On Wed, Nov 02, 2016 at 03:20:47PM -0700, Brandon Williams wrote:
> Add configuration option 'core.allowProtocol' to allow users to create a
> whitelist of allowed protocols for fetch/push/clone in their gitconfig.
>
> For git-submodule.sh, fallback to default whitelist only if the user
> hasn't explicitly set `GIT_ALLOW_PROTOCOL` or doesn't have a whitelist
> in their gitconfig.
This says "what", but not "why". What's the use case?
I can see somebody wanting to pare down the whitelist further (e.g.,
because they are carrying ssh credentials that they don't want to use on
behalf of a malicious repo). But in general I'd expect this setting to
be a function of the environment you're operating in, and not the
on-disk config.
Or is the intent to broaden it for cases where you have a clone that
uses some non-standard protocol, and you want it to Just Work on
subsequent recursive fetches?
> +core.allowProtocol::
> + 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. If the `GIT_ALLOW_PROTOCOL` enviornment variable is set, it is
> + used as the protocol whitelist instead of this config option.
The "not set at all, all protocols are enabled" bit is not quite
correct, is it? It is true for a top-level fetch, but not for submodule
recursion (and especially since you are talking about submodule
recursion immediately before, it is rather confusing).
> --- a/git-submodule.sh
> +++ b/git-submodule.sh
> @@ -27,7 +27,8 @@ cd_to_toplevel
> #
> # If the user has already specified a set of allowed protocols,
> # we assume they know what they're doing and use that instead.
> -: ${GIT_ALLOW_PROTOCOL=file:git:http:https:ssh}
> +config_whitelist=$(git config core.allowProtocol)
> +: ${GIT_ALLOW_PROTOCOL=${config_whitelist:-file:git:http:https:ssh}}
The original uses "=" without a ":" so that an empty variable takes
precedence over the stock list (i.e., allowing nothing). Would you want
the same behavior for the config variable? I.e.:
# this should probably allow nothing, right?
git config core.allowProtocol ""
I think you'd have to check the return code of "git config" to
distinguish those cases.
> diff --git a/transport.c b/transport.c
> index d57e8de..b1098cd 100644
> --- a/transport.c
> +++ b/transport.c
> @@ -652,7 +652,7 @@ static const struct string_list *protocol_whitelist(void)
>
> if (enabled < 0) {
> const char *v = getenv("GIT_ALLOW_PROTOCOL");
> - if (v) {
> + if (v || !git_config_get_value("core.allowProtocol", &v)) {
> string_list_split(&allowed, v, ':', -1);
> string_list_sort(&allowed);
> enabled = 1;
I thought at first we'd have to deal with leaking "v", but "get_value"
is the "raw" version that gives you the uninterpreted value. I think
that means it may give you NULL, though if we see an implicit bool like:
[core]
allowProtocol
That's nonsense, of course, but we would still segfault. I
think the easiest way to test is:
git -c core.allowProtocol fetch
which seems to segfault for me with this patch.
-Peff