Just a general followup in case tl;dr The point of traffic flow security/confidentiality is to hide the effects of the user traffic on the secure tunnel output. With IPTFS there is a complete decoupling so that one cannot infer anything about the encapsulated traffic from the IPsec tunnel data packets (when they are sent, how big they are, etc), there are other (more complex) methods for obfuscation that may or may not be better.
In any case, having the user data traffic directly determine the IPsec tunnel behavior is inherently less secure than if it doesn't, so the idea that one could find an equivalence between a tunnel mode SA and a transport mode SA doesn't work here. For some uses of IPsec it may work, but not always. In order to make transport mode work (e.g., to support the Cisco-preferred, thus common, GRE+transport IPsec config) we are going to have to do more standards work and probably put various limitations etc on the types of user IP that can be input (so that we can cache and replicate that information at will) -- but that does not represent an equivalence. Thanks, Chris. > On May 10, 2020, at 8:33 AM, Christian Hopps <cho...@chopps.org> wrote: > >> On May 9, 2020, at 7:23 AM, Neale Ranns via lists.fd.io >> <nranns=cisco....@lists.fd.io> wrote: >> >> >> >> Hi Chris, >> >> >>> Are there other properties of a tunnel mode SA that you need that are lost >>> with this approach? >> >> I need to use tunnel mode SAs provided by IKEv2. Transport mode is an >> optional (normally on-the-wire IKEv2 negotiated) feature of IPsec. These >> tunnel mode SAs will have IPTFS enabled on them, and that functionality is >> only defined for IPsec tunnel mode SAs. >> >> >> The only difference in VPP between a transport and tunnel mode SA is the >> presence of the encap. So I think it’s fair to say that what you need is an >> interface to interact with the L[23] system, ‘encap’ to describe how to >> encap/decap packets (i.e. what to copy from overlay/underlay (DSCP, ECN, >> etc) and an SA (for the algo set); >> >> Interface + encap + SA >> >> VPP doesn’t model encap separately. So it’s a question of where you add the >> parenthesis. >> >> (interface + encap) + SA = ipip tunnel + transport mode SA >> >> Or >> >> Interface + (encap + SA) = ipsec dedicated interface + tunnel mode SA >> >> In both cases the same information is available, it’s just modelled >> differently. The first model is used since it reuses the types/functionality >> that VPP already has to support other use case, without the need for a >> dedicated interface type. Is it not possible for you to work with the first >> model, or is it less convenient? > > SO, I have implemented > https://tools.ietf.org/html/draft-ietf-ipsecme-iptfs-01 in VPP 19.08. The > functionality is working as specified in the draft using tunnel mode SAs. > > Conceptually what happens (commonly) is this: > > > Pkt Pkt Single IPsec > Tunnel Pkt > --- --- > -------------------------------------- > [UA]..[Un] ---> user-intf [ VPP ] sa-tunnel-intf ---> [IP(SATunnel) + ESP + > [UA]..[Un][Pad]] > > > The encpasulation *has* to occur at the SA tunnel point, not pre-encapsulated > by a generic IP-IP interface with a transport mode SA attached to it > downstream. > > The key here is that there is not a 1-1 mapping of user IP packets to IPsec > packets. FWIW, this isn't just a problem for this particular IPTFS > technology, there are other simple cases (e.g., sending only pad IPsec > packets for limited traffic flow confidentiality) where there is not a 1-1 > mapping between user IP packets and SA tunnel mode packets. > > Now, re-architecting IPTFS to exist outside of IPsec so that it could be a > new generic IP tunnel technology is certainly a fun idea (topic for another > thread), it's just not an option, or relevant to the functionality that > appears to have been lost in VPP. > > Here's a packet trace for how this works (incoming ping): > > USER-SIDE: > > 00:00:08:845351: dpdk-input > ... > ICMP echo_request checksum 0xaea9 > 00:00:08:845366: ethernet-input > 00:00:08:845382: ip4-input-no-checksum > ICMP: 11.11.11.253 -> 12.12.12.12 > ICMP echo_request checksum 0xaea9 > 00:00:08:845389: ip4-lookup > ICMP: 11.11.11.253 -> 12.12.12.12 > ICMP echo_request checksum 0xaea9 > 00:00:08:845396: ip4-midchain > ICMP: 11.11.11.253 -> 12.12.12.12 > ICMP echo_request checksum 0xaea9 > 00:00:08:845402: iptfs-encap4-tun > sa_index: 1 > > > AGGREGATING AND QUEUEING