rsync: fix regression with _FORTIFY_SOURCE=2

  nativeBuildInputs = [ perl ];

  patches = [

    # https://github.com/WayneD/rsync/issues/511#issuecomment-1774612577

    # original source: https://build.opensuse.org/package/view_file/network/rsync/rsync-fortified-strlcpy-fix.patch?expand=1&rev=3f8dd2f4a404c96c0f69176e60893714

    ./rsync-fortified-strlcpy-fix.patch

  ];

  buildInputs = [ libiconv zlib popt ]

    ++ lib.optional enableACLs acl

    ++ lib.optional enableZstd zstd

From 1f83963f59960150e8c46112daa8411324c1f209 Mon Sep 17 00:00:00 2001

From: Jiri Slaby <jslaby@suse.cz>

Date: Fri, 18 Aug 2023 08:26:20 +0200

Subject: [PATCH] exclude: fix crashes with fortified strlcpy()

Fortified (-D_FORTIFY_SOURCE=2 for gcc) builds make strlcpy() crash when

its third parameter (size) is larger than the buffer:

  $ rsync -FFXHav '--filter=merge global-rsync-filter' Align-37-43/ xxx

  sending incremental file list

  *** buffer overflow detected ***: terminated

It's in the exclude code in setup_merge_file():

  strlcpy(y, save, MAXPATHLEN);

Note the 'y' pointer was incremented, so it no longer points to memory

with MAXPATHLEN "owned" bytes.

Fix it by remembering the number of copied bytes into the 'save' buffer

and use that instead of MAXPATHLEN which is clearly incorrect.

Fixes #511.

---

 exclude.c | 5 +++--

 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/exclude.c b/exclude.c

index ffe55b167..1a5de3b9e 100644

--- a/exclude.c

+++ b/exclude.c

@@ -720,7 +720,8 @@ static BOOL setup_merge_file(int mergelist_num, filter_rule *ex,

 	parent_dirscan = True;

 	while (*y) {

 		char save[MAXPATHLEN];

-		strlcpy(save, y, MAXPATHLEN);

+		/* copylen is strlen(y) which is < MAXPATHLEN. +1 for \0 */

+		size_t copylen = strlcpy(save, y, MAXPATHLEN) + 1;

 		*y = '\0';

 		dirbuf_len = y - dirbuf;

 		strlcpy(x, ex->pattern, MAXPATHLEN - (x - buf));

@@ -734,7 +735,7 @@ static BOOL setup_merge_file(int mergelist_num, filter_rule *ex,

 			lp->head = NULL;

 		}

 		lp->tail = NULL;

-		strlcpy(y, save, MAXPATHLEN);

+		strlcpy(y, save, copylen);

 		while ((*x++ = *y++) != '/') {}

 	}

 	parent_dirscan = False;