8000 Merge pull request #6420 from derrickstolee/commit-graph-hashing · libgit2/libgit2@e45b25e · GitHub
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ethomsonethomson
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Merge pull request #6420 from derrickstolee/commit-graph-hashing
commit-graph: only verify csum on git_commit_graph_open().
2 parents a3841af + 6de3221 commit e45b25e

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3 files changed

+68
-10
lines changed

3 files changed

+68
-10
lines changed

‎src/libgit2/commit_graph.c

Lines changed: 24 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -200,8 +200,7 @@ int git_commit_graph_file_parse(
200200
const unsigned char *chunk_hdr;
201201
struct git_commit_graph_chunk *last_chunk;
202202
uint32_t i;
203-
off64_t last_chunk_offset, chunk_offset, trailer_offset;
204-
unsigned char checksum[GIT_HASH_SHA1_SIZE];
203+
uint64_t last_chunk_offset, chunk_offset, trailer_offset;
205204
size_t checksum_size;
206205
int error;
207206
struct git_commit_graph_chunk chunk_oid_fanout = {0}, chunk_oid_lookup = {0},
@@ -234,16 +233,11 @@ int git_commit_graph_file_parse(
234233
return commit_graph_error("wrong commit-graph size");
235234
memcpy(file->checksum, (data + trailer_offset), checksum_size);
236235

237-
if (git_hash_buf(checksum, data, (size_t)trailer_offset, GIT_HASH_ALGORITHM_SHA1) < 0)
238-
return commit_graph_error("could not calculate signature");
239-
if (memcmp(checksum, file->checksum, checksum_size) != 0)
240-
return commit_graph_error("index signature mismatch");
241-
242236
chunk_hdr = data + sizeof(struct git_commit_graph_header);
243237
last_chunk = NULL;
244238
for (i = 0; i < hdr->chunks; ++i, chunk_hdr += 12) {
245-
chunk_offset = ((off64_t)ntohl(*((uint32_t *)(chunk_hdr + 4)))) << 32
246-
| ((off64_t)ntohl(*((uint32_t *)(chunk_hdr + 8))));
239+
chunk_offset = ((uint64_t)ntohl(*((uint32_t *)(chunk_hdr + 4)))) << 32
240+
| ((uint64_t)ntohl(*((uint32_t *)(chunk_hdr + 8))));
247241
if (chunk_offset < last_chunk_offset)
248242
return commit_graph_error("chunks are non-monotonic");
249243
if (chunk_offset >= trailer_offset)
@@ -331,9 +325,29 @@ int git_commit_graph_new(git_commit_graph **cgraph_out, const char *objects_dir,
331325
return error;
332326
}
333327

328+
int git_commit_graph_validate(git_commit_graph *cgraph) {
329+
unsigned char checksum[GIT_HASH_SHA1_SIZE];
330+
size_t checksum_size = GIT_HASH_SHA1_SIZE;
331+
size_t trailer_offset = cgraph->file->graph_map.len - checksum_size;
332+
333+
if (cgraph->file->graph_map.len < checksum_size)
334+
return commit_graph_error("map length too small");
335+
336+
if (git_hash_buf(checksum, cgraph->file->graph_map.data, trailer_offset, GIT_HASH_ALGORITHM_SHA1) < 0)
337+
return commit_graph_error("could not calculate signature");
338+
if (memcmp(checksum, cgraph->file->checksum, checksum_size) != 0)
339+
return commit_graph_error("index signature mismatch");
340+
341+
return 0;
342+
}
343+
334344
int git_commit_graph_open(git_commit_graph **cgraph_out, const char *objects_dir)
335345
{
336-
return git_commit_graph_new(cgraph_out, objects_dir, true);
346+
int error = git_commit_graph_new(cgraph_out, objects_dir, true);
347+
if (!error) {
348+
return git_commit_graph_validate(*cgraph_out);
349+
}
350+
return error;
337351
}
338352

339353
int git_commit_graph_file_open(git_commit_graph_file **file_out, const char *path)

‎src/libgit2/commit_graph.h

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -106,6 +106,9 @@ struct git_commit_graph {
106106
/** Create a new commit-graph, optionally opening the underlying file. */
107107
int git_commit_graph_new(git_commit_graph **cgraph_out, const char *objects_dir, bool open_file);
108108

109+
/** Validate the checksum of a commit graph */
110+
int git_commit_graph_validate(git_commit_graph *cgraph);
111+
109112
/** Open and validate a commit-graph file. */
110113
int git_commit_graph_file_open(git_commit_graph_file **file_out, const char *path);
111114

‎tests/libgit2/graph/commitgraph.c

Lines changed: 41 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -124,3 +124,44 @@ void test_graph_commitgraph__writer(void)
124124
git_commit_graph_writer_free(w);
125125
git_repository_free(repo);
126126
}
127+
128+
void test_graph_commitgraph__validate(void)
129+
{
130+
git_repository *repo;
131+
struct git_commit_graph *cgraph;
132+
git_str objects_dir = GIT_STR_INIT;
133+
134+
cl_git_pass(git_repository_open(&repo, cl_fixture("testrepo.git")));
135+
cl_git_pass(git_str_joinpath(&objects_dir, git_repository_path(repo), "objects"));
136+
137+
/* git_commit_graph_open() calls git_commit_graph_validate() */
138+
cl_git_pass(git_commit_graph_open(&cgraph, git_str_cstr(&objects_dir)));
139+
140+
git_commit_graph_free(cgraph);
141+
git_str_dispose(&objects_dir);
142+
git_repository_free(repo);
143+
}
144+
145+
void test_graph_commitgraph__validate_corrupt(void)
146+
{
147+
git_repository *repo;
148+
struct git_commit_graph *cgraph;
149+
int fd = -1;
150+
151+
cl_fixture_sandbox("testrepo.git");
152+
cl_git_pass(git_repository_open(&repo, cl_git_sandbox_path(1, "testrepo.git", NULL)));
153+
154+
/* corrupt commit graph checksum at the end of the file */
155+
cl_assert((fd = p_open(cl_git_sandbox_path(0, "testrepo.git", "objects", "info", "commit-graph", NULL), O_WRONLY)) > 0);
156+
cl_assert(p_lseek(fd, -5, SEEK_END) > 0);
157+
cl_must_pass(p_write(fd, "\0\0", 2));
158+
cl_must_pass(p_close(fd));
159+
160+
/* git_commit_graph_open() calls git_commit_graph_validate() */
161+
cl_git_fail(git_commit_graph_open(&cgraph, cl_git_sandbox_path(1, "testrepo.git", "objects", NULL)));
162+
163+
git_commit_graph_free(cgraph);
164+
git_repository_free(repo);
165+
166+
cl_fixture_cleanup("testrepo.git");
167+
}

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