[PATCHv3 0/13] credential helpers

@@ -379,6 +379,11 @@ test_config () {
 	git config "$@"
 }
 
+test_config_global () {
+	test_when_finished "test_unconfig --global '$1'" &&
+	git config --global "$@"
+}
+
 # Use test_set_prereq to tell that a particular prerequisite is available.
 # The prerequisite can later be checked for in two ways:
 #

@@ -66,7 +66,7 @@ test_expect_success 'cloning password-protected repository can fail' '
 
 test_expect_success 'http auth can use user/pass in URL' '
 	>askpass-query &&
-	echo wrong >askpass-reponse &&
+	echo wrong >askpass-response &&
 	git clone "$HTTPD_URL_USER_PASS/auth/repo.git" clone-auth-none &&
 	test_cmp askpass-expect-none askpass-query
 '

@@ -167,6 +167,7 @@
 /gitweb/static/gitweb.js
 /gitweb/static/gitweb.min.*
 /test-chmtime
+/test-credential
 /test-ctype
 /test-date
 /test-delta

@@ -0,0 +1,241 @@
+credentials API
+===============
+
+The credentials API provides an abstracted way of gathering username and
+password credentials from the user (even though credentials in the wider
+world can take many forms, in this document the word "credential" always
+refers to a username and password pair).
+
+Data Structures
+---------------
+
+`struct credential`::
+
+	This struct represents a single username/password combination
+	along with any associated context. All string fields should be
+	heap-allocated (or NULL if they are not known or not applicable).
+	The meaning of the individual context fields is the same as
+	their counterparts in the helper protocol; see the section below
+	for a description of each field.
++
+The `helpers` member of the struct is a `string_list` of helpers.  Each
+string specifies an external helper which will be run, in order, to
+either acquire or store credentials. See the section on credential
+helpers below.
++
+This struct should always be initialized with `CREDENTIAL_INIT` or
+`credential_init`.
+
+
+Functions
+---------
+
+`credential_init`::
+
+	Initialize a credential structure, setting all fields to empty.
+
+`credential_clear`::
+
+	Free any resources associated with the credential structure,
+	returning it to a pristine initialized state.
+
+`credential_fill`::
+
+	Instruct the credential subsystem to fill the username and
+	password fields of the passed credential struct by first
+	consulting helpers, then asking the user. After this function
+	returns, the username and password fields of the credential are
+	guaranteed to be non-NULL. If an error occurs, the function will
+	die().
+
+`credential_reject`::
+
+	Inform the credential subsystem that the provided credentials
+	have been rejected. This will cause the credential subsystem to
+	notify any helpers of the rejection (which allows them, for
+	example, to purge the invalid credentials from storage).  It
+	will also free() the username and password fields of the
+	credential and set them to NULL (readying the credential for
+	another call to `credential_fill`). Any errors from helpers are
+	ignored.
+
+`credential_approve`::
+
+	Inform the credential subsystem that the provided credentials
+	were successfully used for authentication.  This will cause the
+	credential subsystem to notify any helpers of the approval, so
+	that they may store the result to be used again.  Any errors
+	from helpers are ignored.
+
+Example
+-------
+
+The example below shows how the functions of the credential API could be
+used to login to a fictitious "foo" service on a remote host:
+
+-----------------------------------------------------------------------
+int foo_login(struct foo_connection *f)
+{
+	int status;
+	/*
+	 * Create a credential with some context; we don't yet know the
+	 * username or password.
+	 */
+
+	struct credential c = CREDENTIAL_INIT;
+	c.protocol = xstrdup("foo");
+	c.host = xstrdup(f->hostname);
+
+	/*
+	 * Fill in the username and password fields by contacting
+	 * helpers and/or asking the user. The function will die if it
+	 * fails.
+	 */
+	credential_fill(&c);
+
+	/*
+	 * Otherwise, we have a username and password. Try to use it.
+	 */
+	status = send_foo_login(f, c.username, c.password);
+	switch (status) {
+	case FOO_OK:
+		/* It worked. Store the credential for later use. */
+		credential_accept(&c);
+		break;
+	case FOO_BAD_LOGIN:
+		/* Erase the credential from storage so we don't try it
+		 * again. */
+		credential_reject(&c);
+		break;
+	default:
+		/*
+		 * Some other error occured. We don't know if the
+		 * credential is good or bad, so report nothing to the
+		 * credential subsystem.
+		 */
+	}
+
+	/* Free any associated resources. */
+	credential_clear(&c);
+
+	return status;
+}
+-----------------------------------------------------------------------
+
+
+Credential Helpers
+------------------
+
