smtp_mail: Added support to MAIL FROM for the optional AUTH parameter

Added a new CURLOPT_MAIL_AUTH option that allows the calling program to
set the optional AUTH parameter in the MAIL FROM command.

When this option is specified and an authentication mechanism is used
to communicate with the mail server then the AUTH parameter will be
included in the MAIL FROM command. This is particularly useful when the
calling program is acting as a relay in a trusted environment and
performing server to server communication, as it allows the relaying
server to specify the address of the mailbox that was used to
authenticate and send the original email.

include/curl/curl.h

@@ -1518,6 +1518,9 @@ typedef enum {
   /* Enable/disable specific SSL features with a bitmask, see CURLSSLOPT_* */
   CINIT(SSL_OPTIONS, LONG, 216),
 
+  /* set the SMTP auth originator */
+  CINIT(MAIL_AUTH, OBJECTPOINT, 217),
+
   CURLOPT_LASTENTRY /* the last unused */
 } CURLoption;
 

lib/smtp.c

@@ -893,6 +893,7 @@ static CURLcode smtp_state_auth_resp(struct connectdata *conn,
 static CURLcode smtp_mail(struct connectdata *conn)
 {
   char *from = NULL;
+  char *auth = NULL;
   char *size = NULL;
   CURLcode result = CURLE_OK;
   struct SessionHandle *data = conn->data;
@@ -909,26 +910,49 @@ static CURLcode smtp_mail(struct connectdata *conn)
   if(!from)
     return CURLE_OUT_OF_MEMORY;
 
-  /* calculate the optional SIZE parameter */
+  /* calculate the optional AUTH parameter */
-  if(conn->data->set.infilesize > 0) {
+  if(data->set.str[STRING_MAIL_AUTH] && conn->proto.smtpc.authused) {
-    size = aprintf("%" FORMAT_OFF_T, data->set.infilesize);
+    if(data->set.str[STRING_MAIL_AUTH][0] == '<')
+      auth = aprintf("%s", data->set.str[STRING_MAIL_AUTH]);
+    else
+      auth = aprintf("<%s>", data->set.str[STRING_MAIL_AUTH]);
 
-    if(!size) {
+    if(!auth) {
       Curl_safefree(from);
 
       return CURLE_OUT_OF_MEMORY;
     }
   }
 
-  /* send MAIL FROM */
+  /* calculate the optional SIZE parameter */
-  if(!size)
+  if(conn->data->set.infilesize > 0) {
-    result = Curl_pp_sendf(&conn->proto.smtpc.pp, "MAIL FROM:%s", from);
+    size = aprintf("%" FORMAT_OFF_T, data->set.infilesize);
-  else
-    result = Curl_pp_sendf(&conn->proto.smtpc.pp, "MAIL FROM:%s SIZE=%s",
-                           from, size);
 
-  Curl_safefree(size);
+    if(!size) {
       Curl_safefree(from);
+      Curl_safefree(auth);
+
+      return CURLE_OUT_OF_MEMORY;
+    }
+  }
+
+  /* send MAIL FROM */
+  if(!auth && !size)
+    result = Curl_pp_sendf(&conn->proto.smtpc.pp,
+                           "MAIL FROM:%s", from);
+  else if(auth && !size)
+    result = Curl_pp_sendf(&conn->proto.smtpc.pp,
+                           "MAIL FROM:%s AUTH=%s", from, auth);
+  else if(auth && size)
+    result = Curl_pp_sendf(&conn->proto.smtpc.pp,
+                           "MAIL FROM:%s AUTH=%s SIZE=%s", from, auth, size);
+  else
+    result = Curl_pp_sendf(&conn->proto.smtpc.pp,
+                           "MAIL FROM:%s SIZE=%s", from, size);
+
+  Curl_safefree(from);
+  Curl_safefree(auth);
+  Curl_safefree(size);
 
   if(result)
     return result;
@@ -1308,7 +1332,7 @@ static CURLcode smtp_connect(struct connectdata *conn,
   pp->conn = conn;
 
   if(!*path) {
-    if(!Curl_gethostname(localhost, sizeof localhost))
+    if(!Curl_gethostname(localhost, sizeof(localhost)))
       path = localhost;
     else
       path = "localhost";

lib/url.c

@@ -2402,6 +2402,11 @@ CURLcode Curl_setopt(struct SessionHandle *data, CURLoption option,
                        va_arg(param, char *));
     break;
 
+  case CURLOPT_MAIL_AUTH:
+    result = setstropt(&data->set.str[STRING_MAIL_AUTH],
+                       va_arg(param, char *));
+    break;
+
   case CURLOPT_MAIL_RCPT:
     /* get a list of mail recipients */
     data->set.mail_rcpt = va_arg(param, struct curl_slist *);

lib/urldata.h

@@ -1335,6 +1335,7 @@ enum dupstring {
   STRING_SOCKS5_GSSAPI_SERVICE,  /* GSSAPI service name */
 #endif
   STRING_MAIL_FROM,
+  STRING_MAIL_AUTH,
 
 #ifdef USE_TLS_SRP
   STRING_TLSAUTH_USERNAME,     /* TLS auth <username> */