add SMTP DANE support

1 files changed, 110 insertions, 51 deletions

diff --git a/qmail-remote.c b/qmail-remote.c
index b5b93d5..4227718 100644
--- a/qmail-remote.c
+++ b/qmail-remote.c
@@ -62,16 +62,24 @@ struct ip_address partner;
 # include "tls.h"
 # include "ssl_timeoutio.h"
 # include <openssl/x509v3.h>
+# include <validator/validator.h>
+# include <validator/val_dane.h>
+
 # define EHLO 1
+# define CLIENTCERT "control/clientcert.pem"
 
 int tls_init();
 const char *ssl_err_str = 0;
 char **myargv;
-#endif 
+val_context_t *dane_context = NULL;
+int dane_context_failed = 0;
+struct val_danestatus *dane_status = NULL;
+#endif
 
 void out(s) char *s; { if (substdio_puts(subfdoutsmall,s) == -1) _exit(0); }
 void zero() { if (substdio_put(subfdoutsmall,"\0",1) == -1) _exit(0); }
-void zerodie() { zero(); substdio_flush(subfdoutsmall); _exit(0); }
+void zeroflush()  { zero(); substdio_flush(subfdoutsmall); }
+void zerodie() { zeroflush(); _exit(0); }
 void outsafe(sa) stralloc *sa; { int i; char ch;
 for (i = 0;i < sa->len;++i) {
 ch = sa->s[i]; if (ch < 33) ch = '?'; if (ch > 126) ch = '?';
@@ -213,7 +221,6 @@ unsigned long smtpcode()
   return code;
 }
 
-#ifdef EHLO
 saa ehlokw = {0}; /* list of EHLO keywords and parameters */
 int maxehlokwlen = 0;
 
@@ -270,7 +277,6 @@ unsigned long ehlo()
 
   return 250;
 }
-#endif
 
 void outsmtptext()
 {
@@ -284,9 +290,7 @@ void outsmtptext()
   }
 }
 
-void quit(prepend,append)
-char *prepend;
-char *append;
+void smtp_quit()
 {
 #ifdef TLS
   /* shouldn't talk to the client unless in an appropriate state */
@@ -295,9 +299,14 @@ char *append;
 #endif
   substdio_putsflush(&smtpto,"QUIT\r\n");
   /* waiting for remote side is just too ridiculous */
+}
+
+void quit2(char *prepend, char *append, int flagdie)
+{
+  smtp_quit();
   out(prepend);
   outhost();
-  out(append);
+  if (append) out(append);
   out(".\n");
   outsmtptext();
 
@@ -324,7 +333,11 @@ char *append;
   }
 #endif
 
-  zerodie();
+  (flagdie) ? zerodie() : zeroflush();
+}
+
+void quit(char *prepend, char *append) {
+  quit2(prepend, append, 1);
 }
 
 void blast()
@@ -355,7 +368,7 @@ void blast()
 #ifdef TLS
 char *partner_fqdn = 0;
 
-# define TLS_QUIT quit(ssl ? "; connected to " : "; connecting to ", "")
+# define TLS_QUIT quit(ssl ? "; connected to " : "; connecting to ", NULL)
 void tls_quit(const char *s1, const char *s2)
 {
   out(s1); if (s2) { out(": "); out(s2); } TLS_QUIT;
@@ -376,6 +389,11 @@ int match_partner(const char *s, int len)
 /* don't want to fail handshake if certificate can't be verified */
 int verify_cb(int preverify_ok, X509_STORE_CTX *ctx) { return 1; }
 
