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Fix AES-CTR compatibility issue in ipsec

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r361390 decreased blocksize of AES-CTR from 16 to 1.
Because of that ESP payload is no longer aligned to 16 bytes
before being encrypted and sent.
This is a good change since RFC3686 specifies that the last block
doesn't need to be aligned.
Since FreeBSD before r361390 couldn't decrypt partial blocks encrypted
with AES-CTR we need to enforce 16 byte alignment in order to preserve
compatibility.
Add a sysctl(on by default) to control it.

Submitted by: Kornel Duleba <mindal@semihalf.com>
Reviewed by: jhb
Obtained from: Semihalf
Sponsored by: Stormshield
Differential Revision: https://reviews.freebsd.org/D24999
This commit is contained in:
Marcin Wojtas 2020-05-26 14:16:26 +00:00
parent da6526096f
commit b01edfb515
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=361507
1 changed files with 12 additions and 1 deletions
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13
sys/netipsec/xform_esp.c
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@ -80,6 +80,8 @@
#include <opencrypto/xform.h>
VNET_DEFINE(int, esp_enable) = 1;
VNET_DEFINE_STATIC(int, esp_ctr_compatibility) = 1;
#define V_esp_ctr_compatibility VNET(esp_ctr_compatibility)
VNET_PCPUSTAT_DEFINE(struct espstat, espstat);
VNET_PCPUSTAT_SYSINIT(espstat);
@ -90,6 +92,9 @@ VNET_PCPUSTAT_SYSUNINIT(espstat);
SYSCTL_DECL(_net_inet_esp);
SYSCTL_INT(_net_inet_esp, OID_AUTO, esp_enable,
CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(esp_enable), 0, "");
SYSCTL_INT(_net_inet_esp, OID_AUTO, ctr_compatibility,
CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(esp_ctr_compatibility), 0,
"Align AES-CTR encrypted transmitted frames to blocksize");
SYSCTL_VNET_PCPUSTAT(_net_inet_esp, IPSECCTL_STATS, stats,
struct espstat, espstat,
"ESP statistics (struct espstat, netipsec/esp_var.h");
@ -652,8 +657,14 @@ esp_output(struct mbuf *m, struct secpolicy *sp, struct secasvar *sav,
rlen = m->m_pkthdr.len - skip; /* Raw payload length. */
/*
* RFC4303 2.4 Requires 4 byte alignment.
* Old versions of FreeBSD can't decrypt partial blocks encrypted
* with AES-CTR. Align payload to native_blocksize (16 bytes)
* in order to preserve compatibility.
*/
blks = MAX(4, espx->blocksize); /* Cipher blocksize */
if (SAV_ISCTR(sav) && V_esp_ctr_compatibility)
blks = MAX(4, espx->native_blocksize); /* Cipher blocksize */
else
blks = MAX(4, espx->blocksize);
/* XXX clamp padding length a la KAME??? */
padding = ((blks - ((rlen + 2) % blks)) % blks) + 2;