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From 59e63838913eee47f5c120a6c53d4565af638158 Mon Sep 17 00:00:00 2001
From: Christos Zoulas <christos@zoulas.com>
Date: Tue, 11 Nov 2014 17:48:23 +0000
Subject: [PATCH] PR/398: Correctly truncate pascal strings (fixes out of
bounds read of 1, 2, or 4 bytes).
---
src/softmagic.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/src/softmagic.c b/src/softmagic.c
index dbb670a..2b15f2c 100644
--- a/src/softmagic.c
+++ b/src/softmagic.c
@@ -822,14 +822,17 @@ mconvert(struct magic_set *ms, struct magic *m)
size_t sz = file_pstring_length_size(m);
char *ptr1 = p->s, *ptr2 = ptr1 + sz;
size_t len = file_pstring_get_length(m, ptr1);
- if (len >= sizeof(p->s)) {
+ sz = sizeof(p->s) - sz; /* maximum length of string */
+ if (len >= sz) {
/*
* The size of the pascal string length (sz)
* is 1, 2, or 4. We need at least 1 byte for NUL
* termination, but we've already truncated the
* string by p->s, so we need to deduct sz.
+ * Because we can use one of the bytes of the length
+ * after we shifted as NUL termination.
*/
- len = sizeof(p->s) - sz;
+ len = sz;
}
while (len--)
*ptr1++ = *ptr2++;