+/*
+ * @return  1  ...on success
+ * @return  0  ...TLS failed, continue plaintext
+ * @return  -1 ...skip to next MX
+ */
 int tls_init()
 {
   int i;
@@ -402,26 +420,52 @@ int tls_init()
          return 0;
       }
       alloc_free(tmp.s);
+
       if (env_get("NOTLS")) return 0;
     }
   }
- 
+
+  /* DANE starts here */
+  int dane_retval = VAL_DANE_INTERNAL_ERROR;
+  int tls_required = (smtps || servercert != NULL);
+
+  if (partner_fqdn && !servercert && !dane_context_failed) {
+    if (val_create_context(NULL, &dane_context) != VAL_NO_ERROR) {
+      dane_context_failed = 1;
+      out("lUnable to initialize libval context\n");
+      zeroflush();
+    }
+
+    /* DANE lookup TLSA records */
+    if (dane_context) {
+      if (dane_status != NULL)
+        val_free_dane(dane_status);
+      struct val_daneparams dane_params = {
+        .port  = smtp_port,
+        .proto = DANE_PARAM_PROTO_TCP
+      };
+      dane_retval = val_getdaneinfo(dane_context, partner_fqdn, &dane_params, &dane_status);
+      if (dane_retval == VAL_DANE_NOERROR)
+        tls_required = 1;
+    }
+  }
+
   if (!smtps) {
     stralloc *sa = ehlokw.sa;
     unsigned int len = ehlokw.len;
     /* look for STARTTLS among EHLO keywords */
     for ( ; len && case_diffs(sa->s, "STARTTLS"); ++sa, --len) ;
     if (!len) {
-      if (!servercert) return 0;
-      out("ZNo TLS achieved while "); out(servercert);
-      out(" exists"); smtptext.len = 0; TLS_QUIT;
+      if (!tls_required) return 0;
+      out("ZNo TLS achieved while TLS is required by configuration");
+      smtptext.len = 0; TLS_QUIT;
     }
   }
 
   SSL_library_init();
   ctx = SSL_CTX_new(SSLv23_client_method());
   if (!ctx) {
-    if (!smtps && !servercert) return 0;
+    if (!tls_required) return 0;
     smtptext.len = 0;
     tls_quit_error("ZTLS error initializing ctx");
   }
@@ -437,20 +481,19 @@ int tls_init()
   }
 
   /* let the other side complain if it needs a cert and we don't have one */
-# define CLIENTCERT "control/clientcert.pem"
   if (SSL_CTX_use_certificate_chain_file(ctx, CLIENTCERT))
     SSL_CTX_use_RSAPrivateKey_file(ctx, CLIENTCERT, SSL_FILETYPE_PEM);
-# undef CLIENTCERT
 
   myssl = SSL_new(ctx);
   SSL_CTX_free(ctx);
   if (!myssl) {
-    if (!smtps && !servercert) return 0;
+    if (!tls_required) return 0;
     smtptext.len = 0;
     tls_quit_error("ZTLS error initializing ssl");
   }
 
-  if (!smtps) substdio_putsflush(&smtpto, "STARTTLS\r\n");
+  if (!smtps)
+    substdio_putsflush(&smtpto, "STARTTLS\r\n");
 
   /* while the server is preparing a responce, do something else */
   if (control_readfile(&saciphers, "control/tlsclientciphers", 0) == -1)
@@ -460,10 +503,15 @@ int tls_init()
       if (!saciphers.s[i]) saciphers.s[i] = ':';
     ciphers = saciphers.s;
   }
-  else ciphers = "DEFAULT";
+  else
+    ciphers = "DEFAULT";
   SSL_set_cipher_list(myssl, ciphers);
   alloc_free(saciphers.s);
 
+  /* set SNI hostname */
+  if (partner_fqdn)
+    SSL_set_tlsext_host_name(myssl, partner_fqdn);
+
   /* SSL_set_options(myssl, SSL_OP_NO_TLSv1); */
   SSL_set_fd(myssl, smtpfd);
 
