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add -mutual-tls-san option #874

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2 changes: 2 additions & 0 deletions cli/config.go
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@ type Config struct {
TLSKeyFile string
MutualTLSCAFile string
MutualTLSCNRegex string
MutualTLSSANRegex string
TLSRemoteCAs string
MutualTLSCertFile string
MutualTLSKeyFile string
Expand Down Expand Up @@ -83,6 +84,7 @@ func registerFlags(c *Config, f *flag.FlagSet) {
f.StringVar(&c.TLSKeyFile, "tls-key", "", "Other endpoint CA private key")
f.StringVar(&c.MutualTLSCAFile, "mutual-tls-ca", "", "Mutual TLS - require clients be signed by this CA ")
f.StringVar(&c.MutualTLSCNRegex, "mutual-tls-cn", "", "Mutual TLS - regex for whitelist of allowed client CNs")
f.StringVar(&c.MutualTLSSANRegex, "mutual-tls-san", "", "Mutual TLS - regex for whitelist of allowed client SANs")
f.StringVar(&c.TLSRemoteCAs, "tls-remote-ca", "", "CAs to trust for remote TLS requests")
f.StringVar(&c.MutualTLSCertFile, "mutual-tls-client-cert", "", "Mutual TLS - client certificate to call remote instance requiring client certs")
f.StringVar(&c.MutualTLSKeyFile, "mutual-tls-client-key", "", "Mutual TLS - client key to call remote instance requiring client certs")
Expand Down
31 changes: 28 additions & 3 deletions cli/serve/serve.go
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Original file line number Diff line number Diff line change
Expand Up @@ -51,16 +51,16 @@ Usage of serve:
[-metadata file] [-remote remote_host] [-config config] \
[-responder cert] [-responder-key key] \
[-tls-cert cert] [-tls-key key] [-mutual-tls-ca ca] [-mutual-tls-cn regex] \
[-tls-remote-ca ca] [-mutual-tls-client-cert cert] [-mutual-tls-client-key key] \
[-db-config db-config] [-disable endpoint[,endpoint]]
[-mutual-tls-san regex] [-tls-remote-ca ca] [-mutual-tls-client-cert cert] \
[-mutual-tls-client-key key] [-db-config db-config] [-disable endpoint[,endpoint]]

Flags:
`

// Flags used by 'cfssl serve'
var serverFlags = []string{"address", "port", "min-tls-version", "ca", "ca-key", "ca-bundle", "int-bundle", "int-dir",
"metadata", "remote", "config", "responder", "responder-key", "tls-key", "tls-cert", "mutual-tls-ca",
"mutual-tls-cn", "tls-remote-ca", "mutual-tls-client-cert", "mutual-tls-client-key", "db-config", "disable"}
"mutual-tls-cn", "mutual-tls-san", "tls-remote-ca", "mutual-tls-client-cert", "mutual-tls-client-key", "db-config", "disable"}

var (
conf cli.Config
Expand Down Expand Up @@ -354,6 +354,31 @@ func serverMain(args []string, c cli.Config) error {
http.Error(w, "Invalid CN", http.StatusForbidden)
})
}

if conf.MutualTLSSANRegex != "" {
log.Debugf(`Requiring any SAN matches regex "%s" for client connections`, conf.MutualTLSSANRegex)
re, err := regexp.Compile(conf.MutualTLSSANRegex)
if err != nil {
return fmt.Errorf("malformed SAN regex: %s", err)
}
server.Handler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
if r != nil && r.TLS != nil && len(r.TLS.PeerCertificates) > 0 {
for _, name := range r.TLS.PeerCertificates[0].DNSNames {
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@kisom kisom Mar 21, 2018

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The SAN list includes more than DNS names; if you look at the Certificate structure, it has

        // Subject Alternate Name values
        DNSNames       []string
        EmailAddresses []string
        IPAddresses    []net.IP
        URIs           []*url.URL

so this should probably also check more than the DNS names.

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@adamjacobmuller adamjacobmuller Mar 22, 2018

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Hi Kisom,

I'd considered this, but, should it?

I wasn't too sure what the use-case would be for validating based on those other attributes, but, validating based on the DNSNames is ultimately arbitrary.

If I updated to validate against all of them, do you consider this merge ready/worthy?

-Adam

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@kisom kisom Mar 22, 2018

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@adamjacobmuller Other than that, it looks fine.

if re.MatchString(name) {
http.DefaultServeMux.ServeHTTP(w, r)
return
}
}
log.Warningf(`Rejected client cert CN "%s", SANs [%s] does not match regex %s`,
r.TLS.PeerCertificates[0].Subject.CommonName,
strings.Join(r.TLS.PeerCertificates[0].DNSNames, ", "),
conf.MutualTLSCNRegex,
)
}
http.Error(w, "No Valid SAN", http.StatusForbidden)
})
}

log.Info("Now listening with mutual TLS on https://", addr)
return server.ListenAndServeTLS(conf.TLSCertFile, conf.TLSKeyFile)
}
Expand Down