Am 17.02.21 um 19:31 schrieb Jeff King:
> On Sun, Feb 14, 2021 at 11:10:57AM +0100, René Scharfe. wrote:
>
>> Allow restricting the tags used by the placeholder %(describe) with the
>> options match and exclude. E.g. the following command describes the
>> current commit using official version tags, without those for release
>> candidates:
>>
>> $ git log -1 --format='%(describe:match=v[0-9]*,exclude=*rc*)'
>
> An interesting side effect of this series is that it allows remote users
> asking for archives to fill in this data, too (by using export-subst
> placeholders). That includes servers allowing "git archive --remote",
> but also services like GitHub that will run git-archive on behalf of
> clients.
>
> I wonder what avenues for mischief this provides. Certainly using extra
> CPU to run git-describe.
A repository can contain millions of files, each file can contain
millions of $Format:...$ sequences and each of them can contain millions
of %(describe) placeholders. Each of them could have different match or
exclude args to prevent caching. Allowing a single request to cause
trillions of calls of git describe sounds excessive. Let's limit this.
-- >8 --
Subject: [PATCH] archive: expand only a single %(describe) per archive
Every %(describe) placeholder in $Format:...$ strings in files with the
attribute export-subst is expanded by calling git describe. This can
potentially result in a lot of such calls per archive. That's OK for
local repositories under control of the user of git archive, but could
be a problem for hosted repositories.
Expand only a single %(describe) placeholder per archive for now to
avoid denial-of-service attacks. We can make this limit configurable
later if needed, but let's start out simple.
Reported-by: Jeff King <peff@xxxxxxxx>
Signed-off-by: René Scharfe <l.s.r@xxxxxx>
---
Documentation/gitattributes.txt | 3 ++-
archive.c | 16 ++++++++++------
archive.h | 2 ++
pretty.c | 8 ++++++++
pretty.h | 5 +++++
t/t5001-archive-attr.sh | 14 ++++++++++++++
6 files changed, 41 insertions(+), 7 deletions(-)
diff --git a/Documentation/gitattributes.txt b/Documentation/gitattributes.txt
index e84e104f93..0a60472bb5 100644
--- a/Documentation/gitattributes.txt
+++ b/Documentation/gitattributes.txt
@@ -1174,7 +1174,8 @@ tag then no replacement will be done. The placeholders are the same
as those for the option `--pretty=format:` of linkgit:git-log[1],
except that they need to be wrapped like this: `$Format:PLACEHOLDERS$`
in the file. E.g. the string `$Format:%H$` will be replaced by the
-commit hash.
+commit hash. However, only one `%(describe)` placeholder is expanded
+per archive to avoid denial-of-service attacks.
Packing objects
diff --git a/archive.c b/archive.c
index 5919d9e505..2dd2236ae0 100644
--- a/archive.c
+++ b/archive.c
@@ -37,13 +37,10 @@ void init_archivers(void)
static void format_subst(const struct commit *commit,
const char *src, size_t len,
- struct strbuf *buf)
+ struct strbuf *buf, struct pretty_print_context *ctx)
{
char *to_free = NULL;
struct strbuf fmt = STRBUF_INIT;
- struct pretty_print_context ctx = {0};
- ctx.date_mode.type = DATE_NORMAL;
- ctx.abbrev = DEFAULT_ABBREV;
if (src == buf->buf)
to_free = strbuf_detach(buf, NULL);
@@ -61,7 +58,7 @@ static void format_subst(const struct commit *commit,
strbuf_add(&fmt, b + 8, c - b - 8);
strbuf_add(buf, src, b - src);
- format_commit_message(commit, fmt.buf, buf, &ctx);
+ format_commit_message(commit, fmt.buf, buf, ctx);
len -= c + 1 - src;
src = c + 1;
