From 4feb75957aec000797f8130dca30f2b8e2db37ee Mon Sep 17 00:00:00 2001
From: TapTap <taptap.programming@gmail.com>
Date: Sat, 8 Aug 2026 20:08:30 +0200
Subject: [PATCH] fix: validate delta output and integration test skips

---
 src/shared/delta.c                 | 14 ++++++++++++--
 tests/integration/test_features.py |  2 +-
 tests/integration/test_ssh.py      | 16 +++++++++++++---
 tests/test_delta.c                 | 17 +++++++++++++++++
 4 files changed, 43 insertions(+), 6 deletions(-)

diff --git a/src/shared/delta.c b/src/shared/delta.c
index f9f7c84..d166f30 100644
--- a/src/shared/delta.c
+++ b/src/shared/delta.c
@@ -458,7 +458,8 @@ Delta* delta_deserialize(const Data* data) {
 
 void* delta_apply(const void* old_data, uint64_t old_size, const Delta* delta,
                   uint32_t block_size) {
-  if (!old_data || !delta)
+  if (!old_data || !delta || (delta->new_file_size > 0 && delta->instructions == NULL) ||
+      (delta->instruction_count > 0 && block_size == 0))
     return NULL;
 
   void* output = malloc((size_t)delta->new_file_size);
@@ -472,10 +473,15 @@ void* delta_apply(const void* old_data, uint64_t old_size, const Delta* delta,
   for (uint32_t i = 0; i < delta->instruction_count; i++) {
     if (delta->instructions[i].type == DELTA_INSTR_BLOCK_MATCH) {
       uint64_t src_offset = (uint64_t)delta->instructions[i].match.block_index * block_size;
+      if (src_offset > UINT64_MAX - delta->instructions[i].match.block_offset) {
+        free(output);
+        return NULL;
+      }
       src_offset += delta->instructions[i].match.block_offset;
       uint32_t len = delta->instructions[i].match.length;
 
-      if (src_offset + len > old_size) {
+      if (src_offset > old_size || (uint64_t)len > old_size - src_offset ||
+          out_pos > delta->new_file_size || (uint64_t)len > delta->new_file_size - out_pos) {
         free(output);
         return NULL;
       }
@@ -483,6 +489,10 @@ void* delta_apply(const void* old_data, uint64_t old_size, const Delta* delta,
       out_pos += len;
     } else {
       uint32_t len = delta->instructions[i].literal.length;
+      if (out_pos > delta->new_file_size || (uint64_t)len > delta->new_file_size - out_pos) {
+        free(output);
+        return NULL;
+      }
       memcpy(out + out_pos, delta->instructions[i].literal.data, len);
       out_pos += len;
     }
diff --git a/tests/integration/test_features.py b/tests/integration/test_features.py
index 63a5bf6..65bac5c 100644
--- a/tests/integration/test_features.py
+++ b/tests/integration/test_features.py
@@ -238,7 +238,7 @@ class TestProgress:
         )
         assert result.returncode == 0, f"Exit {result.returncode}: {result.stderr[:100]}"
         output = result.stdout + result.stderr
-        assert len(output) >= 0
+        assert output, "--progress produced no output"
 
 
 class TestBandwidthLimit:
diff --git a/tests/integration/test_ssh.py b/tests/integration/test_ssh.py
index 82b86ef..bad3790 100644
--- a/tests/integration/test_ssh.py
+++ b/tests/integration/test_ssh.py
@@ -52,9 +52,11 @@ def _check_ssh():
         pass
 
 
+_check_ssh()
+
+
 @pytest.fixture(scope="module", autouse=True)
 def setup_test_data():
-    _check_ssh()
     if SSH_AVAILABLE:
         generate_test_files(SOURCE_DIR, full=False)
         clean_dir(DEST_DIR)
@@ -84,8 +86,12 @@ def _run_ssh_test(name, flags, expected_missing=None):
     return make_result(name, True, duration)
 
 
-@pytest.mark.skipif(not SSH_AVAILABLE, reason="SSH to localhost not available")
 class TestSSHStandard:
+    @pytest.fixture(autouse=True)
+    def require_ssh(self):
+        if not SSH_AVAILABLE:
+            pytest.skip("SSH to localhost not available")
+
     def test_standard(self):
         r = _run_ssh_test("SSH (localhost)", [])
         assert r["status"] == "Success", r["error"]
@@ -119,8 +125,12 @@ class TestSSHStandard:
         assert r["status"] == "Success", r["error"]
 
 
-@pytest.mark.skipif(not SSH_AVAILABLE, reason="SSH to localhost not available")
 class TestSSHFeatures:
+    @pytest.fixture(autouse=True)
+    def require_ssh(self):
+        if not SSH_AVAILABLE:
+            pytest.skip("SSH to localhost not available")
+
     def test_archive(self):
         r = _run_ssh_test("SSH Archive (-a)", ["-a"])
         assert r["status"] == "Success", r["error"]
diff --git a/tests/test_delta.c b/tests/test_delta.c
index 09a6467..a55309d 100644
--- a/tests/test_delta.c
+++ b/tests/test_delta.c
@@ -323,6 +323,22 @@ static void test_large_file_delta() {
   free(new_data);
 }
 
+static void test_delta_apply_rejects_output_overflow() {
+  uint8_t old_data[8] = {0};
+  uint8_t literal_data[2] = {'x', 'y'};
+  DeltaInstruction instruction = {
+      .type = DELTA_INSTR_LITERAL,
+      .literal = {.data = literal_data, .length = sizeof(literal_data)},
+  };
+  Delta delta = {
+      .new_file_size = 1,
+      .instruction_count = 1,
+      .instructions = &instruction,
+  };
+
+  EXPECT_TRUE(delta_apply(old_data, sizeof(old_data), &delta, 1) == NULL);
+}
+
 void test_delta() {
   test_adler32_basic();
   test_adler32_different_data();
@@ -338,4 +354,5 @@ void test_delta() {
   test_should_attempt();
   test_is_worthwhile();
   test_large_file_delta();
+  test_delta_apply_rejects_output_overflow();
 }
-- 
2.52.0