strongSwan

Siehe auch

strongSwan unterscheidet seit Version 5.x zwischen der ursprünglichen „deprecated“ Konfigurationsmöglichkeiten (und dem strongswan-Kommando unter RHEL / ipsec unter Debian), und der mit dem neuen swanctl-Kommando aufkommenden Config-Language.

Links

Doku: https://docs.strongswan.org/docs/5.9/index.html
- https://docs.strongswan.org/docs/5.9/swanctl/swanctlConf.html
- https://docs.strongswan.org/docs/5.9/config/IKEv2CipherSuites.html
Source Code: git clone git://git.strongswan.org/strongswan.git
Migration der ipsec.conf zu swanctl.conf:
- Doku: https://wiki.strongswan.org/projects/strongswan/wiki/Fromipsecconf
- Python-Tool ipsec2swanctl: https://gitlab.com/Thermi/ipsec2swanctl

Begriffe:

Charon: ist der IKE-Daemon von strongSwan.
IKE: Internet Key Exchange, Austausch von Schlüsseln. IKE gibt es in v1 (Einsatz wird nicht empfohlen) und v2.
KNL: IPsec/Networking kernel interface
PFS: Perfect Forward Secrecy, z.B. per Diffie-Hellman-Group
PRF: Pseudo-Random Functions
PSK: Pre-Shared Key
SA: Security Association = ausgehandelte gemeinsame Algorithmen, Modi und Schlüssel zwischen zwei Endpunkten. Nutzen Shared Secrets. Security Associations laufen nach einer gewissen Zeit ab.
Transportmodus: Gateway-to-Gateway oder Host-to-Host
Tunnelmodus: Network-to-Network oder Site-to-Site
Encapsulation Protokolle (jeweils alternativ):
- AH: Authentication Header, für Datenintegrität
- ESP (meist der Standard): Encapsulating Security Payload, teil des IPSec-Protokollstacks, verschlüsselt und authentifiziert Datenpakete. Wird in Phase 2 Quick Mode ausgehandelt

Welche Angaben werden zur Einrichtung benötigt?

Art der Verbindung (transport oder tunnel)
IKE-Version: IKEv1 oder IKEv2 (empfohlen)
Public und Private IP Adresse, Gateway, CIDR Netzmaske für die lokale Maschine
Public und Private IP Adresse der Gegenstelle, zu der man sich verbindet
Shared Secret Passwort (falls Authentifizierung per PSK erfolgt)
Werte für IKE-Group und ESP-Group

Installation

# from EPEL-Repository
dnf -y install strongswan

echo "net.ipv4.ip_forward = 1" >> /etc/sysctl.conf
echo "net.ipv6.conf.all.forwarding = 1" >> /etc/sysctl.conf
echo "net.ipv4.conf.all.accept_redirects = 0" >> /etc/sysctl.conf
echo "net.ipv4.conf.all.send_redirects = 0" >> /etc/sysctl.conf

Firewall:

lokale Firewall > remote: Port 500/udp und Proto ESP freigeben
remote > lokale Firewall: Port 500/udp
SNAT-Regel: Client lokal > Client remote
Translated Source: Original Linux routet dann selbst nativ (nicht per ip r ersichtlich) in den IPsec-Tunnel.

Verwendung (`swanctl`-basiert)

Globale Konfiguration:

/etc/strongswan/strongswan.conf

charon {
    load_modular = yes
    plugins {
        include strongswan.d/charon/*.conf
    }
    interfaces_use = eth0
}

include strongswan.d/*.conf

Logging. Damit das Logfile erfolgreich geschrieben werden kann, muss auch SELinux passend konfiguriert werden:

semanage fcontext --add --type ipsec_log_t "/var/log/charon\.log.*"
touch /var/log/charon.log
restorecon /var/log/charon.log

/etc/strongswan/strongswan.conf

charon {
    ...
    filelog {
        charon {
            # path to the log file, specify this as section name in versions prior to 5.7.0
            path = /var/log/charon.log
            # add a timestamp prefix
            time_format = %b %e %T
            # prepend connection name, simplifies grepping
            ike_name = yes
            # overwrite existing files
            append = no
            # increase default loglevel for all daemon subsystems
            default = 2
            # flush each line to disk
            flush_line = yes
        }
        stderr {
            # more detailed loglevel for a specific subsystem, overriding the
            # default loglevel.
            asn = 1
            cfg = 3
            chd = 3
            enc = 1
            ike = 2
            job = 1
            knl = 2
            mgr = 3
            net = 1
        }
    }
}

Die einzelnen Log-Level:

-1: Absolutely silent
0: Very basic auditing logs, (e.g. SA up/SA down)
1: Generic control flow with errors, a good default to see whats going on
2: More detailed debugging control flow
3: Including RAW data dumps in hex
4: Also include sensitive material in dumps, e.g. keys

Beispiel-Konfiguration einer Site2Site-Connection (<connname> z.B. durch den Namen der Gegenstelle ersetzen) mit zwei Subnetzen:

/etc/strongswan/swanctl/conf.d/connname.conf

connections {
    <connname> {
        include /etc/strongswan/swanctl/conf.d/ike_sa_default.conf
        rekey_time = 24h
        reauth_time = 0
        version = 1
        remote_addrs = 1.2.3.4
        local_addrs = 2.3.4.5
        # https://docs.strongswan.org/strongswan-docs/5.9/config/IKEv2CipherSuites.html
        # IKE Policy: encryptionAlgo-integrityAlgo-PRF-DHKeyExchangeGroup
        proposals = aes256-sha256-modp2048, default
        children {
            connname1 {
                # IPSec Parameters / ESP:
                include /etc/strongswan/swanctl/conf.d/child_sa_default.conf
                start_action = start
                # for non-AEAD: integrityAlgo-encryptionAlgo-optDHGroup-optExtendedSequenceNumberMode
                esp_proposals = sha256-aes256-modp2048, default
                local_ts = 192.0.2.0/24
                remote_ts = 172.30.0.0/16
                rekey_time = 8h
            }
            connname2 {
                # IPSec Parameters / ESP:
                include /etc/strongswan/swanctl/conf.d/child_sa_default.conf
                start_action = start
                # for non-AEAD: integrityAlgo-encryptionAlgo-optDHGroup-optExtendedSequenceNumberMode
                esp_proposals = sha256-aes256-modp2048, default
                local_ts = 192.0.5.0/24
                remote_ts = 192.0.2.0/16
                rekey_time = 8h
            }
        }
        local {
            auth = psk
        }
        remote {
            auth = psk
        }
    }
}

secrets {
    ike-<connname> {
        secret = mypassword
        id-0 = 1.2.3.4
        id-1 = 2.3.4.5
    }
}

Als Dienst:

systemctl enable --now strongswan

Status abfragen, bei Verwendung der neuen Language:

swanctl --list-conns
swanctl --list-sas

Gezielt eine einzelne Verbindung ab- und neu aufbauen:

swanctl --terminate --child $CHILD_SA_NAME
swanctl --initiate --child $CHILD_SA_NAME

swanctl Cheat Sheet

swanctl --counters         (-C)  list or reset IKE event counters
swanctl --flush-certs      (-f)  flush cached certificates
swanctl --help             (-h)  show usage information
swanctl --initiate         (-i)  initiate a connection
swanctl --install          (-p)  install a trap or shunt policy
swanctl --list-algs        (-g)  show loaded algorithms
swanctl --list-authorities (-B)  list loaded authority configurations
swanctl --list-certs       (-x)  list stored certificates
swanctl --list-conns       (-L)  list loaded configurations
swanctl --list-pols        (-P)  list currently installed policies
swanctl --list-pools       (-A)  list loaded pool configurations
swanctl --list-sas         (-l)  list currently active IKE_SAs
swanctl --load-all         (-q)  load credentials, authorities, pools and connections
swanctl --load-authorities (-b)  (re-)load authority configuration
swanctl --load-conns       (-c)  (re-)load connection configuration
swanctl --load-creds       (-s)  (re-)load credentials
swanctl --load-pools       (-a)  (re-)load pool configuration
swanctl --log              (-T)  trace logging output
swanctl --monitor-sa       (-m)  monitor for IKE_SA and CHILD_SA changes
swanctl --redirect         (-d)  redirect an IKE_SA
swanctl --rekey            (-R)  rekey an SA
swanctl --reload-settings  (-r)  reload daemon strongswan.conf
swanctl --stats            (-S)  show daemon stats information
swanctl --terminate        (-t)  terminate a connection
swanctl --uninstall        (-u)  uninstall a trap or shunt policy
swanctl --version          (-v)  show version information

Default /etc/strongswan/swanctl/swanctl.conf

# Section defining IKE connection configurations.
# connections {

    # Section for an IKE connection named <conn>.
    # <conn> {

        # IKE major version to use for connection.
        # version = 0

        # Local address(es) to use for IKE communication, comma separated.
        # local_addrs = %any

        # Remote address(es) to use for IKE communication, comma separated.
        # remote_addrs = %any

        # Local UDP port for IKE communication.
        # local_port = 500

        # Remote UDP port for IKE communication.
        # remote_port = 500

        # Comma separated proposals to accept for IKE.
        # proposals = default

        # Virtual IPs to request in configuration payload / Mode Config.
        # vips =

        # Use Aggressive Mode in IKEv1.
        # aggressive = no

        # Set the Mode Config mode to use.
        # pull = yes

        # Differentiated Services Field Codepoint to set on outgoing IKE packets
        # (six binary digits).
        # dscp = 000000

        # Enforce UDP encapsulation by faking NAT-D payloads.
        # encap = no

        # Enables MOBIKE on IKEv2 connections.
        # mobike = yes

        # Interval of liveness checks (DPD).
        # dpd_delay = 0s

        # Timeout for DPD checks (IKEV1 only).
        # dpd_timeout = 0s

        # Use IKE UDP datagram fragmentation (yes, accept, no or force).
        # fragmentation = yes

        # Use childless IKE_SA initiation (allow, force or never).
        # childless = allow

        # Send certificate requests payloads (yes or no).
        # send_certreq = yes

        # Send certificate payloads (always, never or ifasked).
        # send_cert = ifasked

        # String identifying the Postquantum Preshared Key (PPK) to be used.
        # ppk_id =

        # Whether a Postquantum Preshared Key (PPK) is required for this
        # connection.
        # ppk_required = no

        # Number of retransmission sequences to perform during initial connect.
        # keyingtries = 1

        # Connection uniqueness policy (never, no, keep or replace).
        # unique = no

        # Time to schedule IKE reauthentication.
        # reauth_time = 0s

        # Time to schedule IKE rekeying.
        # rekey_time = 4h

        # Hard IKE_SA lifetime if rekey/reauth does not complete, as time.
        # over_time = 10% of rekey_time/reauth_time

        # Range of random time to subtract from rekey/reauth times.
        # rand_time = over_time

        # Comma separated list of named IP pools.
        # pools =

        # Default inbound XFRM interface ID for children.
        # if_id_in = 0

        # Default outbound XFRM interface ID for children.
        # if_id_out = 0

        # Whether this connection is a mediation connection.
        # mediation = no

        # The name of the connection to mediate this connection through.
        # mediated_by =

        # Identity under which the peer is registered at the mediation server.
        # mediation_peer =

        # Section for a local authentication round.
        # local<suffix> {

            # Optional numeric identifier by which authentication rounds are
            # sorted.  If not specified rounds are ordered by their position in
            # the config file/VICI message.
            # round = 0

            # Comma separated list of certificate candidates to use for
            # authentication.
            # certs =

            # Section for a certificate candidate to use for authentication.
            # cert<suffix> =

            # Comma separated list of raw public key candidates to use for
            # authentication.
            # pubkeys =

            # Authentication to perform locally (pubkey, psk, xauth[-backend] or
            # eap[-method]).
            # auth = pubkey

            # IKE identity to use for authentication round.
            # id =

            # Client EAP-Identity to use in EAP-Identity exchange and the EAP
            # method.
            # eap_id = id

            # Server side EAP-Identity to expect in the EAP method.
            # aaa_id = remote-id

            # Client XAuth username used in the XAuth exchange.
            # xauth_id = id

            # cert<suffix> {

                # Absolute path to the certificate to load.
                # file =

                # Hex-encoded CKA_ID of the certificate on a token.
                # handle =

                # Optional slot number of the token that stores the certificate.
                # slot =

                # Optional PKCS#11 module name.
                # module =

            # }

        # }

        # Section for a remote authentication round.
        # remote<suffix> {

            # Optional numeric identifier by which authentication rounds are
            # sorted.  If not specified rounds are ordered by their position in
            # the config file/VICI message.
            # round = 0

            # IKE identity to expect for authentication round.
            # id = %any

            # Identity to use as peer identity during EAP authentication.
            # eap_id = id

            # Authorization group memberships to require.
            # groups =

            # Certificate policy OIDs the peer's certificate must have.
            # cert_policy =

            # Comma separated list of certificate to accept for authentication.
            # certs =

            # Section for a certificate to accept for authentication.
            # cert<suffix> =

            # Comma separated list of CA certificates to accept for
            # authentication.
            # cacerts =

            # Section for a CA certificate to accept for authentication.
            # cacert<suffix> =

            # Identity in CA certificate to accept for authentication.
            # ca_id =

            # Comma separated list of raw public keys to accept for
            # authentication.
            # pubkeys =

            # Certificate revocation policy, (strict, ifuri or relaxed).
            # revocation = relaxed

            # Authentication to expect from remote (pubkey, psk, xauth[-backend]
            # or eap[-method]).
            # auth = pubkey

            # cert<suffix> {

                # Absolute path to the certificate to load.
                # file =

                # Hex-encoded CKA_ID of the certificate on a token.
                # handle =

                # Optional slot number of the token that stores the certificate.
                # slot =

                # Optional PKCS#11 module name.
                # module =

            # }

            # cacert<suffix> {

                # Absolute path to the certificate to load.
                # file =

                # Hex-encoded CKA_ID of the CA certificate on a token.
                # handle =

                # Optional slot number of the token that stores the CA
                # certificate.
                # slot =

                # Optional PKCS#11 module name.
                # module =

            # }

        # }

        # children {

            # CHILD_SA configuration sub-section.
            # <child> {

                # AH proposals to offer for the CHILD_SA.
                # ah_proposals =

                # ESP proposals to offer for the CHILD_SA.
                # esp_proposals = default

                # Use incorrect 96-bit truncation for HMAC-SHA-256.
                # sha256_96 = no

                # Local traffic selectors to include in CHILD_SA.
                # local_ts = dynamic

                # Remote selectors to include in CHILD_SA.
                # remote_ts = dynamic

                # Time to schedule CHILD_SA rekeying.
                # rekey_time = 1h

                # Maximum lifetime before CHILD_SA gets closed, as time.
                # life_time = rekey_time + 10%

                # Range of random time to subtract from rekey_time.
                # rand_time = life_time - rekey_time

                # Number of bytes processed before initiating CHILD_SA rekeying.
                # rekey_bytes = 0

                # Maximum bytes processed before CHILD_SA gets closed.
                # life_bytes = rekey_bytes + 10%

                # Range of random bytes to subtract from rekey_bytes.
                # rand_bytes = life_bytes - rekey_bytes

                # Number of packets processed before initiating CHILD_SA
                # rekeying.
                # rekey_packets = 0

                # Maximum number of packets processed before CHILD_SA gets
                # closed.
                # life_packets = rekey_packets + 10%

                # Range of random packets to subtract from packets_bytes.
                # rand_packets = life_packets - rekey_packets

                # Updown script to invoke on CHILD_SA up and down events.
                # updown =

                # Hostaccess variable to pass to updown script.
                # hostaccess = no

                # IPsec Mode to establish (tunnel, transport, transport_proxy,
                # beet, pass or drop).
                # mode = tunnel

                # Whether to install IPsec policies or not.
                # policies = yes

                # Whether to install outbound FWD IPsec policies or not.
                # policies_fwd_out = no

                # Action to perform on DPD timeout (clear, trap or restart).
                # dpd_action = clear

                # Enable IPComp compression before encryption.
                # ipcomp = no

                # Timeout before closing CHILD_SA after inactivity.
                # inactivity = 0s

                # Fixed reqid to use for this CHILD_SA.
                # reqid = 0

                # Optional fixed priority for IPsec policies.
                # priority = 0

                # Optional interface name to restrict IPsec policies.
                # interface =

                # Netfilter mark and mask for input traffic.
                # mark_in = 0/0x00000000

                # Whether to set *mark_in* on the inbound SA.
                # mark_in_sa = no

                # Netfilter mark and mask for output traffic.
                # mark_out = 0/0x00000000

                # Netfilter mark applied to packets after the inbound IPsec SA
                # processed them.
                # set_mark_in = 0/0x00000000

                # Netfilter mark applied to packets after the outbound IPsec SA
                # processed them.
                # set_mark_out = 0/0x00000000

                # Inbound XFRM interface ID.
                # if_id_in = 0

                # Outbound XFRM interface ID.
                # if_id_out = 0

                # Optional security label (e.g. SELinux context), IKEv2 only.
                # Refer to label_mode for details on how labels are processed.
                # label =

                # Security label mode (system, simple or selinux), IKEv2 only.
                # label_mode = system

                # Traffic Flow Confidentiality padding.
                # tfc_padding = 0

                # IPsec replay window to configure for this CHILD_SA.
                # replay_window = 32

                # Enable hardware offload for this CHILD_SA, if supported by the
                # IPsec implementation.
                # hw_offload = no

                # Whether to copy the DF bit to the outer IPv4 header in tunnel
                # mode.
                # copy_df = yes

                # Whether to copy the ECN header field to/from the outer IP
                # header in tunnel mode.
                # copy_ecn = yes

                # Whether to copy the DSCP header field to/from the outer IP
                # header in tunnel mode.
                # copy_dscp = out

                # Action to perform after loading the configuration (none, trap,
                # start).
                # start_action = none

                # Action to perform after a CHILD_SA gets closed (none, trap,
                # start).
                # close_action = none

            # }

        # }

    # }

# }

# Section defining secrets for IKE/EAP/XAuth authentication and private key
# decryption.
# secrets {

    # EAP secret section for a specific secret.
    # eap<suffix> {

        # Value of the EAP/XAuth secret.
        # secret =

        # Identity the EAP/XAuth secret belongs to.
        # id<suffix> =

    # }

    # XAuth secret section for a specific secret.
    # xauth<suffix> {

    # }

    # NTLM secret section for a specific secret.
    # ntlm<suffix> {

        # Value of the NTLM secret.
        # secret =

        # Identity the NTLM secret belongs to.
        # id<suffix> =

    # }

    # IKE preshared secret section for a specific secret.
    # ike<suffix> {

        # Value of the IKE preshared secret.
        # secret =

        # IKE identity the IKE preshared secret belongs to.
        # id<suffix> =

    # }

    # Postquantum Preshared Key (PPK) section for a specific secret.
    # ppk<suffix> {

        # Value of the PPK.
        # secret =

        # PPK identity the PPK belongs to.
        # id<suffix> =

    # }

    # Private key decryption passphrase for a key in the private folder.
    # private<suffix> {

        # File name in the private folder for which this passphrase should be
        # used.
        # file =

        # Value of decryption passphrase for private key.
        # secret =

    # }

    # Private key decryption passphrase for a key in the rsa folder.
    # rsa<suffix> {

        # File name in the rsa folder for which this passphrase should be used.
        # file =

        # Value of decryption passphrase for RSA key.
        # secret =

    # }

    # Private key decryption passphrase for a key in the ecdsa folder.
    # ecdsa<suffix> {

        # File name in the ecdsa folder for which this passphrase should be
        # used.
        # file =

        # Value of decryption passphrase for ECDSA key.
        # secret =

    # }

    # Private key decryption passphrase for a key in the pkcs8 folder.
    # pkcs8<suffix> {

        # File name in the pkcs8 folder for which this passphrase should be
        # used.
        # file =

        # Value of decryption passphrase for PKCS#8 key.
        # secret =

    # }

    # PKCS#12 decryption passphrase for a container in the pkcs12 folder.
    # pkcs12<suffix> {

        # File name in the pkcs12 folder for which this passphrase should be
        # used.
        # file =

        # Value of decryption passphrase for PKCS#12 container.
        # secret =

    # }

    # Definition for a private key that's stored on a token/smartcard.
    # token<suffix> {

        # Hex-encoded CKA_ID of the private key on the token.
        # handle =

        # Optional slot number to access the token.
        # slot =

        # Optional PKCS#11 module name to access the token.
        # module =

        # Optional PIN required to access the key on the token. If none is
        # provided the user is prompted during an interactive --load-creds call.
        # pin =

    # }

# }

# Section defining named pools.
# pools {

    # Section defining a single pool with a unique name.
    # <name> {

        # Addresses allocated in pool.
        # addrs =

        # Comma separated list of additional attributes from type <attr>.
        # <attr> =

    # }

# }

# Section defining attributes of certification authorities.
# authorities {

    # Section defining a certification authority with a unique name.
    # <name> {

        # CA certificate belonging to the certification authority.
        # cacert =

        # Absolute path to the certificate to load.
        # file =

        # Hex-encoded CKA_ID of the CA certificate on a token.
        # handle =

        # Optional slot number of the token that stores the CA certificate.
        # slot =

        # Optional PKCS#11 module name.
        # module =

        # Comma-separated list of CRL distribution points.
        # crl_uris =

        # Comma-separated list of OCSP URIs.
        # ocsp_uris =

        # Defines the base URI for the Hash and URL feature supported by IKEv2.
        # cert_uri_base =

    # }

# }

# Include config snippets
include conf.d/*.conf

Deprecated strongSwan

Beispiel-Konfiguration einer Host-to-Host-Connection:

/etc/strongswan/ipsec.conf

config setup
    strictcrlpolicy=yes
    uniqueids = no

# Add connections here.
# Sample VPN connections
conn sample-self-signed
    leftsubnet=10.1.0.0/16
    leftcert=selfCert.der
    leftsendcert=never
    right=192.168.0.2
    rightsubnet=10.2.0.0/16
    rightcert=peerCert.der
    auto=start

conn sample-with-ca-cert
    leftsubnet=10.1.0.0/16
    leftcert=myCert.pem
    right=192.168.0.2
    rightsubnet=10.2.0.0/16
    rightid="C=CH, O=Linux strongSwan CN=peer name"
    auto=start

Manueller Start:

strongswan start
strongswan up sample-with-ca-cert

Status abfragen, bei Verwendung der „deprecated“ Language:

strongswan status
strongswan statusall

ipsec.secrets - strongSwan IPsec Credentials (wird von Charon verwaltet):

/etc/strongswan/ipsec.secrets

# customer:
192.0.2.19 1.2.3.4 : PSK "my-secret-psk"
192.0.2.20 %any : PSK "other-secret-psk"

DH Groups

Diffie-Hellman Key Groups:

