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authorJoerg Sonnenberger <joerg@britannica.bec.de>2011-08-21 18:51:53 +0200
committerMihai Moldovan <ionic@ionic.de>2015-02-16 06:16:41 +0100
commit6acafc9334828da22446380c81af81bde14b5d86 (patch)
tree5067b7b4ffa5511cea999ebba976a1890a9d5340 /nx-X11/lib/font
parentb04f11915e29d9563d279e1326f61b50ea414dba (diff)
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Do proper input validation to fix for CVE-2011-2895.
It ensures that all valid input can be decompressed, checks that the overflow conditions doesn't happen and generally tightens the validation of the LZW stream and doesn't pessimize the inner loop for no good reason. It's derived from a change in libarchive from 2004. v2: backports to nx-libs 3.6.x (Mihai Moldovan) Signed-off-by: Matthieu Herrb <matthieu.herrb@laas.fr> Reviewed-by: Tomas Hoger <thoger@redhat.com>
Diffstat (limited to 'nx-X11/lib/font')
-rw-r--r--nx-X11/lib/font/fontfile/decompress.c31
1 files changed, 17 insertions, 14 deletions
diff --git a/nx-X11/lib/font/fontfile/decompress.c b/nx-X11/lib/font/fontfile/decompress.c
index 553b31585..12b9f0a57 100644
--- a/nx-X11/lib/font/fontfile/decompress.c
+++ b/nx-X11/lib/font/fontfile/decompress.c
@@ -99,7 +99,7 @@ static char_type magic_header[] = { "\037\235" }; /* 1F 9D */
#define FIRST 257 /* first free entry */
#define CLEAR 256 /* table clear output code */
-#define STACK_SIZE 8192
+#define STACK_SIZE 65300
typedef struct _compressedFILE {
BufFilePtr file;
@@ -180,14 +180,12 @@ BufFilePushCompressed (BufFilePtr f)
file->tab_suffix[code] = (char_type) code;
}
file->free_ent = ((file->block_compress) ? FIRST : 256 );
+ file->oldcode = -1;
file->clear_flg = 0;
file->offset = 0;
file->size = 0;
file->stackp = file->de_stack;
bzero(file->buf, BITS);
- file->finchar = file->oldcode = getcode (file);
- if (file->oldcode != -1)
- *file->stackp++ = file->finchar;
return BufFileCreate ((char *) file,
BufCompressedFill,
0,
@@ -232,9 +230,6 @@ BufCompressedFill (BufFilePtr f)
if (buf == bufend)
break;
- if (oldcode == -1)
- break;
-
code = getcode (file);
if (code == -1)
break;
@@ -243,26 +238,34 @@ BufCompressedFill (BufFilePtr f)
for ( code = 255; code >= 0; code-- )
file->tab_prefix[code] = 0;
file->clear_flg = 1;
- file->free_ent = FIRST - 1;
- if ( (code = getcode (file)) == -1 ) /* O, untimely death! */
- break;
+ file->free_ent = FIRST;
+ oldcode = -1;
+ continue;
}
incode = code;
/*
* Special case for KwKwK string.
*/
if ( code >= file->free_ent ) {
+ if ( code > file->free_ent || oldcode == -1 ) {
+ /* Bad stream. */
+ return BUFFILEEOF;
+ }
*stackp++ = finchar;
code = oldcode;
}
-
++ /*
++ * The above condition ensures that code < free_ent.
++ * The construction of tab_prefixof in turn guarantees that
++ * each iteration decreases code and therefore stack usage is
++ * bound by 1 << BITS - 256.
++ */
+
/*
* Generate output characters in reverse order
*/
while ( code >= 256 )
{
- if (stackp - de_stack >= STACK_SIZE - 1)
- return BUFFILEEOF;
*stackp++ = file->tab_suffix[code];
code = file->tab_prefix[code];
}
@@ -272,7 +275,7 @@ BufCompressedFill (BufFilePtr f)
/*
* Generate the new entry.
*/
- if ( (code=file->free_ent) < file->maxmaxcode ) {
+ if ( (code=file->free_ent) < file->maxmaxcode && oldcode != -1) {
file->tab_prefix[code] = (unsigned short)oldcode;
file->tab_suffix[code] = finchar;
file->free_ent = code+1;