transport: add from_user parameter to is_transport_allowed

Add a from_user parameter to is_transport_allowed() to allow http to be
able to distinguish between protocol restrictions for redirects versus
initial requests.  CURLOPT_REDIR_PROTOCOLS can now be set differently
from CURLOPT_PROTOCOLS to disallow use of protocols with the "user"
policy in redirects.

This change allows callers to query if a transport protocol is allowed,
given that the caller knows that the protocol is coming from the user
(1) or not from the user (0) such as redirects in libcurl.  If unknown a
-1 should be provided which falls back to reading
`GIT_PROTOCOL_FROM_USER` to determine if the protocol came from the
user.

Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/transport.c b/transport.c
index fbd799d062..f50c31a572 100644
--- a/transport.c
+++ b/transport.c
@@ -676,7 +676,7 @@ static enum protocol_allow_config get_protocol_config(const char *type)
 	return PROTOCOL_ALLOW_USER_ONLY;
 }
 
-int is_transport_allowed(const char *type)
+int is_transport_allowed(const char *type, int from_user)
 {
 	const struct string_list *whitelist = protocol_whitelist();
 	if (whitelist)
@@ -688,7 +688,9 @@ int is_transport_allowed(const char *type)
 	case PROTOCOL_ALLOW_NEVER:
 		return 0;
 	case PROTOCOL_ALLOW_USER_ONLY:
-		return git_env_bool("GIT_PROTOCOL_FROM_USER", 1);
+		if (from_user < 0)
+			from_user = git_env_bool("GIT_PROTOCOL_FROM_USER", 1);
+		return from_user;
 	}
 
 	die("BUG: invalid protocol_allow_config type");
@@ -696,7 +698,7 @@ int is_transport_allowed(const char *type)
 
 void transport_check_allowed(const char *type)
 {
-	if (!is_transport_allowed(type))
+	if (!is_transport_allowed(type, -1))
 		die("transport '%s' not allowed", type);
 }