fix emergency file replacement vulnerability

Resolves: rhbz#2277586

nano-7.2-emergency-file-replace-vuln.patch

@@ -0,0 +1,96 @@
+From 5e7a3c2e7e118c7f12d5dfda9f9140f638976aa2 Mon Sep 17 00:00:00 2001
+From: Benno Schulenberg <bensberg@telfort.nl>
+Date: Sun, 28 Apr 2024 10:51:52 +0200
+Subject: files: run `chmod` and `chown` on the descriptor, not on the filename
+
+This closes a window of opportunity where the emergency file could be
+replaced by a malicious symlink.
+
+The issue was reported by `MartinJM` and `InvisibleMeerkat`.
+
+Problem existed since version 2.2.0, commit 123110c5, when chmodding
+and chowning of the emergency .save file was added.
+---
+ src/definitions.h |  2 +-
+ src/files.c       | 13 ++++++++++++-
+ src/nano.c        | 12 +-----------
+ 3 files changed, 14 insertions(+), 13 deletions(-)
+
+diff --git a/src/definitions.h b/src/definitions.h
+index af3a793..55d8235 100644
+--- a/src/definitions.h
++++ b/src/definitions.h
+@@ -288,7 +288,7 @@ typedef enum {
+ } message_type;
+ 
+ typedef enum {
+-	OVERWRITE, APPEND, PREPEND
++	OVERWRITE, APPEND, PREPEND, EMERGENCY
+ } kind_of_writing_type;
+ 
+ typedef enum {
+diff --git a/src/files.c b/src/files.c
+index 57c2001..584b579 100644
+--- a/src/files.c
++++ b/src/files.c
+@@ -1763,6 +1763,8 @@ bool write_file(const char *name, FILE *thefile, bool normal,
+ #endif
+ 	char *realname = real_dir_from_tilde(name);
+ 		/* The filename after tilde expansion. */
++	int fd = 0;
++		/* The descriptor that is assigned when opening the file. */
+ 	char *tempname = NULL;
+ 		/* The name of the temporary file we use when prepending. */
+ 	linestruct *line = openfile->filetop;
+@@ -1846,7 +1848,6 @@ bool write_file(const char *name, FILE *thefile, bool normal,
+ 	 * For an emergency file, access is restricted to just the owner. */
+ 	if (thefile == NULL) {
+ 		mode_t permissions = (normal ? RW_FOR_ALL : S_IRUSR|S_IWUSR);
+-		int fd;
+ 
+ #ifndef NANO_TINY
+ 		block_sigwinch(TRUE);
+@@ -1972,6 +1973,16 @@ bool write_file(const char *name, FILE *thefile, bool normal,
+ 		}
+ #endif
+ 
++#if !defined(NANO_TINY) && defined(HAVE_CHMOD) && defined(HAVE_CHOWN)
++	/* Change permissions and owner of an emergency save file to the values
++	 * of the original file, but ignore any failure as we are in a hurry. */
++	if (method == EMERGENCY && fd && openfile->statinfo) {
++		IGNORE_CALL_RESULT(fchmod(fd, openfile->statinfo->st_mode));
++		IGNORE_CALL_RESULT(fchown(fd, openfile->statinfo->st_uid,
++											openfile->statinfo->st_gid));
++	}
++#endif
++
+ 	if (fclose(thefile) != 0) {
+ 		statusline(ALERT, _("Error writing %s: %s"), realname, strerror(errno));
+ 
+diff --git a/src/nano.c b/src/nano.c
+index 90b4a0b..973054f 100644
+--- a/src/nano.c
++++ b/src/nano.c
+@@ -337,18 +337,8 @@ void emergency_save(const char *filename)
+ 
+ 	if (*targetname == '\0')
+ 		fprintf(stderr, _("\nToo many .save files\n"));
+-	else if (write_file(targetname, NULL, SPECIAL, OVERWRITE, NONOTES)) {
++	else if (write_file(targetname, NULL, SPECIAL, EMERGENCY, NONOTES))
+ 		fprintf(stderr, _("\nBuffer written to %s\n"), targetname);
+-#if !defined(NANO_TINY) && defined(HAVE_CHMOD) && defined(HAVE_CHOWN)
+-		/* Try to chmod/chown the saved file to the values of the original file,
+-		 * but ignore any failure as we are in a hurry to get out. */
+-		if (openfile->statinfo) {
+-			IGNORE_CALL_RESULT(chmod(targetname, openfile->statinfo->st_mode));
+-			IGNORE_CALL_RESULT(chown(targetname, openfile->statinfo->st_uid,
+-													openfile->statinfo->st_gid));
+-		}
+-#endif
+-	}
+ 
+ 	free(targetname);
+ 	free(plainname);
+-- 
+cgit v1.1
+

nano.spec

@@ -8,7 +8,7 @@
 Summary:         A small text editor
 Name:            nano
 Version:         7.2
-Release:         4%{?dist}
+Release:         5%{?dist}
 License:         GPL-3.0-or-later
 URL:             https://www.nano-editor.org
 
@@ -26,6 +26,8 @@ Source11:        nano-default-editor.sh
 Source12:        nano-default-editor.csh
 Source13:        nano-default-editor.fish
 
+Patch0:          nano-7.2-emergency-file-replace-vuln.patch
+
 BuildRequires:   file-devel
 BuildRequires:   gettext-devel
 BuildRequires:   gcc
@@ -133,6 +135,9 @@ install -Dpm 0644 %{SOURCE13} %{buildroot}%{_datadir}/fish/vendor_conf.d/%{basen
 
 
 %changelog
+* Mon May 06 2024 Lukáš Zaoral <lzaoral@redhat.com> - 7.2-5
+- fix emergency file replacement vulnerability (rhbz#2277586)
+
 * Thu Jul 20 2023 Fedora Release Engineering <releng@fedoraproject.org> - 7.2-4
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_39_Mass_Rebuild