+Credential helpers are programs executed by git to fetch or save
+credentials from and to long-term storage (where "long-term" is simply
+longer than a single git process; e.g., credentials may be stored
+in-memory for a few minutes, or indefinitely on disk).
+
+Each helper is specified by a single string. The string is transformed
+by git into a command to be executed using these rules:
+
+  1. If the helper string begins with "!", it is considered a shell
+     snippet, and everything after the "!" becomes the command.
+
+  2. Otherwise, if the helper string begins with an absolute path, the
+     verbatim helper string becomes the command.
+
+  3. Otherwise, the string "git credential-" is prepended to the helper
+     string, and the result becomes the command.
+
+The resulting command then has an "operation" argument appended to it
+(see below for details), and the result is executed by the shell.
+
+Here are some example specifications:
+
+----------------------------------------------------
+# run "git credential-foo"
+foo
+
+# same as above, but pass an argument to the helper
+foo --bar=baz
+
+# the arguments are parsed by the shell, so use shell
+# quoting if necessary
+foo --bar="whitespace arg"
+
+# you can also use an absolute path, which will not use the git wrapper
+/path/to/my/helper --with-arguments
+
+# or you can specify your own shell snippet
+!f() { echo "password=`cat $HOME/.secret`"; }; f
+----------------------------------------------------
+
+Generally speaking, rule (3) above is the simplest for users to specify.
+Authors of credential helpers should make an effort to assist their
+users by naming their program "git-credential-$NAME", and putting it in
+the $PATH or $GIT_EXEC_PATH during installation, which will allow a user
+to enable it with `git config credential.helper $NAME`.
+
+When a helper is executed, it will have one "operation" argument
+appended to its command line, which is one of:
+
+`get`::
+
+	Return a matching credential, if any exists.
+
+`store`::
+
+	Store the credential, if applicable to the helper.
+
+`erase`::
+
+	Remove a matching credential, if any, from the helper's storage.
+
+The details of the credential will be provided on the helper's stdin
+stream. The credential is split into a set of named attributes.
+Attributes are provided to the helper, one per line. Each attribute is
+specified by a key-value pair, separated by an `=` (equals) sign,
+followed by a newline. The key may contain any bytes except `=`,
+newline, or NUL. The value may contain any bytes except newline or NUL.
+In both cases, all bytes are treated as-is (i.e., there is no quoting,
+and one cannot transmit a value with newline or NUL in it). The list of
+attributes is terminated by a blank line or end-of-file.
+
+Git will send the following attributes (but may not send all of
+them for a given credential; for example, a `host` attribute makes no
+sense when dealing with a non-network protocol):
+
+`protocol`::
+
+	The protocol over which the credential will be used (e.g.,
+	`https`).
+
+`host`::
+
+	The remote hostname for a network credential.
+
+`path`::
+
+	The path with which the credential will be used. E.g., for
+	accessing a remote https repository, this will be the
+	repository's path on the server.
+
+`username`::
+
+	The credential's username, if we already have one (e.g., from a
+	URL, from the user, or from a previously run helper).
+
+`password`::
+
+	The credential's password, if we are asking it to be stored.
+
+For a `get` operation, the helper should produce a list of attributes
+on stdout in the same format. A helper is free to produce a subset, or
+even no values at all if it has nothing useful to provide. Any provided
+attributes will overwrite those already known about by git.
+
+For a `store` or `erase` operation, the helper's output is ignored.
+If it fails to perform the requested operation, it may complain to
+stderr to inform the user. If it does not support the requested
+operation (e.g., a read-only store), it should silently ignore the
+request.
+
+If a helper receives any other operation, it should silently ignore the
+request. This leaves room for future operations to be added (older
+helpers will just ignore the new requests).

@@ -431,6 +431,7 @@ PROGRAM_OBJS += sh-i18n--envsubst.o
 PROGRAMS += $(patsubst %.o,git-%$X,$(PROGRAM_OBJS))
 
 TEST_PROGRAMS_NEED_X += test-chmtime
+TEST_PROGRAMS_NEED_X += test-credential
 TEST_PROGRAMS_NEED_X += test-ctype
 TEST_PROGRAMS_NEED_X += test-date
 TEST_PROGRAMS_NEED_X += test-delta

@@ -525,6 +526,7 @@ LIB_H += compat/win32/poll.h
 LIB_H += compat/win32/dirent.h
 LIB_H += connected.h
 LIB_H += convert.h
+LIB_H += credential.h
 LIB_H += csum-file.h
 LIB_H += decorate.h
 LIB_H += delta.h

