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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@peff.net>
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
pull/986/head
René Scharfe 1 year ago committed by Junio C Hamano
parent
commit
96099726dd
  1. 3
      Documentation/gitattributes.txt
  2. 16
      archive.c
  3. 2
      archive.h
  4. 8
      pretty.c
  5. 5
      pretty.h
  6. 14
      t/t5001-archive-attr.sh

3
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

16
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);

2
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 */

8
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");

5
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

14
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

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