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[PATCHv3 12/13] credentials: add "store" helper

From
Jeff King <peff@peff.net>
Date
Dec 10, 2011, 10:34 UTC
Message-ID
<20111210103444.GL16529@sigill.intra.peff.net>
In-Reply-To
<20111210102827.GA16460@sigill.intra.peff.net>

This is like "cache", except that we actually put the credentials on disk. This can be terribly insecure, of course, but we do what we can to protect them by filesystem permissions, and we warn the user in the documentation.

This is not unlike using .netrc to store entries, but it's a little more user-friendly. Instead of putting credentials in place ahead of time, we transparently store them after prompting the user for them once.

Signed-off-by: Jeff King <peff@peff.net>
---
This version has the "don't erase everything" protection we discussed.
 .gitignore                             |    1 +
 Documentation/git-credential-store.txt |   75 +++++++++++++++
 Documentation/gitcredentials.txt       |    5 +
 Makefile                               |    1 +
 credential-store.c                     |  157 ++++++++++++++++++++++++++++++++
 t/t0302-credential-store.sh            |    9 ++
 6 files changed, 248 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/git-credential-store.txt
 create mode 100644 credential-store.c
 create mode 100755 t/t0302-credential-store.sh
diff --git a/.gitignore b/.gitignore
index a6b0bd4..2b7a3f9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -32,6 +32,7 @@
 /git-count-objects
 /git-credential-cache
 /git-credential-cache--daemon
+/git-credential-store
 /git-cvsexportcommit
 /git-cvsimport
 /git-cvsserver
diff --git a/Documentation/git-credential-store.txt b/Documentation/git-credential-store.txt
new file mode 100644
index 0000000..3109346
--- /dev/null
+++ b/Documentation/git-credential-store.txt
@@ -0,0 +1,75 @@
+git-credential-store(1)
+=======================
+
+NAME
+----
+git-credential-store - helper to store credentials on disk
+
+SYNOPSIS
+--------
+-------------------
+git config credential.helper 'store [options]'
+-------------------
+
+DESCRIPTION
+-----------
+
+NOTE: Using this helper will store your passwords unencrypted on disk,
+protected only by filesystem permissions. If this is not an acceptable
+security tradeoff, try linkgit:git-credential-cache[1], or find a helper
+that integrates with secure storage provided by your operating system.
+
+This command stores credentials indefinitely on disk for use by future
+git programs.
+
+You probably don't want to invoke this command directly; it is meant to
+be used as a credential helper by other parts of git. See
+linkgit:gitcredentials[7] or `EXAMPLES` below.
+
+OPTIONS
+-------
+
+--store=<path>::
+
+	Use `<path>` to store credentials. The file will have its
+	filesystem permissions set to prevent other users on the system
+	from reading it, but will not be encrypted or otherwise
+	protected. Defaults to `~/.git-credentials`.
+
+EXAMPLES
+--------
+
+The point of this helper is to reduce the number of times you must type
+your username or password. For example:
+
+------------------------------------------
+$ git config credential.helper store
+$ git push http://example.com/repo.git
+Username: <type your username>
+Password: <type your password>
+
+[several days later]
+$ git push http://example.com/repo.git
+[your credentials are used automatically]
+------------------------------------------
+
+STORAGE FORMAT
+--------------
+
+The `.git-credentials` file is stored in plaintext. Each credential is
+stored on its own line as a URL like:
+
+------------------------------
+https://user:pass@example.com
+------------------------------
+
+When git needs authentication for a particular URL context,
+credential-store will consider that context a pattern to match against
+each entry in the credentials file.  If the protocol, hostname, and
+username (if we already have one) match, then the password is returned
+to git. See the discussion of configuration in linkgit:gitcredentials[7]
+for more information.
+
+GIT
+---
+Part of the linkgit:git[1] suite
diff --git a/Documentation/gitcredentials.txt b/Documentation/gitcredentials.txt
index 4e3f860..066f825 100644
--- a/Documentation/gitcredentials.txt
+++ b/Documentation/gitcredentials.txt
@@ -71,6 +71,11 @@ cache::
 	Cache credentials in memory for a short period of time. See
 	linkgit:git-credential-cache[1] for details.
 
