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From fe9b4ce23f82a3b2564123bbc3c674cc07a04f2b 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 | 76 +++++++++++++++++++++++++++++++++---------------------
 1 file changed, 46 insertions(+), 30 deletions(-)

diff --git a/lib/tftp.c b/lib/tftp.c
index 022648a..8ab9d71 100644
--- a/lib/tftp.c
+++ b/lib/tftp.c
@@ -405,13 +405,14 @@ 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,
@@ -498,31 +499,46 @@ static CURLcode tftp_send_first(tftp_state_data_t *state, tftp_event_t event)
     sbytes = 4 + strlen(filename) + strlen(mode);
 
     /* add tsize option */
-    if(data->set.upload && (data->set.infilesize != -1))
-      snprintf( buf, sizeof(buf), "%" FORMAT_OFF_T, data->set.infilesize );
-    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);
-    /* 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 );
-
-    /* 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 );
+    {
+      CURLcode result;
+      if(data->set.upload && (data->set.infilesize != -1))
+        snprintf( buf, sizeof(buf), "%" FORMAT_OFF_T, data->set.infilesize );
+      else
+        strcpy(buf, "0"); /* the destination is large enough */
+
+      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);
+      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);
+      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
        not have a size_t argument, like older unixes that want an 'int' */
-- 
2.20.1


From ea5ca5f9ee1a4588061fc8b5a10c5b65fb68a0cd 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 8ab9d71..af3b288 100644
--- a/lib/tftp.c
+++ b/lib/tftp.c
@@ -961,6 +961,7 @@ static CURLcode tftp_connect(struct connectdata *conn, bool *done)
   CURLcode code;
   tftp_state_data_t *state;
   int blksize, rc;
+  int need_blksize;
 
   blksize = TFTP_BLKSIZE_DEFAULT;
 
@@ -979,15 +980,20 @@ 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;
@@ -1001,7 +1007,7 @@ 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