New 'preconnect' keyword to execute a command prior to opening an SMTP

connection (Daniel Richard G.).

7 files changed, 64 insertions, 2 deletions

diff --git a/NEWS b/NEWS
index 11e06af..68f715e 100644
--- a/NEWS
+++ b/NEWS
@@ -3,12 +3,15 @@ News
 
   * Version 0.4.2 (under development):
   
+    * New 'preconnect' keyword to execute a command prior to opening an SMTP
+    connection (Daniel Richard G.).
+    
     * Fixed a bug which prevented to send mail when libesmtp had no
     openssl support (Tomas Kondor).
     
     * New 'default' keyword for identities (Vitezslav Batrla).
 
-  * Version 0.4.1 (2004-07-14):
+  * Version 0.4.1 (2003-07-14):
   
     * Packaging fixes.
 
diff --git a/esmtprc.5 b/esmtprc.5
index 2bf6a01..b807bcb 100644
--- a/esmtprc.5
+++ b/esmtprc.5
@@ -69,6 +69,16 @@ It can be one of \fBenabled\fR, \fBdisabled\fR or \fBrequired\fR. It defaults to
 Set the certificate passphrase for the StartTLS extension.
 
 .TP
+\fBpreconnect\fR
+Shell command to execute prior to opening an SMTP connection.
+
+This may be useful in conjunction with application-level transports (e.g.
+\fBssh\fR with its port-forwarding functionality) to secure the SMTP
+connection. \fBEsmtp\fR will wait for the command to exit before
+proceeding. If the command returns a non-zero status, delivery will be
+aborted.
+
+.TP
 \fBidentity\fR
 Define an identity.
 
diff --git a/lexer.l b/lexer.l
index 1a269f8..9529d0e 100644
--- a/lexer.l
+++ b/lexer.l
@@ -60,6 +60,7 @@ user(name)?	{ BEGIN(NAME); return USERNAME; }
 pass(word)?	{ BEGIN(NAME); return PASSWORD; }
 (start)?tls	{ return STARTTLS; }
 (certificate_)?passphrase	{ return CERTIFICATE_PASSPHRASE; }
+preconnect	{ return PRECONNECT; }
 mda		{ return MDA; }
 
 =		{ return MAP; }
diff --git a/parser.y b/parser.y
index fdbb769..428e1c3 100644
--- a/parser.y
+++ b/parser.y
@@ -54,7 +54,7 @@ void yyerror (const char *s);
     char *sval;
 }
 
-%token IDENTITY DEFAULT HOSTNAME USERNAME PASSWORD STARTTLS CERTIFICATE_PASSPHRASE MDA
+%token IDENTITY DEFAULT HOSTNAME USERNAME PASSWORD STARTTLS CERTIFICATE_PASSPHRASE PRECONNECT MDA
 
 %token MAP
 
@@ -100,6 +100,7 @@ statement	: HOSTNAME map STRING	{ identity->host = xstrdup($3); SET_DEFAULT_IDEN
 		| STARTTLS map ENABLED	{ identity->starttls = Starttls_ENABLED; SET_DEFAULT_IDENTITY; }
 		| STARTTLS map REQUIRED	{ identity->starttls = Starttls_REQUIRED; SET_DEFAULT_IDENTITY; }
 		| CERTIFICATE_PASSPHRASE map STRING { identity->certificate_passphrase = xstrdup($3); SET_DEFAULT_IDENTITY; }
+		| PRECONNECT map STRING	{ identity->preconnect = xstrdup($3); SET_DEFAULT_IDENTITY; }
 		| MDA map STRING	{ mda = xstrdup($3); }
 		| DEFAULT		{ default_identity = identity; }
 		;
diff --git a/sample.esmtprc b/sample.esmtprc
index f44db65..e1f1572 100644
--- a/sample.esmtprc
+++ b/sample.esmtprc
@@ -24,6 +24,10 @@ password = "PASSWORD"
 #
 #certificate_passphrase = "CERTIFICATE_PASSPHRASE"
 
+# Command to run before contacting the SMTP server
+#
+#preconnect = "ssh -f -L 2025:mail.isp.com:25 user@shell.isp.com 'sleep 5'"
+
 
 # Same as above but for a different identity which can be selected with the
 # '-f' flag. You can have as many you like.
diff --git a/smtp.c b/smtp.c
index 87b086b..f536cec 100644
--- a/smtp.c
+++ b/smtp.c
@@ -13,6 +13,7 @@
 #include <string.h>
 #include <signal.h>
 #include <errno.h>
+#include <sys/wait.h>
 
 #include <auth-client.h>
 #include <libesmtp.h>
@@ -429,6 +430,43 @@ void smtp_send(message_t *msg)
 				goto failure;
 	}
 
+	/* Execute pre-connect command if one was specified. */
+	if (identity->preconnect)
+	{
+		int ret, exit_status;
+
+		if (verbose)
+			fprintf (stdout, "Executing pre-connect command: %s\n", identity->preconnect);
+
+		ret = system (identity->preconnect);
+		exit_status = WEXITSTATUS(ret);
+
+		/* Check whether the child process caught a signal meant for us */
+		if (WIFSIGNALED(ret))
+		{
+			int sig = WTERMSIG(ret);
+
+			if (sig == SIGINT || sig == SIGQUIT)
+			{
+				fprintf (stderr, "Pre-connect command received signal %d\n", sig);
+				exit (EX_SOFTWARE);
+			}
+		}
+
+		if (ret == -1)
+		{
+			fputs ("Error executing pre-connect command\n", stderr);
+			exit (EX_OSERR);
+		}
+
+		if (exit_status != 0)
+		{
+			fprintf (stderr, "Pre-connect command \"%s\" exited with non-zero status %d\n",
+				 identity->preconnect, exit_status);
+			exit (EX_SOFTWARE);
+		}
+	}
+
 	/* Initiate a connection to the SMTP server and transfer the message. */
 	if (!smtp_start_session (session))
 	{
diff --git a/smtp.h b/smtp.h
index cc3fac8..5df10ca 100644
--- a/smtp.h
+++ b/smtp.h
@@ -38,6 +38,11 @@ typedef struct {
 	enum starttls_option starttls;
 	char *certificate_passphrase;
 	/*@}*/
+
+	/** \name Pre-connect Command */
+	/*@{*/
+	char *preconnect;
+	/*@}*/
 } identity_t;
 
 /**