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* [COMMITTED 2.31] gconv: Do not emit spurious NUL character in ISO-2022-JP-3 (bug 28524)
@ 2021-12-05 14:17 Aurelien Jarno
  0 siblings, 0 replies; only message in thread
From: Aurelien Jarno @ 2021-12-05 14:17 UTC (permalink / raw)
  To: libc-stable; +Cc: Nikita Popov

From: Nikita Popov <npv1310@gmail.com>

Bugfix 27256 has introduced another issue:
In conversion from ISO-2022-JP-3 encoding, it is possible
to force iconv to emit extra NUL character on internal state reset.
To do this, it is sufficient to feed iconv with escape sequence
which switches active character set.
The simplified check 'data->__statep->__count != ASCII_set'
introduced by the aforementioned bugfix picks that case and
behaves as if '\0' character has been queued thus emitting it.

To eliminate this issue, these steps are taken:
* Restore original condition
'(data->__statep->__count & ~7) != ASCII_set'.
It is necessary since bits 0-2 may contain
number of buffered input characters.
* Check that queued character is not NUL.
Similar step is taken for main conversion loop.

Bundled test case follows following logic:
* Try to convert ISO-2022-JP-3 escape sequence
switching active character set
* Reset internal state by providing NULL as input buffer
* Ensure that nothing has been converted.

Signed-off-by: Nikita Popov <npv1310@gmail.com>
(cherry picked from commit ff012870b2c02a62598c04daa1e54632e020fd7d)
---
 NEWS                      |  1 +
 iconvdata/Makefile        |  6 +++-
 iconvdata/bug-iconv15.c   | 60 +++++++++++++++++++++++++++++++++++++++
 iconvdata/iso-2022-jp-3.c | 28 ++++++++++++------
 4 files changed, 86 insertions(+), 9 deletions(-)
 create mode 100644 iconvdata/bug-iconv15.c

diff --git a/NEWS b/NEWS
index 98d4b24ab4..4d52ccfaa0 100644
--- a/NEWS
+++ b/NEWS
@@ -38,6 +38,7 @@ The following bugs are resolved with this release:
   [26932] libc: sh: Multiple floating point functions defined as stubs only
   [27130] "rep movsb" performance issue
   [27177] GLIBC_TUNABLES=glibc.cpu.x86_ibt=on:glibc.cpu.x86_shstk=on doesn't work
+  [28524] Conversion from ISO-2022-JP-3 with iconv may emit spurious NULs
 
 Security related changes:
 
diff --git a/iconvdata/Makefile b/iconvdata/Makefile
index 72a91416d3..8fbb67a52b 100644
--- a/iconvdata/Makefile
+++ b/iconvdata/Makefile
@@ -1,4 +1,5 @@
 # Copyright (C) 1997-2020 Free Software Foundation, Inc.
+# Copyright (C) The GNU Toolchain Authors.
 # This file is part of the GNU C Library.
 
 # The GNU C Library is free software; you can redistribute it and/or
@@ -73,7 +74,8 @@ modules.so := $(addsuffix .so, $(modules))
 ifeq (yes,$(build-shared))
 tests = bug-iconv1 bug-iconv2 tst-loading tst-e2big tst-iconv4 bug-iconv4 \
 	tst-iconv6 bug-iconv5 bug-iconv6 tst-iconv7 bug-iconv8 bug-iconv9 \
-	bug-iconv10 bug-iconv11 bug-iconv12 bug-iconv13 bug-iconv14
+	bug-iconv10 bug-iconv11 bug-iconv12 bug-iconv13 bug-iconv14 \
+	bug-iconv15
 ifeq ($(have-thread-library),yes)
 tests += bug-iconv3
 endif
@@ -318,6 +320,8 @@ $(objpfx)bug-iconv12.out: $(objpfx)gconv-modules \
 			  $(addprefix $(objpfx),$(modules.so))
 $(objpfx)bug-iconv14.out: $(objpfx)gconv-modules \
 			  $(addprefix $(objpfx),$(modules.so))
+$(objpfx)bug-iconv15.out: $(addprefix $(objpfx), $(gconv-modules)) \
+			  $(addprefix $(objpfx),$(modules.so))
 
