From dafb9211c77788d7ea124aca18205e924d1ac48a Mon Sep 17 00:00:00 2001
From: Rob Landley <rob@landley.net>
Date: Fri, 16 Apr 2021 01:39:08 -0500
Subject: cpio: continue past TRAILER!!! (like kernel does) but error on empty
 archive.

---
 tests/cpio.test   |  3 +++
 toys/posix/cpio.c | 20 +++++++++++---------
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/tests/cpio.test b/tests/cpio.test
index 7e2955a1..3955800f 100755
--- a/tests/cpio.test
+++ b/tests/cpio.test
@@ -59,3 +59,6 @@ testing "-id keeps existing files" "echo new >a/b && cpio -id <a.cpio 2>/dev/nul
 testing "-iu replaces existing files; no error" "echo new >a/b && cpio -iu <a.cpio && cat a/b" "old\n" "" ""
 testing "-idu replaces existing files; no error" "echo new >a/b && cpio -idu <a.cpio && cat a/b" "old\n" "" ""
 rm -rf a a.cpio
+
+testing "error on empty file" \
+  "setsid cpio -i < /dev/null 2>/dev/null || echo err" "err\n" "" ""
diff --git a/toys/posix/cpio.c b/toys/posix/cpio.c
index b60e19b4..d90be7f3 100644
--- a/toys/posix/cpio.c
+++ b/toys/posix/cpio.c
@@ -72,7 +72,7 @@ static unsigned x8u(char *hex)
   // Because scanf gratuitously treats %*X differently than printf does.
   sprintf(pattern, "%%%dX%%n", inpos);
   sscanf(hex, pattern, &val, &outpos);
-  if (inpos != outpos) error_exit("bad header");
+  if (inpos != outpos) error_exit("bad hex");
 
   return val;
 }
@@ -80,7 +80,7 @@ static unsigned x8u(char *hex)
 void cpio_main(void)
 {
   // Subtle bit: FLAG_o is 1 so we can just use it to select stdin/stdout.
-  int pipe, afd = FLAG(o);
+  int pipe, afd = FLAG(o), empty = 1;
   pid_t pid = 0;
 
   // In passthrough mode, parent stays in original dir and generates archive
@@ -111,18 +111,21 @@ void cpio_main(void)
 
   // read cpio archive
 
-  if (FLAG(i) || FLAG(t)) for (;;) {
+  if (FLAG(i) || FLAG(t)) for (;; empty = 0) {
     char *name, *tofree, *data;
     unsigned size, mode, uid, gid, timestamp;
     int test = FLAG(t), err = 0;
 
     // Read header and name.
-    if (!(size =readall(afd, toybuf, 110))) break;
+    if (!(size = readall(afd, toybuf, 110))) {
+      if (empty) error_exit("empty archive");
+      else break;
+    }
     if (size != 110 || memcmp(toybuf, "070701", 6)) error_exit("bad header");
     tofree = name = strpad(afd, x8u(toybuf+94), 110);
     if (!strcmp("TRAILER!!!", name)) {
-      if (CFG_TOYBOX_FREE) free(tofree);
-      break;
+      free(tofree);
+      continue;
     }
 
     // If you want to extract absolute paths, "cd /" and run cpio.
@@ -283,9 +286,8 @@ void cpio_main(void)
     }
     if (CFG_TOYBOX_FREE) free(name);
 
-    memset(toybuf, 0, sizeof(toybuf));
-    xwrite(afd, toybuf,
-       sprintf(toybuf, "070701%040X%056X%08XTRAILER!!!", 1, 0x0b, 0)+4);
+    // nlink=1, namesize=11, with padding
+    dprintf(afd, "070701%040X%056X%08XTRAILER!!!%c%c%c%c", 1, 11, 0, 0, 0, 0,0);
   }
   if (TT.F) xclose(afd);
 
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