master 86325f960a 1/3: bindat (strz): Error on null byte if packing variable-length string

[Lars Ingebrigtsen]

branch: master
commit 86325f960af8eb1df712e2f26e2b708f80c14ac6
Author: Richard Hansen <rhansen@rhansen.org>
Commit: Lars Ingebrigtsen <larsi@gnus.org>

    bindat (strz): Error on null byte if packing variable-length string
    
    * lisp/emacs-lisp/bindat.el (strz): Signal an error if a null byte is
    encountered while packing a string to a variable-length strz field.
    * test/lisp/emacs-lisp/bindat-tests.el (strz): Add tests (bug#55938).
---
 lisp/emacs-lisp/bindat.el            | 5 +++++
 test/lisp/emacs-lisp/bindat-tests.el | 7 ++++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/lisp/emacs-lisp/bindat.el b/lisp/emacs-lisp/bindat.el
index 2d6589b52d..9ba89a5e3f 100644
--- a/lisp/emacs-lisp/bindat.el
+++ b/lisp/emacs-lisp/bindat.el
@@ -444,6 +444,11 @@ e.g. corresponding to STRUCT.FIELD1[INDEX2].FIELD3..."
   (let* ((v (string-to-unibyte v))
          (len (length v)))
     (dotimes (i len)
+      (when (= (aref v i) 0)
+        ;; Alternatively we could pretend that this was the end of
+        ;; the string and stop packing, but then bindat-length would
+        ;; need to scan the input string looking for a null byte.
+        (error "Null byte encountered in input strz string"))
       (aset bindat-raw (+ bindat-idx i) (aref v i)))
     (setq bindat-idx (+ bindat-idx len 1))))
 
diff --git a/test/lisp/emacs-lisp/bindat-tests.el 
b/test/lisp/emacs-lisp/bindat-tests.el
index 8bb3baa485..7d1233ded7 100644
--- a/test/lisp/emacs-lisp/bindat-tests.el
+++ b/test/lisp/emacs-lisp/bindat-tests.el
@@ -240,7 +240,12 @@
 
   (ert-deftest bindat-test--strz-varlen-pack ()
     (should (equal (bindat-pack spec "") "\0"))
-    (should (equal (bindat-pack spec "abc") "abc\0")))
+    (should (equal (bindat-pack spec "abc") "abc\0"))
+    ;; Null bytes in the input string break unpacking.
+    (should-error (bindat-pack spec "\0"))
+    (should-error (bindat-pack spec "\0x"))
+    (should-error (bindat-pack spec "x\0"))
+    (should-error (bindat-pack spec "x\0y")))
 
   (ert-deftest bindat-test--strz-varlen-unpack ()
     (should (equal (bindat-unpack spec "\0") ""))