test for segment size change

xtest/test_tdfs.py

@@ -127,16 +127,6 @@ def test_manifest_validity_with_assertions(
 
 ## TAMPER FUNCTIONS
 
-
-def break_binding(manifest: tdfs.Manifest) -> tdfs.Manifest:
-    #  base64 decode policy from manifest.encryptionInformation.policy
-    p = manifest.encryptionInformation.policy_object
-    p.body.dataAttributes = []
-    p.body.dissem = ["[email protected]"]
-    manifest.encryptionInformation.policy_object = p
-    return manifest
-
-
 def change_last_three(byt: bytes) -> bytes:
     new_three = "".join(
         random.choices(string.ascii_lowercase + string.digits, k=3)
@@ -146,15 +136,28 @@ def change_last_three(byt: bytes) -> bytes:
         return change_last_three(byt)
     return byt[:-3] + new_three
 
+def change_policy(manifest: tdfs.Manifest) -> tdfs.Manifest:
+    #  base64 decode policy from manifest.encryptionInformation.policy
+    p = manifest.encryptionInformation.policy_object
+    p.body.dataAttributes = []
+    p.body.dissem = ["[email protected]"]
+    manifest.encryptionInformation.policy_object = p
+    return manifest
+
+def change_policy_binding(manifest: tdfs.Manifest) -> tdfs.Manifest:
+    pb = manifest.encryptionInformation.keyAccess[0].policyBinding
+    altered_pb = base64.b64encode(change_last_three(base64.b64decode(pb)))
+    manifest.encryptionInformation.keyAccess[0].policyBinding = altered_pb
+    return manifest
 
-def break_root_signature(manifest: tdfs.Manifest) -> tdfs.Manifest:
+def change_root_signature(manifest: tdfs.Manifest) -> tdfs.Manifest:
     root_sig = manifest.encryptionInformation.integrityInformation.rootSignature.sig
     altered_sig = base64.b64encode(change_last_three(base64.b64decode(root_sig)))
     manifest.encryptionInformation.integrityInformation.rootSignature.sig = altered_sig
     return manifest
 
 
-def break_segment_signature(manifest: tdfs.Manifest) -> tdfs.Manifest:
+def change_segment_hash(manifest: tdfs.Manifest) -> tdfs.Manifest:
     assert manifest.encryptionInformation.integrityInformation.segments
     segments = manifest.encryptionInformation.integrityInformation.segments
     # choose a random segment
@@ -165,17 +168,36 @@ def break_segment_signature(manifest: tdfs.Manifest) -> tdfs.Manifest:
     manifest.encryptionInformation.integrityInformation.segments[index] = segment
     return manifest
 
+def change_segment_size(manifest: tdfs.Manifest) -> tdfs.Manifest:
+    assert manifest.encryptionInformation.integrityInformation.segments
+    segments = manifest.encryptionInformation.integrityInformation.segments
+    # choose a random segment
+    index = random.randrange(len(segments))
+    segment = segments[index]
+    segment.encryptedSegmentSize = segment.segmentSize + 1
+    manifest.encryptionInformation.integrityInformation.segments[index] = segment
+    return manifest
+
+def change_encrypted_segment_size(manifest: tdfs.Manifest) -> tdfs.Manifest:
+    assert manifest.encryptionInformation.integrityInformation.segments
+    segments = manifest.encryptionInformation.integrityInformation.segments
+    # choose a random segment
+    index = random.randrange(len(segments))
+    segment = segments[index]
+    segment.encryptedSegmentSize = segment.encryptedSegmentSize + 1
+    manifest.encryptionInformation.integrityInformation.segments[index] = segment
+    return manifest
 
-## TAMPER TESTS
 
+## TAMPER TESTS
 
 def test_tdf_with_unbound_policy(
     encrypt_sdk: tdfs.sdk_type, decrypt_sdk: tdfs.sdk_type, pt_file: str, tmp_dir: str
 ) -> None:
     skip_hexless_skew(encrypt_sdk, decrypt_sdk)
     ct_file = do_encrypt_with(pt_file, encrypt_sdk, "ztdf", tmp_dir)
     assert os.path.isfile(ct_file)
-    b_file = tdfs.update_manifest("unbound_policy", ct_file, break_binding)
+    b_file = tdfs.update_manifest("unbound_policy", ct_file, change_policy)
     fname = os.path.basename(b_file).split(".")[0]
     rt_file = f"{tmp_dir}test-{fname}.untdf"
     try:
@@ -192,7 +214,7 @@ def test_tdf_with_altered_root_sig(
     skip_hexless_skew(encrypt_sdk, decrypt_sdk)
     ct_file = do_encrypt_with(pt_file, encrypt_sdk, "ztdf", tmp_dir)
     assert os.path.isfile(ct_file)
-    b_file = tdfs.update_manifest("broken_root_sig", ct_file, break_root_signature)
+    b_file = tdfs.update_manifest("broken_root_sig", ct_file, change_root_signature)
     fname = os.path.basename(b_file).split(".")[0]
     rt_file = f"{tmp_dir}test-{fname}.untdf"
     try:
@@ -209,7 +231,7 @@ def test_tdf_with_altered_seg_sig(
     skip_hexless_skew(encrypt_sdk, decrypt_sdk)
     ct_file = do_encrypt_with(pt_file, encrypt_sdk, "ztdf", tmp_dir)
     assert os.path.isfile(ct_file)
-    b_file = tdfs.update_manifest("broken_seg_sig", ct_file, break_segment_signature)
+    b_file = tdfs.update_manifest("broken_seg_sig", ct_file, change_segment_hash)
     fname = os.path.basename(b_file).split(".")[0]
     rt_file = f"{tmp_dir}test-{fname}.untdf"
     try:
@@ -219,6 +241,22 @@ def test_tdf_with_altered_seg_sig(
         assert b"signature" in exc.output
         assert b"tamper" in exc.output or b"IntegrityError" in exc.output
 
+def test_tdf_with_altered_seg_size(
+    encrypt_sdk: tdfs.sdk_type, decrypt_sdk: tdfs.sdk_type, pt_file: str, tmp_dir: str
+):
+    skip_hexless_skew(encrypt_sdk, decrypt_sdk)
+    ct_file = do_encrypt_with(pt_file, encrypt_sdk, "ztdf", tmp_dir)
+    assert os.path.isfile(ct_file)
+    b_file = tdfs.update_manifest("broken_seg_size", ct_file, change_segment_size)
+    fname = os.path.basename(b_file).split(".")[0]
+    rt_file = f"{tmp_dir}test-{fname}.untdf"
+    try:
+        tdfs.decrypt(decrypt_sdk, b_file, rt_file, "ztdf")
+        assert False, "decrypt succeeded unexpectedly"
+    except subprocess.CalledProcessError as exc:
+        assert b"segment" in exc.output
+        assert b"tamper" in exc.output or b"IntegrityError" in exc.output
+
 
 ## ASSERTION TESTS