iemejia commented on code in PR #3842:
URL: https://github.com/apache/avro/pull/3842#discussion_r3563665919
##########
lang/c/src/value-read.c:
##########
@@ -53,7 +53,15 @@ read_array_value(avro_reader_t reader, avro_value_t *dest)
while (block_count != 0) {
if (block_count < 0) {
- block_count = block_count * -1;
+ /* Safe negation: avoid undefined behavior when
+ * block_count == INT64_MIN, since -INT64_MIN is not
+ * representable in int64_t (CWE-190). Use the
+ * -(x+1)+1 idiom to negate without overflow. */
+ block_count = -(block_count + 1) + 1;
+ if (block_count <= 0) {
+ avro_set_error("Invalid array block count");
+ return EINVAL;
+ }
Review Comment:
Good catch. The `-(block_count + 1) + 1` idiom indeed still overflows when
`block_count == INT64_MIN` because `-(INT64_MIN + 1)` yields `INT64_MAX`, and
`INT64_MAX + 1` is UB. Replaced with an explicit `INT64_MIN` guard followed by
`block_count = -block_count;`.
##########
lang/c/src/value-read.c:
##########
@@ -89,7 +97,15 @@ read_map_value(avro_reader_t reader, avro_value_t *dest)
while (block_count != 0) {
if (block_count < 0) {
- block_count = block_count * -1;
+ /* Safe negation: avoid undefined behavior when
+ * block_count == INT64_MIN, since -INT64_MIN is not
+ * representable in int64_t (CWE-190). Use the
+ * -(x+1)+1 idiom to negate without overflow. */
+ block_count = -(block_count + 1) + 1;
+ if (block_count <= 0) {
+ avro_set_error("Invalid map block count");
+ return EINVAL;
+ }
Review Comment:
Fixed the same way as the array path: explicit `INT64_MIN` guard + simple
negation.
##########
lang/c/tests/test_avro_4275.c:
##########
@@ -0,0 +1,377 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to you under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+ * implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+/**
+ * Regression test for INT64_MIN negation overflow in read_array_value()
+ * and read_map_value() (CWE-190).
+ *
+ * The Avro binary format encodes block counts as zigzag-encoded varints.
+ * A negative block count means the absolute value is the actual count,
+ * preceded by a byte-size field. When block_count == INT64_MIN, the
+ * negation overflows (undefined behavior in C). This test verifies that
+ * the decoder rejects such malformed input gracefully.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+#include <avro.h>
+
+/*
+ * Zigzag encoding of INT64_MIN is 0xFFFFFFFFFFFFFFFF, which encodes as
+ * the 10-byte varint: FF FF FF FF FF FF FF FF FF 01
+ */
+static const char int64min_block_count[] = {
+ '\xFF', '\xFF', '\xFF', '\xFF', '\xFF',
+ '\xFF', '\xFF', '\xFF', '\xFF', '\x01'
+};
+
+/*
+ * A valid array with negative block count: [-3] means 3 items follow,
+ * preceded by the block byte-size.
+ *
+ * Layout:
+ * 05 = varint 5 = zigzag(-3) => block_count = -3
+ * 06 = varint 6 = zigzag(3) => block_size = 3 bytes
+ * 14 28 3C = zigzag ints: 10, 20, 30
+ * 00 = terminator (block_count = 0)
+ */
+static const char valid_neg_block_array[] = {
+ '\x05', /* block_count = -3 */
+ '\x06', /* block_size = 3 */
+ '\x14', '\x28', '\x3C', /* ints: 10, 20, 30 */
+ '\x00' /* terminator */
+};
+
+/*
+ * A valid map with negative block count: [-2] means 2 entries follow.
+ *
+ * Layout:
+ * 03 = varint 3 = zigzag(-2) => block_count = -2
+ * 0E = varint 14 = zigzag(7) => block_size = 7 bytes
+ * 02 61 14 = key "a" (len=1, 'a'), value int 10
+ * 02 62 28 = key "b" (len=1, 'b'), value int 20
+ * 00 = terminator
+ */
+static const char valid_neg_block_map[] = {
+ '\x03', /* block_count = -2 */
+ '\x0E', /* block_size = 7 */
+ '\x02', '\x61', '\x14', /* key "a", value 10 */
+ '\x02', '\x62', '\x28', /* key "b", value 20 */
Review Comment:
You're right, the two entries total 6 bytes (each is: 1-byte string length
varint + 1-byte key + 1-byte int varint = 3 bytes). Fixed the block_size from
`0x0E` (zigzag 7) to `0x0C` (zigzag 6) and updated the comment to match.
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