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