diff mbox series

[v2,4/4] promisor-remote: check advertised name or URL

Message ID 20240910163000.1985723-5-christian.couder@gmail.com (mailing list archive)
State New
Headers show
Series Introduce a "promisor-remote" capability | expand

Commit Message

Christian Couder Sept. 10, 2024, 4:30 p.m. UTC
A previous commit introduced a "promisor.acceptFromServer" configuration
variable with only "None" or "All" as valid values.

Let's introduce "KnownName" and "KnownUrl" as valid values for this
configuration option to give more choice to a client about which
promisor remotes it might accept among those that the server advertised.

In case of "KnownName", the client will accept promisor remotes which
are already configured on the client and have the same name as those
advertised by the client. This could be useful in a corporate setup
where servers and clients are trusted to not switch names and URLs, but
where some kind of control is still useful.

In case of "KnownUrl", the client will accept promisor remotes which
have both the same name and the same URL configured on the client as the
name and URL advertised by the server. This is the most secure option,
so it should be used if possible.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
---
 Documentation/config/promisor.txt     | 22 ++++++---
 promisor-remote.c                     | 54 +++++++++++++++++++--
 t/t5710-promisor-remote-capability.sh | 68 +++++++++++++++++++++++++++
 3 files changed, 134 insertions(+), 10 deletions(-)

Comments

Patrick Steinhardt Sept. 30, 2024, 7:57 a.m. UTC | #1
Oh, so here you address my previous comments. I'd propose to either
squash those two commits or to not introduce "acceptFromServer" in the
preceding commit in the first place.

On Tue, Sep 10, 2024 at 06:30:00PM +0200, Christian Couder wrote:
> diff --git a/Documentation/config/promisor.txt b/Documentation/config/promisor.txt
> index 9cbfe3e59e..d1364bc018 100644
> --- a/Documentation/config/promisor.txt
> +++ b/Documentation/config/promisor.txt
> @@ -12,9 +12,19 @@ promisor.advertise::
>  promisor.acceptFromServer::
>  	If set to "all", a client will accept all the promisor remotes
>  	a server might advertise using the "promisor-remote"
> -	capability. Default is "none", which means no promisor remote
> -	advertised by a server will be accepted. By accepting a
> -	promisor remote, the client agrees that the server might omit
> -	objects that are lazily fetchable from this promisor remote
> -	from its responses to "fetch" and "clone" requests from the
> -	client. See linkgit:gitprotocol-v2[5].
> +	capability. If set to "knownName" the client will accept
> +	promisor remotes which are already configured on the client
> +	and have the same name as those advertised by the client.

Wait, does this mean that a server can start advertising new promisor
remotes at any point in time and we'd backfill them on the client
whenever we execute git-fetch(1)? That sounds fishy to me -- I wouldn't
want anything to touch my configuration after I have created the repo
unless I explicitly tell it to.

If so, how does this handle the case where I manually added a remote
that by accident (or malicious intent of the server) that matches one of
the newly-advertised promisor remotes? This goes back to one of my
previous comments, where I said that it's likely not a good idea to let
the remote dictate names of our remotes in the first place.

If not, where do the known names come from?

Patrick
diff mbox series

Patch

diff --git a/Documentation/config/promisor.txt b/Documentation/config/promisor.txt
index 9cbfe3e59e..d1364bc018 100644
--- a/Documentation/config/promisor.txt
+++ b/Documentation/config/promisor.txt
@@ -12,9 +12,19 @@  promisor.advertise::
 promisor.acceptFromServer::
 	If set to "all", a client will accept all the promisor remotes
 	a server might advertise using the "promisor-remote"
-	capability. Default is "none", which means no promisor remote
-	advertised by a server will be accepted. By accepting a
-	promisor remote, the client agrees that the server might omit
-	objects that are lazily fetchable from this promisor remote
-	from its responses to "fetch" and "clone" requests from the
-	client. See linkgit:gitprotocol-v2[5].
+	capability. If set to "knownName" the client will accept
+	promisor remotes which are already configured on the client
+	and have the same name as those advertised by the client. This
+	is not very secure, but could be used in a corporate setup
+	where servers and clients are trusted to not switch name and
+	URLs. If set to "knownUrl", the client will accept promisor
+	remotes which have both the same name and the same URL
+	configured on the client as the name and URL advertised by the
+	server. This is more secure than "all" or "knownUrl", so it
+	should be used if possible instead of those options. Default
+	is "none", which means no promisor remote advertised by a
+	server will be accepted. By accepting a promisor remote, the
+	client agrees that the server might omit objects that are
+	lazily fetchable from this promisor remote from its responses
+	to "fetch" and "clone" requests from the client. See
+	linkgit:gitprotocol-v2[5].
diff --git a/promisor-remote.c b/promisor-remote.c
index baacbe9d94..f713595eb0 100644
--- a/promisor-remote.c
+++ b/promisor-remote.c
@@ -367,19 +367,54 @@  char *promisor_remote_info(struct repository *repo)
 	return strbuf_detach(&sb, NULL);
 }
 
