58 lines
2.1 KiB
Diff
58 lines
2.1 KiB
Diff
From 26b9d22dd24c17eb118d0205bf7b02b75d435e3c Mon Sep 17 00:00:00 2001
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From: "Alexander E. Patrakov" <patrakov@gmail.com>
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Date: Thu, 5 Jun 2014 22:29:25 +0600
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Subject: [PATCH] rtp-recv: fix crash on empty UDP packets (CVE-2014-3970)
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On FIONREAD returning 0 bytes, we cannot return success, as the caller
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(rtpoll_work_cb in module-rtp-recv.c) would then try to
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pa_memblock_unref(chunk.memblock) and, because memblock is NULL, trigger
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an assertion.
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Also we have to read out the possible empty packet from the socket, so
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that the kernel doesn't tell us again and again about it.
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Signed-off-by: Alexander E. Patrakov <patrakov@gmail.com>
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---
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src/modules/rtp/rtp.c | 25 +++++++++++++++++++++++--
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1 file changed, 23 insertions(+), 2 deletions(-)
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diff --git a/src/modules/rtp/rtp.c b/src/modules/rtp/rtp.c
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index 570737e..7b75e0e 100644
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--- a/src/modules/rtp/rtp.c
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+++ b/src/modules/rtp/rtp.c
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@@ -182,8 +182,29 @@ int pa_rtp_recv(pa_rtp_context *c, pa_memchunk *chunk, pa_mempool *pool, struct
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goto fail;
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}
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- if (size <= 0)
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- return 0;
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+ if (size <= 0) {
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+ /* size can be 0 due to any of the following reasons:
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+ *
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+ * 1. Somebody sent us a perfectly valid zero-length UDP packet.
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+ * 2. Somebody sent us a UDP packet with a bad CRC.
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+ *
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+ * It is unknown whether size can actually be less than zero.
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+ *
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+ * In the first case, the packet has to be read out, otherwise the
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+ * kernel will tell us again and again about it, thus preventing
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+ * reception of any further packets. So let's just read it out
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+ * now and discard it later, when comparing the number of bytes
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+ * received (0) with the number of bytes wanted (1, see below).
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+ *
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+ * In the second case, recvmsg() will fail, thus allowing us to
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+ * return the error.
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+ *
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+ * Just to avoid passing zero-sized memchunks and NULL pointers to
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+ * recvmsg(), let's force allocation of at least one byte by setting
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+ * size to 1.
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+ */
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+ size = 1;
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+ }
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if (c->memchunk.length < (unsigned) size) {
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size_t l;
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--
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2.0.0
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