Extra paranoia around STARTTLS-with-data-in-buffer.

[exim.git] / src / src / smtp_in.c

diff --git a/src/src/smtp_in.c b/src/src/smtp_in.c
index 0fcedc8216cb68719cdb5f416c3276f4330ca22a..500000be446a0c0dec2333d9675a42c819e25fca 100644 (file)
--- a/src/src/smtp_in.c
+++ b/src/src/smtp_in.c
@@ -49,7 +49,7 @@ the data can be quite long. */
 /* Structure for SMTP command list */
 
 typedef struct {
-  char *name;
+  const char *name;
   int len;
   short int cmd;
   short int has_arg;
@@ -376,7 +376,7 @@ Returns:      nothing
 */
 
 void
-smtp_printf(char *format, ...)
+smtp_printf(const char *format, ...)
 {
 va_list ap;
 
@@ -390,7 +390,7 @@ smtp_printf(), bearing in mind that in C a vararg function can't directly
 call another vararg function, only a function which accepts a va_list. */
 
 void
-smtp_vprintf(char *format, va_list ap)
+smtp_vprintf(const char *format, va_list ap)
 {
 BOOL yield;
 
@@ -3844,6 +3844,23 @@ while (done <= 0)
     toomany = FALSE;
     cmd_list[CMD_LIST_STARTTLS].is_mail_cmd = FALSE;
 
+    /* There's an attack where more data is read in past the STARTTLS command
+    before TLS is negotiated, then assumed to be part of the secure session
+    when used afterwards; we use segregated input buffers, so are not
+    vulnerable, but we want to note when it happens and, for sheer paranoia,
+    ensure that the buffer is "wiped".
+    Pipelining sync checks will normally have protected us too, unless disabled
+    by configuration. */
+
+    if (receive_smtp_buffered())
+      {
+      DEBUG(D_any)
+        debug_printf("Non-empty input buffer after STARTTLS; naive attack?");
+      if (tls_active < 0)
+        smtp_inend = smtp_inptr = smtp_inbuffer;
+      /* and if TLS is already active, tls_server_start() should fail */
+      }
+
     /* Attempt to start up a TLS session, and if successful, discard all
     knowledge that was obtained previously. At least, that's what the RFC says,
     and that's what happens by default. However, in order to work round YAEB,