@@ -611,6 +613,7 @@ LIB_OBJS += connect.o
 LIB_OBJS += connected.o
 LIB_OBJS += convert.o
 LIB_OBJS += copy.o
+LIB_OBJS += credential.o
 LIB_OBJS += csum-file.o
 LIB_OBJS += ctype.o
 LIB_OBJS += date.o

@@ -0,0 +1,234 @@
+#include "cache.h"
+#include "credential.h"
+#include "string-list.h"
+#include "run-command.h"
+
+void credential_init(struct credential *c)
+{
+	memset(c, 0, sizeof(*c));
+	c->helpers.strdup_strings = 1;
+}
+
+void credential_clear(struct credential *c)
+{
+	free(c->protocol);
+	free(c->host);
+	free(c->path);
+	free(c->username);
+	free(c->password);
+	string_list_clear(&c->helpers, 0);
+
+	credential_init(c);
+}
+
+static void credential_describe(struct credential *c, struct strbuf *out)
+{
+	if (!c->protocol)
+		return;
+	strbuf_addf(out, "%s://", c->protocol);
+	if (c->username && *c->username)
+		strbuf_addf(out, "%s@", c->username);
+	if (c->host)
+		strbuf_addstr(out, c->host);
+	if (c->path)
+		strbuf_addf(out, "/%s", c->path);
+}
+
+static char *credential_ask_one(const char *what, struct credential *c)
+{
+	struct strbuf desc = STRBUF_INIT;
+	struct strbuf prompt = STRBUF_INIT;
+	char *r;
+
+	credential_describe(c, &desc);
+	if (desc.len)
+		strbuf_addf(&prompt, "%s for '%s': ", what, desc.buf);
+	else
+		strbuf_addf(&prompt, "%s: ", what);
+
+	/* FIXME: for usernames, we should do something less magical that
+	 * actually echoes the characters. However, we need to read from
+	 * /dev/tty and not stdio, which is not portable (but getpass will do
+	 * it for us). http.c uses the same workaround. */
+	r = git_getpass(prompt.buf);
+
+	strbuf_release(&desc);
+	strbuf_release(&prompt);
+	return xstrdup(r);
+}
+
+static void credential_getpass(struct credential *c)
+{
+	if (!c->username)
+		c->username = credential_ask_one("Username", c);
+	if (!c->password)
+		c->password = credential_ask_one("Password", c);
+}
+
+int credential_read(struct credential *c, FILE *fp)
+{
+	struct strbuf line = STRBUF_INIT;
+
+	while (strbuf_getline(&line, fp, '\n') != EOF) {
+		char *key = line.buf;
+		char *value = strchr(key, '=');
+
+		if (!line.len)
+			break;
+
+		if (!value) {
+			warning("invalid credential line: %s", key);
+			strbuf_release(&line);
+			return -1;
+		}
+		*value++ = '\0';
+
+		if (!strcmp(key, "username")) {
+			free(c->username);
+			c->username = xstrdup(value);
+		} else if (!strcmp(key, "password")) {
+			free(c->password);
+			c->password = xstrdup(value);
+		} else if (!strcmp(key, "protocol")) {
+			free(c->protocol);
+			c->protocol = xstrdup(value);
+		} else if (!strcmp(key, "host")) {
+			free(c->host);
+			c->host = xstrdup(value);
+		} else if (!strcmp(key, "path")) {
+			free(c->path);
+			c->path = xstrdup(value);
+		}
+		/*
+		 * Ignore other lines; we don't know what they mean, but
+		 * this future-proofs us when later versions of git do
+		 * learn new lines, and the helpers are updated to match.
+		 */
+	}
+
+	strbuf_release(&line);
+	return 0;
+}
+
+static void credential_write_item(FILE *fp, const char *key, const char *value)
+{
+	if (!value)
+		return;
+	fprintf(fp, "%s=%s\n", key, value);
+}
+
+static void credential_write(const struct credential *c, FILE *fp)
+{
+	credential_write_item(fp, "protocol", c->protocol);
+	credential_write_item(fp, "host", c->host);
+	credential_write_item(fp, "path", c->path);
+	credential_write_item(fp, "username", c->username);
+	credential_write_item(fp, "password", c->password);
+}
+
+static int run_credential_helper(struct credential *c,
+				 const char *cmd,
+				 int want_output)
+{
+	struct child_process helper;
+	const char *argv[] = { NULL, NULL };
+	FILE *fp;
+
+	memset(&helper, 0, sizeof(helper));
+	argv[0] = cmd;
+	helper.argv = argv;
+	helper.use_shell = 1;
+	helper.in = -1;
+	if (want_output)
+		helper.out = -1;
+	else
+		helper.no_stdout = 1;
+
+	if (start_command(&helper) < 0)
+		return -1;
+
+	fp = xfdopen(helper.in, "w");
+	credential_write(c, fp);
+	fclose(fp);
+
+	if (want_output) {
+		int r;
+		fp = xfdopen(helper.out, "r");
+		r = credential_read(c, fp);
+		fclose(fp);
+		if (r < 0) {
+			finish_command(&helper);
+			return -1;
+		}
+	}
+
+	if (finish_command(&helper))
+		return -1;
+	return 0;
+}
+
+static int credential_do(struct credential *c, const char *helper,
+			 const char *operation)
+{
+	struct strbuf cmd = STRBUF_INIT;
+	int r;
+
+	if (helper[0] == '!')
+		strbuf_addstr(&cmd, helper + 1);
+	else if (is_absolute_path(helper))
+		strbuf_addstr(&cmd, helper);
+	else
+		strbuf_addf(&cmd, "git credential-%s", helper);
+
+	strbuf_addf(&cmd, " %s", operation);
+	r = run_credential_helper(c, cmd.buf, !strcmp(operation, "get"));
+
+	strbuf_release(&cmd);
+	return r;
+}
+
+void credential_fill(struct credential *c)
+{
+	int i;
+
+	if (c->username && c->password)
+		return;
+
+	for (i = 0; i < c->helpers.nr; i++) {
+		credential_do(c, c->helpers.items[i].string, "get");
+		if (c->username && c->password)
+			return;
+	}
+
+	credential_getpass(c);
+	if (!c->username && !c->password)
+		die("unable to get password from user");
+}
+
+void credential_approve(struct credential *c)
+{
+	int i;
+
+	if (c->approved)
+		return;
+	if (!c->username || !c->password)
+		return;
+
+	for (i = 0; i < c->helpers.nr; i++)
+		credential_do(c, c->helpers.items[i].string, "store");
+	c->approved = 1;
+}
+
+void credential_reject(struct credential *c)
+{
+	int i;
+
+	for (i = 0; i < c->helpers.nr; i++)
+		credential_do(c, c->helpers.items[i].string, "erase");
+
+	free(c->username);
+	c->username = NULL;
+	free(c->password);
+	c->password = NULL;
+	c->approved = 0;
+}

