From 81b17eef0baaefa725602ac2a8d335bceccd97eb Mon Sep 17 00:00:00 2001
From: mivirl <>
Date: Sat, 2 Mar 2024 19:52:35 -0600
Subject: [PATCH] server: Limit ports used to 46515-46550

---
 README.md           |  7 +++++--
 src/server.sh       | 10 +++++++++-
 src/start-server.sh |  4 +++-
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index 159099a..e7a90af 100644
--- a/README.md
+++ b/README.md
@@ -43,6 +43,9 @@ directory to the remote system, then `cd` to that directory and run:
 ./busybox sh start_server.sh
 ```
 
+By default the server uses the ports 46515-46550. This can be changed in
+`start_server.sh`
+
 ### Client
 
 To deploy on the client, you'll need to transfer the `build/_output/client`
@@ -56,7 +59,7 @@ directory to the remote system, then `cd` to that directory and run:
 
 Once the server is running and a client has connected, files will appear on the
 server in `srv/clients/` with the following naming scheme:
-- `_auth-key` - Key used to authenticate clients and store files in the correct
+- `_auth-key` - Key used to authenticate clients
 - `_files.log` - Log of files as they are received on the server
 - `_info.txt` - Contains basic information about the client
 - `_processes.log` - Log of processes as they are run on the client
@@ -65,7 +68,7 @@ server in `srv/clients/` with the following naming scheme:
    transferred as they are written on the client
 - `C__commandname` - Command output, continuously transferred
 
-Logs can be monitored as they come in using `lnav`:
+Logs can be monitored as they come in using [lnav](https://lnav.org):
 
 ```sh
 ./lnav -r srv/clients
diff --git a/src/server.sh b/src/server.sh
index b6245d4..52e785a 100644
--- a/src/server.sh
+++ b/src/server.sh
@@ -1,5 +1,13 @@
 #!./busybox sh
 
+if [ $# -ne 2 ]; then
+    echo "Usage: $0 file_port_start file_port_num"
+    exit 1
+fi
+
+FILE_PORT_START=$1
+FILE_PORT_NUM=$2
+
 SRVDIR=$(pwd)
 
 verify_input() {
@@ -124,7 +132,7 @@ while read -r COMMAND; do
         SLEEPTIME=0
         while true; do
             sleep $(( RANDOM % (SLEEPTIME + 5) + 1 ))
-            PORT=$(( (RANDOM * 2 + RANDOM % 2) % 64511 + 1024 ))
+            PORT=$(( (RANDOM * 2 + RANDOM % 2) % FILE_PORT_NUM + FILE_PORT_START ))
             nc -w 7 -l -p "$PORT" > "$FILENAME" 2>/dev/null &
             NC_PID=$!
             # Wait for nc to fail. There seems to be a bug with busybox sh where
diff --git a/src/start-server.sh b/src/start-server.sh
index 80cc5cc..b150210 100644
--- a/src/start-server.sh
+++ b/src/start-server.sh
@@ -1,6 +1,8 @@
 #!./busybox sh
 
 SRVPORT=46515
+FILE_PORT_START=46516
+FILE_PORT_NUM=45
 CWD=$(pwd)
 
 # -----------------------------------------------------------------------------
@@ -8,4 +10,4 @@ CWD=$(pwd)
 
 mkdir -p "$CWD/srv/clients"
 cd "$CWD/srv"
-tcpsvd -c 4096 0.0.0.0 "$SRVPORT" ../busybox sh ../server.sh
+tcpsvd -c 4096 0.0.0.0 "$SRVPORT" ../busybox sh ../server.sh "$FILE_PORT_START" "$FILE_PORT_NUM"
-- 
2.39.5