diff options
Diffstat (limited to 'src/src/tls-openssl.c')
| -rw-r--r-- | src/src/tls-openssl.c | 156 |
1 files changed, 143 insertions, 13 deletions
diff --git a/src/src/tls-openssl.c b/src/src/tls-openssl.c index d99de53d6..678288ca3 100644 --- a/src/src/tls-openssl.c +++ b/src/src/tls-openssl.c @@ -359,6 +359,9 @@ typedef struct { #ifdef EXIM_HAVE_OPENSSL_TLSEXT static SSL_CTX *server_sni = NULL; #endif +#ifdef EXIM_HAVE_ALPN +static BOOL server_seen_alpn = FALSE; +#endif static char ssl_errstring[256]; @@ -2140,9 +2143,9 @@ bad: return SSL_TLSEXT_ERR_ALERT_FATAL; * Callback to handle ALPN * *************************************************/ -/* SSL_CTX_set_alpn_select_cb() */ -/* Called on server when client offers ALPN, after the SNI callback. -If set and not e?smtp then we dump the connection */ +/* Called on server if tls_alpn nonblank after expansion, +when client offers ALPN, after the SNI callback. +If set and not matching the list then we dump the connection */ static int tls_server_alpn_cb(SSL *ssl, const uschar ** out, uschar * outlen, @@ -2150,6 +2153,7 @@ tls_server_alpn_cb(SSL *ssl, const uschar ** out, uschar * outlen, { const exim_openssl_state_st * state = arg; +server_seen_alpn = TRUE; DEBUG(D_tls) { debug_printf("Received TLS ALPN offer:"); @@ -2159,23 +2163,32 @@ DEBUG(D_tls) if (pos + 1 + siz > inlen) siz = inlen - pos - 1; debug_printf(" '%.*s'", siz, in + pos + 1); } - debug_printf("\n"); + debug_printf(". Our list: '%s'\n", tls_alpn); } /* Look for an acceptable ALPN */ + if ( inlen > 1 /* at least one name */ && in[0]+1 == inlen /* filling the vector, so exactly one name */ - && ( Ustrncmp(in+1, "smtp", in[0]) == 0 - || Ustrncmp(in+1, "esmtp", in[0]) == 0 - ) ) + ) { - *out = in; /* we checked for exactly one, so can just point to it */ - *outlen = inlen; - return SSL_TLSEXT_ERR_OK; /* use ALPN */ + const uschar * list = tls_alpn; + int sep = 0; + for (uschar * name; name = string_nextinlist(&list, &sep, NULL, 0); ) + if (Ustrncmp(in+1, name, in[0]) == 0) + { + *out = in; /* we checked for exactly one, so can just point to it */ + *outlen = inlen; + return SSL_TLSEXT_ERR_OK; /* use ALPN */ + } } -/* Reject unacceptable ALPN */ -/* This will be fatal to the TLS conn; would be nice to kill TCP also */ +/* More than one name from clilent, or name did not match our list. */ + +/* This will be fatal to the TLS conn; would be nice to kill TCP also. +Maybe as an option in future; for now leave control to the config (must-tls). */ + +DEBUG(D_tls) debug_printf("TLS ALPN rejected\n"); return SSL_TLSEXT_ERR_ALERT_FATAL; } #endif /* EXIM_HAVE_ALPN */ @@ -2649,8 +2662,20 @@ if (!host) /* server */ tls_certificate */ SSL_CTX_set_tlsext_servername_callback(ctx, tls_servername_cb); SSL_CTX_set_tlsext_servername_arg(ctx, state); + # ifdef EXIM_HAVE_ALPN - SSL_CTX_set_alpn_select_cb(ctx, tls_server_alpn_cb, state); + if (tls_alpn && *tls_alpn) + { + uschar * exp_alpn; + if ( expand_check(tls_alpn, US"tls_alpn", &exp_alpn, errstr) + && *exp_alpn && !isblank(*exp_alpn)) + { + tls_alpn = exp_alpn; /* subprocess so ok to overwrite */ + SSL_CTX_set_alpn_select_cb(ctx, tls_server_alpn_cb, state); + } + else + tls_alpn = NULL; + } # endif } # ifndef DISABLE_OCSP @@ -3226,6 +3251,30 @@ if (SSL_session_reused(ssl)) } #endif +#ifdef EXIM_HAVE_ALPN +/* If require-alpn, check server_seen_alpn here. Else abort TLS */ +if (!tls_alpn || !