[PATCH v4 1/4] git-credential-store: support multiple credential files

* [PATCH v4 1/4] git-credential-store: support multiple credential files
@ 2015-03-18  7:04 Paul Tan
  2015-03-18  7:04 ` [PATCH v4 2/4] git-credential-store: support XDG_CONFIG_HOME Paul Tan
                   ` (3 more replies)
  0 siblings, 4 replies; 15+ messages in thread
From: Paul Tan @ 2015-03-18  7:04 UTC (permalink / raw)
  To: git; +Cc: Matthieu Moy, Junio C Hamano, Jeff King, Eric Sunshine, Paul Tan

Previously, git-credential-store only supported storing credentials in a
single file: ~/.git-credentials. In order to support the XDG base
directory specification[1], git-credential-store needs to be able to
lookup and erase credentials from multiple files, as well as to pick the
appropriate file to write to so that the credentials can be found on
subsequent lookups.

[1] http://standards.freedesktop.org/basedir-spec/basedir-spec-0.7.html

Note that some credential storage files may not be owned, readable or
writable by the user, as they may be system-wide files that are meant to
apply to every user.

Instead of a single file path, lookup_credential(), remove_credential()
and store_credential() now take a precedence-ordered string_list of
file paths. lookup_credential() expects both user-specific and
system-wide credential files to be provided to support the use case of
system administrators setting default credentials for users.
remove_credential() and store_credential() expect only the user-specific
credential files to be provided as usually the only config files that
users are allowed to edit are their own user-specific ones.

lookup_credential() will read these (user-specific and system-wide) file
paths in order until it finds the 1st matching credential and print it.
As some files may be private and thus unreadable, any file which cannot
be read will be ignored silently.

remove_credential() will erase credentials from all (user-specific)
files in the list.  This is because if credentials are only erased from
the file with the highest precedence, a matching credential may still be
found in a file further down the list. (Note that due to the lockfile
code, this requires the directory to be writable, which should be so for
user-specific config files)

store_credential() will write the credentials to the first existing
(user-specific) file in the list. If none of the files in the list
exist, store_credential() will write to the filename specified by the
first item of the filename list. For backwards compatibility, this
filename should be "~/.git-credentials".

Helped-by: Matthieu Moy <Matthieu.Moy@grenoble-inp.fr>
Helped-by: Junio C Hamano <gitster@pobox.com>
Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Paul Tan <pyokagan@gmail.com>
---

The previous version can be found at [1].

[1] http://thread.gmane.org/gmane.comp.version-control.git/265305/focus=265309

The changes are as follows:

* Remove default_fn argument from store_credential(). It now uses the
first item of the filenames string_list. Thanks Jeff, Matthieu and
Junio for your input in this discussion.

* Change filename string_list fns to duplicate strings by default
(STRING_LIST_INIT_DUP). This is to make memory ownership explicit --
when the string_list receives the file paths from xdg_config_home()
and expand_user_path(), it is responsible for freeing those strings.
Thanks Jeff for pointing this out.

 credential-store.c | 79 +++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 54 insertions(+), 25 deletions(-)

diff --git a/credential-store.c b/credential-store.c
index 925d3f4..8dad479 100644
--- a/credential-store.c
+++ b/credential-store.c
@@ -6,7 +6,7 @@
 
 static struct lock_file credential_lock;
 
-static void parse_credential_file(const char *fn,
+static int parse_credential_file(const char *fn,
 				  struct credential *c,
 				  void (*match_cb)(struct credential *),
 				  void (*other_cb)(struct strbuf *))
@@ -14,18 +14,20 @@ static void parse_credential_file(const char *fn,
 	FILE *fh;
 	struct strbuf line = STRBUF_INIT;
 	struct credential entry = CREDENTIAL_INIT;
+	int found_credential = 0;
 
 	fh = fopen(fn, "r");
 	if (!fh) {
-		if (errno != ENOENT)
+		if (errno != ENOENT && errno != EACCES)
 			die_errno("unable to open %s", fn);
-		return;
+		return found_credential;
 	}
 
 	while (strbuf_getline(&line, fh, '\n') != EOF) {
 		credential_from_url(&entry, line.buf);
 		if (entry.username && entry.password &&
 		    credential_match(c, &entry)) {
+			found_credential = 1;
 			if (match_cb) {
 				match_cb(&entry);
 				break;
@@ -38,6 +40,7 @@ static void parse_credential_file(const char *fn,
 	credential_clear(&entry);
 	strbuf_release(&line);
 	fclose(fh);
+	return found_credential;
 }
 
 static void print_entry(struct credential *c)
@@ -64,21 +67,10 @@ static void rewrite_credential_file(const char *fn, struct credential *c,
 		die_errno("unable to commit credential store");
 }
 
