Fix compression being omitted for JWEs with arbitrary content

The JWE content was compressed only when claims was used as payload, but
when using arbitrary content, the compression was omitted, while keeping
the "zip" header field, leading to decompression failing.

impl/src/main/java/io/jsonwebtoken/impl/DefaultJwtBuilder.java

@@ -693,14 +693,14 @@ private String encrypt(final Payload content, final Key key, final Provider keyP
         Assert.stateNotNull(keyAlgFunction, "KeyAlgorithm function cannot be null.");
         assertPayloadEncoding("JWE");
 
+        ByteArrayOutputStream out = new ByteArrayOutputStream(4096);
         InputStream plaintext;
         if (content.isClaims()) {
-            ByteArrayOutputStream out = new ByteArrayOutputStream(4096);
             writeAndClose("JWE Claims", content, out);
-            plaintext = Streams.of(out.toByteArray());
         } else {
-            plaintext = content.toInputStream();
+            writeAndClose("JWE Content", content, out);
         }
+        plaintext = Streams.of(out.toByteArray());
 
         //only expose (mutable) JweHeader functionality to KeyAlgorithm instances, not the full headerBuilder
         // (which exposes this JwtBuilder and shouldn't be referenced by KeyAlgorithms):

impl/src/test/groovy/io/jsonwebtoken/JwtsTest.groovy

@@ -22,6 +22,7 @@ import io.jsonwebtoken.impl.io.Streams
 import io.jsonwebtoken.impl.lang.Bytes
 import io.jsonwebtoken.impl.lang.Services
 import io.jsonwebtoken.impl.security.*
+import io.jsonwebtoken.io.CompressionAlgorithm
 import io.jsonwebtoken.io.Decoders
 import io.jsonwebtoken.io.Deserializer
 import io.jsonwebtoken.io.Encoders
@@ -1398,6 +1399,97 @@ class JwtsTest {
         }
     }
 
+    @Test
+    void testJweCompressionWithArbitraryContentString() {
+        def codecs = [Jwts.ZIP.DEF, Jwts.ZIP.GZIP]
+
+        for (CompressionAlgorithm zip : codecs) {
+
+            for (AeadAlgorithm enc : Jwts.ENC.get().values()) {
+
+                SecretKey key = enc.key().build()
+
+                String payload = 'hello, world!'
+
+                // encrypt and compress:
+                String jwe = Jwts.builder()
+                    .content(payload)
+                    .compressWith(zip)
+                    .encryptWith(key, enc)
+                    .compact()
+
+                //decompress and decrypt:
+                def jwt = Jwts.parser()
+                    .decryptWith(key)
+                    .build()
+                    .parseEncryptedContent(jwe)
+                assertEquals payload, new String(jwt.getPayload(), StandardCharsets.UTF_8)
+            }
+        }
+    }
+
+    @Test
+    void testJweCompressionWithArbitraryContentByteArray() {
+        def codecs = [Jwts.ZIP.DEF, Jwts.ZIP.GZIP]
+
+        for (CompressionAlgorithm zip : codecs) {
+
+            for (AeadAlgorithm enc : Jwts.ENC.get().values()) {
+
+                SecretKey key = enc.key().build()
+
+                byte[] payload = new byte[14];
+                Randoms.secureRandom().nextBytes(payload)
+
+                // encrypt and compress:
+                String jwe = Jwts.builder()
+                        .content(payload)
+                        .compressWith(zip)
+                        .encryptWith(key, enc)
+                        .compact()
+
+                //decompress and decrypt:
+                def jwt = Jwts.parser()
+                        .decryptWith(key)
+                        .build()
+                        .parseEncryptedContent(jwe)
+                assertArrayEquals payload, jwt.getPayload()
+            }
+        }
+    }
+
+    @Test
+    void testJweCompressionWithArbitraryContentInputStream() {
+        def codecs = [Jwts.ZIP.DEF, Jwts.ZIP.GZIP]
+
+        for (CompressionAlgorithm zip : codecs) {
+
+            for (AeadAlgorithm enc : Jwts.ENC.get().values()) {
+
+                SecretKey key = enc.key().build()
+
+                byte[] payloadBytes = new byte[14];
+                Randoms.secureRandom().nextBytes(payloadBytes)
+
+                ByteArrayInputStream payload = new ByteArrayInputStream(payloadBytes)
+
+                // encrypt and compress:
+                String jwe = Jwts.builder()
+                        .content(payload)
+                        .compressWith(zip)
+                        .encryptWith(key, enc)
+                        .compact()
+
+                //decompress and decrypt:
+                def jwt = Jwts.parser()
+                        .decryptWith(key)
+                        .build()
+                        .parseEncryptedContent(jwe)
+                assertArrayEquals payloadBytes, jwt.getPayload()
+            }
+        }
+    }
+
     @Test
     void testPasswordJwes() {