Merge branch 'bw/transport-protocol-policy'

Finer-grained control of what protocols are allowed for transports
during clone/fetch/push have been enabled via a new configuration
mechanism.

* bw/transport-protocol-policy:
  http: respect protocol.*.allow=user for http-alternates
  transport: add from_user parameter to is_transport_allowed
  http: create function to get curl allowed protocols
  transport: add protocol policy config option
  http: always warn if libcurl version is too old
  lib-proto-disable: variable name fix

Documentation/config.txt

@@ -2318,6 +2318,52 @@ pretty.<name>::
 	Note that an alias with the same name as a built-in format
 	will be silently ignored.
 
+protocol.allow::
+	If set, provide a user defined default policy for all protocols which
+	don't explicitly have a policy (`protocol.<name>.allow`).  By default,
+	if unset, known-safe protocols (http, https, git, ssh, file) have a
+	default policy of `always`, known-dangerous protocols (ext) have a
+	default policy of `never`, and all other protocols have a default
+	policy of `user`.  Supported policies:
++
+--
+
+* `always` - protocol is always able to be used.
+
+* `never` - protocol is never able to be used.
+
+* `user` - protocol is only able to be used when `GIT_PROTOCOL_FROM_USER` is
+  either unset or has a value of 1.  This policy should be used when you want a
+  protocol to be directly usable by the user but don't want it used by commands which
+  execute clone/fetch/push commands without user input, e.g. recursive
+  submodule initialization.
+
+--
+
+protocol.<name>.allow::
+	Set a policy to be used by protocol `<name>` with clone/fetch/push
+	commands. See `protocol.allow` above for the available policies.
++
+The protocol names currently used by git are:
++
+--
+  - `file`: any local file-based path (including `file://` URLs,
+    or local paths)
+
+  - `git`: the anonymous git protocol over a direct TCP
+    connection (or proxy, if configured)
+
+  - `ssh`: git over ssh (including `host:path` syntax,
+    `ssh://`, etc).
+
+  - `http`: git over http, both "smart http" and "dumb http".
+    Note that this does _not_ include `https`; if you want to configure
+    both, you must do so individually.
+
+  - any external helpers are named by their protocol (e.g., use
+    `hg` to allow the `git-remote-hg` helper)
+--
+
 pull.ff::
 	By default, Git does not create an extra merge commit when merging
 	a commit that is a descendant of the current commit. Instead, the

Documentation/git.txt

@@ -1161,30 +1161,20 @@ of clones and fetches.
 	cloning a repository to make a backup).
 
 `GIT_ALLOW_PROTOCOL`::
-	If set, provide a colon-separated list of protocols which are
-	allowed to be used with fetch/push/clone. This is useful to
-	restrict recursive submodule initialization from an untrusted
-	repository. Any protocol not mentioned will be disallowed (i.e.,
-	this is a whitelist, not a blacklist). If the variable is not
-	set at all, all protocols are enabled.  The protocol names
-	currently used by git are:
-
-	  - `file`: any local file-based path (including `file://` URLs,
-	    or local paths)
-
-	  - `git`: the anonymous git protocol over a direct TCP
-	    connection (or proxy, if configured)
-
-	  - `ssh`: git over ssh (including `host:path` syntax,
-	    `ssh://`, etc).
-
-	  - `http`: git over http, both "smart http" and "dumb http".
-	    Note that this does _not_ include `https`; if you want both,
-	    you should specify both as `http:https`.
-
-	  - any external helpers are named by their protocol (e.g., use
-	    `hg` to allow the `git-remote-hg` helper)
-
+	If set to a colon-separated list of protocols, behave as if
+	`protocol.allow` is set to `never`, and each of the listed
+	protocols has `protocol.<name>.allow` set to `always`
+	(overriding any existing configuration). In other words, any
+	protocol not mentioned will be disallowed (i.e., this is a
+	whitelist, not a blacklist). See the description of
+	`protocol.allow` in linkgit:git-config[1] for more details.
+
+`GIT_PROTOCOL_FROM_USER`::
+	Set to 0 to prevent protocols used by fetch/push/clone which are
+	configured to the `user` state.  This is useful to restrict recursive
+	submodule initialization from an untrusted repository or for programs
+	which feed potentially-untrusted URLS to git commands.  See
+	linkgit:git-config[1] for more details.
 
