572cd24c49
The block number is a 16-bit counter which only allows to fetch files no bigger than 65535 * blksize. To avoid this limit, the counter is rolled over. This behavior isn't defined in RFC 1350 but is handled by many TFTP servers and it's what GRUB was doing before implicitly due an overflow. Closes-Bug: #1938559 Signed-off-by: Jiping Ma <jiping.ma2@windriver.com> Change-Id: I4a0c04cf15b87f6f40c7a979d20fb3c57657cefd
46 lines
1.8 KiB
Diff
46 lines
1.8 KiB
Diff
From 250304ce7a6f31e3999d128183fe299b99ec95aa Mon Sep 17 00:00:00 2001
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From: Javier Martinez Canillas <javierm@redhat.com>
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Date: Mon, 24 Aug 2020 14:46:27 +0200
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Subject: [PATCH] tftp: roll over block counter to prevent timeouts with data
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packets
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The block number is a 16-bit counter which only allows to fetch
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files no bigger than 65535 * blksize. To avoid this limit, the
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counter is rolled over. This behavior isn't defined in RFC 1350
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but is handled by many TFTP servers and it's what GRUB was doing
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before implicitly due an overflow.
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Suggested-by: Peter Jones <pjones@redhat.com>
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Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
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Signed-off-by: Jiping Ma <jiping.ma2@windriver.com>
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---
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grub-core/net/tftp.c | 12 ++++++++++--
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1 file changed, 10 insertions(+), 2 deletions(-)
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diff --git a/grub-core/net/tftp.c b/grub-core/net/tftp.c
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index 79c16f9..eab9ab7 100644
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--- a/grub-core/net/tftp.c
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+++ b/grub-core/net/tftp.c
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@@ -183,8 +183,16 @@ tftp_receive (grub_net_udp_socket_t sock __attribute__ ((unused)),
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return GRUB_ERR_NONE;
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}
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- /* Ack old/retransmitted block. */
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- if (grub_be_to_cpu16 (tftph->u.data.block) < data->block + 1)
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+ /*
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+ * Ack old/retransmitted block.
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+ *
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+ * The block number is a 16-bit counter which only allows to fetch
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+ * files no bigger than 65535 * blksize. To avoid this limit, the
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+ * counter is rolled over. This behavior isn't defined in RFC 1350
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+ * but is handled by many TFTP servers and it's what GRUB was doing
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+ * before implicitly due an overflow.
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+ */
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+ if (grub_be_to_cpu16 (tftph->u.data.block) < ((data->block + 1) & 0xffffu))
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ack (data, grub_be_to_cpu16 (tftph->u.data.block));
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/* Ignore unexpected block. */
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else if (grub_be_to_cpu16 (tftph->u.data.block) > data->block + 1)
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--
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2.31.1
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