credential: parse URL without host as empty host, not unset

We may feed a URL like "cert:///path/to/cert.pem" into the credential
machinery to get the key for a client-side certificate. That
credential has no hostname field, which is about to be disallowed (to
avoid confusion with protocols where a helper _would_ expect a
hostname).

This means as of the next patch, credential helpers won't work for
unlocking certs. Let's fix that by doing two things:

  - when we parse a url with an empty host, set the host field to the
    empty string (asking only to match stored entries with an empty
    host) rather than NULL (asking to match _any_ host).

  - when we build a cert:// credential by hand, similarly assign an
    empty string

It's the latter that is more likely to impact real users in practice,
since it's what's used for http connections. But we don't have good
infrastructure to test it.

The url-parsing version will help anybody using git-credential in a
script, and is easy to test.

Signed-off-by: Jeff King <peff@peff.net>
Reviewed-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>

3 files changed, 19 insertions, 2 deletions

diff --git a/credential.c b/credential.c
index eeeac3242e..d1bb71b41a 100644
--- a/credential.c
+++ b/credential.c
@@ -373,8 +373,7 @@ int credential_from_url_gently(struct credential *c, const char *url,
 
 	if (proto_end - url > 0)
 		c->protocol = xmemdupz(url, proto_end - url);
-	if (slash - host > 0)
-		c->host = url_decode_mem(host, slash - host);
+	c->host = url_decode_mem(host, slash - host);
 	/* Trim leading and trailing slashes from path */
 	while (*slash == '/')
 		slash++;
diff --git a/http.c b/http.c
index a5bd5d62c2..29de6bbb23 100644
--- a/http.c
+++ b/http.c
@@ -524,6 +524,7 @@ static int has_cert_password(void)
 		return 0;
 	if (!cert_auth.password) {
 		cert_auth.protocol = xstrdup("cert");
+		cert_auth.host = xstrdup("");
 		cert_auth.username = xstrdup("");
 		cert_auth.path = xstrdup(ssl_cert);
 		credential_fill(&cert_auth);
diff --git a/t/t0300-credentials.sh b/t/t0300-credentials.sh
index f4c5d7ff91..1c1010bc54 100755
--- a/t/t0300-credentials.sh
+++ b/t/t0300-credentials.sh
@@ -414,4 +414,21 @@ test_expect_success 'url parser ignores embedded newlines' '
 	EOF
 '
 
+test_expect_success 'host-less URLs are parsed as empty host' '
+	check fill "verbatim foo bar" <<-\EOF
+	url=cert:///path/to/cert.pem
+	--
+	protocol=cert
+	host=
+	path=path/to/cert.pem
+	username=foo
+	password=bar
+	--
+	verbatim: get
+	verbatim: protocol=cert
+	verbatim: host=
+	verbatim: path=path/to/cert.pem
+	EOF
+'
+
 test_done