+store::
+
+	Store credentials indefinitely on disk. See
+	linkgit:git-credential-store[1] for details.
+
 You may also have third-party helpers installed; search for
 `credential-*` in the output of `git help -a`, and consult the
 documentation of individual helpers.  Once you have selected a helper,
diff --git a/Makefile b/Makefile
index 7ad2fe3..b144f1a 100644
--- a/Makefile
+++ b/Makefile
@@ -429,6 +429,7 @@ PROGRAM_OBJS += http-backend.o
 PROGRAM_OBJS += sh-i18n--envsubst.o
 PROGRAM_OBJS += credential-cache.o
 PROGRAM_OBJS += credential-cache--daemon.o
+PROGRAM_OBJS += credential-store.o
 
 PROGRAMS += $(patsubst %.o,git-%$X,$(PROGRAM_OBJS))
 
diff --git a/credential-store.c b/credential-store.c
new file mode 100644
index 0000000..26f7589
--- /dev/null
+++ b/credential-store.c
@@ -0,0 +1,157 @@
+#include "cache.h"
+#include "credential.h"
+#include "string-list.h"
+#include "parse-options.h"
+
+static struct lock_file credential_lock;
+
+static void parse_credential_file(const char *fn,
+				  struct credential *c,
+				  void (*match_cb)(struct credential *),
+				  void (*other_cb)(struct strbuf *))
+{
+	FILE *fh;
+	struct strbuf line = STRBUF_INIT;
+	struct credential entry = CREDENTIAL_INIT;
+
+	fh = fopen(fn, "r");
+	if (!fh) {
+		if (errno != ENOENT)
+			die_errno("unable to open %s", fn);
+		return;
+	}
+
+	while (strbuf_getline(&line, fh, '\n') != EOF) {
+		credential_from_url(&entry, line.buf);
+		if (entry.username && entry.password &&
+		    credential_match(c, &entry)) {
+			if (match_cb) {
+				match_cb(&entry);
+				break;
+			}
+		}
+		else if (other_cb)
+			other_cb(&line);
+	}
+
+	credential_clear(&entry);
+	strbuf_release(&line);
+	fclose(fh);
+}
+
+static void print_entry(struct credential *c)
+{
+	printf("username=%s\n", c->username);
+	printf("password=%s\n", c->password);
+}
+
+static void print_line(struct strbuf *buf)
+{
+	strbuf_addch(buf, '\n');
+	write_or_die(credential_lock.fd, buf->buf, buf->len);
+}
+
+static void rewrite_credential_file(const char *fn, struct credential *c,
+				    struct strbuf *extra)
+{
+	if (hold_lock_file_for_update(&credential_lock, fn, 0) < 0)
+		die_errno("unable to get credential storage lock");
+	if (extra)
+		print_line(extra);
+	parse_credential_file(fn, c, NULL, print_line);
+	if (commit_lock_file(&credential_lock) < 0)
+		die_errno("unable to commit credential store");
+}
+
+static void store_credential(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, ':');
+	strbuf_addstr_urlencode(&buf, c->password, 1);
+	strbuf_addch(&buf, '@');
+	if (c->host)
+		strbuf_addstr_urlencode(&buf, c->host, 1);
+	if (c->path) {
+		strbuf_addch(&buf, '/');
+		strbuf_addstr_urlencode(&buf, c->path, 0);
+	}
+
+	rewrite_credential_file(fn, c, &buf);
+	strbuf_release(&buf);
+}
+
+static void remove_credential(const char *fn, struct credential *c)
+{
+	/*
+	 * Sanity check that we actually have something to match
+	 * against. The input we get is a restrictive pattern,
+	 * so technically a blank credential means "erase everything".
+	 * But it is too easy to accidentally send this, since it is equivalent
+	 * 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);
+}
+
+static int lookup_credential(const char *fn, struct credential *c)
+{
+	parse_credential_file(fn, c, print_entry, NULL);
+	return c->username && c->password;
+}
+
+int main(int argc, const char **argv)
+{
+	const char * const usage[] = {
+		"git credential-store [options] <action>",
+		NULL
+	};
+	const char *op;
+	struct credential c = CREDENTIAL_INIT;
+	char *file = NULL;
+	struct option options[] = {
+		OPT_STRING(0, "file", &file, "path",
+			   "fetch and store credentials in <path>"),
+		OPT_END()
+	};
+
+	umask(077);
+
+	argc = parse_options(argc, argv, NULL, options, usage, 0);
+	if (argc != 1)
+		usage_with_options(usage, options);
+	op = argv[0];
+
+	if (!file)
+		file = expand_user_path("~/.git-credentials");
+	if (!file)
+		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);
+	else if (!strcmp(op, "erase"))
+		remove_credential(file, &c);
+	else if (!strcmp(op, "store"))
+		store_credential(file, &c);
+	else
+		; /* Ignore unknown operation. */
+
+	return 0;
+}
diff --git a/t/t0302-credential-store.sh b/t/t0302-credential-store.sh
new file mode 100755
index 0000000..f61b40c
--- /dev/null
+++ b/t/t0302-credential-store.sh
@@ -0,0 +1,9 @@
+#!/bin/sh
+
+test_description='credential-store tests'
+. ./test-lib.sh
+. "$TEST_DIRECTORY"/lib-credential.sh
+
+helper_test store
+
+test_done