OCCURS - The packet is encapsulated (along with any > others currently waiting) into the next-to-be-sent IPTFS packet, which is > queued to be sent on a timer from another thread, that output thread follows: > > > SEUCRE-SIDE: > > Packet 1 > > This is the next IPTFS packet to send (in this case it just has the 1 ping > packet inside but usually has multiple when there's real traffic): > > 00:00:08:851581: handoff_trace > HANDED-OFF: from thread 1 trace index 0 > 00:00:08:851581: iptfs-output > IPTFS Basic Header: flags: 0 resv 0 offset 0:[output gen: 526 pkt 0 of 1]: > datablock 0: type: IPv4 offset: 4 pktlen: 84 > datablock 1: type: Pad offset: 88 pktlen: 1382 > 00:00:08:851622: dpdk-esp4-encrypt > spi 1112 seq 1 seq_hi 0 iv_size 0 trunc_size 0 > pad_bytes 0 next_header 143 > cipher none auth none > IPTFS Basic Header: flags: 0 resv 0 offset 0 > > This is the output from the DPDK encryption offload (same packet as above but > encrypted) > > Packet 2 > > 00:00:08:851659: dpdk-crypto-input > cryptodev-id 0 next-index 1 > 00:00:08:851663: ip4-lookup > fib 0 dpo-idx 3 flow hash: 0x00000000 > IPSEC_ESP: 13.13.13.11 -> 13.13.13.12 > 00:00:08:851671: ip4-rewrite > 00:00:08:851676: TenGigabitEthernet65/0/1-output > TenGigabitEthernet65/0/1 > IP4: f8:f2:1e:3c:08:29 -> f8:f2:1e:3c:09:b1 > IPSEC_ESP: 13.13.13.11 -> 13.13.13.12 > 00:00:08:851682: TenGigabitEthernet65/0/1-tx > TenGigabitEthernet65/0/1 tx queue 5 > buffer 0x3feb11e: current data -32, length 1514, buffer-pool 0, ref-count > 1, totlen-nifb 0, trace handle 0x5000001 > > > To arrive at this setup the code I add myself as a feature. > > VNET_FEATURE_INIT (iptfs_encap4_tun_feat_node, static) = { > .arc_name = "ip4-output", > .node_name = "iptfs-encap4-tun", > .runs_before = VNET_FEATURES ("esp4-encrypt-tun", "dpdk-esp4-encrypt-tun"), > }; > > ipsec_add_feature ("ip4-output", "iptfs-encap4-tun", > &tfsm->encap4_tun_feature_index); > > then inside ipsec_tunnel_feature_set I do (in a callback, but whatever): > > vnet_feature_enable_disable_with_index ( > arc, tfsm->encap4_tun_feature_index, t->sw_if_index, enable, > &t->output_sa_index, sizeof (t->output_sa_index)); > > To enable the IPTFS feature on the ipsec* interface arc. > > If I have missed a simple way to do this with the new code, I'm all ears and > thankful for help. :) > > Thanks, > Chris. > > >> >> /neale >> >> >> >> >> There will be future work in IETF/ipsecme to enable a form of transport mode >> support in IPTFS to handle the Cisco-preferred GRE with transport mode IPsec >> configuration, but that is not available today, and obviously won't be the >> only option standardized. >> >> Thanks, >> Chris. >> >> >>> /neale >>> >>> >>> >>> >>> >>> >>> Thanks, >>> Chris. >>> >>> >>>> >>>> I did read through the Wiki and it seems that this change was motivated >>>> by wanting to cleanup the IPsec API, but that hardly seems like >>>> justification to eliminate the efficient use of an entire variant of >>>> commonly used IPsec functionality. >>>> >>>> Cleaning up the API was one motivation. It was a pain that each time we >>>> added new attributes to SA creation (like ESN, UDP, algo=foo) (for use >>>> with the SPD) we had to make similar changes to both the ipsec and >>>> ipsec_gre create APIs. The other motivation was removing 2 interface types >>>> that did exactly the same as the existing ipip and gre tunnels (and the >>>> same goes for their APIs too, like how do I configure what DCSP, ECN, DF >>>> to copy on encap/decap). >>>> >>>> /neale >>>> >>>> >>>> >>>> Could we bring back the functionality using more "acceptable to the >>>> project" APIs or something? >>>> >>>> Thanks, >>>> Chris. >>>> >>>>> >>>>> /neale >>>>> >>>>> >>>>> From: <vpp-dev@lists.fd.io> on behalf of Christian Hopps >>>>> <cho...@chopps.org> >>>>> Date: Wednesday 6 May 2020 at 14:32 >>>>> To: vpp-dev <vpp-dev@lists.fd.io> >>>>> Cc: Christian Hopps <cho...@chopps.org> >>>>> Subject: [vpp-dev] IPsec tunnel interfaces? >>>>> >>>>> Hi, vpp-dev, >>>>> >>>>> Post 19.08 seems to have removed IPsec logical interfaces. >>>>> >>>>> One cannot always use transport mode IPsec. >>>>> >>>>> How can I get the efficiency of route based (FIB) IPsec w/o transport >>>>> mode? Adding superfluous encapsulations (wasting bandwidth) to replace >>>>> this (seemingly lost, hope not) functionality is not an option. >>>>> >>>>> Thanks, >>>>> Chris. >>>>> >>> >>> >> >> > >
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