iemejia commented on code in PR #3858:
URL: https://github.com/apache/avro/pull/3858#discussion_r3565149864
##########
lang/c/src/value-read.c:
##########
@@ -38,6 +39,73 @@ static int
read_value(avro_reader_t reader, avro_value_t *dest);
+/*
+ * Minimum number of bytes a single value of the given schema can occupy on the
+ * wire. Used to reject an array/map block count that could not be backed by
the
+ * bytes remaining. A type that can encode to zero bytes (null) returns 0,
which
+ * disables the collection check for it (so an array of nulls is not falsely
+ * rejected). A recursion guard breaks self-referencing schemas.
+ */
+static int64_t
+min_bytes_per_element(avro_schema_t schema, int depth)
+{
+ if (schema == NULL || depth > 64) {
+ return 0;
+ }
Review Comment:
Fixed in 896a688: min_bytes_per_element() now returns 1 (not 0) when the
depth guard trips, so the collection check stays enabled for a crafted
deep/recursive schema; a valid recursive value always encodes to at least 1
byte.
##########
lang/c/tests/test_avro_4293.c:
##########
@@ -0,0 +1,222 @@
+/*
+ * 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.
+ */
+
+/*
+ * A bytes/string value is encoded as a length prefix followed by that many
+ * bytes of data. A malicious or truncated input can declare a huge length with
+ * little or no actual data, which previously caused a correspondingly huge
+ * allocation before the shortfall was noticed. When the reader knows how many
+ * bytes remain (a memory-backed reader), the declared length must be rejected
+ * before allocating for it.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+#include <avro.h>
Review Comment:
Fixed in 896a688: the test now includes <errno.h>.
##########
lang/c/tests/test_avro_4293.c:
##########
@@ -0,0 +1,222 @@
+/*
+ * 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.
+ */
+
+/*
+ * A bytes/string value is encoded as a length prefix followed by that many
+ * bytes of data. A malicious or truncated input can declare a huge length with
+ * little or no actual data, which previously caused a correspondingly huge
+ * allocation before the shortfall was noticed. When the reader knows how many
+ * bytes remain (a memory-backed reader), the declared length must be rejected
+ * before allocating for it.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+#include <avro.h>
+
+/* Decodes buf against the given schema and returns the avro_value_read rc.
+ * A non-zero rc means the read was rejected. */
+static int try_decode(avro_value_iface_t *iface, const char *buf, size_t
buf_size)
+{
+ int rc;
+ avro_value_t decoded;
+ avro_reader_t reader;
+
+ rc = avro_generic_value_new(iface, &decoded);
+ if (rc != 0) {
+ fprintf(stderr, "avro_generic_value_new failed: %s\n",
avro_strerror());
+ return -1;
+ }
+
+ reader = avro_reader_memory(buf, buf_size);
+ if (reader == NULL) {
+ fprintf(stderr, "avro_reader_memory failed\n");
+ avro_value_decref(&decoded);
+ return -1;
+ }
+
+ rc = avro_value_read(reader, &decoded);
+
+ avro_reader_free(reader);
+ avro_value_decref(&decoded);
+ return rc;
+}
+
+static int check_rejects_oversized(const char *schema_literal, const char
*label)
+{
+ avro_schema_t schema = NULL;
+ avro_value_iface_t *iface = NULL;
+ int rc;
+ int ret = EXIT_FAILURE;
+
+ /*
+ * A length prefix declaring 127 bytes (zig-zag long 254 -> varint
+ * 0xFE 0x01), followed by no data at all. The reader has 0 bytes
+ * remaining after the prefix, so a declared length of 127 must be
+ * rejected before allocating.
+ */
+ const char oversized[] = { (char) 0xFE, (char) 0x01 };
+
+ if (avro_schema_from_json_length(schema_literal, strlen(schema_literal),
+ &schema) != 0) {
+ fprintf(stderr, "%s: failed to parse schema: %s\n", label,
avro_strerror());
+ return EXIT_FAILURE;
+ }
+
+ iface = avro_generic_class_from_schema(schema);
+ if (iface == NULL) {
+ fprintf(stderr, "%s: failed to create iface\n", label);
+ avro_schema_decref(schema);
+ return EXIT_FAILURE;
+ }
+
+ rc = try_decode(iface, oversized, sizeof(oversized));
+ if (rc == 0) {
+ fprintf(stderr, "%s: FAIL - oversized length was accepted\n",
label);
+ } else {
+ fprintf(stderr, "%s: oversized length rejected as expected:
%s\n",
+ label, avro_strerror());
+ ret = EXIT_SUCCESS;
+ }
Review Comment:
Fixed in 896a688: the test now asserts the rejection code is EINVAL (what
the availability checks return), so it no longer passes on the pre-fix
ENOSPC-after-allocation behavior.
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