@@ -0,0 +1,28 @@
+#ifndef CREDENTIAL_H
+#define CREDENTIAL_H
+
+#include "string-list.h"
+
+struct credential {
+	struct string_list helpers;
+	unsigned approved:1;
+
+	char *username;
+	char *password;
+	char *protocol;
+	char *host;
+	char *path;
+};
+
+#define CREDENTIAL_INIT { STRING_LIST_INIT_DUP }
+
+void credential_init(struct credential *);
+void credential_clear(struct credential *);
+
+void credential_fill(struct credential *);
+void credential_approve(struct credential *);
+void credential_reject(struct credential *);
+
+int credential_read(struct credential *, FILE *);
+
+#endif /* CREDENTIAL_H */

@@ -0,0 +1,33 @@
+#!/bin/sh
+
+# Try a set of credential helpers; the expected stdin,
+# stdout and stderr should be provided on stdin,
+# separated by "--".
+check() {
+	read_chunk >stdin &&
+	read_chunk >expect-stdout &&
+	read_chunk >expect-stderr &&
+	test-credential "$@" <stdin >stdout 2>stderr &&
+	test_cmp expect-stdout stdout &&
+	test_cmp expect-stderr stderr
+}
+
+read_chunk() {
+	while read line; do
+		case "$line" in
+		--) break ;;
+		*) echo "$line" ;;
+		esac
+	done
+}
+
+
+cat >askpass <<\EOF
+#!/bin/sh
+echo >&2 askpass: $*
+what=`echo $1 | cut -d" " -f1 | tr A-Z a-z | tr -cd a-z`
+echo "askpass-$what"
+EOF
+chmod +x askpass
+GIT_ASKPASS="$PWD/askpass"
+export GIT_ASKPASS