 Discussion[[Discussion]]
 ------------------------

git-submodule.sh

@@ -21,14 +21,10 @@ require_work_tree
 wt_prefix=$(git rev-parse --show-prefix)
 cd_to_toplevel
 
-# Restrict ourselves to a vanilla subset of protocols; the URLs
-# we get are under control of a remote repository, and we do not
-# want them kicking off arbitrary git-remote-* programs.
-#
-# If the user has already specified a set of allowed protocols,
-# we assume they know what they're doing and use that instead.
-: ${GIT_ALLOW_PROTOCOL=file:git:http:https:ssh}
-export GIT_ALLOW_PROTOCOL
+# Tell the rest of git that any URLs we get don't come
+# directly from the user, so it can apply policy as appropriate.
+GIT_PROTOCOL_FROM_USER=0
+export GIT_PROTOCOL_FROM_USER
 
 command=
 branch=

http-walker.c

@@ -3,6 +3,7 @@
 #include "walker.h"
 #include "http.h"
 #include "list.h"
+#include "transport.h"
 
 struct alt_base {
 	char *base;
@@ -160,6 +161,32 @@ static void prefetch(struct walker *walker, unsigned char *sha1)
 #endif
 }
 
+static int is_alternate_allowed(const char *url)
+{
+	const char *protocols[] = {
+		"http", "https", "ftp", "ftps"
+	};
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(protocols); i++) {
+		const char *end;
+		if (skip_prefix(url, protocols[i], &end) &&
+		    starts_with(end, "://"))
+			break;
+	}
+
+	if (i >= ARRAY_SIZE(protocols)) {
+		warning("ignoring alternate with unknown protocol: %s", url);
+		return 0;
+	}
+	if (!is_transport_allowed(protocols[i], 0)) {
+		warning("ignoring alternate with restricted protocol: %s", url);
+		return 0;
+	}
+
+	return 1;
+}
+
 static void process_alternates_response(void *callback_data)
 {
 	struct alternates_request *alt_req =
@@ -274,17 +301,20 @@ static void process_alternates_response(void *callback_data)
 				struct strbuf target = STRBUF_INIT;
 				strbuf_add(&target, base, serverlen);
 				strbuf_add(&target, data + i, posn - i - 7);
-				warning("adding alternate object store: %s",
-					target.buf);
-				newalt = xmalloc(sizeof(*newalt));
-				newalt->next = NULL;
-				newalt->base = strbuf_detach(&target, NULL);
-				newalt->got_indices = 0;
-				newalt->packs = NULL;
-
-				while (tail->next != NULL)
-					tail = tail->next;
-				tail->next = newalt;
+
+				if (is_alternate_allowed(target.buf)) {
+					warning("adding alternate object store: %s",
+						target.buf);
+					newalt = xmalloc(sizeof(*newalt));
+					newalt->next = NULL;
+					newalt->base = strbuf_detach(&target, NULL);
+					newalt->got_indices = 0;
+					newalt->packs = NULL;
+
+					while (tail->next != NULL)
+						tail = tail->next;
+					tail->next = newalt;
+				}
 			}
 		}
 		i = posn + 1;

http.c

@@ -636,11 +636,25 @@ void setup_curl_trace(CURL *handle)
 	curl_easy_setopt(handle, CURLOPT_DEBUGDATA, NULL);
 }
 
+static long get_curl_allowed_protocols(int from_user)
+{
+	long allowed_protocols = 0;
+
+	if (is_transport_allowed("http", from_user))
+		allowed_protocols |= CURLPROTO_HTTP;
+	if (is_transport_allowed("https", from_user))
+		allowed_protocols |= CURLPROTO_HTTPS;
+	if (is_transport_allowed("ftp", from_user))
+		allowed_protocols |= CURLPROTO_FTP;
+	if (is_transport_allowed("ftps", from_user))
+		allowed_protocols |= CURLPROTO_FTPS;
+
+	return allowed_protocols;
+}
 
 static CURL *get_curl_handle(void)
 {
 	CURL *result = curl_easy_init();
-	long allowed_protocols = 0;
 
 	if (!result)
 		die("curl_easy_init failed");
@@ -736,20 +750,13 @@ static CURL *get_curl_handle(void)
 	curl_easy_setopt(result, CURLOPT_POST301, 1);
 #endif
 #if LIBCURL_VERSION_NUM >= 0x071304
-	if (is_transport_allowed("http"))
-		allowed_protocols |= CURLPROTO_HTTP;
-	if (is_transport_allowed("https"))
-		allowed_protocols |= CURLPROTO_HTTPS;
-	if (is_transport_allowed("ftp"))
-		allowed_protocols |= CURLPROTO_FTP;
-	if (is_transport_allowed("ftps"))
-		allowed_protocols |= CURLPROTO_FTPS;
-	curl_easy_setopt(result, CURLOPT_REDIR_PROTOCOLS, allowed_protocols);
-	curl_easy_setopt(result, CURLOPT_PROTOCOLS, allowed_protocols);
+	curl_easy_setopt(result, CURLOPT_REDIR_PROTOCOLS,
+			 get_curl_allowed_protocols(0));
+	curl_easy_setopt(result, CURLOPT_PROTOCOLS,
+			 get_curl_allowed_protocols(-1));
 #else
-	if (transport_restrict_protocols())
-		warning("protocol restrictions not applied to curl redirects because\n"
-			"your curl version is too old (>= 7.19.4)");
+	warning("protocol restrictions not applied to curl redirects because\n"
+		"your curl version is too old (>= 7.19.4)");
 #endif
 	if (getenv("GIT_CURL_VERBOSE"))
 		curl_easy_setopt(result, CURLOPT_VERBOSE, 1L);