From 63f9837b4ccf600da79314e8667f91bda69988fc Mon Sep 17 00:00:00 2001
From: Thomas Vegas <>
Date: Sat, 31 Aug 2019 16:59:56 +0200
Subject: [PATCH 1/2] tftp: return error when packet is too small for options

Upstream-commit: 82f3ba3806a34fe94dcf9e5c9b88deda6679ca1b
Signed-off-by: Kamil Dudka <kdudka@redhat.com>
---
 lib/tftp.c | 53 +++++++++++++++++++++++++++++++++--------------------
 1 file changed, 33 insertions(+), 20 deletions(-)

diff --git a/lib/tftp.c b/lib/tftp.c
index 289cda2..4532170 100644
--- a/lib/tftp.c
+++ b/lib/tftp.c
@@ -404,13 +404,14 @@ static CURLcode tftp_parse_option_ack(tftp_state_data_t *state,
   return CURLE_OK;
 }
 
-static size_t tftp_option_add(tftp_state_data_t *state, size_t csize,
-                              char *buf, const char *option)
+static CURLcode tftp_option_add(tftp_state_data_t *state, size_t *csize,
+                                char *buf, const char *option)
 {
-  if(( strlen(option) + csize + 1) > (size_t)state->blksize)
-    return 0;
+  if(( strlen(option) + *csize + 1) > (size_t)state->blksize)
+    return CURLE_TFTP_ILLEGAL;
   strcpy(buf, option);
-  return strlen(option) + 1;
+  *csize += strlen(option) + 1;
+  return CURLE_OK;
 }
 
 static CURLcode tftp_connect_for_tx(tftp_state_data_t *state,
@@ -511,26 +512,38 @@ static CURLcode tftp_send_first(tftp_state_data_t *state, tftp_event_t event)
       else
         strcpy(buf, "0"); /* the destination is large enough */
 
-      sbytes += tftp_option_add(state, sbytes,
-                                (char *)state->spacket.data + sbytes,
-                                TFTP_OPTION_TSIZE);
-      sbytes += tftp_option_add(state, sbytes,
-                                (char *)state->spacket.data + sbytes, buf);
+      result = tftp_option_add(state, &sbytes,
+                               (char *)state->spacket.data + sbytes,
+                               TFTP_OPTION_TSIZE);
+      if(result == CURLE_OK)
+        result = tftp_option_add(state, &sbytes,
+                                 (char *)state->spacket.data + sbytes, buf);
+
       /* add blksize option */
       snprintf(buf, sizeof(buf), "%d", state->requested_blksize);
-      sbytes += tftp_option_add(state, sbytes,
-                                (char *)state->spacket.data + sbytes,
-                                TFTP_OPTION_BLKSIZE);
-      sbytes += tftp_option_add(state, sbytes,
-                                (char *)state->spacket.data + sbytes, buf);
+      if(result == CURLE_OK)
+        result = tftp_option_add(state, &sbytes,
+                                 (char *)state->spacket.data + sbytes,
+                                 TFTP_OPTION_BLKSIZE);
+      if(result == CURLE_OK)
+        result = tftp_option_add(state, &sbytes,
+                                 (char *)state->spacket.data + sbytes, buf);
 
       /* add timeout option */
       snprintf(buf, sizeof(buf), "%d", state->retry_time);
-      sbytes += tftp_option_add(state, sbytes,
-                                (char *)state->spacket.data + sbytes,
-                                TFTP_OPTION_INTERVAL);
-      sbytes += tftp_option_add(state, sbytes,
-                                (char *)state->spacket.data + sbytes, buf);
+      if(result == CURLE_OK)
+        result = tftp_option_add(state, &sbytes,
+                                 (char *)state->spacket.data + sbytes,
+                                 TFTP_OPTION_INTERVAL);
+      if(result == CURLE_OK)
+        result = tftp_option_add(state, &sbytes,
+                                 (char *)state->spacket.data + sbytes, buf);
+
+      if(result != CURLE_OK) {
+        failf(data, "TFTP buffer too small for options");
+        free(filename);
+        return CURLE_TFTP_ILLEGAL;
+      }
     }
 
     /* the typecase for the 3rd argument is mostly for systems that do
-- 
2.20.1


From b6b12a4cfe00c4850a1d6cee4cf267f00dee5987 Mon Sep 17 00:00:00 2001
From: Thomas Vegas <>
Date: Sat, 31 Aug 2019 17:30:51 +0200
Subject: [PATCH 2/2] tftp: Alloc maximum blksize, and use default unless OACK
 is received

Fixes potential buffer overflow from 'recvfrom()', should the server
return an OACK without blksize.

Bug: https://curl.haxx.se/docs/CVE-2019-5482.html
CVE-2019-5482

Upstream-commit: facb0e4662415b5f28163e853dc6742ac5fafb3d
Signed-off-by: Kamil Dudka <kdudka@redhat.com>
---
 lib/tftp.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/lib/tftp.c b/lib/tftp.c
index 4532170..5651b62 100644
--- a/lib/tftp.c
+++ b/lib/tftp.c
@@ -982,6 +982,7 @@ static CURLcode tftp_connect(struct connectdata *conn, bool *done)
 {
   tftp_state_data_t *state;
   int blksize;
+  int need_blksize;
 
   blksize = TFTP_BLKSIZE_DEFAULT;
 
@@ -996,15 +997,20 @@ static CURLcode tftp_connect(struct connectdata *conn, bool *done)
       return CURLE_TFTP_ILLEGAL;
   }
 
+  need_blksize = blksize;
+  /* default size is the fallback when no OACK is received */
+  if(need_blksize < TFTP_BLKSIZE_DEFAULT)
+    need_blksize = TFTP_BLKSIZE_DEFAULT;
+
   if(!state->rpacket.data) {
-    state->rpacket.data = calloc(1, blksize + 2 + 2);
+    state->rpacket.data = calloc(1, need_blksize + 2 + 2);
 
     if(!state->rpacket.data)
       return CURLE_OUT_OF_MEMORY;
   }
 
   if(!state->spacket.data) {
-    state->spacket.data = calloc(1, blksize + 2 + 2);
+    state->spacket.data = calloc(1, need_blksize + 2 + 2);
 
     if(!state->spacket.data)
       return CURLE_OUT_OF_MEMORY;
@@ -1018,7 +1024,7 @@ static CURLcode tftp_connect(struct connectdata *conn, bool *done)
   state->sockfd = state->conn->sock[FIRSTSOCKET];
   state->state = TFTP_STATE_START;
   state->error = TFTP_ERR_NONE;
-  state->blksize = blksize;
+  state->blksize = TFTP_BLKSIZE_DEFAULT; /* Unless updated by OACK response */
   state->requested_blksize = blksize;
 
   ((struct sockaddr *)&state->local_addr)->sa_family =
-- 
2.20.1