@@ -0,0 +1,195 @@
+#!/bin/sh
+
+test_description='basic credential helper tests'
+. ./test-lib.sh
+. "$TEST_DIRECTORY"/lib-credential.sh
+
+test_expect_success 'setup helper scripts' '
+	cat >dump <<-\EOF &&
+	whoami=`echo $0 | sed s/.*git-credential-//`
+	echo >&2 "$whoami: $*"
+	while IFS== read key value; do
+		echo >&2 "$whoami: $key=$value"
+		eval "$key=$value"
+	done
+	EOF
+
+	cat >git-credential-useless <<-\EOF &&
+	#!/bin/sh
+	. ./dump
+	exit 0
+	EOF
+	chmod +x git-credential-useless &&
+
+	cat >git-credential-verbatim <<-\EOF &&
+	#!/bin/sh
+	user=$1; shift
+	pass=$1; shift
+	. ./dump
+	test -z "$user" || echo username=$user
+	test -z "$pass" || echo password=$pass
+	EOF
+	chmod +x git-credential-verbatim &&
+
+	PATH="$PWD:$PATH"
+'
+
+test_expect_success 'credential_fill invokes helper' '
+	check fill "verbatim foo bar" <<-\EOF
+	--
+	username=foo
+	password=bar
+	--
+	verbatim: get
+	EOF
+'
+
+test_expect_success 'credential_fill invokes multiple helpers' '
+	check fill useless "verbatim foo bar" <<-\EOF
+	--
+	username=foo
+	password=bar
+	--
+	useless: get
+	verbatim: get
+	EOF
+'
+
+test_expect_success 'credential_fill stops when we get a full response' '
+	check fill "verbatim one two" "verbatim three four" <<-\EOF
+	--
+	username=one
+	password=two
+	--
+	verbatim: get
+	EOF
+'
+
+test_expect_success 'credential_fill continues through partial response' '
+	check fill "verbatim one \"\"" "verbatim two three" <<-\EOF
+	--
+	username=two
+	password=three
+	--
+	verbatim: get
+	verbatim: get
+	verbatim: username=one
+	EOF
+'
+
+test_expect_success 'credential_fill passes along metadata' '
+	check fill "verbatim one two" <<-\EOF
+	protocol=ftp
+	host=example.com
+	path=foo.git
+	--
+	username=one
+	password=two
+	--
+	verbatim: get
+	verbatim: protocol=ftp
+	verbatim: host=example.com
+	verbatim: path=foo.git
+	EOF
+'
+
+test_expect_success 'credential_approve calls all helpers' '
+	check approve useless "verbatim one two" <<-\EOF
+	username=foo
+	password=bar
+	--
+	--
+	useless: store
+	useless: username=foo
+	useless: password=bar
+	verbatim: store
+	verbatim: username=foo
+	verbatim: password=bar
+	EOF
+'
+
+test_expect_success 'do not bother storing password-less credential' '
+	check approve useless <<-\EOF
+	username=foo
+	--
+	--
+	EOF
+'
+
+
+test_expect_success 'credential_reject calls all helpers' '
+	check reject useless "verbatim one two" <<-\EOF
+	username=foo
+	password=bar
+	--
+	--
+	useless: erase
+	useless: username=foo
+	useless: password=bar
+	verbatim: erase
+	verbatim: username=foo
+	verbatim: password=bar
+	EOF
+'
+
+test_expect_success 'usernames can be preserved' '
+	check fill "verbatim \"\" three" <<-\EOF
+	username=one
+	--
+	username=one
+	password=three
+	--
+	verbatim: get
+	verbatim: username=one
+	EOF
+'
+
+test_expect_success 'usernames can be overridden' '
+	check fill "verbatim two three" <<-\EOF
+	username=one
+	--
+	username=two
+	password=three
+	--
+	verbatim: get
+	verbatim: username=one
+	EOF
+'
+
+test_expect_success 'do not bother completing already-full credential' '
+	check fill "verbatim three four" <<-\EOF
+	username=one
+	password=two
+	--
+	username=one
+	password=two
+	--
+	EOF
+'
+
+# We can't test the basic terminal password prompt here because
+# getpass() tries too hard to find the real terminal. But if our
+# askpass helper is run, we know the internal getpass is working.
+test_expect_success 'empty helper list falls back to internal getpass' '
+	check fill <<-\EOF
+	--
+	username=askpass-username
+	password=askpass-password
+	--
+	askpass: Username:
+	askpass: Password:
+	EOF
+'
+
+test_expect_success 'internal getpass does not ask for known username' '
+	check fill <<-\EOF
+	username=foo
+	--
+	username=foo
+	password=askpass-password
+	--
+	askpass: Password:
+	EOF
+'
+
+test_done

