From b01edfb515c96c7b437127f62a809da45435d2e7 Mon Sep 17 00:00:00 2001 From: Marcin Wojtas Date: Tue, 26 May 2020 14:16:26 +0000 Subject: [PATCH] Fix AES-CTR compatibility issue in ipsec 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 Reviewed by: jhb Obtained from: Semihalf Sponsored by: Stormshield Differential Revision: https://reviews.freebsd.org/D24999 --- sys/netipsec/xform_esp.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/sys/netipsec/xform_esp.c b/sys/netipsec/xform_esp.c index 214df48157c9..8a378c4adaf8 100644 --- a/sys/netipsec/xform_esp.c +++ b/sys/netipsec/xform_esp.c @@ -80,6 +80,8 @@ #include 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;