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Fix JWT alg:none bypass on the refresh-token lesson (Challenge-56) #491

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Fix JWT alg:none bypass on the refresh-token lesson (Challenge-56) #491

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a30f123
fix(build): bump lombok to 1.18.46 for JDK 25 CI compatibility
beanbeah Aug 9, 2026
cd40ab3
fix(jwt): reject alg:none tokens on the refresh-token checkout/newTok…
beanbeah Aug 9, 2026
7116686
fix(jwt): correct parseClaimsJws() return type (Jws<Claims>, not Jwt<…
beanbeah Aug 9, 2026
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2 changes: 1 addition & 1 deletion pom.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -238,7 +238,7 @@
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.36</version>
<version>1.18.46</version>
<scope>provided</scope>
<optional>true</optional>
</dependency>
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17 changes: 8 additions & 9 deletions src/main/java/org/owasp/webgoat/lessons/jwt/JWTRefreshEndpoint.java
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Expand Up @@ -10,9 +10,8 @@

import io.jsonwebtoken.Claims;
import io.jsonwebtoken.ExpiredJwtException;
import io.jsonwebtoken.Header;
import io.jsonwebtoken.Jwt;
import io.jsonwebtoken.JwtException;
import io.jsonwebtoken.Jws;
import io.jsonwebtoken.Jwts;
import java.util.ArrayList;
import java.util.Date;
Expand Down Expand Up @@ -88,13 +87,11 @@ public ResponseEntity<AttackResult> checkout(
return ResponseEntity.status(HttpStatus.UNAUTHORIZED).build();
}
try {
Jwt jwt = Jwts.parser().setSigningKey(JWT_PASSWORD).parse(token.replace("Bearer ", ""));
Claims claims = (Claims) jwt.getBody();
Jws<Claims> jwt =
Jwts.parser().setSigningKey(JWT_PASSWORD).parseClaimsJws(token.replace("Bearer ", ""));
Claims claims = jwt.getBody();
String user = (String) claims.get("user");
if ("Tom".equals(user)) {
if ("none".equals(jwt.getHeader().get("alg"))) {
return ok(success(this).feedback("jwt-refresh-alg-none").build());
}
return ok(success(this).build());
}
return ok(failed(this).feedback("jwt-refresh-not-tom").feedbackArgs(user).build());
Expand All @@ -117,13 +114,15 @@ public ResponseEntity newToken(
String user;
String refreshToken;
try {
Jwt<Header, Claims> jwt =
Jwts.parser().setSigningKey(JWT_PASSWORD).parse(token.replace("Bearer ", ""));
Jws<Claims> jwt =
Jwts.parser().setSigningKey(JWT_PASSWORD).parseClaimsJws(token.replace("Bearer ", ""));
user = (String) jwt.getBody().get("user");
refreshToken = (String) json.get("refresh_token");
} catch (ExpiredJwtException e) {
user = (String) e.getClaims().get("user");
refreshToken = (String) json.get("refresh_token");
} catch (JwtException e) {
return ResponseEntity.status(HttpStatus.UNAUTHORIZED).build();
}

if (user == null || refreshToken == null) {
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8 changes: 4 additions & 4 deletions src/test/java/org/owasp/webgoat/lessons/jwt/JWTRefreshEndpointTest.java
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Expand Up @@ -77,22 +77,22 @@ void solveAssignment() throws Exception {
}

@Test
void solutionWithAlgNone() throws Exception {
void algNoneTokenShouldBeRejected() throws Exception {
String tokenWithNoneAlgorithm =
Jwts.builder()
.setHeaderParam("alg", "none")
.addClaims(Map.of("admin", "true", "user", "Tom"))
.compact();

// Now checkout with the new token from Tom
// An unsigned "alg":"none" token must never be accepted as a valid token for Tom.
mockMvc
.perform(
MockMvcRequestBuilders.post("/JWT/refresh/checkout")
.header("Authorization", "Bearer " + tokenWithNoneAlgorithm))
.andExpect(status().isOk())
.andExpect(jsonPath("$.lessonCompleted", is(true)))
.andExpect(jsonPath("$.lessonCompleted", is(false)))
.andExpect(
jsonPath("$.feedback", CoreMatchers.is(messages.getMessage("jwt-refresh-alg-none"))));
jsonPath("$.feedback", CoreMatchers.is(messages.getMessage("jwt-invalid-token"))));
}

@Test
Expand Down
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