git/t/t5701-git-serve.sh
Taylor Blau 8c735b11de upload-pack: disallow object-info capability by default
We added an "object-info" capability to the v2 upload-pack protocol in
a2ba162cda (object-info: support for retrieving object info,
2021-04-20). In the almost 3 years since, we have not added any
client-side support, and it does not appear to exist in other
implementations either (JGit understands the verb on the server side,
but not on the client side).

Since this largely unused code is accessible over the network by
default, it increases the attack surface of upload-pack. I don't know of
any particularly severe problem, but one issue is that because of the
request/response nature of the v2 protocol, it will happily read an
unbounded number of packets, adding each one to a string list (without
regard to whether they are objects we know about, duplicates, etc).

This may be something we want to improve in the long run, but in the
short term it makes sense to disable the feature entirely. We'll add a
config option as an escape hatch for anybody who wants to develop the
feature further.

A more gentle option would be to add the config option to let people
disable it manually, but leave it enabled by default. But given that
there's no client side support, that seems like the wrong balance with
security.

Disabling by default will slow adoption a bit once client-side support
does become available (there were some patches[1] in 2022, but nothing
got merged and there's been nothing since). But clients have to deal
with older servers that do not understand the option anyway (and the
capability system handles that), so it will just be a matter of servers
flipping their config at that point (and hopefully once any unbounded
allocations have been addressed).

[jk: this is a patch that GitHub has been running for several years, but
     rebased forward and with a new commit message for upstream]