-static void store_credential(const char *fn, struct credential *c)
+static void store_credential_file(const char *fn, struct credential *c)
 {
 	struct strbuf buf = STRBUF_INIT;
 
-	/*
-	 * Sanity check that what we are storing is actually sensible.
-	 * In particular, we can't make a URL without a protocol field.
-	 * Without either a host or pathname (depending on the scheme),
-	 * we have no primary key. And without a username and password,
-	 * we are not actually storing a credential.
-	 */
-	if (!c->protocol || !(c->host || c->path) ||
-	    !c->username || !c->password)
-		return;
-
 	strbuf_addf(&buf, "%s://", c->protocol);
 	strbuf_addstr_urlencode(&buf, c->username, 1);
 	strbuf_addch(&buf, ':');
@@ -95,8 +87,35 @@ static void store_credential(const char *fn, struct credential *c)
 	strbuf_release(&buf);
 }
 
-static void remove_credential(const char *fn, struct credential *c)
+static void store_credential(const struct string_list *fns, struct credential *c)
 {
+	struct string_list_item *fn;
+
+	/*
+	 * Sanity check that what we are storing is actually sensible.
+	 * In particular, we can't make a URL without a protocol field.
+	 * Without either a host or pathname (depending on the scheme),
+	 * we have no primary key. And without a username and password,
+	 * we are not actually storing a credential.
+	 */
+	if (!c->protocol || !(c->host || c->path) || !c->username || !c->password)
+		return;
+
+	for_each_string_list_item(fn, fns)
+		if (!access(fn->string, F_OK)) {
+			store_credential_file(fn->string, c);
+			return;
+		}
+	/* Write credential to the filename specified by fns->items[0], thus
+	 * creating it */
+	if (fns->nr)
+		store_credential_file(fns->items[0].string, c);
+}
+
+static void remove_credential(const struct string_list *fns, struct credential *c)
+{
+	struct string_list_item *fn;
+
 	/*
 	 * Sanity check that we actually have something to match
 	 * against. The input we get is a restrictive pattern,
@@ -105,14 +124,20 @@ static void remove_credential(const char *fn, struct credential *c)
 	 * to empty input. So explicitly disallow it, and require that the
 	 * pattern have some actual content to match.
 	 */
-	if (c->protocol || c->host || c->path || c->username)
-		rewrite_credential_file(fn, c, NULL);
+	if (!c->protocol && !c->host && !c->path && !c->username)
+		return;
+	for_each_string_list_item(fn, fns)
+		if (!access(fn->string, F_OK))
+			rewrite_credential_file(fn->string, c, NULL);
 }
 
-static int lookup_credential(const char *fn, struct credential *c)
+static void lookup_credential(const struct string_list *fns, struct credential *c)
 {
-	parse_credential_file(fn, c, print_entry, NULL);
-	return c->username && c->password;
+	struct string_list_item *fn;
+
+	for_each_string_list_item(fn, fns)
+		if (parse_credential_file(fn->string, c, print_entry, NULL))
+			return; /* Found credential */
 }
 
 int main(int argc, char **argv)
@@ -123,6 +148,7 @@ int main(int argc, char **argv)
 	};
 	const char *op;
 	struct credential c = CREDENTIAL_INIT;
+	struct string_list fns = STRING_LIST_INIT_DUP;
 	char *file = NULL;
 	struct option options[] = {
 		OPT_STRING(0, "file", &file, "path",
@@ -139,20 +165,23 @@ int main(int argc, char **argv)
 
 	if (!file)
 		file = expand_user_path("~/.git-credentials");
-	if (!file)
+	if (file)
+		string_list_append(&fns, file);
+	else
 		die("unable to set up default path; use --file");
 
 	if (credential_read(&c, stdin) < 0)
 		die("unable to read credential");
 
 	if (!strcmp(op, "get"))
-		lookup_credential(file, &c);
+		lookup_credential(&fns, &c);
 	else if (!strcmp(op, "erase"))
-		remove_credential(file, &c);
+		remove_credential(&fns, &c);
 	else if (!strcmp(op, "store"))
-		store_credential(file, &c);
+		store_credential(&fns, &c);
 	else
 		; /* Ignore unknown operation. */
 
+	string_list_clear(&fns, 0);
 	return 0;
 }
-- 
2.1.4

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