From c15d2f71d4ca568556c98a877eca771337eec5bd Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Fri, 11 Sep 2015 15:27:22 -0600
Subject: [PATCH] file/untar: fix handling of a broken tar file

Closes #1049
---
 pkgs/racket-test/tests/file/unpackers.rkt | 16 +++++++++++++++-
 racket/collects/file/untar.rkt            |  9 +++++----
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/pkgs/racket-test/tests/file/unpackers.rkt b/pkgs/racket-test/tests/file/unpackers.rkt
index 23d0fc7a36..43707ce389 100644
--- a/pkgs/racket-test/tests/file/unpackers.rkt
+++ b/pkgs/racket-test/tests/file/unpackers.rkt
@@ -174,8 +174,22 @@
 (define (unzip-tests [preserve-timestamps? #f])
   (when zip-exe (test do (run-tests (make-unzip-tests* preserve-timestamps?)))))
 
+(define (untar-of-invalid-tests)
+  ;; Make sure we don't get an internal error for this misformatted tar file:
+  (define bad-tar.gz
+    (bytes-append #"\37\213\b\b!D\363U\0\3test.tar\0\355\321A\n\302@\f\205\341\254=\305\334\240\223qb\316\323"
+                  #"\205]YZl\274\277V\21\334\210(\fR\370\277M\26\t\344\301\213\343\22\235\264\225o\334m\235"
+                  #"\352\226_\347\223h1\257\207\252V\\\262j\325*\311\32\347\272\273,\321\237S\222q8\365\21\357"
+                  #"\357>\3557*\326\376\207ij\371\343\321\277\177\321\377\336r\221T\272\30\347\326\341\350?v\377"
+                  #"\16\1\0\0\0\0\0\0\0\0\0\0\0\0\340'W\327\1)\27\0(\0\0"))
+  (test (regexp-match?
+         #rx"^unt"
+         (with-handlers ([exn? exn-message])
+           (untgz (open-input-bytes bad-tar.gz) #:filter (lambda args #f))))))
+
 (module+ main (tests))
 (define (tests)
   (test do (untar-tests)
         do (unzip-tests)
-        do (unzip-tests #t)))
+        do (unzip-tests #t)
+        do (untar-of-invalid-tests)))
diff --git a/racket/collects/file/untar.rkt b/racket/collects/file/untar.rkt
index bce385eb9b..d524d4c1c3 100644
--- a/racket/collects/file/untar.rkt
+++ b/racket/collects/file/untar.rkt
@@ -162,10 +162,11 @@
     ;; traditional:
     (define skip-tail
       (- len
-         (for/or ([i (in-range len 0 -1)])
-           (case (integer->char (bytes-ref bstr (sub1 i)))
-             [(#\space #\nul) #f]
-             [else i]))))
+         (or (for/or ([i (in-range len 0 -1)])
+               (case (integer->char (bytes-ref bstr (sub1 i)))
+                 [(#\space #\nul) #f]
+                 [else i]))
+             (error 'untar "bad number ~e at ~a" bstr (file-position in)))))
     (for/fold ([v 0]) ([i (in-range (- len skip-tail))])
       (define b (bytes-ref bstr i))
       (if (<= (char->integer #\0) b (char->integer #\7))