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cat-file: validate remote atoms with an allow-list 

`strstr()` is not enough to validate the format placeholders in
`remote-object-info` causing two errors:

1. Atoms recognized by `expand_atom()` but the remote doesn't returns 1,
   but `data->type` contains garbage causing segfault.

2. `expand_atom()` returns 0 for unknown atoms, calling
   `strbuf_expand_bad_format()` which ends up dying, blocking local
   queries if the same format is shared.

Add an allow-list with the supported atoms at the top of `expand_atom()`.
In remote mode, unsupported atoms return 1 leaving the buffer empty,
honoring how `for-each-ref` handles known but inapplicable atoms.

As extra safety, initialize `data->type` to `OBJ_BAD` and add a `NULL`
check for `type_name()` so uninitialized data doesn't cause segfault.

Update tests that expect previous `die()` behavior to expect an empty
string and add an explicit test for empty string return on unknown
placeholder.

Update cat-file command documentation regarding `remote-object-info`.

Mentored-by: Karthik Nayak <karthik.188@gmail.com>
Mentored-by: Chandra Pratap <chandrapratap3519@gmail.com>
Signed-off-by: Pablo Sabater <pabloosabaterr@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
seen
Pablo Sabater 2026-07-01 14:18:46 +02:00 committed by Junio C Hamano
parent 7134a94db6
commit 03e2e84446
3 changed files with 57 additions and 13 deletions
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2
Documentation/git-cat-file.adoc
View File

@ -451,7 +451,7 @@ CAVEATS

Note that since only `%(objectname)` and `%(objectsize)` are currently
supported by the `remote-object-info` command. Using any other placeholder in
the format string will raise an error.
the format string will return an empty string in its position.

Note that the sizes of objects on disk are reported accurately, but care
should be taken in drawing conclusions about which refs or objects are

41
builtin/cat-file.c
View File

@ -336,8 +336,18 @@ struct expand_data {
* optimized out.
*/
unsigned skip_object_info : 1;

/*
* Flags about when an object info is being fetched from remote.
*/
unsigned is_remote:1;
};
#define EXPAND_DATA_INIT { .mode = S_IFINVALID, .type = OBJ_BAD }

static const char *remote_object_info_atoms[] = {
"objectname",
"objectsize",
};
#define EXPAND_DATA_INIT { .mode = S_IFINVALID }

static int is_atom(const char *atom, const char *s, int slen)
{
@ -348,14 +358,31 @@ static int is_atom(const char *atom, const char *s, int slen)
static int expand_atom(struct strbuf *sb, const char *atom, int len,
struct expand_data *data)
{
if (data->is_remote) {
size_t i, allowed_nr = ARRAY_SIZE(remote_object_info_atoms);
for (i = 0; i < allowed_nr; i++)
if (is_atom(remote_object_info_atoms[i], atom, len))
break;

/*
* On remote, skip unsupported atoms returning an empty sb,
* honoring how for-each-ref handles known but inapplicable
* atoms (e.g. %(tagger)).
*/
if (i == allowed_nr)
return 1;
}

if (is_atom("objectname", atom, len)) {
if (!data->mark_query)
strbuf_add_oid_hex(sb, &data->oid);
} else if (is_atom("objecttype", atom, len)) {
if (data->mark_query)
if (data->mark_query) {
data->info.typep = &data->type;
else
strbuf_addstr(sb, type_name(data->type));
} else {
const char *t = type_name(data->type);
strbuf_addstr(sb, t ? t : "");
}
} else if (is_atom("objectsize", atom, len)) {
if (data->mark_query)
data->info.sizep = &data->size;
@ -711,10 +738,6 @@ static int get_remote_info(struct batch_options *opt,
CALLOC_ARRAY(*remote_object_info, object_info_oids->nr);
gtransport->smart_options->object_info_oids = object_info_oids;

/* 'objectsize' is the only option currently supported */
if (!strstr(opt->format, "%(objectsize)"))
die(_("%s is currently not supported with remote-object-info"), opt->format);

string_list_append(&object_info_options, "size");

if (object_info_options.nr > 0) {
@ -844,7 +867,9 @@ static void parse_cmd_remote_object_info(struct batch_options *opt,
*/
data->size = *remote_object_info[i].sizep;
opt->batch_mode = BATCH_MODE_INFO;
data->is_remote = 1;
batch_object_write(argv[i + 1], output, opt, data, NULL, 0);
data->is_remote = 0;
} else {
report_object_status(opt, oid_to_hex(&data->oid), &data->oid, "missing");
}

27
t/t1017-cat-file-remote-object-info.sh
View File

@ -236,6 +236,21 @@ test_expect_success 'remote-object-info does not die on missing oid like info' '
)
'

# This tests depends on %(objecttype) not being supported yet, once supported
# it needs to be updated.
test_expect_success 'unsupported placeholder on remote returns empty string' '
(
set_transport_variables "$daemon_parent" &&
cd "$daemon_parent/daemon_client_empty" &&

echo "" >expect &&
git cat-file --batch-command="%(objecttype)" >actual <<-EOF &&
remote-object-info "$GIT_DAEMON_URL/parent" $hello_oid
EOF
test_cmp expect actual
)
'

# Test --batch-command remote-object-info with 'git://' and
# transfer.advertiseobjectinfo set to false, i.e. server does not have object-info capability
test_expect_success 'batch-command remote-object-info git:// fails when transfer.advertiseobjectinfo=false' '
@ -575,10 +590,12 @@ test_expect_success 'remote-object-info fails on unsupported filter option (obje
set_transport_variables "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
cd "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&

test_must_fail git cat-file --batch-command="%(objectsize:disk)" 2>err <<-EOF &&
echo "$hello_oid " >expect &&

git cat-file --batch-command="%(objectname) %(objectsize:disk)" >actual <<-EOF &&
remote-object-info "$HTTPD_URL/smart/http_parent" $hello_oid
EOF
test_grep "%(objectsize:disk) is currently not supported with remote-object-info" err
test_cmp expect actual
)
'

@ -587,10 +604,12 @@ test_expect_success 'remote-object-info fails on unsupported filter option (delt
set_transport_variables "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
cd "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&

test_must_fail git cat-file --batch-command="%(deltabase)" 2>err <<-EOF &&
echo "" >expect &&

git cat-file --batch-command="%(deltabase)" >actual <<-EOF &&
remote-object-info "$HTTPD_URL/smart/http_parent" $hello_oid
EOF
test_grep "%(deltabase) is currently not supported with remote-object-info" err
test_cmp expect actual
)
'