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fix sym_val() buffer overrun

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Fix 'Bug 3' where too long SYMBOL=string in run-time config file could
overflow a local buffer and clobber the stack.

Valid value is only one character long after processing an 'escaped'
encoded character which can be at most 6 characters (plus terminator):
backslash M backslash and up three digits.  If/when UTF8 gets added
the number of digits will increase.  Use a truncated copy of the input
(substantially bigger than 6+1); ignore any excess.
This commit is contained in:
PatR
2020-01-14 02:05:14 -08:00
parent a842fda44c
commit 74de7d31e0
2 changed files with 13 additions and 9 deletions
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3
doc/fixes36.5
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@@ -1,4 +1,4 @@
$NHDT-Branch: NetHack-3.6 $:$NHDT-Revision: 1.2 $ $NHDT-Date: 1578972411 2020/01/14 03:26:51 $
$NHDT-Branch: NetHack-3.6 $:$NHDT-Revision: 1.3 $ $NHDT-Date: 1578996303 2020/01/14 10:05:03 $
fixes36.5 contains a terse summary of changes made to 3.6.4 in order to
produce 3.6.5 as well as any post-release fixes in binaries.
@@ -9,6 +9,7 @@ General Fixes and Modified Features
have string_for_opt() return empty_optstr on failure
ensure existing callers of string_for_opt() check return value before using it
fix potential buffer overflow in add_menu_coloring()
fix potential buffer overflow in sym_val()
Fixes to Post-3.6.4 Problems that Were Exposed Via git Repository

19
src/options.c
View File

@@ -1,4 +1,4 @@
/* NetHack 3.6 options.c $NHDT-Date: 1578972408 2020/01/14 03:26:48 $ $NHDT-Branch: NetHack-3.6 $:$NHDT-Revision: 1.395 $ */
/* NetHack 3.6 options.c $NHDT-Date: 1578996303 2020/01/14 10:05:03 $ $NHDT-Branch: NetHack-3.6 $:$NHDT-Revision: 1.396 $ */
/* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
/*-Copyright (c) Michael Allison, 2008. */
/* NetHack may be freely redistributed. See license for details. */
@@ -952,8 +952,8 @@ int maxlen;
*/
STATIC_OVL void
escapes(cp, tp)
const char *cp;
char *tp;
const char *cp; /* might be 'tp', updating in place */
char *tp; /* result is never longer than 'cp' */
{
static NEARDATA const char oct[] = "01234567", dec[] = "0123456789",
hex[] = "00112233445566778899aAbBcCdDeEfF";
@@ -6177,9 +6177,9 @@ char *buf;
int
sym_val(strval)
const char *strval;
const char *strval; /* up to 4*BUFSZ-1 long; only first few chars matter */
{
char buf[QBUFSZ];
char buf[QBUFSZ], tmp[QBUFSZ]; /* to hold trucated copy of 'strval' */
buf[0] = '\0';
if (!strval[0] || !strval[1]) { /* empty, or single character */
@@ -6200,7 +6200,7 @@ const char *strval;
/* not simple quote or basic backslash;
strip closing quote and let escapes() deal with it */
} else {
char *p, tmp[QBUFSZ];
char *p;
(void) strncpy(tmp, strval + 1, sizeof tmp - 1);
tmp[sizeof tmp - 1] = '\0';
@@ -6209,8 +6209,11 @@ const char *strval;
escapes(tmp, buf);
} /* else buf[0] stays '\0' */
}
} else /* not lone char nor single quote */
escapes(strval, buf);
} else { /* not lone char nor single quote */
(void) strncpy(tmp, strval + 1, sizeof tmp - 1);
tmp[sizeof tmp - 1] = '\0';
escapes(tmp, buf);
}
return (int) *buf;
}