DH1: enstpricht „modp768“ bit Modular Exponential (MODP) algorithm.
DH2: modp1024-bit MODP algorithm.
DH14: modp2048-bit MODP group.
DH15: modp3072-bit MODP algorithm.
DH16: modp4096-bit MODP algorithm.
DH19: modp256-bit random Elliptic Curve Groups modulo a Prime (ECP groups) algorithm. (IKEv2 only)
DH20: 384-bit random ECP groups algorithm. (IKEv2 only)
DH21: 521-bit random ECP groups algorithm. (IKEv2 only)
DH24: modp2048-bit MODP Group with 256-bit prime order subgroup. (IKEv2 only)

Route based vs Policy based

Im Unterschied zu anderer VPN-Software wie beispielsweise OpenVPN verwendet IPsec standardmässig keine Routen, sondern sogenannte Policies. Dies erkennt man unter anderem daran, dass strongSwan nach dem Start kein neues Netzwerk-Interface (siehe ip addr) anlegt. Stattdessen kann man die aktuellen Policies wie folgt einsehen:

ip xfrm policy show
ip -statistic xfrm policy show

ip xfrm state
ip -statistic xfrm state

ip xfrm monitor
ip xfrm monitor all

Wer IPsec so konfiguieren möchte, dass tatsächlich Routen verwendet werden, folgt https://docs.strongswan.org/strongswan-docs/5.9/features/routeBasedVpn.html.

Deinstallation

dnf remove trousers strongswan
rm -rf /etc/strongswan

In älteren Versionen User und Group „tss“ entfernen.

Troubleshooting

Logging:

tail -f /var/log/messages
# or
journalctl -fx -u strongswan

Bemerkung

Wer IPsec-Traffic monitoren will und auf /var/log/messages und iptables schaut, sollte bedenken, dass die IP-Pakete durch die IPsec-Funktionen des Kernels Pre- und Postrouted werden - iptables wird die in der Regel also nicht zu Gesicht bekommen.

Ist die Gegenstelle erreichbar?

dnf -y install nmap-ncat
ncat -z --udp --verbose --wait 3 ipsec.example.com 500

Testen des entfernten VPN-Servers (vorher müssen dazu alle IPSec-Services gestoppt werden):

dnf -y install ike-scan
ike-scan ipsex.example.com -vvv --ikev2

unterminated string detected, oder syntax error, unexpected STRING_ERROR, expecting NAME or NEWLINE or '}':

Lag in unserem Fall an Double-Quotes im Passwort der secret-Angabe.

Traffic mithilfe von tcpdump beobachten (siehe https://docs.strongswan.org/docs/5.9/install/trafficDumps.html)

tcpdump -nn -p --interface eth2 esp or net 192.168.0.112/32 -e

# more details, decapsulated

iptables -t raw -I PREROUTING -p esp -j NFLOG --nflog-group 5
iptables -t raw -I PREROUTING -p ah -j NFLOG --nflog-group 5
iptables -t raw -I PREROUTING -p udp -m multiport --dports 500,4500 -j NFLOG --nflog-group 5

iptables -t raw -I OUTPUT -p esp -j NFLOG --nflog-group 5
iptables -t raw -I OUTPUT -p ah -j NFLOG --nflog-group 5
iptables -t raw -I OUTPUT -p udp -m multiport --dports 500,4500 -j NFLOG --nflog-group 5

iptables -t mangle -I PREROUTING -m policy --pol ipsec --dir in -j NFLOG --nflog-group 5
iptables -t mangle -I POSTROUTING -m policy --pol ipsec --dir out -j NFLOG --nflog-group 5

iptables -t filter -I INPUT -m addrtype --dst-type LOCAL -m policy --pol ipsec --dir in -j NFLOG --nflog-group 5

iptables -t filter -I FORWARD -m addrtype ! --dst-type LOCAL -m policy --pol ipsec --dir in -j NFLOG --nflog-group 5

iptables -t filter -I OUTPUT -m policy --pol ipsec --dir out -j NFLOG --nflog-group 5

# Getting the traffic
tcpdump --snapshot-length 0 -n --interface nflog:5