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[PATCH 15/24] bundle-uri: fetch a list of bundles

From
Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>
Date
May 20, 2022, 18:40 UTC
Message-ID
<ceb253ec445b7275943e1c04ac51f12869271e91.1653072042.git.gitgitgadget@gmail.com>
In-Reply-To
<pull.1234.git.1653072042.gitgitgadget@gmail.com>
From: Derrick Stolee <derrickstolee@github.com>

When the content at a given bundle URI is not understood as a bundle (based on inspecting the initial content), then Git currently gives up and ignores that content. Independent bundle providers may want to split up the bundle content into multiple bundles, but still make them available from a single URI.

Teach Git to attempt parsing the bundle URI content as a Git config file providing the key=value pairs for a bundle list. Git then looks at the mode of the list to see if ANY single bundle is sufficient or if ALL bundles are required. The content at the selected URIs are downloaded and the content is inspected again, creating a recursive process.

To guard the recursion against malformed or malicious content, limit the recursion depth to a reasonable four for now. This can be converted to a configured value in the future if necessary. The value of four is twice as high as expected to be useful (a bundle list is unlikely to point to more bundle lists).

RFC TODO: add tests for this feature right now.
Signed-off-by: Derrick Stolee <derrickstolee@github.com>
---
 bundle-uri.c | 213 ++++++++++++++++++++++++++++++++++++++++++++++-----
 bundle-uri.h |   6 ++
 2 files changed, 200 insertions(+), 19 deletions(-)
diff --git a/bundle-uri.c b/bundle-uri.c
index ab4b6385fc0..601e6e87822 100644
--- a/bundle-uri.c
+++ b/bundle-uri.c
@@ -35,9 +35,10 @@ void init_bundle_list(struct bundle_list *list)
 static int clear_remote_bundle_info(struct remote_bundle_info *bundle,
 				    void *data)
 {
-	free(bundle->id);
-	free(bundle->uri);
+	FREE_AND_NULL(bundle->id);
+	FREE_AND_NULL(bundle->uri);
 	strbuf_release(&bundle->file);
+	bundle->unbundled = 0;
 	return 0;
 }
 
@@ -336,18 +337,102 @@ static int unbundle_from_file(struct repository *r, const char *file)
 	return result;
 }
 
+struct bundle_list_context {
+	struct repository *r;
+	struct bundle_list *list;
+	enum bundle_list_mode mode;
+	int count;
+	int depth;
+};
+
+/*
+ * This early definition is necessary because we use indirect recursion:
+ *
+ * While iterating through a bundle list that was downloaded as part
+ * of fetch_bundle_uri_internal(), iterator methods eventually call it
+ * again, but with depth + 1.
+ */
+static int fetch_bundle_uri_internal(struct repository *r,
+				     struct remote_bundle_info *bundle,
+				     int depth,
+				     struct bundle_list *list);
+
+static int download_bundle_to_file(struct remote_bundle_info *bundle, void *data)
+{
+	struct bundle_list_context *ctx = data;
+
+	if (ctx->mode == BUNDLE_MODE_ANY && ctx->count)
+		return 0;
+
+	ctx->count++;
+	return fetch_bundle_uri_internal(ctx->r, bundle, ctx->depth + 1, ctx->list);
+}
+
+static int download_bundle_list(struct repository *r,
+				struct bundle_list *local_list,
+				struct bundle_list *global_list,
+				int depth)
+{
+	struct bundle_list_context ctx = {
+		.r = r,
+		.list = global_list,
+		.depth = depth + 1,
+		.mode = local_list->mode,
+	};
+
+	return for_all_bundles_in_list(local_list, download_bundle_to_file, &ctx);
+}
+
+static int fetch_bundle_list_in_config_format(struct repository *r,
+					      struct bundle_list *global_list,
+					      struct remote_bundle_info *bundle,
+					      int depth)
+{
+	int result;
+	struct bundle_list list_from_bundle;
+
+	init_bundle_list(&list_from_bundle);
+
+	if ((result = parse_bundle_list_in_config_format(bundle->uri,
+							 bundle->file.buf,
+							 &list_from_bundle)))
+		goto cleanup;
+
+	if (list_from_bundle.mode == BUNDLE_MODE_NONE) {
+		warning(_("unrecognized bundle mode from URI '%s'"),
+			bundle->uri);
+		result = -1;
+		goto cleanup;
+	}
+
+	if ((result = download_bundle_list(r, &list_from_bundle,
+					   global_list, depth)))
+		goto cleanup;
+
+cleanup:
+	clear_bundle_list(&list_from_bundle);
+	return result;
+}
+
 /**
  * This limits the recursion on fetch_bundle_uri_internal() when following
  * bundle lists.
  */
 static int max_bundle_uri_depth = 4;
 
