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top: Fix out-of-bounds read/write in show_... REVERTED

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I'm reverting this patch to prepare for some alternate
solution. In that solution I will address point #1 but
point #2 is based on a wrong assumption. There will be
no binary data ever found in the 'glob' passed to this
show_special() function. It is now always simple text.

------------------------------------------------ original commit message
This patch fixes two problems:

1/ In the switch case 0, if sub_end is at the very end of lin[], the two
null-byte writes are off-by-two (a stack-based buffer overflow). Replace
this end-of-string "emulation" with an equivalent test on ch (and then
goto/break out of the loop).

2/ "sub_end += 2" jumps over the null-byte terminator in lin[] if the
line contains a raw (without a tilde) \001-\010 character. Detect such a
null-byte terminator and goto/break out of the loop.

Note: in the case of a raw \001-\010 character, the character at
"sub_end + 1" is never processed (it is skipped/jumped over); this is
not a security problem anymore (since 2/ was fixed), so we decided not
to change this behavior, for backward-compatibility.
------------------------------------------------------------------------

Reference(s):
. original qualys patch
0116-top-Fix-out-of-bounds-read-write-in-show_special.patch
commit ed8f6d9cc6

Signed-off-by: Jim Warner <james.warner@comcast.net>
This commit is contained in:
Jim Warner 2018-05-18 00:00:00 -05:00 committed by Craig Small
parent fdb58974e2
commit 2fb269a5b0
1 changed files with 2 additions and 3 deletions
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top/top.c
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@ -963,6 +963,8 @@ static void show_special (int interact, const char *glob) {
if ('~' == ch) ch = *(sub_end + 1) - '0';
switch (ch) {
case 0: // no end delim, captab makes normal
*(sub_end + 1) = '\0'; // extend str end, then fall through
*(sub_end + 2) = '\0'; // ( +1 optimization for usual path )
case 1: case 2: case 3: case 4:
case 5: case 6: case 7: case 8:
*sub_end = '\0';
@ -971,8 +973,6 @@ static void show_special (int interact, const char *glob) {
rp = scat(rp, tmp);
room -= (sub_end - sub_beg);
room += utf8_delta(sub_beg);
if (!ch) goto done_substrings;
if (!*(sub_end + 1)) goto done_substrings;
sub_beg = (sub_end += 2);
break;
default: // nothin' special, just text
@ -980,7 +980,6 @@ static void show_special (int interact, const char *glob) {
}
if (0 >= room) break; // skip substrings that won't fit
}
done_substrings:
if (interact) PUTT("%s%s\n", row, Cap_clr_eol);
else PUFF("%s%s\n", row, Caps_endline);