Routing gopher requests (reverse proxy) + Tor

Routing gopher requests (reverse proxy) + Tor

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║1 ...........Posted: 2025-02-25........... 1║
║2* ......Tags: sysadmin gopher linux ...... *2║
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I host different Gopher Protocol services which use different ports on one box.
So I kind of need a *reverse proxy* of sorts. I wanted to make sure I could
access all of them using port 70.

The idea:

* Don't touch my existing Gopher Protocol service
* Have a new Gopher service running on port 70
* On the new Gopher service, associate certain internal ports with certain
selectors
* for example if a selector beginning with `/phorum` is requested on port 70, I
want to strip the `/phorum` bit, then request localhost 7070 and serve that
* For all internal links, prepend the selector and change the port to 70

In other words, I have various Gopher Protocol services running on different
ports, but with xinetd I serve them all on port 70, just under different
selectors. This is basically a Gopher Protocol routing/reverse proxy!

## It's running live!

I use this configuration on this server.

`gopher://gopher.someodd.zip:70/1/someodd/`: basically puts my localhost 7071
gopher service to be served on port 70, under the `/someodd` selector.

`gopher://gopher.someodd.zip:70/1/phorum/`: serves phorum (running on localhost
7070) on port 70, under the `/someodd` selector.

This configuration also offers a service index at
`gopher://gopher.someodd.zip/`.

## Configure the server

Install `xnetd`:

```
sudo apt-get install -y xinetd
```

Add this file `/etc/xinetd.d/gopher`:

```
service gopher
{
type = UNLISTED
port = 70
socket_type = stream
wait = no
user = root
server = /usr/local/bin/gopher_router.sh
log_on_success += USERID
log_on_failure += USERID
log_type = FILE /var/log/xinetd_gopher.log
disable = no
}
```

Create this script `/usr/local/bin/gopher_router.sh`:

```
#!/bin/bash

# Read the selector from stdin
read selector

# Function to process and replace paths and ports in the response
process_response() {
local prefix="$1"
local port="$2"
local target_host="gopher.someodd.zip"
local target_port="70"

# Strip the prefix from the selector and ensure the leading slash is retained
local stripped_selector="${selector#$prefix}"
if [[ "$stripped_selector" != /* ]]; then
stripped_selector="/$stripped_selector"
fi

# Send the selector to the appropriate service and process the response
echo "$stripped_selector" | nc localhost $port | \
sed -e "/\t${target_host}\t${port}/s|\t/|\t${prefix}/|g" \
-e "s|$${target_host}$\t${port}|\1\t${target_port}|g"
}

# Handle the selector
case "$selector" in
"/phorum"*)
process_response "/phorum" 7070
;;
*)
process_response "/" 7071
;;
esac
```

Restart:

```
sudo systemctl restart xinetd
```

For testing:

```
echo "/parent2/little-notes" | nc localhost 70
```

Also `ufw` (firewall entry):

```
sudo ufw allow 70/tcp comment 'gopher (router)'
```

## Bonus

### Serve default menu

You could even serve a default menu:

```
# Handle the selector
case "$selector" in
"/phorum"*)
process_response "/phorum" 7070
;;
"/someodd"*)
process_response "/someodd" 7071
;;
*)
# Return a Gopher menu with links to /phorum and /someodd
echo "1Phorum link /phorum gopher.someodd.zip 70"
echo "1someodd link /someodd gopher.someodd.zip 70"
echo ""
;;
esac
```

### Handle rewriting for Tor

in `/etc/xinetd.d/gopher`:

```
service gopher
{
type = UNLISTED
port = 70
socket_type = stream
wait = no
user = root
server = /bin/bash
server_args = /usr/local/bin/gopher_router.sh
log_on_success += USERID
log_on_failure += USERID
log_type = FILE /var/log/xinetd_gopher.log
disable = no
}
```

now i updated my routing script:

```
#!/bin/bash

# Read the selector from stdin
read selector

# Function to check if the connection is coming from Tor
is_tor_connection() {
# Check if the remote IP address matches known Tor patterns
if [[ "$REMOTE_HOST" == "::ffff:127.0.0.1" ]]; then
# Assuming Tor traffic comes from localhost for hidden services
return 0
fi
return 1
}

# Function to process and replace paths and ports in the response
process_response() {
local prefix="$1"
local port="$2"
local target_host="gopher.someodd.zip"
local target_port="70"

# Check if Tor was used and adjust the target host
if is_tor_connection; then
target_host="xj2o2wylbqkprajldswuyxm6dffca4eepegelblgvux3uuqmtb2l56id.onion"
fi

# Strip the prefix from the selector and ensure the leading slash is retained
local stripped_selector="${selector#$prefix}"
if [[ "$stripped_selector" != /* ]]; then
stripped_selector="/$stripped_selector"
fi

# Send the selector to the appropriate service and process the response
echo "$stripped_selector" | nc localhost $port | \
sed -e "s|\tgopher.someodd.zip\t${port}|\t${target_host}\t${target_port}|g" \
-e "s|\tgopher.someodd.zip/|\t${target_host}/|g"
}

# Handle the selector
case "$selector" in
"/phorum"*)
process_response "/phorum" 7070
;;
*)
process_response "/" 7071
;;
esac
```

## yet another update

sorry i need to clean up this article, but i realized for phorum until i release
a prefix-adding feature for slectors in phorum i need to rewrite the links in
phorum.

```
#!/bin/bash
# Read the selector from stdin
read selector

# Function to check if the connection is coming from Tor
is_tor_connection() {
# Check if the remote IP address matches known Tor patterns
if [[ "$REMOTE_HOST" == "::ffff:127.0.0.1" ]]; then
# Assuming Tor traffic comes from localhost for hidden services
return 0
fi
return 1
}

# Function to process and replace paths and ports in the response
process_response() {
local prefix="$1"
local port="$2"
local rewrite_selectors_to_use_prefix="$3"
local target_host="gopher.someodd.zip"
local target_port="70"

# Check if Tor was used and adjust the target host
if is_tor_connection; then
target_host="xj2o2wylbqkprajldswuyxm6dffca4eepegelblgvux3uuqmtb2l56id.onion"
fi

# Strip the prefix from the selector and ensure the leading slash is retained
local stripped_selector="${selector#$prefix}"
if [[ "$stripped_selector" != /* ]]; then
stripped_selector="/$stripped_selector"
fi

# Send the selector to the appropriate service and process the response
if [[ "$rewrite_selectors_to_use_prefix" == "true" ]]; then
# When rewriting is enabled, add the prefix to all selectors in the response
echo "$stripped_selector" | nc localhost $port | \
sed -e "s|\tgopher.someodd.zip\t${port}|\t${target_host}\t${target_port}|g" \
-e "s|\tgopher.someodd.zip/|\t${target_host}/|g" \
-e "s|\t/|\t${prefix}/|g"
else
# Original behavior without selector rewriting
echo "$stripped_selector" | nc localhost $port | \
sed -e "s|\tgopher.someodd.zip\t${port}|\t${target_host}\t${target_port}|g" \
-e "s|\tgopher.someodd.zip/|\t${target_host}/|g"
fi
}

# Handle the selector
case "$selector" in
"/phorum"*)
process_response "/phorum" 7070 "true"
;;
*)
process_response "/" 7071 "false"
;;
esac
```