Add cp file-write

Along the lines of GTFOBins#122.

Author: cyrus-and

_gtfobins/cp.md

@@ -4,14 +4,24 @@ functions:
     - code: |
         LFILE=file_to_read
         cp "$LFILE" /dev/stdout
+  file-write:
+    - code: |
+        LFILE=file_to_write
+        echo "DATA" | cp /dev/stdin "$LFILE"
   suid:
+    - code: |
+        LFILE=file_to_write
+        echo "DATA" | ./cp /dev/stdin "$LFILE"
     - description: This can be used to copy and then read or write files from a restricted file systems or with elevated privileges.
       code: |
         LFILE=file_to_write
         TF=$(mktemp)
         echo "DATA" > $TF
         ./cp $TF $LFILE
   sudo:
+    - code: |
+        LFILE=file_to_write
+        echo "DATA" | sudo cp /dev/stdin "$LFILE"
     - description: This can be used to copy and then read or write files from a restricted file systems or with elevated privileges.
       code: |
         LFILE=file_to_write