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Clean up format_hex_ex()

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Fix a potential null-pointer dereference, and make the code a bit more
readable while doing so.

The NULL dereference could not be triggered, because the current code
never called format_hex_ex() with maxouput == 0 and separator == NULL.
But it's nicer to not depend on that.

Our use of int vs size_t for lengths needs some attention too, but I'm
not pulling that into this patch.  Instead I decided to just make the
(previously existing) assumption that INT_MAX <= SIZE_MAX explicit by
adding a static_assert().

Signed-off-by: Steffan Karger <steffan.karger@fox-it.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <1480343200-25908-1-git-send-email-steffan.karger@fox-it.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg13259.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
This commit is contained in:
Steffan Karger 2016-11-28 15:26:40 +01:00 committed by Gert Doering
parent 718257811b
commit 294040102f
1 changed files with 9 additions and 6 deletions
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15
src/openvpn/buffer.c
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@ -438,13 +438,16 @@ format_hex_ex (const uint8_t *data, int size, int maxoutput,
unsigned int space_break_flags, const char* separator,
struct gc_arena *gc)
{
struct buffer out = alloc_buf_gc (maxoutput ? maxoutput :
((size * 2) + (size / (space_break_flags & FHE_SPACE_BREAK_MASK)) * (int) strlen (separator) + 2),
gc);
int i;
for (i = 0; i < size; ++i)
const size_t bytes_per_hexblock = space_break_flags & FHE_SPACE_BREAK_MASK;
const size_t separator_len = separator ? strlen (separator) : 0;
static_assert (INT_MAX <= SIZE_MAX, "Code assumes INT_MAX <= SIZE_MAX");
const size_t out_len = maxoutput > 0 ? maxoutput :
((size * 2) + ((size / bytes_per_hexblock) * separator_len) + 2);
struct buffer out = alloc_buf_gc (out_len, gc);
for (int i = 0; i < size; ++i)
{
if (separator && i && !(i % (space_break_flags & FHE_SPACE_BREAK_MASK)))
if (separator && i && !(i % bytes_per_hexblock))
buf_printf (&out, "%s", separator);
if (space_break_flags & FHE_CAPS)
buf_printf (&out, "%02X", data[i]);