+/**
+ * Recursively download all bundles advertised at the given URI
+ * to files. If the file is a bundle, then add it to the given
+ * 'list'. Otherwise, expect a bundle list and recurse on the
+ * URIs in that list according to the list mode (ANY or ALL).
+ */
 static int fetch_bundle_uri_internal(struct repository *r,
-				     const char *uri,
-				     int depth)
+				     struct remote_bundle_info *bundle,
+				     int depth,
+				     struct bundle_list *list)
 {
 	int result = 0;
-	struct strbuf filename = STRBUF_INIT;
+	struct remote_bundle_info *bcopy;
 
 	if (depth >= max_bundle_uri_depth) {
 		warning(_("exceeded bundle URI recursion limit (%d)"),
@@ -355,31 +440,121 @@ static int fetch_bundle_uri_internal(struct repository *r,
 		return -1;
 	}
 
-	find_temp_filename(&filename);
-	if ((result = copy_uri_to_file(uri, filename.buf)))
+	if (!bundle->file.len)
+		find_temp_filename(&bundle->file);
+	if ((result = copy_uri_to_file(bundle->uri, bundle->file.buf)))
 		goto cleanup;
 
-	if ((result = !is_bundle(filename.buf, 0)))
-		goto cleanup;
-
-	if ((result = unbundle_from_file(r, filename.buf)))
+	if ((result = !is_bundle(bundle->file.buf, 1))) {
+		result = fetch_bundle_list_in_config_format(
+				r, list, bundle, depth);
 		goto cleanup;
+	}
 
-	git_config_set_multivar_gently("log.excludedecoration",
-					"refs/bundle/",
-					"refs/bundle/",
-					CONFIG_FLAGS_FIXED_VALUE |
-					CONFIG_FLAGS_MULTI_REPLACE);
+	/* Copy the bundle and insert it into the global list. */
+	CALLOC_ARRAY(bcopy, 1);
+	bcopy->id = xstrdup(bundle->id);
+	strbuf_init(&bcopy->file, 0);
+	strbuf_add(&bcopy->file, bundle->file.buf, bundle->file.len);
+	strbuf_detach(&bundle->file, NULL);
+	hashmap_entry_init(&bcopy->ent, strhash(bcopy->id));
+	hashmap_add(&list->bundles, &bcopy->ent);
 
 cleanup:
-	unlink(filename.buf);
-	strbuf_release(&filename);
+	if (bundle->file.len)
+		unlink(bundle->file.buf);
 	return result;
 }
 
+struct attempt_unbundle_context {
+	struct repository *r;
+	int success_count;
+	int failure_count;
+};
+
+static int attempt_unbundle(struct remote_bundle_info *info, void *data)
+{
+	struct attempt_unbundle_context *ctx = data;
+
+	if (info->unbundled || !unbundle_from_file(ctx->r, info->file.buf)) {
+		ctx->success_count++;
+		info->unbundled = 1;
+	} else {
+		ctx->failure_count++;
+	}
+
+	return 0;
+}
+
+static int unbundle_all_bundles(struct repository *r,
+				struct bundle_list *list)
+{
+	int last_success_count = -1;
+	struct attempt_unbundle_context ctx = {
+		.r = r,
+	};
+
+	/*
+	 * Iterate through all bundles looking for ones that can
+	 * successfully unbundle. If any succeed, then perhaps another
+	 * will succeed in the next attempt.
+	 */
+	while (last_success_count < ctx.success_count) {
+		last_success_count = ctx.success_count;
+
+		ctx.success_count = 0;
+		ctx.failure_count = 0;
+		for_all_bundles_in_list(list, attempt_unbundle, &ctx);
+	}
+
+	if (ctx.success_count)
+		git_config_set_multivar_gently("log.excludedecoration",
+						"refs/bundle/",
+						"refs/bundle/",
+						CONFIG_FLAGS_FIXED_VALUE |
+						CONFIG_FLAGS_MULTI_REPLACE);
+
+	if (ctx.failure_count) {
+		warning(_("failed to unbundle %d bundles"),
+			ctx.failure_count);
+		return -1;
+	}
+
+	return 0;
+}
+
+static int unlink_bundle(struct remote_bundle_info *info, void *data)
+{
+	if (info->file.buf)
+		unlink_or_warn(info->file.buf);
+	return 0;
+}
+
 int fetch_bundle_uri(struct repository *r, const char *uri)
 {
-	return fetch_bundle_uri_internal(r, uri, 0);
+	int result;
+	struct bundle_list list;
+	struct remote_bundle_info bundle = {
+		.uri = xstrdup(uri),
+		.id = xstrdup("<root>"),
+		.file = STRBUF_INIT,
+	};
+
+	init_bundle_list(&list);
+
+	/* If a bundle is added to this global list, then it is required. */
+	list.mode = BUNDLE_MODE_ALL;
+
+	if ((result = fetch_bundle_uri_internal(r, &bundle, 0, &list)))
+		goto cleanup;
+
+	result = unbundle_all_bundles(r, &list);
+
+cleanup:
+	for_all_bundles_in_list(&list, unlink_bundle, NULL);
+	clear_bundle_list(&list);
+	clear_remote_bundle_info(&bundle, NULL);
+	return result;
 }
 
