletions src/main/java/de/usd/cstchef/operations/encryption/RsaCipherBuilder.java
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Original file line number Diff line number Diff line change
@@ -0,0 +1,118 @@
package de.usd.cstchef.operations.encryption;

import java.security.Key;
import java.util.LinkedHashSet;

import javax.crypto.Cipher;
import javax.crypto.spec.OAEPParameterSpec;
import javax.crypto.spec.PSource;

import java.security.spec.MGF1ParameterSpec;

/**
* Central place that knows how to turn a user selected RSA padding (and, for
* OAEP, the two message digests) into an initialised {@link Cipher}.
*
* Keeping this logic in one small class means the UI operations
* ({@code RsaEncryption} / {@code RsaDecryption}) only have to read their combo
* boxes and hand the values over. Supporting a new padding or digest in the
* future is a one line change to the constants below.
*/
public class RsaCipherBuilder {

/** Selectable padding modes shown in the operations' "Padding" combo box. */
public static final String PADDING_PKCS1 = "PKCS1Padding";
public static final String PADDING_OAEP = "OAEPPadding";

public static final String[] PADDINGS = new String[] {
PADDING_PKCS1,
PADDING_OAEP
};

/**
* Message digests offered for the OAEP hash and the MGF1 hash. These are
* the digests SunJCE accepts inside an {@link OAEPParameterSpec}. Add new
* entries here to make them available in both RSA operations at once.
*/
public static final String[] DIGESTS = new String[] {
"SHA-1",
"SHA-224",
"SHA-256",
"SHA-384",
"SHA-512"
};

public static final String DEFAULT_DIGEST = "SHA-256";

/**
* Whether a padding name selects OAEP. Matches both the simple PEM choice
* ({@link #PADDING_OAEP}) and the provider's named variants used in KeyStore
* mode (e.g. {@code OAEPWITHSHA-256ANDMGF1PADDING}).
*/
public static boolean isOaep(String padding) {
return padding != null && padding.toUpperCase().contains("OAEP");
}

/**
* Build the padding list for KeyStore mode. We keep whatever the security
* provider advertises (so previously saved recipes still match) but make
* sure an OAEP option is always present. Some JVMs / Burp's bundled JRE
* advertise a reduced RSA padding list, which otherwise leaves the user
* with no way to pick OAEP even though we support it.
*/
public static String[] keyStorePaddings(String[] providerPaddings) {
LinkedHashSet<String> paddings = new LinkedHashSet<>();
if (providerPaddings != null) {
for (String padding : providerPaddings) {
if (padding != null && !padding.isEmpty()) {
paddings.add(padding);
}
}
}

// Fall back to PKCS1 if the provider advertised nothing usable.
if (paddings.isEmpty()) {
paddings.add(PADDING_PKCS1);
}

boolean hasOaep = false;
for (String padding : paddings) {
if (isOaep(padding)) {
hasOaep = true;
break;
}
}
if (!hasOaep) {
paddings.add(PADDING_OAEP);
}

return paddings.toArray(new String[0]);
}

/**
* Build and initialise an RSA {@link Cipher}.
*
* @param mode {@link Cipher#ENCRYPT_MODE} or {@link Cipher#DECRYPT_MODE}
* @param key the public (encrypt) or private (decrypt) key
* @param padding one of {@link #PADDINGS}
* @param oaepHash OAEP digest, one of {@link #DIGESTS} (ignored for PKCS1)
* @param mgf1Hash MGF1 digest, one of {@link #DIGESTS} (ignored for PKCS1)
*/
public static Cipher build(int mode, Key key, String padding, String oaepHash, String mgf1Hash) throws Exception {
if (PADDING_OAEP.equals(padding)) {
Cipher cipher = Cipher.getInstance("RSA/ECB/OAEPPadding");
OAEPParameterSpec spec = new OAEPParameterSpec(
oaepHash,
"MGF1",
new MGF1ParameterSpec(mgf1Hash),
PSource.PSpecified.DEFAULT);
cipher.init(mode, key, spec);
return cipher;
}

// Default / backwards compatible behaviour: RSA with PKCS#1 v1.5 padding.
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
cipher.init(mode, key);
return cipher;
}
}
89 changes: 84 additions & 5 deletions src/main/java/de/usd/cstchef/operations/encryption/RsaDecryption.java
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
package de.usd.cstchef.operations.encryption;

import java.awt.Component;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedReader;
Expand Down Expand Up @@ -28,6 +29,10 @@ public class RsaDecryption extends KeystoreOperation {

private VariableTextArea privateKeyTextArea;

private JComboBox<String> pemPadding;
private JComboBox<String> pemOaepHash;
private JComboBox<String> pemMgf1Hash;

private JComboBox<String> typeComboBox;

private static String[] inOutModes = new String[] { "Raw", "Hex", "Base64" };
Expand All @@ -38,6 +43,8 @@ public class RsaDecryption extends KeystoreOperation {
protected JComboBox<String> inputMode;
protected JComboBox<String> outputMode;
protected JComboBox<String> paddings;
protected JComboBox<String> ksOaepHash;
protected JComboBox<String> ksMgf1Hash;

private String lastSelection = "PEM";

Expand Down Expand Up @@ -74,17 +81,29 @@ protected ByteArray perform(ByteArray input) throws Exception {
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
RSAPrivateKey privateKey = (RSAPrivateKey) keyFactory.generatePrivate(keySpec);

Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.DECRYPT_MODE, privateKey);
Cipher cipher = RsaCipherBuilder.build(Cipher.DECRYPT_MODE, privateKey,
(String) pemPadding.getSelectedItem(),
(String) pemOaepHash.getSelectedItem(),
(String) pemMgf1Hash.getSelectedItem());
return factory.createByteArray(cipher.doFinal(input.getBytes()));
}
else if(typeComboBox.getSelectedItem().equals("KeyStore")) {
if( ! this.keyAvailable.isSelected() )
throw new IllegalArgumentException("No private key available.");

String padding = (String)paddings.getSelectedItem();
Cipher cipher = Cipher.getInstance(String.format("%s/%s/%s", algorithm, cipherMode, padding));
cipher.init(Cipher.DECRYPT_MODE, this.selectedEntry.getPrivateKey());
Cipher cipher;
if(RsaCipherBuilder.isOaep(padding)) {
// Named OAEP transformations (e.g. OAEPWITHSHA-256ANDMGF1PADDING) leave MGF1 at
// SHA-1 in SunJCE, so build an explicit OAEPParameterSpec with both chosen digests.
cipher = RsaCipherBuilder.build(Cipher.DECRYPT_MODE, this.selectedEntry.getPrivateKey(),
RsaCipherBuilder.PADDING_OAEP,
(String) ksOaepHash.getSelectedItem(),
(String) ksMgf1Hash.getSelectedItem());
} else {
cipher = Cipher.getInstance(String.format("%s/%s/%s", algorithm, cipherMode, padding));
cipher.init(Cipher.DECRYPT_MODE, this.selectedEntry.getPrivateKey());
}

String selectedInputMode = (String)inputMode.getSelectedItem();
String selectedOutputMode = (String)outputMode.getSelectedItem();
Expand Down Expand Up @@ -155,14 +174,35 @@ public void createMyUI() {
CipherUtils utils = CipherUtils.getInstance();
CipherInfo info = utils.getCipherInfo(this.algorithm);

this.paddings = new JComboBox<>(info.getPaddings());
this.paddings = new JComboBox<>(RsaCipherBuilder.keyStorePaddings(info.getPaddings()));
this.addUIElement("Padding", this.paddings);

this.ksOaepHash = new JComboBox<>(RsaCipherBuilder.DIGESTS);
this.ksOaepHash.setSelectedItem(RsaCipherBuilder.DEFAULT_DIGEST);
this.addUIElement("OAEP Hash", this.ksOaepHash);

this.ksMgf1Hash = new JComboBox<>(RsaCipherBuilder.DIGESTS);
this.ksMgf1Hash.setSelectedItem(RsaCipherBuilder.DEFAULT_DIGEST);
this.addUIElement("MGF1 Hash", this.ksMgf1Hash);

this.inputMode = new JComboBox<>(inOutModes);
this.addUIElement("Input", this.inputMode);

this.outputMode = new JComboBox<>(inOutModes);
this.addUIElement("Output", this.outputMode);

// The OAEP/MGF1 digests only apply to OAEP paddings, so only show them then.
this.paddings.addActionListener(e -> updateKeyStoreOaepVisibility());
updateKeyStoreOaepVisibility();
}

private void updateKeyStoreOaepVisibility() {
boolean oaep = RsaCipherBuilder.isOaep((String) this.paddings.getSelectedItem());
setRowVisible(this.ksOaepHash, oaep);
setRowVisible(this.ksMgf1Hash, oaep);
validate();
repaint();
updateStepPanel();
}

private void clearUI() {
Expand All @@ -182,6 +222,45 @@ private void clearUI() {
private void createUIForPEM() {
this.privateKeyTextArea = new VariableTextArea();
this.addUIElement("Private Key", this.privateKeyTextArea);

this.pemPadding = new JComboBox<>(RsaCipherBuilder.PADDINGS);
this.addUIElement("Padding", this.pemPadding);

this.pemOaepHash = new JComboBox<>(RsaCipherBuilder.DIGESTS);
this.pemOaepHash.setSelectedItem(RsaCipherBuilder.DEFAULT_DIGEST);
this.addUIElement("OAEP Hash", this.pemOaepHash);

this.pemMgf1Hash = new JComboBox<>(RsaCipherBuilder.DIGESTS);
this.pemMgf1Hash.setSelectedItem(RsaCipherBuilder.DEFAULT_DIGEST);
this.addUIElement("MGF1 Hash", this.pemMgf1Hash);

// The OAEP/MGF1 digests only apply to OAEP padding, so only show them then.
this.pemPadding.addActionListener(e -> updatePemOaepVisibility());
updatePemOaepVisibility();
}

// Show the OAEP/MGF1 hash rows only while OAEP padding is selected.
private void updatePemOaepVisibility() {
boolean oaep = RsaCipherBuilder.PADDING_OAEP.equals(this.pemPadding.getSelectedItem());
setRowVisible(this.pemOaepHash, oaep);
setRowVisible(this.pemMgf1Hash, oaep);
validate();
repaint();
updateStepPanel();
}

private void setRowVisible(Component comp, boolean visible) {
Component row = comp.getParent();
Component[] comps = getContentBoxComponents();
for (int i = 0; i < comps.length; i++) {
if (comps[i] == row) {
comps[i].setVisible(visible);
if (i + 1 < comps.length) {
comps[i + 1].setVisible(visible); // the spacing strut that follows the row
}
break;
}
}
}

public void updateStepPanel() {
Expand Down
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