+static uschar *
+expand_getlistele(int field, uschar * list)
+{
+uschar * tlist= list;
+int sep= 0;
+uschar dummy;
+
+if(field<0)
+{
+ for(field++; string_nextinlist(&tlist, &sep, &dummy, 1); ) field++;
+ sep= 0;
+}
+if(field==0) return NULL;
+while(--field>0 && (string_nextinlist(&list, &sep, &dummy, 1))) ;
+return string_nextinlist(&list, &sep, NULL, 0);
+}
+
+
+/* Certificate fields, by name. Worry about by-OID later */
+/* Names are chosen to not have common prefixes */
+
+#ifdef SUPPORT_TLS
+typedef struct
+{
+uschar * name;
+int namelen;
+uschar * (*getfn)(void * cert, uschar * mod);
+} certfield;
+static certfield certfields[] =
+{ /* linear search; no special order */
+ { US"version", 7, &tls_cert_version },
+ { US"serial_number", 13, &tls_cert_serial_number },
+ { US"subject", 7, &tls_cert_subject },
+ { US"notbefore", 9, &tls_cert_not_before },
+ { US"notafter", 8, &tls_cert_not_after },
+ { US"issuer", 6, &tls_cert_issuer },
+ { US"signature", 9, &tls_cert_signature },
+ { US"sig_algorithm", 13, &tls_cert_signature_algorithm },
+ { US"subj_altname", 12, &tls_cert_subject_altname },
+ { US"ocsp_uri", 8, &tls_cert_ocsp_uri },
+ { US"crl_uri", 7, &tls_cert_crl_uri },
+};
+
+static uschar *
+expand_getcertele(uschar * field, uschar * certvar)
+{
+var_entry * vp;
+certfield * cp;
+
+if (!(vp = find_var_ent(certvar)))
+ {
+ expand_string_message =
+ string_sprintf("no variable named \"%s\"", certvar);
+ return NULL; /* Unknown variable name */
+ }
+/* NB this stops us passing certs around in variable. Might
+want to do that in future */
+if (vp->type != vtype_cert)
+ {
+ expand_string_message =
+ string_sprintf("\"%s\" is not a certificate", certvar);
+ return NULL; /* Unknown variable name */
+ }
+if (!*(void **)vp->value)
+ return NULL;
+
+if (*field >= '0' && *field <= '9')
+ return tls_cert_ext_by_oid(*(void **)vp->value, field, 0);
+
+for(cp = certfields;
+ cp < certfields + nelements(certfields);
+ cp++)
+ if (Ustrncmp(cp->name, field, cp->namelen) == 0)
+ {
+ uschar * modifier = *(field += cp->namelen) == ','
+ ? ++field : NULL;
+ return (*cp->getfn)( *(void **)vp->value, modifier );
+ }
+
+expand_string_message =
+ string_sprintf("bad field selector \"%s\" for certextract", field);
+return NULL;
+}
+#endif /*SUPPORT_TLS*/