 /**
diff --git a/bundle-uri.h b/bundle-uri.h
index b0183870336..adce5dc07e2 100644
--- a/bundle-uri.h
+++ b/bundle-uri.h
@@ -36,6 +36,12 @@ struct remote_bundle_info {
 	 * an empty string.
 	 */
 	struct strbuf file;
+
+	/**
+	 * If the bundle has been unbundled successfully, then
+	 * this boolean is true.
+	 */
+	unsigned unbundled:1;
 };
 
 #define REMOTE_BUNDLE_INFO_INIT { \

-- 
gitgitgadget
Previous: Derrick Stolee via GitGitGadgetNext: Ævar Arnfjörð Bjarmason via GitGitGadget
Message 14 of 25 in “[RFC] Bundle URIs Combined RFC”
  1. 00/24 [RFC] Bundle URIs Combined RFCDerrick Stolee via GitGitGadget, May 20, 2022
  2. 01/24 docs: document bundle URI standardDerrick Stolee via GitGitGadget, May 20, 2022
  3. 02/24 remote-curl: add 'get' capabilityDerrick Stolee via GitGitGadget, May 20, 2022
  4. 06/24 fetch: add 'refs/bundle/' to log.excludeDecorationDerrick Stolee via GitGitGadget, May 20, 2022
  5. 05/24 fetch: add --bundle-uri optionDerrick Stolee via GitGitGadget, May 20, 2022
  6. 04/24 bundle-uri: add support for http(s):// and file://Derrick Stolee via GitGitGadget, May 20, 2022
  7. 03/24 bundle-uri: create basic file-copy logicDerrick Stolee via GitGitGadget, May 20, 2022
  8. 12/24 bundle-uri: unit test "key=value" parsingÆvar Arnfjörð Bjarmason via GitGitGadget, May 20, 2022
  9. 10/24 bundle-uri: create base key-value pair parsingDerrick Stolee via GitGitGadget, May 20, 2022
  10. 07/24 clone: add --bundle-uri optionDerrick Stolee via GitGitGadget, May 20, 2022
  11. 11/24 bundle-uri: create "key=value" line parsingÆvar Arnfjörð Bjarmason via GitGitGadget, May 20, 2022
  12. 14/24 bundle-uri: parse bundle list in config formatDerrick Stolee via GitGitGadget, May 20, 2022
  13. 09/24 bundle-uri: create bundle_list struct and helpersDerrick Stolee via GitGitGadget, May 20, 2022
  14. 15/24 bundle-uri: fetch a list of bundlesDerrick Stolee via GitGitGadget, May 20, 2022
  15. 16/24 protocol v2: add server-side "bundle-uri" skeletonÆvar Arnfjörð Bjarmason via GitGitGadget, May 20, 2022
  16. 08/24 clone: --bundle-uri cannot be combined with --depthDerrick Stolee via GitGitGadget, May 20, 2022
  17. 13/24 bundle-uri: limit recursion depth for bundle listsDerrick Stolee via GitGitGadget, May 20, 2022
  18. 18/24 bundle-uri client: add "git ls-remote-bundle-uri"Ævar Arnfjörð Bjarmason via GitGitGadget, May 20, 2022
  19. 17/24 bundle-uri client: add minimal NOOP clientÆvar Arnfjörð Bjarmason via GitGitGadget, May 20, 2022
  20. 19/24 bundle-uri: serve URI advertisement from bundle.* configDerrick Stolee via GitGitGadget, May 20, 2022
  21. 22/24 bundle-uri: download bundles from an advertised listDerrick Stolee via GitGitGadget, May 20, 2022
  22. 24/24 t5601: basic bundle URI testsDerrick Stolee via GitGitGadget, May 20, 2022
  23. 20/24 bundle-uri client: add boolean transfer.bundleURI settingÆvar Arnfjörð Bjarmason via GitGitGadget, May 20, 2022
  24. 21/24 bundle-uri: allow relative URLs in bundle listsDerrick Stolee via GitGitGadget, May 20, 2022
  25. 23/24 clone: unbundle the advertised bundlesDerrick Stolee via GitGitGadget, May 20, 2022

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