+/*
+ * Find first index of 'vec' where there is 'val'. 'val' is compared
+ * case insensively to the strings in 'vec'. If not found 'vec->nr' is
+ * returned.
+ */
+static size_t strvec_find_index(struct strvec *vec, const char *val)
+{
+	for (size_t i = 0; i < vec->nr; i++)
+		if (!strcasecmp(vec->v[i], val))
+			return i;
+	return vec->nr;
+}
+
 enum accept_promisor {
 	ACCEPT_NONE = 0,
+	ACCEPT_KNOWN_URL,
+	ACCEPT_KNOWN_NAME,
 	ACCEPT_ALL
 };
 
 static int should_accept_remote(enum accept_promisor accept,
-				const char *remote_name UNUSED,
-				const char *remote_url UNUSED)
+				const char *remote_name, const char *remote_url,
+				struct strvec *names, struct strvec *urls)
 {
+	size_t i;
+
 	if (accept == ACCEPT_ALL)
 		return 1;
 
-	BUG("Unhandled 'enum accept_promisor' value '%d'", accept);
+	i = strvec_find_index(names, remote_name);
+
+	if (i >= names->nr)
+		/* We don't know about that remote */
+		return 0;
+
+	if (accept == ACCEPT_KNOWN_NAME)
+		return 1;
+
+	if (accept != ACCEPT_KNOWN_URL)
+		BUG("Unhandled 'enum accept_promisor' value '%d'", accept);
+
+	if (!strcasecmp(urls->v[i], remote_url))
+		return 1;
+
+	warning(_("known remote named '%s' but with url '%s' instead of '%s'"),
+		remote_name, urls->v[i], remote_url);
+
+	return 0;
 }
 
 static void filter_promisor_remote(struct repository *repo,
@@ -389,10 +424,16 @@  static void filter_promisor_remote(struct repository *repo,
 	struct strbuf **remotes;
 	char *accept_str;
 	enum accept_promisor accept = ACCEPT_NONE;
+	struct strvec names = STRVEC_INIT;
+	struct strvec urls = STRVEC_INIT;
 
 	if (!git_config_get_string("promisor.acceptfromserver", &accept_str)) {
 		if (!accept_str || !*accept_str || !strcasecmp("None", accept_str))
 			accept = ACCEPT_NONE;
+		else if (!strcasecmp("KnownUrl", accept_str))
+			accept = ACCEPT_KNOWN_URL;
+		else if (!strcasecmp("KnownName", accept_str))
+			accept = ACCEPT_KNOWN_NAME;
 		else if (!strcasecmp("All", accept_str))
 			accept = ACCEPT_ALL;
 		else
@@ -403,6 +444,9 @@  static void filter_promisor_remote(struct repository *repo,
 	if (accept == ACCEPT_NONE)
 		return;
 
+	if (accept != ACCEPT_ALL)
+		promisor_info_vecs(repo, &names, &urls);
+
 	/* Parse remote info received */
 
 	remotes = strbuf_split_str(info, ';', 0);
@@ -432,7 +476,7 @@  static void filter_promisor_remote(struct repository *repo,
 		if (remote_url)
 			decoded_url = url_percent_decode(remote_url);
 