-- 
1.7.8.rc2.40.gaf387
Previous: Jeff KingNext: Jeff King
Message 29 of 54 in “[PATCHv3 0/13] credential helpers”
  1. Jeff KingDec 10, 2011
  2. 01/13 test-lib: add test_config_global variantJeff King, Dec 10, 2011
  3. 02/13 t5550: fix typoJeff King, Dec 10, 2011
  4. 03/13 introduce credentials APIJeff King, Dec 10, 2011
  5. Jakub NarebskiDec 10, 2011
  6. Jeff KingDec 10, 2011
  7. 04/13 credential: add function for parsing url componentsJeff King, Dec 10, 2011
  8. 05/13 http: use credential API to get passwordsJeff King, Dec 10, 2011
  9. 06/13 credential: apply helper configJeff King, Dec 10, 2011
  10. 07/13 credential: add credential.*.usernameJeff King, Dec 10, 2011
  11. 08/13 credential: make relevance of http path configurableJeff King, Dec 10, 2011
  12. Jakub NarebskiDec 10, 2011
  13. Jeff KingDec 10, 2011
  14. 09/13 docs: end-user documentation for the credential subsystemJeff King, Dec 10, 2011
  15. 10/13 credentials: add "cache" helperJeff King, Dec 10, 2011
  16. Jonathan NiederJan 10, 2012
  17. Jeff KingJan 10, 2012
  18. Jeff KingJan 10, 2012
  19. Junio C HamanoJan 10, 2012
  20. Jeff KingJan 17, 2012
  21. Junio C HamanoJan 17, 2012
  22. Jonathan NiederJan 10, 2012
  23. Jeff KingJan 10, 2012
  24. Jonathan NiederJan 11, 2012
  25. Jeff KingJan 12, 2012
  26. 11/13 strbuf: add strbuf_add*_urlencodeJeff King, Dec 10, 2011
  27. Jakub NarebskiDec 10, 2011
  28. Jeff KingDec 10, 2011
  29. 12/13 credentials: add "store" helperJeff King, Dec 10, 2011
  30. 13/13 t: add test harness for external credential helpersJeff King, Dec 10, 2011
  31. 0/9 echo characters in username promptJeff King, Dec 10, 2011
  32. 1/9 imap-send: avoid buffer overflowJeff King, Dec 10, 2011
  33. 2/9 imap-send: don't check return value of git_getpassJeff King, Dec 10, 2011
  34. 3/9 move git_getpass to its own source fileJeff King, Dec 10, 2011
  35. 4/9 refactor git_getpass into generic prompt functionJeff King, Dec 10, 2011
  36. 5/9 add generic terminal prompt functionJeff King, Dec 10, 2011
  37. Pete WyckoffDec 15, 2011
  38. Jeff KingDec 15, 2011
  39. Pete WyckoffDec 15, 2011
  40. 6/9 prompt: use git_terminal_promptJeff King, Dec 10, 2011
  41. 7/9 credential: use git_prompt instead of git_getpassJeff King, Dec 10, 2011
  42. 8/9 Makefile: linux has /dev/ttyJeff King, Dec 10, 2011
  43. 9/9 Makefile: OS X has /dev/ttyJeff King, Dec 10, 2011
  44. 1/2 Makefile: Windows lacks /dev/ttyJohannes Sixt, Dec 12, 2011
  45. 2/2 Makefile: optionally exclude code that needs Unix socketsJohannes Sixt, Dec 12, 2011
  46. Jeff KingDec 12, 2011
  47. Junio C HamanoDec 12, 2011
  48. Junio C HamanoDec 13, 2011
  49. Jeff KingDec 13, 2011
  50. Johannes SixtDec 13, 2011
  51. Junio C HamanoDec 14, 2011
  52. Jeff KingDec 12, 2011
  53. Johannes SixtDec 12, 2011
  54. 1/1 contrib: add credential helper for OS X KeychainJeff King, Dec 10, 2011

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