From 1002a0121a8f5a9aee25357769807f2c519fa50b Mon Sep 17 00:00:00 2001
From: Damian Poddebniak <duesee@users.noreply.github.com>
Date: Fri, 24 Jul 2020 19:39:53 +0200
Subject: [PATCH] Detect extra data after STARTTLS response and exit (#387)

---
 src/low-level/imap/mailimap.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/low-level/imap/mailimap.c b/src/low-level/imap/mailimap.c
index bb17119d..4ffcf55d 100644
--- a/src/low-level/imap/mailimap.c
+++ b/src/low-level/imap/mailimap.c
@@ -2428,6 +2428,13 @@ int mailimap_starttls(mailimap * session)
 
   mailimap_response_free(response);
 
+  // Detect if the server send extra data after the STARTTLS response.
+  // This *may* be a "response injection attack".
+  if (session->imap_stream->read_buffer_len != 0) {
+      // Since it is also an IMAP protocol violation, exit.
+      return MAILIMAP_ERROR_STARTTLS;
+  }
+
   switch (error_code) {
   case MAILIMAP_RESP_COND_STATE_OK:
     return MAILIMAP_NO_ERROR;
From 298460a2adaabd2f28f417a0f106cb3b68d27df9 Mon Sep 17 00:00:00 2001
From: Fabian Ising <Murgeye@users.noreply.github.com>
Date: Fri, 24 Jul 2020 19:40:48 +0200
Subject: [PATCH] Detect extra data after STARTTLS responses in SMTP and POP3
 and exit (#388)

* Detect extra data after STLS response and return error

* Detect extra data after SMTP STARTTLS response and return error
---
 src/low-level/pop3/mailpop3.c | 8 ++++++++
 src/low-level/smtp/mailsmtp.c | 8 ++++++++
 2 files changed, 16 insertions(+)

diff --git a/src/low-level/pop3/mailpop3.c b/src/low-level/pop3/mailpop3.c
index ab9535be..e2124bf8 100644
--- a/src/low-level/pop3/mailpop3.c
+++ b/src/low-level/pop3/mailpop3.c
@@ -959,6 +959,14 @@ int mailpop3_stls(mailpop3 * f)
 
   if (r != RESPONSE_OK)
     return MAILPOP3_ERROR_STLS_NOT_SUPPORTED;
+
+  // Detect if the server send extra data after the STLS response.
+  // This *may* be a "response injection attack".
+  if (f->pop3_stream->read_buffer_len != 0) {
+    // Since it is also protocol violation, exit.
+    // There is no error type for STARTTLS errors in POP3
+    return MAILPOP3_ERROR_SSL;
+  }
   
   return MAILPOP3_NO_ERROR;
 }
diff --git a/src/low-level/smtp/mailsmtp.c b/src/low-level/smtp/mailsmtp.c
index b7fc459e..3145cadf 100644
--- a/src/low-level/smtp/mailsmtp.c
+++ b/src/low-level/smtp/mailsmtp.c
@@ -1111,6 +1111,14 @@ int mailesmtp_starttls(mailsmtp * session)
     return MAILSMTP_ERROR_STREAM;
   r = read_response(session);
 
+  // Detect if the server send extra data after the STARTTLS response.
+  // This *may* be a "response injection attack".
+  if (session->stream->read_buffer_len != 0) {
+    // Since it is also protocol violation, exit.
+    // There is no general error type for STARTTLS errors in SMTP
+    return MAILSMTP_ERROR_SSL;
+  }
+
   switch (r) {
   case 220:
     return MAILSMTP_NO_ERROR;
