9 Oct
2005
9 Oct
'05
1:43 p.m.
Hi Alexander,
That is a very good question.
An option you have is to use
tls_verify=1
tls_require_cert=0
This will make ser to request a certificate from the other peer, but if the
peer does not send one the TLS handshake will still succeed.
This is from the readme file:
=====================================================================
* How does verification work?
Verification is the process by which the authentication data provided
by the peers is checked. This data consists usually of a peer certificate,
plus a chain of trusted certification authorities.
If for whatever reason, either of the peers thinks
that the handshake is not valid, the ssl connection is not established.
The reasons could be many: untrusted server certficate, too-weak algorithm,
invalid client cert, no client authentication, ...
The "tls_verify" and "tls_require_certificate" are SER-names for the
OpenSSL defined flags SSL_VERIFY_PEER (tls_verify) and
SSL_VERIFY_FAIL_IF_NO_PEER_CERT (tls_require_certificate).
tls_require_certificate is only used if tls_verify=1.
If we are acting as a server, we always send our server-side certificate
to the client.
- If tls_verify=0, we do not request the client a
client-certificate. This means that the client is not authenticated.
- If tls_verify=1, we (the server) send a client-certificate request to
the client. But the client is free to not provide any. In this case,
tls_require_certificate comes into play:
_ if tls_require_cert=0, the verification process will succedd if
the client does not provide a certificate, or if it provides
one, it verifies correctly against the server's list of
trusted certification authorities.
_ if tls_require_cert=1, the verification process will only succeed
if the client provides a certificate and this verifies correctly
against the server's list of trusted CAs.
=====================================================================
Now, another option:
Create two different domains, one for UAs, the other for inter-proxy
connection.
This way, on the UA domain you can be more lax in the settings
(tls_verify=1, tls_require_cert=0), whereas in the inter-proxy domain you
can force certs (tls_verify=1, tls_require_cert=1).
I guess this you probably don't want to do. If you want just one setup, then
you are forced to use the "less secure" setup so that your UAs can support
it.
Hope it helps,
Cesc
On 10/8/05, Alexander Ph. Lintenhofer <lintenhofer(a)aon.at> wrote:
Hi there,
I have a question concerning TLS in openser:
By switching tls_require_certificate to "on", the peer is forced to send
his certificate for means of mutual authentication.
My problem is, that the peer may be another proxy server whom I want to
authenticate with its cert - but the peer might also be an user agent.
In my situation I use a Snom 360 which has not the possibility to import
an own user-certificate (only a CA-cert for verifying server-certs).
----------- ----------
---------
| snom 360 | <------ TLS -------> | outbound | <----- TLS -----> |
inbound |
----------- server sends cert ---------- mutual AUTH
---------
But when I activate tls_require_certificate=on in the openser.cfg of the
outbound proxy, the snom360 can't register, because it has no user-cert.
On the other hand, when I disable tls_require_certificate, the snom can
register, but the security between the proxies is weak.
Is there an appropriate solution for this problem ?? Maybe I didn't
understand the sample configuration at all....
Thanks in advance and regards,
Philipp
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