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https://bugs.gentoo.org/567608
Fix the extract() function not to access unnecessary array elements;
this avoids an out-of-bounds read when called from btoe() or etob().
Change the insert() function to use similar logic as extract().
--- skey-1.1.5-orig/put.c
+++ skey-1.1.5/put.c
@@ -2221,37 +2221,20 @@
static void insert(char *s, int x, int start, int length)
{
- unsigned char cl;
- unsigned char cc;
- unsigned char cr;
unsigned int y;
- int shift;
+ int end, i;
assert(length <= 11);
assert(start >= 0);
assert(length >= 0);
assert(start + length <= 66);
- shift = ((8 - ((start + length) % 8)) % 8);
- y = (int) x << shift;
- cl = (y >> 16) & 0xff;
- cc = (y >> 8) & 0xff;
- cr = y & 0xff;
- if (shift + length > 16)
- {
- s[start / 8] |= cl;
- s[start / 8 + 1] |= cc;
- s[start / 8 + 2] |= cr;
- }
- else if (shift + length > 8)
- {
- s[start / 8] |= cc;
- s[start / 8 + 1] |= cr;
- }
- else
- {
- s[start / 8] |= cr;
- }
+ end = start + length - 1;
+ y = x << (7 - end % 8);
+ for (i = end / 8; i >= start / 8; i--) {
+ s[i] |= y & 0xff;
+ y >>= 8;
+ }
}
static void standard(char *word)
@@ -2274,22 +2257,22 @@
/* Extract 'length' bits from the char array 's' starting with bit 'start' */
static unsigned int extract(char *s, int start, int length)
{
- unsigned char cl;
- unsigned char cc;
- unsigned char cr;
unsigned int x;
+ int end, i;
assert(length <= 11);
assert(start >= 0);
assert(length >= 0);
assert(start + length <= 66);
- cl = s[start / 8];
- cc = s[start / 8 + 1];
- cr = s[start / 8 + 2];
- x = ((int)(cl << 8 | cc) << 8 | cr);
- x = x >> (24 - (length + (start % 8)));
- x = (x & (0xffff >> (16 - length)));
+ end = start + length - 1;
+ x = 0;
+ for (i = start / 8; i <= end / 8; i++) {
+ x <<= 8;
+ x |= (unsigned char)s[i];
+ }
+ x >>= 7 - end % 8;
+ x &= (1 << length) - 1;
return x;
}
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