[PATCH] config: preserve config file permissions on edits

From: Eric Wong <normalperson@yhbt.net>
Date: May 5, 2014, 21:58 UTC
Message-ID: <20140505215853.GA23299@dcvr.yhbt.net>

Users may already store sensitive data such as imap.pass in .git/config; making the file world-readable when "git config" is called to edit means their password would be compromised on a shared system.

Signed-off-by: Eric Wong <normalperson@yhbt.net>
---
 config.c               | 7 +++++++
 t/t1300-repo-config.sh | 6 ++++++
 2 files changed, 13 insertions(+)

diff --git a/config.c b/config.c
index a30cb5c..a0b6756 100644
--- a/config.c
+++ b/config.c
@@ -1636,6 +1636,13 @@ int git_config_set_multivar_in_file(const char *config_filename,
 			MAP_PRIVATE, in_fd, 0);
 		close(in_fd);
 
+		if (fchmod(fd, st.st_mode & 07777) < 0) {
+			error("fchmod on %s failed: %s",
+				lock->filename, strerror(errno));
+			ret = CONFIG_NO_WRITE;
+			goto out_free;
+		}
+
 		if (store.seen == 0)
 			store.seen = 1;
 
diff --git a/t/t1300-repo-config.sh b/t/t1300-repo-config.sh
index 58cd543..d87693e 100755
--- a/t/t1300-repo-config.sh
+++ b/t/t1300-repo-config.sh
@@ -1158,4 +1158,10 @@ test_expect_failure 'adding a key into an empty section reuses header' '
 	test_cmp expect .git/config
 '
 
+test_expect_success POSIXPERM,PERL 'preserves existing permissions' '
+	chmod 0600 .git/config &&
+	git config imap.pass Hunter2 &&
+	perl -e "die q(badperm) if ((stat(q(.git/config)))[2] & 07777) != 0600"
+'
+
 test_done

-- 
Eric Wong