@@ -0,0 +1,38 @@
+#include "cache.h"
+#include "credential.h"
+#include "string-list.h"
+
+static const char usage_msg[] =
+"test-credential <fill|approve|reject> [helper...]";
+
+int main(int argc, const char **argv)
+{
+	const char *op;
+	struct credential c = CREDENTIAL_INIT;
+	int i;
+
+	op = argv[1];
+	if (!op)
+		usage(usage_msg);
+	for (i = 2; i < argc; i++)
+		string_list_append(&c.helpers, argv[i]);
+
+	if (credential_read(&c, stdin) < 0)
+		die("unable to read credential from stdin");
+
+	if (!strcmp(op, "fill")) {
+		credential_fill(&c);
+		if (c.username)
+			printf("username=%s\n", c.username);
+		if (c.password)
+			printf("password=%s\n", c.password);
+	}
+	else if (!strcmp(op, "approve"))
+		credential_approve(&c);
+	else if (!strcmp(op, "reject"))
+		credential_reject(&c);
+	else
+		usage(usage_msg);
+
+	return 0;
+}

@@ -67,6 +67,10 @@ Functions
 	that they may store the result to be used again.  Any errors
 	from helpers are ignored.
 
+`credential_from_url`::
+
+	Parse a URL into broken-down credential fields.
+
 Example
 -------
 

@@ -2,6 +2,7 @@
 #include "credential.h"
 #include "string-list.h"
 #include "run-command.h"
+#include "url.h"
 
 void credential_init(struct credential *c)
 {

@@ -232,3 +233,54 @@ void credential_reject(struct credential *c)
 	c->password = NULL;
 	c->approved = 0;
 }
+
+void credential_from_url(struct credential *c, const char *url)
+{
+	const char *at, *colon, *cp, *slash, *host, *proto_end;
+
+	credential_clear(c);
+
+	/*
+	 * Match one of:
+	 *   (1) proto://<host>/...
+	 *   (2) proto://<user>@<host>/...
+	 *   (3) proto://<user>:<pass>@<host>/...
+	 */
+	proto_end = strstr(url, "://");
+	if (!proto_end)
+		return;
+	cp = proto_end + 3;
+	at = strchr(cp, '@');
+	colon = strchr(cp, ':');
+	slash = strchrnul(cp, '/');
+
+	if (!at || slash <= at) {
+		/* Case (1) */
+		host = cp;
+	}
+	else if (!colon || at <= colon) {
+		/* Case (2) */
+		c->username = url_decode_mem(cp, at - cp);
+		host = at + 1;
+	} else {
+		/* Case (3) */
+		c->username = url_decode_mem(cp, colon - cp);
+		c->password = url_decode_mem(colon + 1, at - (colon + 1));
+		host = at + 1;
+	}
+
+	if (proto_end - url > 0)
+		c->protocol = xmemdupz(url, proto_end - url);
+	if (slash - host > 0)
+		c->host = url_decode_mem(host, slash - host);
+	/* Trim leading and trailing slashes from path */
+	while (*slash == '/')
+		slash++;
+	if (*slash) {
+		char *p;
+		c->path = url_decode(slash);
+		p = c->path + strlen(c->path) - 1;
+		while (p > c->path && *p == '/')
+			*p-- = '\0';
+	}
+}

@@ -24,5 +24,6 @@ struct credential {
 void credential_reject(struct credential *);
 
 int credential_read(struct credential *, FILE *);
+void credential_from_url(struct credential *, const char *url);
 
 #endif /* CREDENTIAL_H */

@@ -22,6 +22,61 @@ void credential_clear(struct credential *c)
 	credential_init(c);
 }
 
+int credential_match(const struct credential *want,
+		     const struct credential *have)
+{
+#define CHECK(x) (!want->x || (have->x && !strcmp(want->x, have->x)))
+	return CHECK(protocol) &&
+	       CHECK(host) &&
+	       CHECK(path) &&
+	       CHECK(username);
+#undef CHECK
+}
+
+static int credential_config_callback(const char *var, const char *value,
+				      void *data)
+{
+	struct credential *c = data;
+	const char *key, *dot;
+
+	key = skip_prefix(var, "credential.");
+	if (!key)
+		return 0;
+
+	if (!value)
+		return config_error_nonbool(var);
+
+	dot = strrchr(key, '.');
+	if (dot) {
+		struct credential want = CREDENTIAL_INIT;
+		char *url = xmemdupz(key, dot - key);
+		int matched;
+
+		credential_from_url(&want, url);
+		matched = credential_match(&want, c);
+
+		credential_clear(&want);
+		free(url);
+
+		if (!matched)
+			return 0;
+		key = dot + 1;
+	}
+
+	if (!strcmp(key, "helper"))
+		string_list_append(&c->helpers, value);
+
+	return 0;
+}
+
+static void credential_apply_config(struct credential *c)
+{
+	if (c->configured)
+		return;
+	git_config(credential_config_callback, c);
+	c->configured = 1;
+}
+
 static void credential_describe(struct credential *c, struct strbuf *out)
 {
 	if (!c->protocol)

