credential: add an argument to keep state

Until now, our credential code has mostly deal with usernames and
passwords and we've let libcurl deal with the variant of authentication
to be used.  However, now that we have the credential value, the
credential helper can take control of the authentication, so the value
provided might be something that's generated, such as a Digest hash
value.

In such a case, it would be helpful for a credential helper that gets an
erase or store command to be able to keep track of an identifier for the
original secret that went into the computation.  Furthermore, some types
of authentication, such as NTLM and Kerberos, actually need two round
trips to authenticate, which will require that the credential helper
keep some state.

In order to allow for these use cases and others, allow storing state in
a field called "state[]".  This value is passed back to the credential
helper that created it, which avoids confusion caused by parsing values
from different helpers.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 17 insertions, 3 deletions

diff --git a/credential.c b/credential.c
index 3531d74346..48826fb5a2 100644
--- a/credential.c
+++ b/credential.c
@@ -30,6 +30,7 @@ void credential_clear(struct credential *c)
 	free(c->authtype);
 	string_list_clear(&c->helpers, 0);
 	strvec_clear(&c->wwwauth_headers);
+	strvec_clear(&c->state_headers);
 
 	credential_init(c);
 }
@@ -293,8 +294,13 @@ int credential_read(struct credential *c, FILE *fp,
 			c->ephemeral = !!git_config_bool("ephemeral", value);
 		} else if (!strcmp(key, "wwwauth[]")) {
 			strvec_push(&c->wwwauth_headers, value);
-		} else if (!strcmp(key, "capability[]") && !strcmp(value, "authtype")) {
-			credential_set_capability(&c->capa_authtype, op_type);
+		} else if (!strcmp(key, "state[]")) {
+			strvec_push(&c->state_headers, value);
+		} else if (!strcmp(key, "capability[]")) {
+			if (!strcmp(value, "authtype"))
+				credential_set_capability(&c->capa_authtype, op_type);
+			else if (!strcmp(value, "state"))
+				credential_set_capability(&c->capa_state, op_type);
 		} else if (!strcmp(key, "password_expiry_utc")) {
 			errno = 0;
 			c->password_expiry_utc = parse_timestamp(value, NULL, 10);
@@ -337,8 +343,12 @@ static void credential_write_item(FILE *fp, const char *key, const char *value,
 void credential_write(const struct credential *c, FILE *fp,
 		      enum credential_op_type op_type)
 {
-	if (credential_has_capability(&c->capa_authtype, op_type)) {
+	if (credential_has_capability(&c->capa_authtype, op_type))
 		credential_write_item(fp, "capability[]", "authtype", 0);
+	if (credential_has_capability(&c->capa_state, op_type))
+		credential_write_item(fp, "capability[]", "state", 0);
+
+	if (credential_has_capability(&c->capa_authtype, op_type)) {
 		credential_write_item(fp, "authtype", c->authtype, 0);
 		credential_write_item(fp, "credential", c->credential, 0);
 		if (c->ephemeral)
@@ -357,6 +367,10 @@ void credential_write(const struct credential *c, FILE *fp,
 	}
 	for (size_t i = 0; i < c->wwwauth_headers.nr; i++)
 		credential_write_item(fp, "wwwauth[]", c->wwwauth_headers.v[i], 0);
+	if (credential_has_capability(&c->capa_state, op_type)) {
+		for (size_t i = 0; i < c->state_headers.nr; i++)
+			credential_write_item(fp, "state[]", c->state_headers.v[i], 0);
+	}
 }
 
 static int run_credential_helper(struct credential *c,