How to convert between configured algorithm names and reported algorithm names?

[jlearman]

In our system, we do periodic audits to verify that an operator hasn't change configurations. For Strongswan, we have difficulty doing this because different terms are used to configure algorithms than the ones reported (e.g., for swanctl --list-sas.)

Specific example: configuring algorithm aes128ccm128 or aes128ccm16 produces

        encr-alg = AES_GCM_16
        encr-keysize = 128

(or AES_GCM_16-128 from swanctl --list-sas without --pretty, but we use VICI so we'd see the JSON above.)

How can we convert between the two namespaces (configuration vs reporting)?

[strongX509]

The proposal_keywords_static.txt file defines the mapping between the two namespaces.

[jlearman]

Thanks! I had seen that but was hoping for something more maintainable.

That's fine as a workaround for now, but it's not really a solution (for us to pull that file and its dependencies into our repo and write code using it.) I'll open an issue.

[strongX509]

So what would you want? Optionally convert the algorithm output of swanctl --list-sas?

home: #1, ESTABLISHED, IKEv2, e11ab5e6e3811de0_i* 468536e17582c2e8_r
  local  'mijas.strongsec.com' @ 10.10.1.64[4500] [10.10.1.66]
  remote 'vpn.strongswan.org' @ 10.10.0.150[4500]
  AES_CBC-256/HMAC_SHA2_384_192/PRF_HMAC_SHA2_384/CURVE_25519/KE1_KYBER_L3
  established 887s ago, rekeying in 13113s, reauth in 7433s
  queued:  IKE_MOBIKE
  active:  IKE_MOBIKE
  home: #1, reqid 1, INSTALLED, TUNNEL, ESP:AES_GCM_16-256
    installed 888s ago, rekeying in 2570s, expires in 3073s
    in  c7573bf5,  40729 bytes,   220 packets, 24914s ago
    out ccca2ce2,  56898 bytes,   271 packets, 24914s ago
    local  10.10.1.66/32
    remote 0.0.0.0/0 ::/0

which is currently a simple transformation of the vici raw format

list-sa event {
  home {
    uniqueid = 1
    version = 2
    state = ESTABLISHED
    local-host = 10.10.1.64
    local-port = 4500
    local-id = mijas.strongsec.com
    remote-host = 10.10.0.150
    remote-port = 4500
    remote-id = vpn.strongswan.org
    initiator = yes
    initiator-spi = e11ab5e6e3811de0
    responder-spi = 468536e17582c2e8
    encr-alg = AES_CBC
    encr-keysize = 256
    integ-alg = HMAC_SHA2_384_192
    prf-alg = PRF_HMAC_SHA2_384
    dh-group = CURVE_25519
    ake1 = KYBER_L3
    established = 960
    rekey-time = 13040
    reauth-time = 7360
    local-vips = [
      10.10.1.66
    ]
    tasks-queued = [
      IKE_MOBIKE
      CHILD_REKEY
      CHILD_REKEY
    ]
    tasks-active = [
      IKE_MOBIKE
    ]
    child-sas {
      home-1 {
        name = home
        uniqueid = 1
        reqid = 1
        state = INSTALLED
        mode = TUNNEL
        protocol = ESP
        spi-in = c7573bf5
        spi-out = ccca2ce2
        encr-alg = AES_GCM_16
        encr-keysize = 256
        bytes-in = 40729
        packets-in = 220
        use-in = 24987
        bytes-out = 56898
        packets-out = 271
        use-out = 24987
        rekey-time = 2497
        life-time = 3000
        install-time = 961
        local-ts = [
          10.10.1.66/32
        ]
        remote-ts = [
          0.0.0.0/0
          ::/0
        ]
      }
    }
  }
}

[jlearman]

It seems like a simple transformation, but if you try it you might find otherwise. As I pointed out in the issue, there are some N->1 mappings (multiple names for the same algorithm). So, a transform wouldn't work unless we transform the other way (config to list-conn or list-sa output).

Compare the configuration:

VICI command cmd=load-conn msg="&vici.Message{
  keys: []string{
    "_tun_gw2:ZPZJZZEEEIRSK===",
  },
  data: map[string]interface {}{
    "_tun_gw2:ZPZJZZEEEIRSK===": &vici.Message{
      keys: []string{
        "local_addrs",
        "remote_addrs",
        "local",
        "remote",
        "children",
        "version",
        "proposals",
        "encap",
        "send_cert",
        "dpd_delay",
        "remote_port",
        "local_port",
        "if_id_in",
        "if_id_out",
      },
      data: map[string]interface {}{
        "children": &vici.Message{
          keys: []string{
            "_tun_gw2:ZPZJZZEEEIRSK===",
          },
          data: map[string]interface {}{
            "_tun_gw2:ZPZJZZEEEIRSK===": &vici.Message{
              keys: []string{
                "esp_proposals",
                "local_ts",
                "remote_ts",
                "dpd_action",
              },
              data: map[string]interface {}{
                "dpd_action":    "restart",
                "esp_proposals": []string{
                  "aes128gcm16",
                },
                "local_ts": []string{
                  "0.0.0.0/0",
                },
                "remote_ts": []string{
                  "0.0.0.0/0",
                },
              },
            },
          },
        },
        "dpd_delay": "10s",
        "encap":     "yes",
        "if_id_in":  "1",
        "if_id_out": "1",
        "local":     &vici.Message{
          keys: []string{
            "auth",
            "id",
          },
          data: map[string]interface {}{
            "auth": "pubkey",
            "id":   "CN=1, OU=Tenant1, O=Palmetto",
          },
        },
        "local_addrs": []string{
          "1.1.0.10",
        },
        "local_port": "4500",
        "proposals":  []string{
          "default",
        },
        "remote": &vici.Message{
          keys: []string{
            "auth",
            "id",
          },
          data: map[string]interface {}{
            "auth": "pubkey",
            "id":   "/CN=2/OU=Tenant1/O=Palmetto",
          },
        },
        "remote_addrs": []string{
          "1.2.0.10",
        },
        "remote_port": "4500",
        "send_cert":   "always",
        "version":     "2",
      },
    },
  },
}"

with the result:

$ swanctl --list-conns --pretty
list-conn event {
  _tun_gw2:ZPZJZZEEEIRSK=== {
    local_addrs = [
      1.1.0.10
    ]
    remote_addrs = [
      1.2.0.10
    ]
    version = IKEv2
    reauth_time = 0
    rekey_time = 14400
    unique = UNIQUE_NO
    dpd_delay = 10
    local-1 {
      id = CN=1, OU=Tenant1, O=Palmetto
      class = public key
      groups = [
      ]
      cert_policy = [
      ]
      certs = [
      ]
      cacerts = [
      ]
    }
    remote-1 {
      id = CN=2, OU=Tenant1, O=Palmetto
      class = public key
      groups = [
      ]
      cert_policy = [
      ]
      certs = [
      ]
      cacerts = [
      ]
    }
    children {
      _tun_gw2:ZPZJZZEEEIRSK=== {
        mode = TUNNEL
        rekey_time = 3600
        rekey_bytes = 0
        rekey_packets = 0
        dpd_action = start
        close_action = none
        local-ts = [
          0.0.0.0/0
        ]
        remote-ts = [
          0.0.0.0/0
        ]
      }
    }
  }
}

$ swanctl --list-sas --pretty
list-sa event {
  _tun_gw2:ZPZJZZEEEIRSK=== {
    uniqueid = 2
    version = 2
    state = ESTABLISHED
    local-host = 1.1.0.10
    local-port = 4500
    local-id = CN=1, OU=Tenant1, O=Palmetto
    remote-host = 1.2.0.10
    remote-port = 4500
    remote-id = CN=2, OU=Tenant1, O=Palmetto
    initiator-spi = 32a406dd25a19584
    responder-spi = 8d3d12687d58eba8
    nat-remote = yes
    nat-any = yes
    if-id-in = 00000001
    if-id-out = 00000001
    encr-alg = AES_CBC
    encr-keysize = 128
    integ-alg = HMAC_SHA2_256_128
    prf-alg = PRF_HMAC_SHA2_256
    dh-group = ECP_256
    established = 327
    rekey-time = 13986
    child-sas {
      _tun_gw2:ZPZJZZEEEIRSK===-1 {
        name = _tun_gw2:ZPZJZZEEEIRSK===
        uniqueid = 1
        reqid = 1
        state = INSTALLED
        mode = TUNNEL
        protocol = ESP
        encap = yes
        spi-in = c38ee18f
        spi-out = ca40dbf7
        if-id-in = 00000001
        if-id-out = 00000001
        encr-alg = AES_GCM_16
        encr-keysize = 128
        bytes-in = 3116
        packets-in = 43
        use-in = 6
        bytes-out = 3092
        packets-out = 42
        use-out = 3
        rekey-time = 2945
        life-time = 3633
        install-time = 327
        local-ts = [
          0.0.0.0/0
        ]
        remote-ts = [
          0.0.0.0/0
        ]
      }
    }
  }
}

How easy is it to write code that verifies that the result matches the configuration?

Note: the load-conn is golang struct dump; using JSON would be cleaner, and I'm not concerned with that issue here. It was easy for me to get the golang dump and I didn't want to try to convert it to JSON in case I made mistakes.

[jlearman]

I opened issue #2051

The issue addresses the bigger question of how to know whether the current status matches a given configuration.

[jlearman]

While the static proposals file works for a human, it's not quite trivial to figure out how to code mapping between encr-alg = AES_GCM_16, encr-keysize = 128 and aes128gcm16, given different formats of algorithm names. The corresponding entries in the file are:

aes128gcm16,      ENCRYPTION_ALGORITHM, ENCR_AES_GCM_ICV16,      128
aes128gcm128,     ENCRYPTION_ALGORITHM, ENCR_AES_GCM_ICV16,      128

but other entries in the file don't have _ICV suffixes.

Mapping from aes128gcm16, obviously ENCR_AES_GCM_ICV16, 128 applies, but I'd have to figure out the heuristics for when to map and append the ICV suffix.

As I said, it's doable, but it's not really a maintainable solution. Fine as a workaround.