[Swan] AUTH mismatch: Received AUTH != computed AUTH

[Brendan Kearney]

list members,

i am going in circles trying to figure out where i have gone wrong and 
could use some help.  i have a libreswan instance behind my router, thus 
am using NAT-T on the "left" side.  i am trying to test with a client on 
my network, accessing my dyn-dns name (external IP of my router), and 
being forwarded to the libreswan instance.

all the routing is working and connections initiate, but do not complete 
because auth fails.  i get the following logs which indicates the error:

    Sep 12 13:47:23 vpn pluto[1512]: "s2s"[9] 192.168.24.87: local IKE
    proposals (IKE SA responder matching remote proposals):

    Sep 12 13:47:23 vpn pluto[1512]: "s2s"[9] 192.168.24.87:
    1:IKE=AES_GCM_C_256-HMAC_SHA2_512+HMAC_SHA2_256-NONE-ECP_256+ECP_384+ECP_521+MODP2048+MODP3072+MODP4096+MODP8192

    Sep 12 13:47:23 vpn pluto[1512]: "s2s"[9] 192.168.24.87:
    2:IKE=CHACHA20_POLY1305-HMAC_SHA2_512+HMAC_SHA2_256-NONE-ECP_256+ECP_384+ECP_521+MODP2048+MODP3072+MODP4096+MODP8192

    Sep 12 13:47:23 vpn pluto[1512]: "s2s"[9] 192.168.24.87:
    3:IKE=AES_CBC_256-HMAC_SHA2_512+HMAC_SHA2_256-HMAC_SHA2_512_256+HMAC_SHA2_256_128-ECP_256+ECP_384+ECP_521+MODP2048+MODP3072+MODP4096+MODP8192

    Sep 12 13:47:23 vpn pluto[1512]: "s2s"[9] 192.168.24.87:
    4:IKE=AES_GCM_C_128-HMAC_SHA2_512+HMAC_SHA2_256-NONE-ECP_256+ECP_384+ECP_521+MODP2048+MODP3072+MODP4096+MODP8192

    Sep 12 13:47:23 vpn pluto[1512]: "s2s"[9] 192.168.24.87:
    5:IKE=AES_CBC_128-HMAC_SHA2_256-HMAC_SHA2_256_128-ECP_256+ECP_384+ECP_521+MODP2048+MODP3072+MODP4096+MODP8192

    Sep 12 13:47:23 vpn pluto[1512]: "s2s"[9] 192.168.24.87 #84:
    proposal 1:IKE=AES_GCM_C_256-HMAC_SHA2_512-ECP_256 chosen from
    remote proposals
    1:IKE:ENCR=AES_GCM_C_256;PRF=HMAC_SHA2_512;DH=ECP_256[first-match]
    2:IKE:ENCR=AES_GCM_C_256;PRF=HMAC_SHA2_256;DH=ECP_256
    3:IKE:ENCR=AES_CBC_256;PRF=HMAC_SHA2_512;INTEG=HMAC_SHA2_512_256;DH=ECP_256
    4:IKE:ENCR=AES_CBC_256;PRF=HMAC_SHA1;INTEG=HMAC_SHA1_96;DH=ECP_256
    5:IKE:ENCR=AES_CBC_128;PRF=HMAC_SHA2_256;INTEG=HMAC_SHA2_256_128;DH=ECP_256
    6:IKE:ENCR=AES_CBC_128;PRF=HMAC_SHA1;INTEG=HMAC_SHA1_96;DH=ECP_256
    7:IKE:ENCR=3DES;PRF=HMAC_SHA1;INTEG=HMAC_SHA1_96;DH=ECP_256
    8:IKE:ENCR=AES_GCM_C_256;PRF=HMAC_SHA2_512;DH=ECP_384
    9:IKE:ENCR=AES_GCM_C_256;PRF=HMAC_SHA2_256;DH=ECP_384
    10:IKE:ENCR=AES_CBC_256;PRF=HMAC_SHA2_512;INTEG=HMAC_SHA2_512_256;DH=ECP_384
    11:IKE:ENCR=AES_CBC_256;PRF=HMAC_SHA1;INTEG=HMAC_SHA1_96;DH=ECP_384
    12:IKE:ENCR=AES_CBC_128;PRF=HMAC_SHA2_256;INTEG=HMAC_SHA2_256_128;DH=ECP_384
    13:IKE:ENCR=AES_CBC_128;PRF=HMAC_SHA1;INTEG=HMAC_SHA1_96;DH=ECP_384
    14:IKE:ENCR=3DES;PRF=HMAC_SHA1;INTEG=HMAC_SHA1...

    Sep 12 13:47:23 vpn pluto[1512]: "s2s"[9] 192.168.24.87 #84: sent
    IKE_SA_INIT reply {auth=IKEv2 cipher=AES_GCM_16_256 integ=n/a
    prf=HMAC_SHA2_512 group=DH19}

    Sep 12 13:47:23 vpn pluto[1512]: "s2s"[9] 192.168.24.87 #84:
    processing decrypted IKE_AUTH request: SK{IDi,AUTH,SA,TSi,TSr}

    Sep 12 13:47:23 vpn pluto[1512]: "s2s"[9] 192.168.24.87 #84: IKEv2
    mode peer ID is ID_IPV4_ADDR: '192.168.24.87'

    Sep 12 13:47:23 vpn pluto[1512]: "s2s"[9] 192.168.24.87 #84: AUTH
    mismatch: Received AUTH != computed AUTH

    Sep 12 13:47:23 vpn pluto[1512]: "s2s"[9] 192.168.24.87 #84: PSK
    Authentication failed: AUTH mismatch in I2 Auth Payload!

    Sep 12 13:47:23 vpn audit[1512]: CRYPTO_IKE_SA pid=1512 uid=0
    auid=4294967295 ses=4294967295 subj=kernel msg='op=start
    direction=responder conn-name="s2s" connstate=84 ike-version=2.0
    auth=PRESHARED_KEY cipher=aes_gcm_16 ksize=256 integ=none prf=sha512
    pfs=DH19  raddr=192.168.24.87 exe="/usr/libexec/ipsec/pluto"
    hostname=? addr=192.168.152.254 terminal=? res=failed'

    Sep 12 13:47:23 vpn pluto[1512]: "s2s"[9] 192.168.24.87 #84:
    responding to IKE_AUTH message (ID 1) from 192.168.24.87:4500 with
    encrypted notification AUTHENTICATION_FAILED

    Sep 12 13:47:23 vpn pluto[1512]: "s2s"[9] 192.168.24.87 #84:
    encountered fatal error in state STATE_PARENT_R1

    Sep 12 13:47:23 vpn pluto[1512]: "s2s"[9] 192.168.24.87 #84:
    deleting state (STATE_PARENT_R1) aged 0.037191s and NOT sending
    notification

    Sep 12 13:47:23 vpn pluto[1512]: "s2s"[9] 192.168.24.87: deleting
    connection instance with peer 192.168.24.87 {isakmp=#0/ipsec=#0}

the "left" config:

    # Site-to-Site (s2s) Config
    conn s2s
         rekey=yes
         left=192.168.152.254
         leftsubnet=192.168.152.0/24
         right=%any
         ikelifetime=28800s
         authby=secret
         type=tunnel
         auto=add
         ikev2=insist
         fragmentation=yes

the "left" secrets:

    192.168.152.254 %any : PSK "SooperSekretString"

the "right" config

    #Site-to-Site (s2s) Config
    conn s2s
         rekey=yes
         left=%defaultroute
         right=bkearney.ddns.net
         ikelifetime=28800s
         authby=secret
         type=tunnel
         auto=start
         ikev2=insist
         fragmentation=yes

the "right" secrets:

    %any @ext.dyndns.tld : PSK "SooperSekretString"

any insight would be greatly appreciated.  i am at a loss as to where i 
am messing this up.

thank you,

brendan kearney
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