[1] https://lore.kernel.org/git/20220208231911.725273-1-calvinwan@google.com/

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-02-28 14:42:01 -08:00

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#!/bin/sh
test_description='test protocol v2 server commands'
GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
TEST_PASSES_SANITIZE_LEAK=true
. ./test-lib.sh
test_expect_success 'test capability advertisement' '
test_oid_cache <<-EOF &&
wrong_algo sha1:sha256
wrong_algo sha256:sha1
EOF
cat >expect.base <<-EOF &&
version 2
agent=git/$(git version | cut -d" " -f3)
ls-refs=unborn
fetch=shallow wait-for-done
server-option
object-format=$(test_oid algo)
EOF
cat >expect.trailer <<-EOF &&
0000
EOF
cat expect.base expect.trailer >expect &&
GIT_TEST_SIDEBAND_ALL=0 test-tool serve-v2 \
--advertise-capabilities >out &&
test-tool pkt-line unpack <out >actual &&
test_cmp expect actual
'
test_expect_success 'stateless-rpc flag does not list capabilities' '
# Empty request
test-tool pkt-line pack >in <<-EOF &&
0000
EOF
test-tool serve-v2 --stateless-rpc >out <in &&
test_must_be_empty out &&
# EOF
test-tool serve-v2 --stateless-rpc >out &&
test_must_be_empty out
'
test_expect_success 'request invalid capability' '
test-tool pkt-line pack >in <<-EOF &&
foobar
0000
EOF
test_must_fail test-tool serve-v2 --stateless-rpc 2>err <in &&
test_grep "unknown capability" err
'
test_expect_success 'request with no command' '
test-tool pkt-line pack >in <<-EOF &&
agent=git/test
object-format=$(test_oid algo)
0000
EOF
test_must_fail test-tool serve-v2 --stateless-rpc 2>err <in &&
test_grep "no command requested" err
'
test_expect_success 'request invalid command' '
test-tool pkt-line pack >in <<-EOF &&
command=foo
object-format=$(test_oid algo)
agent=git/test
0000
EOF
test_must_fail test-tool serve-v2 --stateless-rpc 2>err <in &&
test_grep "invalid command" err
'
test_expect_success 'request capability as command' '
test-tool pkt-line pack >in <<-EOF &&
command=agent
object-format=$(test_oid algo)
0000
EOF
test_must_fail test-tool serve-v2 --stateless-rpc 2>err <in &&
grep invalid.command.*agent err
'
test_expect_success 'request command as capability' '
test-tool pkt-line pack >in <<-EOF &&
command=ls-refs
object-format=$(test_oid algo)
fetch
0000
EOF
test_must_fail test-tool serve-v2 --stateless-rpc 2>err <in &&
grep unknown.capability err
'
test_expect_success 'requested command is command=value' '
test-tool pkt-line pack >in <<-EOF &&
command=ls-refs=whatever
object-format=$(test_oid algo)
0000
EOF
test_must_fail test-tool serve-v2 --stateless-rpc 2>err <in &&
grep invalid.command.*ls-refs=whatever err
'
test_expect_success 'wrong object-format' '
test-tool pkt-line pack >in <<-EOF &&
command=fetch
agent=git/test
object-format=$(test_oid wrong_algo)
0000
EOF
test_must_fail test-tool serve-v2 --stateless-rpc 2>err <in &&
test_grep "mismatched object format" err
'
# Test the basics of ls-refs
#
test_expect_success 'setup some refs and tags' '
test_commit one &&
git branch dev main &&
test_commit two &&
git symbolic-ref refs/heads/release refs/heads/main &&
git tag -a -m "annotated tag" annotated-tag
'
test_expect_success 'basics of ls-refs' '
test-tool pkt-line pack >in <<-EOF &&
command=ls-refs
object-format=$(test_oid algo)
0000
EOF
cat >expect <<-EOF &&
$(git rev-parse HEAD) HEAD
$(git rev-parse refs/heads/dev) refs/heads/dev
$(git rev-parse refs/heads/main) refs/heads/main
$(git rev-parse refs/heads/release) refs/heads/release
$(git rev-parse refs/tags/annotated-tag) refs/tags/annotated-tag
$(git rev-parse refs/tags/one) refs/tags/one
$(git rev-parse refs/tags/two) refs/tags/two
0000
EOF
test-tool serve-v2 --stateless-rpc <in >out &&
test-tool pkt-line unpack <out >actual &&
test_cmp expect actual
'
test_expect_success 'ls-refs complains about unknown options' '
test-tool pkt-line pack >in <<-EOF &&
command=ls-refs
object-format=$(test_oid algo)
0001
no-such-arg
0000
EOF
test_must_fail test-tool serve-v2 --stateless-rpc 2>err <in &&
grep unexpected.line.*no-such-arg err
'
test_expect_success 'basic ref-prefixes' '
test-tool pkt-line pack >in <<-EOF &&
command=ls-refs
object-format=$(test_oid algo)
0001
ref-prefix refs/heads/main
ref-prefix refs/tags/one
0000
EOF
cat >expect <<-EOF &&
$(git rev-parse refs/heads/main) refs/heads/main
$(git rev-parse refs/tags/one) refs/tags/one
0000
EOF
test-tool serve-v2 --stateless-rpc <in >out &&
test-tool pkt-line unpack <out >actual &&
test_cmp expect actual
'
test_expect_success 'refs/heads prefix' '
test-tool pkt-line pack >in <<-EOF &&
command=ls-refs
object-format=$(test_oid algo)
0001
ref-prefix refs/heads/
0000
EOF
cat >expect <<-EOF &&
$(git rev-parse refs/heads/dev) refs/heads/dev
$(git rev-parse refs/heads/main) refs/heads/main
