Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
Split ESP sequence number handling into a separate file
This makes it easier to set up a unit test for it. Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
- Loading branch information
David Woodhouse
authored and
David Woodhouse
committed
Aug 30, 2016
1 parent
000edae
commit 30931b5
Showing
3 changed files
with
112 additions
and
87 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,109 @@ | ||
| /* | ||
| * OpenConnect (SSL + DTLS) VPN client | ||
| * | ||
| * Copyright © 2008-2015 Intel Corporation. | ||
| * | ||
| * Author: David Woodhouse <dwmw2@infradead.org> | ||
| * | ||
| * This program is free software; you can redistribute it and/or | ||
| * modify it under the terms of the GNU Lesser General Public License | ||
| * version 2.1, as published by the Free Software Foundation. | ||
| * | ||
| * This program is distributed in the hope that it will be useful, but | ||
| * WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | ||
| * Lesser General Public License for more details. | ||
| */ | ||
|
|
||
| #include <config.h> | ||
|
|
||
| #include <stdint.h> | ||
| #include <stdlib.h> | ||
| #include <errno.h> | ||
|
|
||
| #include "openconnect-internal.h" | ||
|
|
||
| /* Eventually we're going to have to have more than one incoming ESP | ||
| context at a time, to allow for the overlap period during a rekey. | ||
| So pass the 'esp' even though for now it's redundant. */ | ||
| int verify_packet_seqno(struct openconnect_info *vpninfo, | ||
| struct esp *esp, uint32_t seq) | ||
| { | ||
| /* | ||
| * For incoming, esp->seq is the next *expected* packet, being | ||
| * the sequence number *after* the latest we have received. | ||
| * | ||
| * Since it must always be true that packet esp->seq-1 has been | ||
| * received, so there's no need to explicitly record that. | ||
| * | ||
| * So the backlog bitmap covers the 64 packets prior to that, | ||
| * with the LSB representing packet (esp->seq - 2), and the MSB | ||
| * representing (esp->seq - 65). A received packet is represented | ||
| * by a zero bit, and a missing packet is represented by a one. | ||
| * | ||
| * Thus we can allow out-of-order reception of packets that are | ||
| * within a reasonable interval of the latest packet received. | ||
| */ | ||
|
|
||
| if (seq == esp->seq) { | ||
| /* The common case. This is the packet we expected next. */ | ||
| esp->seq_backlog <<= 1; | ||
| esp->seq++; | ||
| vpn_progress(vpninfo, PRG_TRACE, | ||
| _("Accepting expected ESP packet with seq %u\n"), | ||
| seq); | ||
| return 0; | ||
| } else if (esp->seq > 65 && seq < esp->seq - 65) { | ||
| /* Too old. We can't know if it's a replay. */ | ||
| vpn_progress(vpninfo, PRG_DEBUG, | ||
| _("Discarding ancient ESP packet with seq %u (expected %u)\n"), | ||
| seq, esp->seq); | ||
| return -EINVAL; | ||
| } else if (seq < esp->seq) { | ||
| /* Within the backlog window, so we remember whether we've seen it or not. */ | ||
| uint64_t mask = 1ULL << (esp->seq - seq - 2); | ||
|
|
||
| if (esp->seq_backlog & mask) { | ||
| vpn_progress(vpninfo, PRG_TRACE, | ||
| _("Accepting out-of-order ESP packet with seq %u (expected %u)\n"), | ||
| seq, esp->seq); | ||
| esp->seq_backlog &= ~mask; | ||
| return 0; | ||
| } | ||
| vpn_progress(vpninfo, PRG_DEBUG, | ||
| _("Discarding replayed ESP packet with seq %u\n"), | ||
| seq); | ||
| return -EINVAL; | ||
| } else { | ||
| /* The packet we were expecting has gone missing; this one is newer. */ | ||
| uint64_t delta = seq - esp->seq; | ||
|
|
||
| if (delta >= 64) { | ||
| /* We jumped a long way into the future. We have not seen | ||
| * any of the previous 32 packets so set the backlog bitmap | ||
| * to all ones. */ | ||
| esp->seq_backlog = 0xffffffffffffffffULL; | ||
| } else if (delta == 63) { | ||
| /* Avoid undefined behaviour that shifting by 64 would incur. | ||
| * The (clear) top bit represents the packet which is currently | ||
| * esp->seq - 1, which we know was already received. */ | ||
| esp->seq_backlog = 0x7fffffffffffffffULL; | ||
| } else { | ||
| /* We have missed (delta) packets. Shift the backlog by that | ||
| * amount *plus* the one we would have shifted it anyway if | ||
| * we'd received the packet we were expecting. The zero bit | ||
| * representing the packet which is currently esp->seq - 1, | ||
| * which we know has been received, ends up at bit position | ||
| * (1<<delta). Then we set all the bits lower than that, which | ||
| * represent the missing packets. */ | ||
| esp->seq_backlog <<= delta + 1; | ||
| esp->seq_backlog |= (1ULL<<delta) - 1; | ||
| } | ||
| vpn_progress(vpninfo, PRG_TRACE, | ||
| _("Accepting later-than-expected ESP packet with seq %u (expected %u)\n"), | ||
| seq, esp->seq); | ||
| esp->seq = seq + 1; | ||
| return 0; | ||
| } | ||
| } | ||
|
|
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters