+/*++
+/* NAME
+/* tlsproxy_server 3
+/* SUMMARY
+/* Postfix TLS proxy server role support
+/* SYNOPSIS
+/* #include <tlsproxy_server.h>
+/*
+/* void pre_jail_init_server(void)
+/*Begin TODO
+/* TLS_APPL_STATE *tlsp_server_init(
+/* TLS_SERVER_PARAMS *tls_params,
+/* TLS_SERVER_INIT_PROPS *init_props)
+/*End TODO
+/* int tlsp_server_start_pre_handshake(TLSP_STATE *state)
+/* DESCRIPTION
+/* This module implements TLS proxy server role support. The legacy
+/* implementation uses the same tlsproxy(8) configuration for all
+/* tls_server_init() and tls_server_start() calls.
+/*
+/* pre_jail_init_server() creates an SSL context based on tlsproxy(8)
+/* server configuration.
+/*Begin TODO
+/* A future version will save a copy of serialized TLS_SERVER_PARAMS
+/* and TLS_SERVER_INIT_PROPS based on tlsproxy(8) server
+/* configuration. These will be used as a reference when receiving
+/* a request for the server role.
+/*
+/* tlsp_server_init() processes a request for the TLS proxy server
+/* role. If the request has not been seen before it checks the
+/* request for relevant differences that would conflict with
+/* tlsproxy(8) server configuration. The result is null when TLS
+/* is not available.
+/*End TODO
+/* tlsp_server_start_pre_handshake() requests the tls_server_start()
+/* handshake. It returns TLSP_STAT_OK when the request succeeds.
+/* Otherwise, it returns TLSP_STAT_ERR and state becomes a dangling
+/* pointer.
+/* DIAGNOSTICS
+/* Problems are logged to \fBsyslogd\fR(8) or \fBpostlogd\fR(8).
+/* LICENSE
+/* .ad
+/* .fi
+/* The Secure Mailer license must be distributed with this software.
+/* HISTORY
+/* .ad
+/* .fi
+/* This service was introduced with Postfix version 2.8.
+/* AUTHOR(S)
+/* Wietse Venema
+/* IBM T.J. Watson Research
+/* P.O. Box 704
+/* Yorktown Heights, NY 10598, USA
+/*
+/* Wietse Venema
+/* Google, Inc.
+/* 111 8th Avenue
+/* New York, NY 10011, USA
+/*
+/* Wietse Venema
+/* porcupine.org
+/*--*/
+
+ /*
+ * System library.
+ */
+#include <sys_defs.h>
+#include <errno.h>
+
+#ifdef STRCASECMP_IN_STRINGS_H
+#include <strings.h>
+#endif
+
+ /*
+ * Utility library.
+ */
+#include <msg.h>
+#include <mymalloc.h>
+
+ /*
+ * Global library.
+ */
+#include <mail_params.h>
+
+ /*
+ * TLS library.
+ */
+#ifdef USE_TLS
+#define TLS_INTERNAL /* XXX */
+#include <tls.h>
+#include <tls_proxy.h>
+
+ /*
+ * Application-specific.
+ */
+#include <tlsproxy.h>
+#include <tlsproxy_server.h>
+
+ /*
+ * TLS per-process status.
+ *
+ * TODO(wietse) delete externally visible state after tlsp_server_init() is
+ * implemented.
+ */
+TLS_APPL_STATE *tlsp_server_ctx;
+static int ask_client_cert;
+const char *server_role_disabled;
+
+/* tlsp_server_start_pre_handshake - turn on TLS or force disconnect */
+
+int tlsp_server_start_pre_handshake(TLSP_STATE *state)
+{
+ TLS_SERVER_START_PROPS props;
+ static char *cipher_grade;
+ static VSTRING *cipher_exclusions;
+
+ /*
+ * The code in this routine is pasted literally from smtpd(8). I am not
+ * going to sanitize this because doing so surely will break things in
+ * unexpected ways.
+ */
+
+ /*
+ * Perform the before-handshake portion of per-session initialization.
+ * Pass a null VSTREAM to indicate that this program will do the
+ * ciphertext I/O, not libtls.
+ *
+ * The cipher grade and exclusions don't change between sessions. Compute
+ * just once and cache.
+ */
+#define ADD_EXCLUDE(vstr, str) \
+ do { \
+ if (*(str)) \
+ vstring_sprintf_append((vstr), "%s%s", \
+ VSTRING_LEN(vstr) ? " " : "", (str)); \
+ } while (0)
+
+ if (cipher_grade == 0) {
+ cipher_grade =
+ var_tlsp_enforce_tls ? var_tlsp_tls_mand_ciph : var_tlsp_tls_ciph;
+ cipher_exclusions = vstring_alloc(10);
+ ADD_EXCLUDE(cipher_exclusions, var_tlsp_tls_excl_ciph);
+ if (var_tlsp_enforce_tls)
+ ADD_EXCLUDE(cipher_exclusions, var_tlsp_tls_mand_excl);
+ if (ask_client_cert)
+ ADD_EXCLUDE(cipher_exclusions, "aNULL");
+ }
+ state->tls_context =
+ TLS_SERVER_START(&props,
+ ctx = tlsp_server_ctx,
+ stream = (VSTREAM *) 0,/* unused */
+ fd = state->ciphertext_fd,
+ timeout = 0, /* unused */
+ requirecert = (var_tlsp_tls_req_ccert
+ && var_tlsp_enforce_tls),
+ enable_rpk = var_tlsp_tls_enable_rpk,
+ serverid = state->server_id,
+ namaddr = state->remote_endpt,
+ cipher_grade = cipher_grade,
+ cipher_exclusions = STR(cipher_exclusions),
+ mdalg = var_tlsp_tls_fpt_dgst);
+
+ if (state->tls_context == 0) {
+ tlsp_state_free(state);
+ return (TLSP_STAT_ERR);
+ }
+
+ /*
+ * XXX Do we care about TLS session rate limits? Good postscreen(8)
+ * clients will occasionally require the tlsproxy to renew their
+ * allowlist status, but bad clients hammering the server can suck up
+ * lots of CPU cycles. Per-client concurrency limits in postscreen(8)
+ * will divert only naive security "researchers".
+ */
+ return (TLSP_STAT_OK);
+}
+
+/* pre_jail_init_server - pre-jail initialization */
+
+void pre_jail_init_server(void)
+{
+ TLS_SERVER_INIT_PROPS props;
+ const char *cert_file;
+ int have_server_cert;
+ int no_server_cert_ok;
+ int require_server_cert;
+
+ /*
+ * The code in this routine is pasted literally from smtpd(8). I am not
+ * going to sanitize this because doing so surely will break things in
+ * unexpected ways.
+ */
+ if (*var_tlsp_tls_level) {
+ switch (tls_level_lookup(var_tlsp_tls_level)) {
+ default:
+ msg_fatal("Invalid TLS level \"%s\"", var_tlsp_tls_level);
+ /* NOTREACHED */
+ break;
+ case TLS_LEV_SECURE:
+ case TLS_LEV_VERIFY:
+ case TLS_LEV_FPRINT:
+ msg_warn("%s: unsupported TLS level \"%s\", using \"encrypt\"",
+ VAR_TLSP_TLS_LEVEL, var_tlsp_tls_level);
+ /* FALLTHROUGH */
+ case TLS_LEV_ENCRYPT:
+ var_tlsp_enforce_tls = var_tlsp_use_tls = 1;
+ break;
+ case TLS_LEV_MAY:
+ var_tlsp_enforce_tls = 0;
+ var_tlsp_use_tls = 1;
+ break;
+ case TLS_LEV_NONE:
+ var_tlsp_enforce_tls = var_tlsp_use_tls = 0;
+ break;
+ }
+ }
+ var_tlsp_use_tls = var_tlsp_use_tls || var_tlsp_enforce_tls;
+ if (!var_tlsp_use_tls) {
+ server_role_disabled = "TLS server role is disabled by configuration";
+ return;
+ }
+
+ /*
+ * Load TLS keys before dropping privileges.
