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Re: [libvirt] [PATCH 2/3] Fix checking of key usage/purpose data



On Wed, Jul 20, 2011 at 02:12:46PM +0100, Daniel P. Berrange wrote:
> From: "Daniel P. Berrange" <berrange redhat com>
> 
> If key usage or purpose data is not present in the cert, the
> RFC recommends that access be allowed. Also fix checking of
> key usage to include requirements for client/server certs,
> and fix key purpose checking to treat data as a list of bits
> ---
>  src/rpc/virnettlscontext.c |   78 +++++++++++++++++++++++++------------------
>  1 files changed, 45 insertions(+), 33 deletions(-)
> 
> diff --git a/src/rpc/virnettlscontext.c b/src/rpc/virnettlscontext.c
> index 402029f..1ee5ab2 100644
> --- a/src/rpc/virnettlscontext.c
> +++ b/src/rpc/virnettlscontext.c
> @@ -111,6 +111,7 @@ static gnutls_x509_crt_t virNetTLSContextSanityCheckCert(bool isServer,
>      char *buffer = NULL;
>      size_t size;
>      unsigned int usage;
> +    bool allowClient = false, allowServer = false;
>  
>      VIR_DEBUG("isServer %d isCA %d certFile %s",
>                isServer, isCA, certFile);
> @@ -193,24 +194,34 @@ static gnutls_x509_crt_t virNetTLSContextSanityCheckCert(bool isServer,
>  
>      VIR_DEBUG("Cert %s key usage status %d usage %d", certFile, status, usage);
>      if (status < 0) {
> -        virNetError(VIR_ERR_SYSTEM_ERROR,
> -                    _("Unable to query certificate %s key usage %s"),
> -                    certFile, gnutls_strerror(status));
> -        goto cleanup;
> +        if (status == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE) {
> +            usage = isCA ? GNUTLS_KEY_KEY_CERT_SIGN :
> +                GNUTLS_KEY_DIGITAL_SIGNATURE|GNUTLS_KEY_KEY_ENCIPHERMENT;
> +        } else {
> +            virNetError(VIR_ERR_SYSTEM_ERROR,
> +                        _("Unable to query certificate %s key usage %s"),
> +                        certFile, gnutls_strerror(status));
> +            goto cleanup;
> +        }
>      }
>  
> -    if (usage & GNUTLS_KEY_KEY_CERT_SIGN) {
> -        if (!isCA) {
> -            virNetError(VIR_ERR_SYSTEM_ERROR, isServer ?
> -                        _("Certificate %s usage is for certificate signing, but wanted a server certificate") :
> -                        _("Certificate %s usage is for certificate signing, but wanted a client certificate"),
> +    if (isCA) {
> +        if (!(usage & GNUTLS_KEY_KEY_CERT_SIGN)) {
> +            virNetError(VIR_ERR_SYSTEM_ERROR,
> +                        _("Certificate %s usage does not permit certificate signing"),
>                          certFile);
>              goto cleanup;
>          }
>      } else {
> -        if (isCA) {
> +        if (!(usage & GNUTLS_KEY_DIGITAL_SIGNATURE)) {
> +            virNetError(VIR_ERR_SYSTEM_ERROR,
> +                        _("Certificate %s usage does not permit digital signature"),
> +                        certFile);
> +            goto cleanup;
> +        }
> +        if (!(usage & GNUTLS_KEY_KEY_ENCIPHERMENT)) {
>              virNetError(VIR_ERR_SYSTEM_ERROR,
> -                        _("Certificate %s usage is for not certificate signing"),
> +                        _("Certificate %s usage does not permit key encipherment"),
>                          certFile);
>              goto cleanup;
>          }
> @@ -221,7 +232,11 @@ static gnutls_x509_crt_t virNetTLSContextSanityCheckCert(bool isServer,
>          status = gnutls_x509_crt_get_key_purpose_oid(cert, i, buffer, &size, NULL);
>  
>          if (status == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE) {
> -            VIR_DEBUG("No key purpose data available, skipping checks");
> +            VIR_DEBUG("No key purpose data available at slot %d", i);
> +
> +            /* If there is no data at all, then we must allow client/server to pass */
> +            if (i == 0)
> +                allowServer = allowClient = true;
>              break;
>          }
>          if (status != GNUTLS_E_SHORT_MEMORY_BUFFER) {
> @@ -246,34 +261,31 @@ static gnutls_x509_crt_t virNetTLSContextSanityCheckCert(bool isServer,
>  
>          VIR_DEBUG("Key purpose %d %s", status, buffer);
>          if (STREQ(buffer, GNUTLS_KP_TLS_WWW_SERVER)) {
> -            if (isCA || !isServer) {
> -                virNetError(VIR_ERR_SYSTEM_ERROR, isCA ?
> -                            _("Certificate %s purpose is TLS server, but wanted a CA certificate") :
> -                            _("Certificate %s client purpose is TLS server, but wanted a TLS client certificate"),
> -                            certFile);
> -                goto cleanup;
> -            }
> +            allowServer = true;
>          } else if (STREQ(buffer, GNUTLS_KP_TLS_WWW_CLIENT)) {
> -            if (isCA || isServer) {
> -                virNetError(VIR_ERR_SYSTEM_ERROR, isCA ?
> -                            _("Certificate %s purpose is TLS client, but wanted a CA certificate") :
> -                            _("Certificate %s server purpose is TLS client, but wanted a TLS server certificate"),
> -                            certFile);
> -                goto cleanup;
> -            }
> +            allowClient = true;
>          } else if (STRNEQ(buffer, GNUTLS_KP_ANY)) {
> -            virNetError(VIR_ERR_SYSTEM_ERROR, (isCA ?
> -                        _("Certificate %s purpose is wrong, wanted a CA certificate") :
> -                        (isServer ?
> -                         _("Certificate %s purpose is wrong, wanted a TLS server certificate") :
> -                         _("Certificate %s purpose is wrong, wanted a TLS client certificate"))),
> -                        certFile);
> -            goto cleanup;
> +            allowServer = allowClient = true;
>          }
>  
>          VIR_FREE(buffer);
>      }
>  
> +    if (!isCA) { /* No purpose checks required for CA certs */
> +        if (isServer && !allowServer) {
> +            virNetError(VIR_ERR_SYSTEM_ERROR,
> +                        _("Certificate %s purpose does not allow use for with a TLS server"),
> +                        certFile);
> +            goto cleanup;
> +        }
> +        if (!isServer && !allowClient) {
> +            virNetError(VIR_ERR_SYSTEM_ERROR,
> +                        _("Certificate %s purpose does not allow use for with a TLS client"),
> +                        certFile);
> +            goto cleanup;
> +        }
> +    }
> +
>  
>      ret = 0;

  Okay, not a trivial change but relax the contraints,

  ACK,

Daniel

-- 
Daniel Veillard      | libxml Gnome XML XSLT toolkit  http://xmlsoft.org/
daniel veillard com  | Rpmfind RPM search engine http://rpmfind.net/
http://veillard.com/ | virtualization library  http://libvirt.org/


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