*tls_alpn) + { DEBUG(D_tls) debug_printf("TLS: was not watching for ALPN\n"); } +else if (!server_seen_alpn) + if (verify_check_host(&hosts_require_alpn) == OK) + { + /* We'd like to send a definitive Alert but OpenSSL provides no facility */ + SSL_shutdown(ssl); + tls_error(US"handshake", NULL, US"ALPN required but not negotiated", errstr); + return FAIL; + } + else + { DEBUG(D_tls) debug_printf("TLS: no ALPN presented in handshake\n"); } +else DEBUG(D_tls) + { + const uschar * name; + unsigned len; + SSL_get0_alpn_selected(ssl, &name, &len); + debug_printf("ALPN negotiated: '%.*s'\n", (int)*name, name+1); + } +#endif + + /* TLS has been set up. Record data for the connection, adjust the input functions to read via TLS, and initialize things. */ @@ -3593,6 +3642,47 @@ if (SSL_session_reused(exim_client_ctx->ssl)) #endif /* !DISABLE_TLS_RESUME */ +#ifdef EXIM_HAVE_ALPN +/* Expand and convert an Exim list to an ALPN list. False return for fail. +NULL plist return for silent no-ALPN. +*/ + +static BOOL +tls_alpn_plist(const uschar * tls_alpn, const uschar ** plist, unsigned * plen, + uschar ** errstr) +{ +uschar * exp_alpn; + +if (!expand_check(tls_alpn, US"tls_alpn", &exp_alpn, errstr)) + return FALSE; + +if (!exp_alpn) + { + DEBUG(D_tls) debug_printf("Setting TLS ALPN forced to fail, not sending\n"); + *plist = NULL; + } +else + { + /* The server implementation only accepts exactly one protocol name + but it's little extra code complexity in the client. */ + + const uschar * list = exp_alpn; + uschar * p = store_get(Ustrlen(exp_alpn), is_tainted(exp_alpn)), * s, * t; + int sep = 0; + uschar len; + + for (t = p; s = string_nextinlist(&list, &sep, NULL, 0); t += len) + { + *t++ = len = (uschar) Ustrlen(s); + memcpy(t, s, len); + } + *plist = (*plen = t - p) ? p : NULL; + } +return TRUE; +} +#endif /* EXIM_HAVE_ALPN */ + + /************************************************* * Start a TLS session in a client * *************************************************/ @@ -3778,6 +3868,28 @@ if (ob->tls_sni) } } +if (ob->tls_alpn) +#ifdef EXIM_HAVE_ALPN + { + const uschar * plist; + unsigned plen; + + if (!tls_alpn_plist(ob->tls_alpn, &plist, &plen, errstr)) + return FALSE; + if (plist) + if (SSL_set_alpn_protos(exim_client_ctx->ssl, plist, plen) != 0) + { + tls_error(US"alpn init", host, NULL, errstr); + return FALSE; + } + else + DEBUG(D_tls) debug_printf("Setting TLS ALPN '%s'\n", ob->tls_alpn); + } +#else + log_write(0, LOG_MAIN, "ALPN unusable with this OpenSSL library version; ignoring \"%s\"\n", + ob->alpn); +#endif + #ifdef SUPPORT_DANE if (conn_args->dane) if (dane_tlsa_load(exim_client_ctx->ssl, host, &conn_args->tlsa_dnsa, errstr) != OK) @@ -3857,6 +3969,24 @@ DEBUG(D_tls) tls_client_resume_posthandshake(exim_client_ctx, tlsp); #endif +#ifdef EXIM_HAVE_ALPN +if (ob->tls_alpn) /* We requested. See what was negotiated. */ + { + const uschar * name; + unsigned len; + + SSL_get0_alpn_selected(exim_client_ctx->ssl, &name, &len); + if (len > 0) + { DEBUG(D_tls) debug_printf("ALPN negotiated %u: '%.*s'\n", len, (int)*name, name+1); } + else if (verify_check_given_host(CUSS &ob->hosts_require_alpn, host) == OK) + { + /* Would like to send a relevant fatal Alert, but OpenSSL has no API */ + tls_error(US"handshake", host, US"ALPN required but not negotiated", errstr); + return FALSE; + } + } +#endif + #ifdef SSL_get_extms_support tlsp->ext_master_secret = SSL_get_extms_support(exim_client_ctx->ssl) == 1; #endif |