From 59e63838913eee47f5c120a6c53d4565af638158 Mon Sep 17 00:00:00 2001 From: Christos Zoulas 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++;