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authorKeith Packard <keithp@keithp.com>2017-07-27 10:08:32 -0700
committerAdam Jackson <ajax@redhat.com>2017-10-04 15:09:13 -0400
commit8bd33a2db7337b2801fc630a57e36b6aeea219d9 (patch)
tree32ca56427f25985e95903c66d9dbdee40598c20e
parent3094c4c6d879215923f2183ecd048b4f5429b182 (diff)
xkb: Handle xkb formated string output safely (CVE-2017-13723)
Generating strings for XKB data used a single shared static buffer, which offered several opportunities for errors. Use a ring of resizable buffers instead, to avoid problems when strings end up longer than anticipated. Reviewed-by: Michal Srb <msrb@suse.com> Signed-off-by: Keith Packard <keithp@keithp.com> Signed-off-by: Julien Cristau <jcristau@debian.org> (cherry picked from commit 94f11ca5cf011ef123bd222cabeaef6f424d76ac)
-rw-r--r--xkb/xkbtext.c40
1 files changed, 20 insertions, 20 deletions
diff --git a/xkb/xkbtext.c b/xkb/xkbtext.c
index ead2b1aee..d2a2567fc 100644
--- a/xkb/xkbtext.c
+++ b/xkb/xkbtext.c
@@ -47,23 +47,27 @@
/***====================================================================***/
-#define BUFFER_SIZE 512
-
-static char textBuffer[BUFFER_SIZE];
-static int tbNext = 0;
+#define NUM_BUFFER 8
+static struct textBuffer {
+ int size;
+ char *buffer;
+} textBuffer[NUM_BUFFER];
+static int textBufferIndex;
static char *
tbGetBuffer(unsigned size)
{
- char *rtrn;
+ struct textBuffer *tb;
- if (size >= BUFFER_SIZE)
- return NULL;
- if ((BUFFER_SIZE - tbNext) <= size)
- tbNext = 0;
- rtrn = &textBuffer[tbNext];
- tbNext += size;
- return rtrn;
+ tb = &textBuffer[textBufferIndex];
+ textBufferIndex = (textBufferIndex + 1) % NUM_BUFFER;
+
+ if (size > tb->size) {
+ free(tb->buffer);
+ tb->buffer = xnfalloc(size);
+ tb->size = size;
+ }
+ return tb->buffer;
}
/***====================================================================***/
@@ -79,8 +83,6 @@ XkbAtomText(Atom atm, unsigned format)
int len;
len = strlen(atmstr) + 1;
- if (len > BUFFER_SIZE)
- len = BUFFER_SIZE - 2;
rtrn = tbGetBuffer(len);
strlcpy(rtrn, atmstr, len);
}
@@ -128,8 +130,6 @@ XkbVModIndexText(XkbDescPtr xkb, unsigned ndx, unsigned format)
len = strlen(tmp) + 1;
if (format == XkbCFile)
len += 4;
- if (len >= BUFFER_SIZE)
- len = BUFFER_SIZE - 1;
rtrn = tbGetBuffer(len);
if (format == XkbCFile) {
strcpy(rtrn, "vmod_");
@@ -140,6 +140,8 @@ XkbVModIndexText(XkbDescPtr xkb, unsigned ndx, unsigned format)
return rtrn;
}
+#define VMOD_BUFFER_SIZE 512
+
char *
XkbVModMaskText(XkbDescPtr xkb,
unsigned modMask, unsigned mask, unsigned format)
@@ -147,7 +149,7 @@ XkbVModMaskText(XkbDescPtr xkb,
register int i, bit;
int len;
char *mm, *rtrn;
- char *str, buf[BUFFER_SIZE];
+ char *str, buf[VMOD_BUFFER_SIZE];
if ((modMask == 0) && (mask == 0)) {
rtrn = tbGetBuffer(5);
@@ -173,7 +175,7 @@ XkbVModMaskText(XkbDescPtr xkb,
len = strlen(tmp) + 1 + (str == buf ? 0 : 1);
if (format == XkbCFile)
len += 4;
- if ((str - (buf + len)) <= BUFFER_SIZE) {
+ if ((str - (buf + len)) <= VMOD_BUFFER_SIZE) {
if (str != buf) {
if (format == XkbCFile)
*str++ = '|';
@@ -199,8 +201,6 @@ XkbVModMaskText(XkbDescPtr xkb,
len = 0;
if (str)
len += strlen(str) + (mm == NULL ? 0 : 1);
- if (len >= BUFFER_SIZE)
- len = BUFFER_SIZE - 1;
rtrn = tbGetBuffer(len + 1);
rtrn[0] = '\0';