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JCL-385: Improve PKCE verifier to always produce spec conforming values #517

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Merged
acoburn merged 1 commit into from
Jun 9, 2023
Merged

JCL-385: Improve PKCE verifier to always produce spec conforming values #517

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4 changes: 3 additions & 1 deletion openid/src/main/java/com/inrupt/client/openid/PKCE.java
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Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,8 @@
*/
public final class PKCE {

private static final BigInteger PADDING = BigInteger.valueOf(2).pow(256);

/**
* Create a PKCE challenge value using the S256 algorithm.
*
Expand Down Expand Up @@ -73,7 +75,7 @@ static String createChallenge(final String verifier, final String alg) {
* @return the Base64URL-encoded verifier
*/
static String createVerifier() {
final byte[] rand = new BigInteger(32 * 8, new SecureRandom()).toByteArray();
final byte[] rand = PADDING.add(new BigInteger(32 * 8, new SecureRandom())).toByteArray();
return Base64.getUrlEncoder().withoutPadding().encodeToString(rand);
}

Expand Down
13 changes: 6 additions & 7 deletions openid/src/test/java/com/inrupt/client/openid/PKCETest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,6 @@
*/
package com.inrupt.client.openid;

import static java.nio.charset.StandardCharsets.UTF_8;
import static org.junit.jupiter.api.Assertions.assertThrows;
import static org.junit.jupiter.api.Assertions.assertTrue;

Expand All @@ -30,16 +29,16 @@ class PKCETest {

@Test
void createChallengeTest() {
assertTrue(PKCE.createChallenge("🐶🐶🐶", "SHA-256").getBytes(UTF_8).length >= 43);
assertTrue(PKCE.createChallenge("🐶🐶🐶", "SHA-256").getBytes(UTF_8).length <= 128);
assertTrue(PKCE.createChallenge("", "SHA-256").getBytes(UTF_8).length >= 43);
assertTrue(PKCE.createChallenge("", "SHA-256").getBytes(UTF_8).length <= 128);
assertTrue(PKCE.createChallenge("🐶🐶🐶", "SHA-256").length() >= 43);
Comment on lines -36 to +32
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@NSeydoux NSeydoux Jun 9, 2023

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For my own understanding, was the .getBytes(UTF_8) useful in the first place?

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@acoburn acoburn Jun 9, 2023

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No, the getBytes test was unnecessary. The spec requires checking the character length of the resulting string, not the size of the byte array. Admittedly, for ASCII strings, the two will be equivalent, but it is unnecessary

assertTrue(PKCE.createChallenge("🐶🐶🐶", "SHA-256").length() <= 128);
assertTrue(PKCE.createChallenge("", "SHA-256").length() >= 43);
assertTrue(PKCE.createChallenge("", "SHA-256").length() <= 128);
assertThrows(NullPointerException.class, () -> PKCE.createChallenge(null, "SHA-256"));
}

@Test
void createVerifierTest() {
assertTrue(PKCE.createVerifier().getBytes(UTF_8).length >= 43);
assertTrue(PKCE.createVerifier().getBytes(UTF_8).length <= 128);
assertTrue(PKCE.createVerifier().length() >= 43);
assertTrue(PKCE.createVerifier().length() <= 128);
}
}