[ml] ssh+kerberos

Ho installato su un PC kerberos [superman] (che funziona mi autentica
gli utenti, funziona anche mod_auth_kerb con apache) e ho qualche
problema con l'autenticazione del server ssh. La distro di questo PC è
una rh 9, ma il server ssh (3.6.1p2) l'ho preso da un fc1 e ricompilato
con l'estensione gssapi. Ho configurato su superman il principal per il
servizio ssh "host/superman.xbedroom.org@xxxxxxxxxxxx" e ho messo le
chiavi nel file /etc/krb5.keytab sempre di superman.

Il problema è il seguente: se avvio una sessione ssh da un host client
[spidey] mi chiede la password e non mi autentica in automatico. Invece
se da superman avvio una sessione ssh verso se stesso mi fa entrare
senza password.

Analizzando i log di ssh ho notato una piccola differenza tra i due
diversi tentativi:

log spidey->superman
[root@superman root]# /usr/sbin/sshd -d
debug1: sshd version OpenSSH_3.6.1p2
debug1: private host key: #0 type 0 RSA1
debug1: read PEM private key done: type RSA
debug1: private host key: #1 type 1 RSA
debug1: read PEM private key done: type DSA
debug1: private host key: #2 type 2 DSA
debug1: Bind to port 22 on 192.168.1.1.
Server listening on 192.168.1.1 port 22.
Generating 768 bit RSA key.
RSA key generation complete.
debug1: Server will not fork when running in debugging mode.
Connection from 192.168.1.3 port 32911
debug1: Client protocol version 2.0; client software version
OpenSSH_3.9p1
debug1: match: OpenSSH_3.9p1 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-1.99-OpenSSH_3.6.1p2
debug1: permanently_set_uid: 74/74
debug1: list_hostkey_types: ssh-rsa,ssh-dss
debug1: GSSAPI mechanism Kerberos (gss-group1-sha1-toWM5Slw5Ew8Mqkay
+al2g==) supported
debug1: GSSAPI mechanism Kerberos (gss-group1-sha1-Se3H81ismmOC3OE
+FwYCiQ==) supported
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: client->server aes128-cbc hmac-md5 none
debug1: kex: server->client aes128-cbc hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST received
debug1: SSH2_MSG_KEX_DH_GEX_GROUP sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_INIT
debug1: SSH2_MSG_KEX_DH_GEX_REPLY sent
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: KEX done
debug1: userauth-request for user xpicio service ssh-connection method
none
debug1: attempt 0 failures 0
debug1: Starting up PAM with username "xpicio"
debug1: PAM setting rhost to "spidey.xbedroom.org"
Failed none for xpicio from 192.168.1.3 port 32911 ssh2

qui mi chiede la Password

log superman->superman
[root@superman root]# /usr/sbin/sshd -d
debug1: sshd version OpenSSH_3.6.1p2
debug1: private host key: #0 type 0 RSA1
debug1: read PEM private key done: type RSA
debug1: private host key: #1 type 1 RSA
debug1: read PEM private key done: type DSA
debug1: private host key: #2 type 2 DSA
debug1: Bind to port 22 on 192.168.1.1.
Server listening on 192.168.1.1 port 22.
Generating 768 bit RSA key.
RSA key generation complete.
debug1: Server will not fork when running in debugging mode.
Connection from 192.168.1.1 port 1047
debug1: Client protocol version 2.0; client software version
OpenSSH_3.6.1p2
debug1: match: OpenSSH_3.6.1p2 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-1.99-OpenSSH_3.6.1p2
debug1: permanently_set_uid: 74/74
debug1: list_hostkey_types: ssh-rsa,ssh-dss
debug1: GSSAPI mechanism Kerberos (gss-group1-sha1-toWM5Slw5Ew8Mqkay
+al2g==) supported
debug1: GSSAPI mechanism Kerberos (gss-group1-sha1-Se3H81ismmOC3OE
+FwYCiQ==) supported
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: client->server aes128-cbc hmac-md5 none
debug1: kex: server->client aes128-cbc hmac-md5 none
debug1: using GSSAPI mechanism Kerberos (gss-group1-sha1-
toWM5Slw5Ew8Mqkay+al2g==)
debug1: Wait SSH2_MSG_GSSAPI_INIT
debug1: Got no client credentials
debug1: gss_complete
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: KEX done
debug1: userauth-request for user xpicio service ssh-connection method
none
debug1: attempt 0 failures 0
debug1: Starting up PAM with username "xpicio"
debug1: PAM setting rhost to "superman.xbedroom.org"
Failed none for xpicio from 192.168.1.1 port 1047 ssh2
debug1: userauth-request for user xpicio service ssh-connection method
external-keyx
debug1: attempt 1 failures 1
Authorized to xpicio, krb5 principal xpicio@xxxxxxxxxxxx (krb5_kuserok)
Accepted gssapi for xpicio from 192.168.1.1 port 1047 ssh2
debug1: monitor_child_preauth: xpicio has been authenticated by
privileged process
Accepted external-keyx for xpicio from 192.168.1.1 port 1047 ssh2

La sostanziale differenza è che nella sessione superman->superman
compare "debug1: using GSSAPI mechanism Kerberos (gss-group1-sha1-
toWM5Slw5Ew8Mqkay+al2g==)" che nell'altra sessione non compare.

Per quanto riguarda i parametri in sshd_config ho usato:
KerberosAuthentication yes
KerberosOrLocalPasswd yes
KerberosTicketCleanup yes

GssapiAuthentication yes
GssapiKeyExchange yes

Suggerimenti?

Bye Bye

PS:come doc base ho usato "single sign on con kerberos e ldap" e un paio
di articoli su Linux&C e Red Hat Magazine.

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