smtp: fix glibcxx assertion failure with zero-length EHLO hostname

Fixes: gromox-2.38-94-g2ff0098a6

Author: jengelh

include/gromox/flusher_common.h

@@ -32,7 +32,7 @@ struct GX_EXPORT envelope_info {
 	void clear();
 
 	char parsed_domain[UDOM_SIZE]{"unknown"};
-	char hello_domain[UDOM_SIZE]{}; /* domain name after helo */
+	std::string hello_domain; /* domain name after helo */
 	char from[UADDR_SIZE]{}; /* envelope's from message */
 	std::vector<std::string> rcpt_to; /* envelope's rcpt to message */
 };

mda/message_enqueue.cpp

@@ -235,7 +235,7 @@ BOOL message_enqueue_try_save_mess(FLUSH_ENTITY *pentity)
 		auto tmp_len = sprintf(tmp_buff, "X-Lasthop: %s\r\nReceived: from %s "
 		          "(%s [%s%s])\r\n\tby %s with %s%s;\r\n\t%s\r\n",
 		          pentity->pconnection->client_addr,
-		          pentity->penvelope->hello_domain,
+		          pentity->penvelope->hello_domain.c_str(),
 		          pentity->penvelope->parsed_domain,
 		          af_type == AF_INET6 ? "IPv6:" : "",
 		          pentity->pconnection->client_addr,

mda/smtp/cmd.cpp

@@ -22,7 +22,7 @@ using namespace gromox;
 
 static BOOL cmdh_check_onlycmd(std::string_view cmd_line, smtp_context &);
 
-int cmdh_helo(std::string_view cmd_line, smtp_context &ctx)
+int cmdh_helo(std::string_view cmd_line, smtp_context &ctx) try
 {
 	auto pcontext = &ctx;
 	int line_length = cmd_line.size();
@@ -33,8 +33,8 @@ int cmdh_helo(std::string_view cmd_line, smtp_context &ctx)
 			/* 502 Command not implemented */
 			return 506;
 		/* copy parameter to hello_domain */
-		strncpy(pcontext->menv.hello_domain, &cmd_line[5], line_length - 5);
-		pcontext->menv.hello_domain[line_length-5] = '\0';
+		cmd_line.remove_prefix(5);
+		pcontext->menv.hello_domain = cmd_line;
     } else if(line_length > 255 + 1 + 4) {
         /* domain name too long */
 		return 502;
@@ -43,9 +43,11 @@ int cmdh_helo(std::string_view cmd_line, smtp_context &ctx)
 	pcontext->menv.clear();
     pcontext->last_cmd = T_HELO_CMD;
 	return 205;
-}    
+} catch (const std::bad_alloc &) {
+	return 416; /* ENOMEM */
+}
 
-static int cmdh_xhlo(std::string_view cmd_line, smtp_context &ctx)
+static int cmdh_xhlo(std::string_view cmd_line, smtp_context &ctx) try
 {
 	auto pcontext = &ctx;
 	int line_length = cmd_line.size();
@@ -58,8 +60,8 @@ static int cmdh_xhlo(std::string_view cmd_line, smtp_context &ctx)
 		if (cmd_line[4] != ' ')
 			return 506;
 		/* copy parameter to hello_domain */
-		strncpy(pcontext->menv.hello_domain, &cmd_line[5], line_length - 5);
-		pcontext->menv.hello_domain[line_length-5] = '\0';
+		cmd_line.remove_prefix(5);
+		pcontext->menv.hello_domain = cmd_line;
     } else if(line_length > 255 + 1 + 4) {
         /* domain name too long */
 		return 202;
@@ -86,6 +88,8 @@ static int cmdh_xhlo(std::string_view cmd_line, smtp_context &ctx)
 
 	pcontext->connection.write(buff, string_length);
     return DISPATCH_CONTINUE;
+} catch (const std::bad_alloc &) {
+	return 416; /* ENOMEM */
 }
 
 int cmdh_lhlo(std::string_view cmd_line, smtp_context &ctx)
@@ -108,7 +112,7 @@ int cmdh_starttls(std::string_view cmd_line, smtp_context &ctx)
 	if (!g_param.support_starttls)
 		return 506;
 	pcontext->last_cmd = T_STARTTLS_CMD;
-	memset(pcontext->menv.hello_domain, '\0', std::size(pcontext->menv.hello_domain));
+	pcontext->menv.hello_domain.clear();
 	pcontext->menv.clear();
 	return 210;
 }

mda/smtp/parser.cpp

@@ -629,7 +629,7 @@ static void smtp_parser_reset_context_session(SMTP_CONTEXT *pcontext)
 	pcontext->pre_rstlen                   = 0;
 	pcontext->stream.clear();
 	pcontext->menv.clear();
-	*pcontext->menv.hello_domain = '\0';
+	pcontext->menv.hello_domain.clear();
 	memset(&pcontext->flusher, 0, sizeof(FLUSH_INFO));
 }