@@ -195,6 +250,8 @@ void credential_fill(struct credential *c)
 	if (c->username && c->password)
 		return;
 
+	credential_apply_config(c);
+
 	for (i = 0; i < c->helpers.nr; i++) {
 		credential_do(c, c->helpers.items[i].string, "get");
 		if (c->username && c->password)

@@ -215,6 +272,8 @@ void credential_approve(struct credential *c)
 	if (!c->username || !c->password)
 		return;
 
+	credential_apply_config(c);
+
 	for (i = 0; i < c->helpers.nr; i++)
 		credential_do(c, c->helpers.items[i].string, "store");
 	c->approved = 1;

@@ -224,6 +283,8 @@ void credential_reject(struct credential *c)
 {
 	int i;
 
+	credential_apply_config(c);
+
 	for (i = 0; i < c->helpers.nr; i++)
 		credential_do(c, c->helpers.items[i].string, "erase");
 

@@ -5,7 +5,8 @@
 
 struct credential {
 	struct string_list helpers;
-	unsigned approved:1;
+	unsigned approved:1,
+		 configured:1;
 
 	char *username;
 	char *password;

@@ -25,5 +26,7 @@ struct credential {
 
 int credential_read(struct credential *, FILE *);
 void credential_from_url(struct credential *, const char *url);
+int credential_match(const struct credential *have,
+		     const struct credential *want);
 
 #endif /* CREDENTIAL_H */

@@ -192,4 +192,46 @@ test_expect_success 'internal getpass does not ask for known username' '
 	EOF
 '
 
+HELPER="!f() {
+		cat >/dev/null
+		echo username=foo
+		echo password=bar
+	}; f"
+test_expect_success 'respect configured credentials' '
+	test_config credential.helper "$HELPER" &&
+	check fill <<-\EOF
+	--
+	username=foo
+	password=bar
+	--
+	EOF
+'
+
+test_expect_success 'match configured credential' '
+	test_config credential.https://example.com.helper "$HELPER" &&
+	check fill <<-\EOF
+	protocol=https
+	host=example.com
+	path=repo.git
+	--
+	username=foo
+	password=bar
+	--
+	EOF
+'
+
+test_expect_success 'do not match configured credential' '
+	test_config credential.https://foo.helper "$HELPER" &&
+	check fill <<-\EOF
+	protocol=https
+	host=bar
+	--
+	username=askpass-username
+	password=askpass-password
+	--
+	askpass: Username for '\''https://bar'\'':
+	askpass: Password for '\''https://askpass-username@bar'\'':
+	EOF
+'
+
 test_done

@@ -101,6 +101,18 @@ test_expect_success 'http auth can request both user and pass' '
 	expect_askpass both user@host
 '
 
+test_expect_success 'http auth respects credential helper config' '
+	test_config_global credential.helper "!f() {
+		cat >/dev/null
+		echo username=user@host
+		echo password=user@host
+	}; f" &&
+	>askpass-query &&
+	echo wrong >askpass-response &&
+	git clone "$HTTPD_URL/auth/repo.git" clone-auth-helper &&
+	expect_askpass none
+'
+
 test_expect_success 'fetch changes via http' '
 	echo content >>file &&
 	git commit -a -m two &&

@@ -3,6 +3,7 @@
 #include "sideband.h"
 #include "run-command.h"
 #include "url.h"
+#include "credential.h"
 
 int active_requests;
 int http_is_verbose;

@@ -41,7 +42,7 @@
 static int curl_ftp_no_epsv;
 static const char *curl_http_proxy;
 static const char *curl_cookie_file;
-static char *user_name, *user_pass, *description;
+static struct credential http_auth = CREDENTIAL_INIT;
 static const char *user_agent;
 
 #if LIBCURL_VERSION_NUM >= 0x071700

@@ -52,7 +53,7 @@
 #define CURLOPT_KEYPASSWD CURLOPT_SSLCERTPASSWD
 #endif
 
-static char *ssl_cert_password;
+static struct credential cert_auth = CREDENTIAL_INIT;
 static int ssl_cert_password_required;
 
 static struct curl_slist *pragma_header;

