From 009bbc0546dd6007cfe987a8ab5f4be0b78c0204 Mon Sep 17 00:00:00 2001
From: Norbert Pocs <npocs@redhat.com>
Date: Fri, 19 May 2023 12:02:52 +0200
Subject: [PATCH] sftp.c: Avoid null dereference

Issue found by covscan (gcc analyzer)

Signed-off-by: Norbert Pocs <npocs@redhat.com>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>
---
 src/sftp.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/sftp.c b/src/sftp.c
index c23d9538..c98fe655 100644
--- a/src/sftp.c
+++ b/src/sftp.c
@@ -1755,6 +1755,10 @@ static int sftp_handle_close(sftp_session sftp, ssh_string handle)
 int sftp_close(sftp_file file){
   int err = SSH_NO_ERROR;
 
+  if (file == NULL) {
+      return err;
+  }
+
   SAFE_FREE(file->name);
   if (file->handle){
     err = sftp_handle_close(file->sftp,file->handle);
@@ -1917,7 +1921,7 @@ void sftp_file_set_blocking(sftp_file handle){
 
 /* Read from a file using an opened sftp file handle. */
 ssize_t sftp_read(sftp_file handle, void *buf, size_t count) {
-  sftp_session sftp = handle->sftp;
+  sftp_session sftp;
   sftp_message msg = NULL;
   sftp_status_message status;
   ssh_string datastring;
@@ -1926,6 +1930,11 @@ ssize_t sftp_read(sftp_file handle, void *buf, size_t count) {
   uint32_t id;
   int rc;
 
+  if (handle == NULL) {
+      return -1;
+  }
+  sftp = handle->sftp;
+
   if (handle->eof) {
     return 0;
   }
@@ -2147,7 +2156,7 @@ int sftp_async_read(sftp_file file, void *data, uint32_t size, uint32_t id){
 }
 
 ssize_t sftp_write(sftp_file file, const void *buf, size_t count) {
-  sftp_session sftp = file->sftp;
+  sftp_session sftp;
   sftp_message msg = NULL;
   sftp_status_message status;
   ssh_buffer buffer;
@@ -2156,6 +2165,11 @@ ssize_t sftp_write(sftp_file file, const void *buf, size_t count) {
   size_t packetlen;
   int rc;
 
+  if (file == NULL) {
+      return -1;
+  }
+  sftp = file->sftp;
+
   buffer = ssh_buffer_new();
   if (buffer == NULL) {
     ssh_set_error_oom(sftp->session);