add-shell will not preserve the current permissions, and if umask is 0
it will create the /etc/shells world writable. To reproduce:
umask 0; add-shell /bin/bash; ls -l /etc/shells
As a workaround we add the current st_mode with xopen3, which at least
will prevent /etc/shells to get more permissions than it previously
had.
Signed-off-by: Natanael Copa <nc...@alpinelinux.org>
---
loginutils/add-remove-shell.c | 11 +++--------
1 file changed, 3 insertions(+), 8 deletions(-)
diff --git a/loginutils/add-remove-shell.c b/loginutils/add-remove-shell.c
index af7c31779..a434d054d 100644
--- a/loginutils/add-remove-shell.c
+++ b/loginutils/add-remove-shell.c
@@ -54,6 +54,7 @@ int add_remove_shell_main(int argc UNUSED_PARAM, char **argv)
FILE *orig_fp;
char *orig_fn;
char *new_fn;
+ struct stat sb;
argv++;
@@ -63,6 +64,7 @@ int add_remove_shell_main(int argc UNUSED_PARAM, char **argv)
orig_fp = fopen_for_read(orig_fn);
new_fn = xasprintf("%s.tmp", orig_fn);
+ xfstat(fileno(orig_fp), &sb, orig_fn);
/*
* O_TRUNC or O_EXCL? At the first glance, O_EXCL looks better,
* since it prevents races. But: (1) it requires a retry loop,
@@ -71,14 +73,7 @@ int add_remove_shell_main(int argc UNUSED_PARAM, char **argv)
* after which it should revert to O_TRUNC.
* For now, I settle for O_TRUNC instead.
*/
- xmove_fd(xopen(new_fn, O_WRONLY | O_CREAT | O_TRUNC), STDOUT_FILENO);
-
- /* TODO:
- struct stat sb;
- xfstat(fileno(orig_fp), &sb);
- xfchown(STDOUT_FILENO, sb.st_uid, sb.st_gid);
- xfchmod(STDOUT_FILENO, sb.st_mode);
- */
+ xmove_fd(xopen3(new_fn, O_WRONLY | O_CREAT | O_TRUNC, sb.st_mode),
STDOUT_FILENO);
if (orig_fp) {
/* Copy old file, possibly skipping removed shell names */
--
2.12.2
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