 $(objpfx)iconv-test.out: run-iconv-test.sh $(objpfx)gconv-modules \
 			 $(addprefix $(objpfx),$(modules.so)) \
diff --git a/iconvdata/bug-iconv15.c b/iconvdata/bug-iconv15.c
new file mode 100644
index 0000000000..cc04bd0313
--- /dev/null
+++ b/iconvdata/bug-iconv15.c
@@ -0,0 +1,60 @@
+/* Bug 28524: Conversion from ISO-2022-JP-3 with iconv
+   may emit spurious NUL character on state reset.
+   Copyright (C) The GNU Toolchain Authors.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <stddef.h>
+#include <iconv.h>
+#include <support/check.h>
+
+static int
+do_test (void)
+{
+  char in[] = "\x1b(I";
+  char *inbuf = in;
+  size_t inleft = sizeof (in) - 1;
+  char out[1];
+  char *outbuf = out;
+  size_t outleft = sizeof (out);
+  iconv_t cd;
+
+  cd = iconv_open ("UTF8", "ISO-2022-JP-3");
+  TEST_VERIFY_EXIT (cd != (iconv_t) -1);
+
+  /* First call to iconv should alter internal state.
+     Now, JISX0201_Kana_set is selected and
+     state value != ASCII_set.  */
+  TEST_VERIFY (iconv (cd, &inbuf, &inleft, &outbuf, &outleft) != (size_t) -1);
+
+  /* No bytes should have been added to
+     the output buffer at this point.  */
+  TEST_VERIFY (outbuf == out);
+  TEST_VERIFY (outleft == sizeof (out));
+
+  /* Second call shall emit spurious NUL character in unpatched glibc.  */
+  TEST_VERIFY (iconv (cd, NULL, NULL, &outbuf, &outleft) != (size_t) -1);
+
+  /* No characters are expected to be produced.  */
+  TEST_VERIFY (outbuf == out);
+  TEST_VERIFY (outleft == sizeof (out));
+
+  TEST_VERIFY_EXIT (iconv_close (cd) != -1);
+
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/iconvdata/iso-2022-jp-3.c b/iconvdata/iso-2022-jp-3.c
index 62cbc54a11..c7b470db61 100644
--- a/iconvdata/iso-2022-jp-3.c
+++ b/iconvdata/iso-2022-jp-3.c
@@ -1,5 +1,6 @@
 /* Conversion module for ISO-2022-JP-3.
    Copyright (C) 1998-2020 Free Software Foundation, Inc.
+   Copyright (C) The GNU Toolchain Authors.
    This file is part of the GNU C Library.
    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998,
    and Bruno Haible <bruno@clisp.org>, 2002.
@@ -81,20 +82,31 @@ enum
    the output state to the initial state.  This has to be done during the
    flushing.  */
 #define EMIT_SHIFT_TO_INIT \
-  if (data->__statep->__count != ASCII_set)			      \
+  if ((data->__statep->__count & ~7) != ASCII_set)			      \
     {									      \
       if (FROM_DIRECTION)						      \
 	{								      \
-	  if (__glibc_likely (outbuf + 4 <= outend))			      \
+	  uint32_t ch = data->__statep->__count >> 6;			      \
+									      \
+	  if (__glibc_unlikely (ch != 0))				      \
 	    {								      \
-	      /* Write out the last character.  */			      \
-	      *((uint32_t *) outbuf) = data->__statep->__count >> 6;	      \
-	      outbuf += sizeof (uint32_t);				      \
-	      data->__statep->__count = ASCII_set;			\
+	      if (__glibc_likely (outbuf + 4 <= outend))		      \
+		{							      \
+		  /* Write out the last character.  */			      \
+		  put32u (outbuf, ch);					      \
+		  outbuf += 4;						      \
+		  data->__statep->__count &= 7;				      \
+		  data->__statep->__count |= ASCII_set;			      \
+		}							      \
+	      else							      \
+		/* We don't have enough room in the output buffer.  */	      \
+		status = __GCONV_FULL_OUTPUT;				      \
 	    }								      \
 	  else								      \
-	    /* We don't have enough room in the output buffer.  */	      \
-	    status = __GCONV_FULL_OUTPUT;				      \
+	    {								      \
+	      data->__statep->__count &= 7;				      \
+	      data->__statep->__count |= ASCII_set;			      \
+	    }								      \
 	}								      \
       else								      \
 	{								      \
-- 
2.30.2


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2021-12-05 14:17 [COMMITTED 2.31] gconv: Do not emit spurious NUL character in ISO-2022-JP-3 (bug 28524) Aurelien Jarno

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