@@ -471,31 +519,29 @@ int tls_init()
   if (!smtps) {
     if (smtpcode() != 220) {
       SSL_free(myssl);
-      if (!servercert) return 0;
-      out("ZSTARTTLS rejected while ");
-      out(servercert); out(" exists"); TLS_QUIT;
+      if (!tls_required) return 0;
+      out("ZSTARTTLS rejected while TLS is required by configuration");
+      TLS_QUIT;
     }
     smtptext.len = 0;
   }
 
   ssl = myssl;
   if (ssl_timeoutconn(timeout, smtpfd, smtpfd, ssl) <= 0) {
-    if (servercert)
+    if (tls_required)
       tls_quit("ZTLS connect failed", ssl_error_str());
     else {
-      /* shouldn't talk to the client unless in an appropriate state */
-      int state = ssl ? ssl->state : SSL_ST_BEFORE;
-      if (state & SSL_ST_OK || (!smtps && state & SSL_ST_BEFORE))
-        substdio_putsflush(&smtpto,"QUIT\r\n");
+      smtp_quit();
 
       out("lTLS connect failed: ");
       out(ssl_error_str());
       out("; retrying without TLS\n");
-      zero();
-      substdio_flush(subfdoutsmall);
+      zeroflush();
 
       env_put("NOTLS=1");
-      execvp(*myargv, myargv);
+      execvp(*myargv, myargv); //FIXME this will cause all mx to be retried
+      out("DUnable to execute myself\n");
+      zerodie();
     }
   }
 
@@ -550,6 +596,17 @@ int tls_init()
 
     X509_free(peercert);
   }
+  /* DANE verify tls connection */
+  else if (dane_retval == VAL_DANE_NOERROR) {
+    int do_certcheck = 0; // ignored. DANE SMTP doesn't do any PKIX checks
+    dane_retval = val_dane_check(dane_context, ssl, dane_status, &do_certcheck);
+    if (dane_retval != VAL_DANE_NOERROR) {
+      out("lNo TLSA record matched: ");
+      out(partner_fqdn);
+      quit2("/", NULL, 0);
+      return -1;
+    }
+  }
 
   if (smtps) if (smtpcode() != 220)
     quit("ZTLS Connected to "," but greeting failed");
@@ -587,44 +644,46 @@ void smtp()
     if (port == 465) smtps = 1;
   if (!smtps)
 #endif
- 
+
   code = smtpcode();
   if (code >= 500 && code < 600) quit("DConnected to "," but greeting failed");
   if (code >= 400 && code < 500) return; /* try next MX, see RFC-2821 */
   if (code != 220) quit("ZConnected to "," but greeting failed");
- 
-#ifdef EHLO
-# ifdef TLS
+
+#ifdef TLS
   if (!smtps)
-# endif
+#endif
   code = ehlo();
 
-# ifdef TLS
-  if (tls_init())
+#ifdef TLS
+  int tls = tls_init();
+  if (tls == -1) {
+    if (ssl)
+      ssl_free(ssl);
+    ssl = NULL;
+    return; /* try next MX */
+  }
+  else if (tls)
     /* RFC2487 says we should issue EHLO (even if we might not need
      * extensions); at the same time, it does not prohibit a server
      * to reject the EHLO and make us fallback to HELO */
     code = ehlo();
-# endif
+#endif
 
   if (code == 250) {
     /* add EHLO response checks here */
 
     /* and if EHLO failed, use HELO */
   } else {
-#endif
- 
-  substdio_puts(&smtpto,"HELO ");
-  substdio_put(&smtpto,helohost.s,helohost.len);
-  substdio_puts(&smtpto,"\r\n");
-  substdio_flush(&smtpto);
-  code = smtpcode();
-  if (code >= 500) quit("DConnected to "," but my name was rejected");
-  if (code != 250) quit("ZConnected to "," but my name was rejected");
- 
-#ifdef EHLO
+    substdio_puts(&smtpto,"HELO ");
+    substdio_put(&smtpto,helohost.s,helohost.len);
+    substdio_puts(&smtpto,"\r\n");
+    substdio_flush(&smtpto);
+    code = smtpcode();
+    if (code >= 500) quit("DConnected to "," but my name was rejected");
+    if (code != 250) quit("ZConnected to "," but my name was rejected");
   }
-#endif
+
   i = 0;
   if (auth_smtp_user.len && auth_smtp_pass.len)  {
     while((i += str_chr(smtptext.s+i,'\n') + 1) &&