-		if (decoded_name && should_accept_remote(accept, decoded_name, decoded_url))
+		if (decoded_name && should_accept_remote(accept, decoded_name, decoded_url, &names, &urls))
 			strvec_push(accepted, decoded_name);
 
 		strbuf_list_free(elems);
@@ -441,6 +485,8 @@  static void filter_promisor_remote(struct repository *repo,
 	}
 
 	free(accept_str);
+	strvec_clear(&names);
+	strvec_clear(&urls);
 	strbuf_list_free(remotes);
 }
 
diff --git a/t/t5710-promisor-remote-capability.sh b/t/t5710-promisor-remote-capability.sh
index 7e44ad15ce..c2c83a5914 100755
--- a/t/t5710-promisor-remote-capability.sh
+++ b/t/t5710-promisor-remote-capability.sh
@@ -117,6 +117,74 @@  test_expect_success "fetch with promisor.acceptfromserver set to 'None'" '
 		--no-local --filter="blob:limit=5k" server client &&
 	test_when_finished "rm -rf client" &&
 
+	# Check that the largest object is not missing on the server
+	check_missing_objects server 0 "" &&
+
+	# Reinitialize server so that the largest object is missing again
+	initialize_server
+'
+
+test_expect_success "fetch with promisor.acceptfromserver set to 'KnownName'" '
+	git -C server config promisor.advertise true &&
+
+	# Clone from server to create a client
+	GIT_NO_LAZY_FETCH=0 git clone -c remote.server2.promisor=true \
+		-c remote.server2.fetch="+refs/heads/*:refs/remotes/server2/*" \
+		-c remote.server2.url="file://$(pwd)/server2" \
+		-c promisor.acceptfromserver=KnownName \
+		--no-local --filter="blob:limit=5k" server client &&
+	test_when_finished "rm -rf client" &&
+
+	# Check that the largest object is still missing on the server
+	check_missing_objects server 1 "$oid"
+'
+
+test_expect_success "fetch with 'KnownName' and different remote names" '
+	git -C server config promisor.advertise true &&
+
+	# Clone from server to create a client
+	GIT_NO_LAZY_FETCH=0 git clone -c remote.serverTwo.promisor=true \
+		-c remote.serverTwo.fetch="+refs/heads/*:refs/remotes/server2/*" \
+		-c remote.serverTwo.url="file://$(pwd)/server2" \
+		-c promisor.acceptfromserver=KnownName \
+		--no-local --filter="blob:limit=5k" server client &&
+	test_when_finished "rm -rf client" &&
+
+	# Check that the largest object is not missing on the server
+	check_missing_objects server 0 "" &&
+
+	# Reinitialize server so that the largest object is missing again
+	initialize_server
+'
+
+test_expect_success "fetch with promisor.acceptfromserver set to 'KnownUrl'" '
+	git -C server config promisor.advertise true &&
+
+	# Clone from server to create a client
+	GIT_NO_LAZY_FETCH=0 git clone -c remote.server2.promisor=true \
+		-c remote.server2.fetch="+refs/heads/*:refs/remotes/server2/*" \
+		-c remote.server2.url="file://$(pwd)/server2" \
+		-c promisor.acceptfromserver=KnownUrl \
+		--no-local --filter="blob:limit=5k" server client &&
+	test_when_finished "rm -rf client" &&
+
+	# Check that the largest object is still missing on the server
+	check_missing_objects server 1 "$oid"
+'
+
+test_expect_success "fetch with 'KnownUrl' and different remote urls" '
+	ln -s server2 serverTwo &&
+
+	git -C server config promisor.advertise true &&
+
+	# Clone from server to create a client
+	GIT_NO_LAZY_FETCH=0 git clone -c remote.server2.promisor=true \
+		-c remote.server2.fetch="+refs/heads/*:refs/remotes/server2/*" \
+		-c remote.server2.url="file://$(pwd)/serverTwo" \
+		-c promisor.acceptfromserver=KnownUrl \
+		--no-local --filter="blob:limit=5k" server client &&
+	test_when_finished "rm -rf client" &&
+
 	# Check that the largest object is not missing on the server
 	check_missing_objects server 0 ""
 '