fix: Java doc for DefaultPKCEProvider.java (#1148)

* fix: Java doc for DefaultPKCEProvider.java

Author: clundin25

oauth2_http/java/com/google/auth/oauth2/DefaultPKCEProvider.java

@@ -36,40 +36,16 @@
 import java.security.SecureRandom;
 import java.util.Base64;
 
+/**
+ * Implements PKCE using only the Java standard library. See https://www.rfc-editor.org/rfc/rfc7636.
+ *
+ * <p>https://developers.google.com/identity/protocols/oauth2/native-app#step1-code-verifier.
+ */
 public class DefaultPKCEProvider implements PKCEProvider {
  private String codeVerifier;
  private CodeChallenge codeChallenge;
  private static final int MAX_CODE_VERIFIER_LENGTH = 127;
 
- private class CodeChallenge {
- private String codeChallenge;
- private String codeChallengeMethod;
-
- CodeChallenge(String codeVerifier) {
- try {
- byte[] bytes = codeVerifier.getBytes();
- MessageDigest md = MessageDigest.getInstance("SHA-256");
- md.update(bytes);
-
- byte[] digest = md.digest();
-
- this.codeChallenge = Base64.getUrlEncoder().encodeToString(digest);
- this.codeChallengeMethod = "S256";
- } catch (NoSuchAlgorithmException e) {
- this.codeChallenge = codeVerifier;
- this.codeChallengeMethod = "plain";
- }
- }
-
- public String getCodeChallenge() {
- return codeChallenge;
- }
-
- public String getCodeChallengeMethod() {
- return codeChallengeMethod;
- }
- }
-
  private String createCodeVerifier() {
  SecureRandom sr = new SecureRandom();
  byte[] code = new byte[MAX_CODE_VERIFIER_LENGTH];
@@ -100,4 +76,34 @@ public String getCodeChallenge() {
  public String getCodeChallengeMethod() {
  return codeChallenge.getCodeChallengeMethod();
  }
+
+ /** Class representing the Code Challenge derived from a Code Verifier string. */
+ private class CodeChallenge {
+ private String codeChallenge;
+ private String codeChallengeMethod;
+
+ CodeChallenge(String codeVerifier) {
+ try {
+ byte[] bytes = codeVerifier.getBytes();
+ MessageDigest md = MessageDigest.getInstance("SHA-256");
+ md.update(bytes);
+
+ byte[] digest = md.digest();
+
+ this.codeChallenge = Base64.getUrlEncoder().encodeToString(digest);
+ this.codeChallengeMethod = "S256";
+ } catch (NoSuchAlgorithmException e) {
+ this.codeChallenge = codeVerifier;
+ this.codeChallengeMethod = "plain";
+ }
+ }
+
+ public String getCodeChallenge() {
+ return codeChallenge;
+ }
+
+ public String getCodeChallengeMethod() {
+ return codeChallengeMethod;
+ }
+ }
 }

oauth2_http/javatests/com/google/auth/oauth2/UserAuthorizerTest.java

@@ -477,7 +477,7 @@ public void revokeAuthorization_revokesAndClears() throws IOException {
  }
 
  @Test(expected = IllegalArgumentException.class)
- public void illegalPKCEProvider() {
+ public void nullCodeVerifierPKCEProvider() {
  PKCEProvider pkce =
  new PKCEProvider() {
  @Override
@@ -487,7 +487,36 @@ public String getCodeVerifier() {
 
  @Override
  public String getCodeChallengeMethod() {
- return null;
+ return "dummy string";
+ }
+
+ @Override
+ public String getCodeChallenge() {
+ return "dummy string";
+ }
+ };
+
+ UserAuthorizer authorizer =
+ UserAuthorizer.newBuilder()
+ .setClientId(CLIENT_ID)
+ .setScopes(DUMMY_SCOPES)
+ .setTokenStore(new MemoryTokensStorage())
+ .setPKCEProvider(pkce)
+ .build();
+ }
+
+ @Test(expected = IllegalArgumentException.class)
+ public void nullCodeChallengePKCEProvider() {
+ PKCEProvider pkce =
+ new PKCEProvider() {
+ @Override
+ public String getCodeVerifier() {
+ return "dummy string";
+ }
+
+ @Override
+ public String getCodeChallengeMethod() {
+ return "dummy string";
  }
 
  @Override
@@ -504,4 +533,33 @@ public String getCodeChallenge() {
  .setPKCEProvider(pkce)
  .build();
  }
+
+ @Test(expected = IllegalArgumentException.class)
+ public void nullCodeChallengeMethodPKCEProvider() {
+ PKCEProvider pkce =
+ new PKCEProvider() {
+ @Override
+ public String getCodeVerifier() {
+ return "dummy string";
+ }
+
+ @Override
+ public String getCodeChallengeMethod() {
+ return null;
+ }
+
+ @Override
+ public String getCodeChallenge() {
+ return "dummy string";
+ }
+ };
+
+ UserAuthorizer authorizer =
+ UserAuthorizer.newBuilder()
+ .setClientId(CLIENT_ID)
+ .setScopes(DUMMY_SCOPES)
+ .setTokenStore(new MemoryTokensStorage())
+ .setPKCEProvider(pkce)
+ .build();
+ }
 }