+ *
+ * Can't use anonymous ciphers if we want client certificates. Must use
+ * anonymous ciphers if we have no certificates.
+ */
+ ask_client_cert = require_server_cert =
+ (var_tlsp_tls_ask_ccert
+ || (var_tlsp_enforce_tls && var_tlsp_tls_req_ccert));
+ if (strcasecmp(var_tlsp_tls_cert_file, "none") == 0) {
+ no_server_cert_ok = 1;
+ cert_file = "";
+ } else {
+ no_server_cert_ok = 0;
+ cert_file = var_tlsp_tls_cert_file;
+ }
+ have_server_cert =
+ (*cert_file || *var_tlsp_tls_dcert_file || *var_tlsp_tls_eccert_file);
+
+ if (*var_tlsp_tls_chain_files != 0) {
+ if (!have_server_cert)
+ have_server_cert = 1;
+ else
+ msg_warn("Both %s and one or more of the legacy "
+ " %s, %s or %s are non-empty; the legacy "
+ " parameters will be ignored",
+ VAR_TLSP_TLS_CHAIN_FILES,
+ VAR_TLSP_TLS_CERT_FILE,
+ VAR_TLSP_TLS_ECCERT_FILE,
+ VAR_TLSP_TLS_DCERT_FILE);
+ }
+ /* Some TLS configuration errors are not show stoppers. */
+ if (!have_server_cert && require_server_cert)
+ msg_warn("Need a server cert to request client certs");
+ if (!var_tlsp_enforce_tls && var_tlsp_tls_req_ccert)
+ msg_warn("Can't require client certs unless TLS is required");
+ /* After a show-stopper error, log a warning. */
+ if (have_server_cert || (no_server_cert_ok && !require_server_cert)) {
+
+ tls_pre_jail_init(TLS_ROLE_SERVER);
+
+ /*
+ * Large parameter lists are error-prone, so we emulate a language
+ * feature that C does not have natively: named parameter lists.
+ */
+ tlsp_server_ctx =
+ TLS_SERVER_INIT(&props,
+ log_param = VAR_TLSP_TLS_LOGLEVEL,
+ log_level = var_tlsp_tls_loglevel,
+ verifydepth = var_tlsp_tls_ccert_vd,
+ cache_type = TLS_MGR_SCACHE_SMTPD,
+ set_sessid = var_tlsp_tls_set_sessid,
+ chain_files = var_tlsp_tls_chain_files,
+ cert_file = cert_file,
+ key_file = var_tlsp_tls_key_file,
+ dcert_file = var_tlsp_tls_dcert_file,
+ dkey_file = var_tlsp_tls_dkey_file,
+ eccert_file = var_tlsp_tls_eccert_file,
+ eckey_file = var_tlsp_tls_eckey_file,
+ CAfile = var_tlsp_tls_CAfile,
+ CApath = var_tlsp_tls_CApath,
+ dh1024_param_file
+ = var_tlsp_tls_dh1024_param_file,
+ dh512_param_file
+ = var_tlsp_tls_dh512_param_file,
+ eecdh_grade = var_tlsp_tls_eecdh,
+ protocols = var_tlsp_enforce_tls ?
+ var_tlsp_tls_mand_proto :
+ var_tlsp_tls_proto,
+ ask_ccert = ask_client_cert,
+ mdalg = var_tlsp_tls_fpt_dgst);
+ } else {
+ msg_warn("No server certs available. TLS can't be enabled");
+ }
+
+ /*
+ * To maintain sanity, allow partial SSL_write() operations, and allow
+ * SSL_write() buffer pointers to change after a WANT_READ or WANT_WRITE
+ * result. This is based on OpenSSL developers talking on a mailing list,
+ * but is not supported by documentation. If this code stops working then
+ * no-one can be held responsible.
+ */
+ if (tlsp_server_ctx)
+ SSL_CTX_set_mode(tlsp_server_ctx->ssl_ctx,
+ SSL_MODE_ENABLE_PARTIAL_WRITE
+ | SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER);
+}
+
+#endif
projects / thirdparty / postfix.git / commitdiff
