thodg/libgit2/fuzzers/commit_graph_fuzzer.c

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• Hash : 3fd57a75
  Author :
  Date : 2021-01-04T18:22:43
  

  commit-graph: Introduce a parser for commit-graph files This change is the first in a series to add support for git's commit-graph. This should speed up commit graph traversals by avoiding object parsing and allowing some operations to terminate earlier. Part of: #5757

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• fuzzers/commit_graph_fuzzer.c

• /*
   * libgit2 commit-graph fuzzer target.
   *
   * Copyright (C) the libgit2 contributors. All rights reserved.
   *
   * This file is part of libgit2, distributed under the GNU GPL v2 with
   * a Linking Exception. For full terms see the included COPYING file.
   */
  
  #include <stdio.h>
  
  #include "git2.h"
  
  #include "buffer.h"
  #include "common.h"
  #include "futils.h"
  #include "hash.h"
  #include "commit_graph.h"
  
  int LLVMFuzzerInitialize(int *argc, char ***argv)
  {
  	GIT_UNUSED(argc);
  	GIT_UNUSED(argv);
  
  	if (git_libgit2_init() < 0) {
  		fprintf(stderr, "Failed to initialize libgit2\n");
  		abort();
  	}
  	return 0;
  }
  
  int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
  {
  	git_commit_graph_file cgraph = {{0}};
  	git_buf commit_graph_buf = GIT_BUF_INIT;
  	git_oid oid = {{0}};
  	bool append_hash = false;
  
  	if (size < 4)
  		return 0;
  
  	/*
  	 * If the first byte in the stream has the high bit set, append the
  	 * SHA1 hash so that the file is somewhat valid.
  	 */
  	append_hash = *data & 0x80;
  	/* Keep a 4-byte alignment to avoid unaligned accesses. */
  	data += 4;
  	size -= 4;
  
  	if (append_hash) {
  		if (git_buf_init(&commit_graph_buf, size + sizeof(oid)) < 0)
  			goto cleanup;
  		if (git_hash_buf(&oid, data, size) < 0) {
  			fprintf(stderr, "Failed to compute the SHA1 hash\n");
  			abort();
  		}
  		memcpy(commit_graph_buf.ptr, data, size);
  		memcpy(commit_graph_buf.ptr + size, &oid, sizeof(oid));
  	} else {
  		git_buf_attach_notowned(&commit_graph_buf, (char *)data, size);
  	}
  
  	if (git_commit_graph_parse(
  			    &cgraph,
  			    (const unsigned char *)git_buf_cstr(&commit_graph_buf),
  			    git_buf_len(&commit_graph_buf))
  	    < 0)
  		goto cleanup;
  
  cleanup:
  	git_commit_graph_close(&cgraph);
  	git_buf_dispose(&commit_graph_buf);
  	return 0;
  }
  

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