fuzz-compress: add fuzzer for compression and decompression

src/fuzz/fuzz-compress.c

@@ -0,0 +1,80 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include <errno.h>
+
+#include "alloc-util.h"
+#include "compress.h"
+#include "fuzz.h"
+
+static int compress(int alg,
+                    const void *src, uint64_t src_size,
+                    void *dst, size_t dst_alloc_size, size_t *dst_size) {
+
+        if (alg == OBJECT_COMPRESSED_LZ4)
+                return compress_blob_lz4(src, src_size, dst, dst_alloc_size, dst_size);
+        if (alg == OBJECT_COMPRESSED_XZ)
+                return compress_blob_xz(src, src_size, dst, dst_alloc_size, dst_size);
+        return -EOPNOTSUPP;
+}
+
+typedef struct header {
+        uint32_t alg:2; /* We have only two compression algorithms so far, but we might add
+                         * more in the future. Let's make this a bit wider so our fuzzer
+                         * cases remain stable in the future. */
+        uint32_t sw_len;
+        uint32_t sw_alloc;
+        uint32_t reserved[3]; /* Extra space to keep fuzz cases stable in case we need to
+                               * add stuff in the future. */
+        uint8_t data[];
+} header;
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+        _cleanup_free_ void *buf = NULL, *buf2 = NULL;
+        int r;
+
+        if (size < offsetof(header, data) + 1)
+                return 0;
+
+        const header *h = (struct header*) data;
+        const size_t data_len = size - offsetof(header, data);
+
+        int alg = h->alg;
+
+        /* We don't want to fill the logs with messages about parse errors.
+         * Disable most logging if not running standalone */
+        if (!getenv("SYSTEMD_LOG_LEVEL"))
+                log_set_max_level(LOG_CRIT);
+
+        log_info("Using compression %s, data size=%zu",
+                 object_compressed_to_string(alg) ?: "(none)",
+                 data_len);
+
+        buf = malloc(MAX(size, 128u)); /* Make the buffer a bit larger for very small data */
+        if (!buf) {
+                log_oom();
+                return 0;
+        }
+
+        size_t csize;
+        r = compress(alg, h->data, data_len, buf, size, &csize);
+        if (r < 0) {
+                log_error_errno(r, "Compression failed: %m");
+                return 0;
+        }
+
+        log_debug("Compressed %zu bytes to → %zu bytes", data_len, csize);
+
+        size_t sw_alloc = MAX(h->sw_alloc, 1u);
+        buf2 = malloc(sw_alloc);
+        if (!buf) {
+                log_oom();
+                return 0;
+        }
+
+        size_t sw_len = MIN(data_len - 1, h->sw_len);
+
+        r = decompress_startswith(alg, buf, csize, &buf2, &sw_alloc, h->data, sw_len, h->data[sw_len]);
+        assert_se(r > 0);
+
+        return 0;
+}

src/fuzz/meson.build

@@ -62,4 +62,8 @@ fuzzers += [
          [libsystemd_journal_remote,
           libshared],
          []],
+
+        [['src/fuzz/fuzz-compress.c'],
+         [libshared],
+         []],
 ]