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From 3b8a7aff228770f4f7b478db606b10cceacea875 Mon Sep 17 00:00:00 2001
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From: Simon McVittie <smcv@collabora.com>
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Date: Mon, 12 Sep 2022 13:14:18 +0100
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Subject: [PATCH] dbus-marshal-validate: Validate length of arrays of
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fixed-length items
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This fast-path previously did not check that the array was made up
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of an integer number of items. This could lead to assertion failures
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and out-of-bounds accesses during subsequent message processing (which
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assumes that the message has already been validated), particularly after
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the addition of _dbus_header_remove_unknown_fields(), which makes it
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more likely that dbus-daemon will apply non-trivial edits to messages.
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Thanks: Evgeny Vereshchagin
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Fixes: e61f13cf "Bug 18064 - more efficient validation for fixed-size type arrays"
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Resolves: https://gitlab.freedesktop.org/dbus/dbus/-/issues/413
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Resolves: CVE-2022-42011
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Signed-off-by: Simon McVittie <smcv@collabora.com>
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(cherry picked from commit 079bbf16186e87fb0157adf8951f19864bc2ed69)
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(cherry picked from commit b9e6a7523085a2cfceaffca7ba1ab4251f12a984)
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---
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dbus/dbus-marshal-validate.c | 13 ++++++++++++-
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1 file changed, 12 insertions(+), 1 deletion(-)
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diff --git a/dbus/dbus-marshal-validate.c b/dbus/dbus-marshal-validate.c
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index ae68414dd..7d0d6cf72 100644
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--- a/dbus/dbus-marshal-validate.c
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+++ b/dbus/dbus-marshal-validate.c
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@@ -503,13 +503,24 @@ validate_body_helper (DBusTypeReader *reader,
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*/
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if (dbus_type_is_fixed (array_elem_type))
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{
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+ /* Note that fixed-size types all have sizes equal to
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+ * their alignments, so this is really the item size. */
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+ alignment = _dbus_type_get_alignment (array_elem_type);
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+ _dbus_assert (alignment == 1 || alignment == 2 ||
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+ alignment == 4 || alignment == 8);
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+
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+ /* Because the alignment is a power of 2, this is
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+ * equivalent to: (claimed_len % alignment) != 0,
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+ * but avoids slower integer division */
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+ if ((claimed_len & (alignment - 1)) != 0)
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+ return DBUS_INVALID_ARRAY_LENGTH_INCORRECT;
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+
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/* bools need to be handled differently, because they can
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* have an invalid value
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*/
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if (array_elem_type == DBUS_TYPE_BOOLEAN)
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{
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dbus_uint32_t v;
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- alignment = _dbus_type_get_alignment (array_elem_type);
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while (p < array_end)
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{
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--
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GitLab
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