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Fixed a possible buffer overrun in ntfs_utf16_to_utf8()

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If an output buffer was provided, ntfs_utf16_to_utf8() limited the
output string length without the terminating null to 'outs_len'.  This
was incorrect because a terminating null was always added to the string,
causing a buffer overrun if the output string happened to have exactly
the maximum length.  This was a longstanding bug.  Fix it by leaving
space for a terminating null.

(contributed by Eric Biggers)
This commit is contained in:
Jean-Pierre André 2017-02-11 09:51:17 +01:00
parent b9624542e0
commit 2052b46639
1 changed files with 10 additions and 4 deletions
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14
libntfs-3g/unistr.c
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@ -544,7 +544,7 @@ fail:
* @ins: input utf16 string buffer
* @ins_len: length of input string in utf16 characters
* @outs: on return contains the (allocated) output multibyte string
* @outs_len: length of output buffer in bytes
* @outs_len: length of output buffer in bytes (ignored if *@outs is NULL)
*
* Return -1 with errno set if string has invalid byte sequence or too long.
*/
@ -563,10 +563,16 @@ static int ntfs_utf16_to_utf8(const ntfschar *ins, const int ins_len,
int halfpair;
halfpair = 0;
if (!*outs)
if (!*outs) {
/* If no output buffer was provided, we will allocate one and
* limit its length to PATH_MAX. Note: we follow the standard
* convention of PATH_MAX including the terminating null. */
outs_len = PATH_MAX;
}
size = utf16_to_utf8_size(ins, ins_len, outs_len);
/* The size *with* the terminating null is limited to @outs_len,
* so the size *without* the terminating null is limited to one less. */
size = utf16_to_utf8_size(ins, ins_len, outs_len - 1);
if (size < 0)
goto out;
@ -877,7 +883,7 @@ fail:
* @ins: input Unicode string buffer
* @ins_len: length of input string in Unicode characters
* @outs: on return contains the (allocated) output multibyte string
* @outs_len: length of output buffer in bytes
* @outs_len: length of output buffer in bytes (ignored if *@outs is NULL)
*
* Convert the input little endian, 2-byte Unicode string @ins, of length
* @ins_len into the multibyte string format dictated by the current locale.