A pack v2 .idx file usually records offset using 64-bit representation
only when the offset does not fit within 31-bit, but you can handcraft
your .idx file to record smaller offset using 64-bit, storing all zero
in the upper 4-byte. By inspecting the original idx file when running
index-pack --verify, encode such low offsets that do not need to be in
64-bit but are encoded using 64-bit just like the original idx file so
that we can still validate the pack/idx pair by comparing the idx file
recomputed with the original.
Signed-off-by: Junio C Hamano <gitster@xxxxxxxxx>
---
* This "fixes" the shortcoming of 3/5 that breaks on a handcrafted .idx
in a way that does not even depend on the off32_limit logic.
builtin/index-pack.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
pack-write.c | 18 +++++++++++++++++-
pack.h | 8 ++++++++
t/t5302-pack-index.sh | 2 +-
4 files changed, 74 insertions(+), 2 deletions(-)
diff --git a/builtin/index-pack.c b/builtin/index-pack.c
index 24a9a16..513fbbc 100644
--- a/builtin/index-pack.c
+++ b/builtin/index-pack.c
@@ -891,6 +891,51 @@ static int git_index_pack_config(const char *k, const char *v, void *cb)
return git_default_config(k, v, cb);
}
+static int cmp_uint32(const void *a_, const void *b_)
+{
+ uint32_t a = *((uint32_t *)a_);
+ uint32_t b = *((uint32_t *)b_);
+
+ return (a < b) ? -1 : (a != b);
+}
+
+static void read_v2_anomalous_offsets(struct packed_git *p,
+ struct pack_idx_option *opts)
+{
+ const uint32_t *idx1, *idx2;
+ uint32_t i;
+
+ /* The address of the 4-byte offset table */
+ idx1 = (((const uint32_t *)p->index_data)
+ + 2 /* 8-byte header */
+ + 256 /* fan out */
+ + 5 * p->num_objects /* 20-byte SHA-1 table */
+ + p->num_objects /* CRC32 table */
+ );
+
+ /* The address of the 8-byte offset table */
+ idx2 = idx1 + p->num_objects;
+
+ for (i = 0; i < p->num_objects; i++) {
+ uint32_t off = ntohl(idx1[i]);
+ if (!(off & 0x80000000))
+ continue;
+ off = off & 0x7fffffff;
+ if (idx2[off * 2])
+ continue;
+ /*
+ * The real offset is ntohl(idx2[off * 2]) in high 4
+ * octets, and ntohl(idx2[off * 2 + 1]) in low 4
+ * octets. But idx2[off * 2] is Zero!!!
+ */
+ ALLOC_GROW(opts->anomaly, opts->anomaly_nr + 1, opts->anomaly_alloc);
+ opts->anomaly[opts->anomaly_nr++] = ntohl(idx2[off * 2 + 1]);
+ }
+
+ if (1 < opts->anomaly_nr)
+ qsort(opts->anomaly, opts->anomaly_nr, sizeof(uint32_t), cmp_uint32);
+}
+
static void read_idx_option(struct pack_idx_option *opts, const char *pack_name)
{
struct packed_git *p = add_packed_git(pack_name, strlen(pack_name), 1);
@@ -903,6 +948,9 @@ static void read_idx_option(struct pack_idx_option *opts, const char *pack_name)
/* Read the attributes from the existing idx file */
opts->version = p->index_version;
+ if (opts->version == 2)
+ read_v2_anomalous_offsets(p, opts);
+
/*
* Get rid of the idx file as we do not need it anymore.
* NEEDSWORK: extract this bit from free_pack_by_name() in
diff --git a/pack-write.c b/pack-write.c
index 92e7eef..9cd3bfb 100644
--- a/pack-write.c
+++ b/pack-write.c
@@ -16,9 +16,25 @@ static int sha1_compare(const void *_a, const void *_b)
return hashcmp(a->sha1, b->sha1);
}
+static int cmp_uint32(const void *a_, const void *b_)
+{
+ uint32_t a = *((uint32_t *)a_);
+ uint32_t b = *((uint32_t *)b_);
+
+ return (a < b) ? -1 : (a != b);
+}
+
static int need_large_offset(off_t offset, const struct pack_idx_option *opts)
{
- return (offset >> 31) || (opts->off32_limit < offset);
+ uint32_t ofsval;
+
+ if ((offset >> 31) || (opts->off32_limit < offset))
+ return 1;
+ if (!opts->anomaly_nr)
+ return 0;
+ ofsval = offset;
+ return !!bsearch(&ofsval, opts->anomaly, opts->anomaly_nr,
+ sizeof(ofsval), cmp_uint32);
}
/*
diff --git a/pack.h b/pack.h
index dddafdd..722a54e 100644
--- a/pack.h
+++ b/pack.h
@@ -41,6 +41,14 @@ struct pack_idx_option {
uint32_t version;
uint32_t off32_limit;
+
+ /*
+ * List of offsets that would fit within off32_limit but
+ * need to be written out as 64-bit entity for byte-for-byte
+ * verification.
+ */
+ int anomaly_alloc, anomaly_nr;
+ uint32_t *anomaly;
};
extern void reset_pack_idx_option(struct pack_idx_option *);
diff --git a/t/t5302-pack-index.sh b/t/t5302-pack-index.sh
index 7c5fa03..76bcaca 100755
--- a/t/t5302-pack-index.sh
+++ b/t/t5302-pack-index.sh
@@ -107,7 +107,7 @@ test_expect_success OFF64_T 'index-pack --verify on 64-bit offset v2 (cheat)' '
git index-pack --verify --index-version=2,0x40000 "test-3-${pack3}.pack"
'
-test_expect_failure OFF64_T 'index-pack --verify on 64-bit offset v2' '
+test_expect_success OFF64_T 'index-pack --verify on 64-bit offset v2' '
git index-pack --verify "test-3-${pack3}.pack"
'
--
1.7.4.1.249.g4aa72
--
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