}
@@ -94,7 +91,7 @@ static void *object_file_to_archive(const struct archiver_args *args,
strbuf_attach(&buf, buffer, *sizep, *sizep + 1);
convert_to_working_tree(args->repo->index, path, buf.buf, buf.len, &buf, &meta);
if (commit)
- format_subst(commit, buf.buf, buf.len, &buf);
+ format_subst(commit, buf.buf, buf.len, &buf, args->pretty_ctx);
buffer = strbuf_detach(&buf, &size);
*sizep = size;
}
@@ -633,12 +630,19 @@ int write_archive(int argc, const char **argv, const char *prefix,
const char *name_hint, int remote)
{
const struct archiver *ar = NULL;
+ struct pretty_print_describe_status describe_status = {0};
+ struct pretty_print_context ctx = {0};
struct archiver_args args;
int rc;
git_config_get_bool("uploadarchive.allowunreachable", &remote_allow_unreachable);
git_config(git_default_config, NULL);
+ describe_status.max_invocations = 1;
+ ctx.date_mode.type = DATE_NORMAL;
+ ctx.abbrev = DEFAULT_ABBREV;
+ ctx.describe_status = &describe_status;
+ args.pretty_ctx = &ctx;
args.repo = repo;
args.prefix = prefix;
string_list_init(&args.extra_files, 1);
diff --git a/archive.h b/archive.h
index 33551b7ee1..49fab71aaf 100644
--- a/archive.h
+++ b/archive.h
@@ -5,6 +5,7 @@
#include "pathspec.h"
struct repository;
+struct pretty_print_context;
struct archiver_args {
struct repository *repo;
@@ -22,6 +23,7 @@ struct archiver_args {
unsigned int convert : 1;
int compression_level;
struct string_list extra_files;
+ struct pretty_print_context *pretty_ctx;
};
/* main api */
diff --git a/pretty.c b/pretty.c
index c612d2ac9b..032e89cd4e 100644
--- a/pretty.c
+++ b/pretty.c
@@ -1247,6 +1247,14 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
struct child_process cmd = CHILD_PROCESS_INIT;
struct strbuf out = STRBUF_INIT;
struct strbuf err = STRBUF_INIT;
+ struct pretty_print_describe_status *describe_status;
+
+ describe_status = c->pretty_ctx->describe_status;
+ if (describe_status) {
+ if (!describe_status->max_invocations)
+ return 0;
+ describe_status->max_invocations--;
+ }
cmd.git_cmd = 1;
strvec_push(&cmd.args, "describe");
diff --git a/pretty.h b/pretty.h
index 7ce6c0b437..27b15947ff 100644
--- a/pretty.h
+++ b/pretty.h
@@ -23,6 +23,10 @@ enum cmit_fmt {
CMIT_FMT_UNSPECIFIED
};
+struct pretty_print_describe_status {
+ unsigned int max_invocations;
+};
+
struct pretty_print_context {
/*
* Callers should tweak these to change the behavior of pp_* functions.
@@ -44,6 +48,7 @@ struct pretty_print_context {
int color;
struct ident_split *from_ident;
unsigned encode_email_headers:1;
+ struct pretty_print_describe_status *describe_status;
/*
* Fields below here are manipulated internally by pp_* functions and
diff --git a/t/t5001-archive-attr.sh b/t/t5001-archive-attr.sh
index e9aa97117a..1c9ce3956b 100755
--- a/t/t5001-archive-attr.sh
+++ b/t/t5001-archive-attr.sh
@@ -128,4 +128,18 @@ test_expect_success 'export-subst' '
test_cmp substfile2 archive/substfile2
'
+test_expect_success 'export-subst expands %(describe) once' '
+ echo "\$Format:%(describe)\$" >substfile3 &&
+ echo "\$Format:%(describe)\$" >>substfile3 &&
+ echo "\$Format:%(describe)${LF}%(describe)\$" >substfile4 &&
+ git add substfile[34] &&
+ git commit -m export-subst-describe &&
+ git tag -m export-subst-describe export-subst-describe &&
+ git archive HEAD >archive-describe.tar &&
+ extract_tar_to_dir archive-describe &&
+ desc=$(git describe) &&
+ grep -F "$desc" archive-describe/substfile[34] >substituted &&
+ test_line_count = 1 substituted
+'
+
test_done
--
2.30.1