$(git rev-parse refs/heads/release) refs/heads/release
0000
EOF
test-tool serve-v2 --stateless-rpc <in >out &&
test-tool pkt-line unpack <out >actual &&
test_cmp expect actual
'
test_expect_success 'ignore very large set of prefixes' '
# generate a large number of ref-prefixes that we expect
# to match nothing; the value here exceeds TOO_MANY_PREFIXES
# from ls-refs.c.
{
echo command=ls-refs &&
echo object-format=$(test_oid algo) &&
echo 0001 &&
perl -le "print \"ref-prefix refs/heads/\$_\" for (1..65536)" &&
echo 0000
} |
test-tool pkt-line pack >in &&
# and then confirm that we see unmatched prefixes anyway (i.e.,
# that the prefix was not applied).
cat >expect <<-EOF &&
$(git rev-parse HEAD) HEAD
$(git rev-parse refs/heads/dev) refs/heads/dev
$(git rev-parse refs/heads/main) refs/heads/main
$(git rev-parse refs/heads/release) refs/heads/release
$(git rev-parse refs/tags/annotated-tag) refs/tags/annotated-tag
$(git rev-parse refs/tags/one) refs/tags/one
$(git rev-parse refs/tags/two) refs/tags/two
0000
EOF
test-tool serve-v2 --stateless-rpc <in >out &&
test-tool pkt-line unpack <out >actual &&
test_cmp expect actual
'
test_expect_success 'peel parameter' '
test-tool pkt-line pack >in <<-EOF &&
command=ls-refs
object-format=$(test_oid algo)
0001
peel
ref-prefix refs/tags/
0000
EOF
cat >expect <<-EOF &&
$(git rev-parse refs/tags/annotated-tag) refs/tags/annotated-tag peeled:$(git rev-parse refs/tags/annotated-tag^{})
$(git rev-parse refs/tags/one) refs/tags/one
$(git rev-parse refs/tags/two) refs/tags/two
0000
EOF
test-tool serve-v2 --stateless-rpc <in >out &&
test-tool pkt-line unpack <out >actual &&
test_cmp expect actual
'
test_expect_success 'symrefs parameter' '
test-tool pkt-line pack >in <<-EOF &&
command=ls-refs
object-format=$(test_oid algo)
0001
symrefs
ref-prefix refs/heads/
0000
EOF
cat >expect <<-EOF &&
$(git rev-parse refs/heads/dev) refs/heads/dev
$(git rev-parse refs/heads/main) refs/heads/main
$(git rev-parse refs/heads/release) refs/heads/release symref-target:refs/heads/main
0000
EOF
test-tool serve-v2 --stateless-rpc <in >out &&
test-tool pkt-line unpack <out >actual &&
test_cmp expect actual
'
test_expect_success 'sending server-options' '
test-tool pkt-line pack >in <<-EOF &&
command=ls-refs
object-format=$(test_oid algo)
server-option=hello
server-option=world
0001
ref-prefix HEAD
0000
EOF
cat >expect <<-EOF &&
$(git rev-parse HEAD) HEAD
0000
EOF
test-tool serve-v2 --stateless-rpc <in >out &&
test-tool pkt-line unpack <out >actual &&
test_cmp expect actual
'
test_expect_success 'unexpected lines are not allowed in fetch request' '
git init server &&
test-tool pkt-line pack >in <<-EOF &&
command=fetch
object-format=$(test_oid algo)
0001
this-is-not-a-command
0000
EOF
(
cd server &&
test_must_fail test-tool serve-v2 --stateless-rpc
) <in >/dev/null 2>err &&
grep "unexpected line: .this-is-not-a-command." err
'
# Test the basics of object-info
#
test_expect_success 'basics of object-info' '
test_config transfer.advertiseObjectInfo true &&
test-tool pkt-line pack >in <<-EOF &&
command=object-info
object-format=$(test_oid algo)
0001
size
oid $(git rev-parse two:two.t)
oid $(git rev-parse two:two.t)
0000
EOF
cat >expect <<-EOF &&
size
$(git rev-parse two:two.t) $(wc -c <two.t | xargs)
$(git rev-parse two:two.t) $(wc -c <two.t | xargs)
0000
EOF
test-tool serve-v2 --stateless-rpc <in >out &&
test-tool pkt-line unpack <out >actual &&
test_cmp expect actual
'
test_expect_success 'test capability advertisement with uploadpack.advertiseBundleURIs' '
test_config uploadpack.advertiseBundleURIs true &&
cat >expect.extra <<-EOF &&
bundle-uri
EOF
cat expect.base \
expect.extra \
expect.trailer >expect &&
GIT_TEST_SIDEBAND_ALL=0 test-tool serve-v2 \
--advertise-capabilities >out &&
test-tool pkt-line unpack <out >actual &&
test_cmp expect actual
'
test_expect_success 'basics of bundle-uri: dies if not enabled' '
test-tool pkt-line pack >in <<-EOF &&
command=bundle-uri
0000
EOF
cat >err.expect <<-\EOF &&
fatal: invalid command '"'"'bundle-uri'"'"'
EOF
cat >expect <<-\EOF &&
ERR serve: invalid command '"'"'bundle-uri'"'"'
EOF
test_must_fail test-tool serve-v2 --stateless-rpc <in >out 2>err.actual &&
test_cmp err.expect err.actual &&
test_must_be_empty out
'
test_expect_success 'object-info missing from capabilities when disabled' '
test_config transfer.advertiseObjectInfo false &&
GIT_TEST_SIDEBAND_ALL=0 test-tool serve-v2 \
--advertise-capabilities >out &&
test-tool pkt-line unpack <out >actual &&
! grep object.info actual
'
test_expect_success 'object-info commands rejected when disabled' '
test_config transfer.advertiseObjectInfo false &&
test-tool pkt-line pack >in <<-EOF &&
command=object-info
EOF
test_must_fail test-tool serve-v2 --stateless-rpc <in 2>err &&
grep invalid.command err
'
test_done