config: preserve config file permissions on edits

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.

[v2: updated for section renames, as noted by Junio]

Signed-off-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/config.c b/config.c
index 314d8ee740bea488d8c79d80b3d91530ad15252d..62de69e148be7ec3383f2aa606a1a2eaffe601f7 100644 (file)
--- a/config.c
+++ b/config.c
@@ -1634,6 +1634,13 @@ 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;
 
@@ -1782,6 +1789,7 @@ int git_config_rename_section_in_file(const char *config_filename,
        int out_fd;
        char buf[1024];
        FILE *config_file;
+       struct stat st;
 
        if (new_name && !section_name_is_ok(new_name)) {
                ret = error("invalid section name: %s", new_name);
@@ -1803,6 +1811,14 @@ int git_config_rename_section_in_file(const char *config_filename,
                goto unlock_and_out;
        }
 
+       fstat(fileno(config_file), &st);
+
+       if (fchmod(out_fd, st.st_mode & 07777) < 0) {
+               ret = error("fchmod on %s failed: %s",
+                               lock->filename, strerror(errno));
+               goto out;
+       }
+
        while (fgets(buf, sizeof(buf), config_file)) {
                int i;
                int length;

diff --git a/t/t1300-repo-config.sh b/t/t1300-repo-config.sh
index 967359344dab8118dfd55816ef08f4809a9f33ad..ba41bc93ee5633c119eeca99d379e76031728644 100755 (executable)
--- a/t/t1300-repo-config.sh
+++ b/t/t1300-repo-config.sh
@@ -1154,4 +1154,14 @@ 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(badset) if ((stat(q(.git/config)))[2] & 07777) != 0600" &&
+       git config --rename-section imap pop &&
+       perl -e \
+         "die q(badrename) if ((stat(q(.git/config)))[2] & 07777) != 0600"
+'
+
 test_done