@@ -136,27 +137,6 @@ static void process_curl_messages(void)
 }
 #endif
 
-static char *git_getpass_with_description(const char *what, const char *desc)
-{
-	struct strbuf prompt = STRBUF_INIT;
-	char *r;
-
-	if (desc)
-		strbuf_addf(&prompt, "%s for '%s': ", what, desc);
-	else
-		strbuf_addf(&prompt, "%s: ", what);
-	/*
-	 * NEEDSWORK: for usernames, we should do something less magical that
-	 * actually echoes the characters. However, we need to read from
-	 * /dev/tty and not stdio, which is not portable (but getpass will do
-	 * it for us). http.c uses the same workaround.
-	 */
-	r = git_getpass(prompt.buf);
-
-	strbuf_release(&prompt);
-	return xstrdup(r);
-}
-
 static int http_options(const char *var, const char *value, void *cb)
 {
 	if (!strcmp("http.sslverify", var)) {

@@ -229,11 +209,11 @@ static int http_options(const char *var, const char *value, void *cb)
 
 static void init_curl_http_auth(CURL *result)
 {
-	if (user_name) {
+	if (http_auth.username) {
 		struct strbuf up = STRBUF_INIT;
-		if (!user_pass)
-			user_pass = xstrdup(git_getpass_with_description("Password", description));
-		strbuf_addf(&up, "%s:%s", user_name, user_pass);
+		credential_fill(&http_auth);
+		strbuf_addf(&up, "%s:%s",
+			    http_auth.username, http_auth.password);
 		curl_easy_setopt(result, CURLOPT_USERPWD,
 				 strbuf_detach(&up, NULL));
 	}

@@ -241,18 +221,14 @@ static void init_curl_http_auth(CURL *result)
 
 static int has_cert_password(void)
 {
-	if (ssl_cert_password != NULL)
-		return 1;
 	if (ssl_cert == NULL || ssl_cert_password_required != 1)
 		return 0;
-	/* Only prompt the user once. */
-	ssl_cert_password_required = -1;
-	ssl_cert_password = git_getpass_with_description("Certificate Password", description);
-	if (ssl_cert_password != NULL) {
-		ssl_cert_password = xstrdup(ssl_cert_password);
-		return 1;
-	} else
-		return 0;
+	if (!cert_auth.password) {
+		cert_auth.protocol = xstrdup("cert");
+		cert_auth.path = xstrdup(ssl_cert);
+		credential_fill(&cert_auth);
+	}
+	return 1;
 }
 
 static CURL *get_curl_handle(void)

@@ -279,7 +255,7 @@ static int has_cert_password(void)
 	if (ssl_cert != NULL)
 		curl_easy_setopt(result, CURLOPT_SSLCERT, ssl_cert);
 	if (has_cert_password())
-		curl_easy_setopt(result, CURLOPT_KEYPASSWD, ssl_cert_password);
+		curl_easy_setopt(result, CURLOPT_KEYPASSWD, cert_auth.password);
 #if LIBCURL_VERSION_NUM >= 0x070903
 	if (ssl_key != NULL)
 		curl_easy_setopt(result, CURLOPT_SSLKEY, ssl_key);

@@ -321,42 +297,6 @@ static int has_cert_password(void)
 	return result;
 }
 
-static void http_auth_init(const char *url)
-{
-	const char *at, *colon, *cp, *slash, *host;
-
-	cp = strstr(url, "://");
-	if (!cp)
-		return;
-
-	/*
-	 * Ok, the URL looks like "proto://something".  Which one?
-	 * "proto://<user>:<pass>@<host>/...",
-	 * "proto://<user>@<host>/...", or just
-	 * "proto://<host>/..."?
-	 */
-	cp += 3;
-	at = strchr(cp, '@');
-	colon = strchr(cp, ':');
-	slash = strchrnul(cp, '/');
-	if (!at || slash <= at) {
-		/* No credentials, but we may have to ask for some later */
-		host = cp;
-	}
-	else if (!colon || at <= colon) {
-		/* Only username */
-		user_name = url_decode_mem(cp, at - cp);
-		user_pass = NULL;
-		host = at + 1;
-	} else {
-		user_name = url_decode_mem(cp, colon - cp);
-		user_pass = url_decode_mem(colon + 1, at - (colon + 1));
-		host = at + 1;
-	}
-
-	description = url_decode_mem(host, slash - host);
-}
-
 static void set_from_env(const char **var, const char *envname)
 {
 	const char *val = getenv(envname);