Implement range bans (#478)

* Implement range bans

People connecting from banned IP ranges are unable to upload
torrents anonymously, and need to manually have their accounts
activated.

This adds a new table "rangebans", and a command line utility,
"rangeban.py", which can be used to add, list and remove rangebans
from the command line.

As an example:

./rangeban.py ban 192.168.0.0/24

This would rangeban anything in this /24.

The temporary_tor column allows automated scripts to clean out and
re-add ever-changing sets of ranges to be banned without affecting
the other ranges.

This has only been tested for IPv4.

* Revise Rangebans

Add an id column, and change "temporary_tor" to "temp". Also
index masked_cidr and mask.

* rangebans: fix enabled and the binary op

kill me

* Add enabling/disabling bans to rangeban.py

* rangebans: fail earlier on garbage arguments

* rangebans: fix linter errors

* rangeban.py: don't shadow builtin keyword 'id'

* rangebans: change temporary ban logic, column

The 'temp' column is now a nullable time column. If the field is
null, the ban is understood to be permanent. If there is a time
in there, it's understood to be the creation time of the ban.

This allows scripts to e.g. delete all temporary bans older than
a certain amount of time.

Also, rename the '_cidr_string' column to 'cidr_string', because
reasons.

* rangeban.py: use ip_address to parse CIDR subnet

* rangebans: fixes to the mask calculation and query

Both were not bugs per-se, but just technically not needed/correct.

* De-meme apparently

rangeban.py

@@ -0,0 +1,119 @@
+#!/usr/bin/env python3
+
+from datetime import datetime
+from ipaddress import ip_address
+import sys
+
+import click
+
+from nyaa import create_app, models
+from nyaa.extensions import db
+
+
+def is_cidr_valid(c):
+    '''Checks whether a CIDR range string is valid.'''
+    try:
+        subnet, mask = c.split('/')
+    except ValueError:
+        return False
+    if int(mask) < 1 or int(mask) > 32:
+        return False
+    try:
+        ip = ip_address(subnet)
+    except ValueError:
+        return False
+    return True
+
+
+def check_str(b):
+    '''Returns a checkmark or cross depending on the condition.'''
+    return '\u2713' if b else '\u2717'
+
+
+@click.group()
+def rangeban():
+    global app
+    app = create_app('config')
+
+
+@rangeban.command()
+@click.option('--temp/--no-temp', help='Mark this entry as one that may be '
+              'cleaned out occasionally.', default=False)
+@click.argument('cidrrange')
+def ban(temp, cidrrange):
+    if not is_cidr_valid(cidrrange):
+        click.secho('{} is not of the format xxx.xxx.xxx.xxx/xx.'
+                    .format(cidrrange), err=True, fg='red')
+        sys.exit(1)
+    with app.app_context():
+        ban = models.RangeBan(cidr_string=cidrrange, temp=datetime.utcnow() if temp else None)
+        db.session.add(ban)
+        db.session.commit()
+        click.echo('Added {} for {}.'.format('temp ban' if temp else 'ban',
+                                             cidrrange))
+
+
+@rangeban.command()
+@click.argument('cidrrange')
+def unban(cidrrange):
+    if not is_cidr_valid(cidrrange):
+        click.secho('{} is not of the format xxx.xxx.xxx.xxx/xx.'
+                    .format(cidrrange), err=True, fg='red')
+        sys.exit(1)
+    with app.app_context():
+        # Dunno why this wants _cidr_string and not cidr_string, probably
+        # due to this all being a janky piece of shit.
+        bans = models.RangeBan.query.filter(
+            models.RangeBan._cidr_string == cidrrange).all()
+        if len(bans) == 0:
+            click.echo('Ban not found.')
+        for b in bans:
+            click.echo('Unbanned {}'.format(b.cidr_string))
+            db.session.delete(b)
+        db.session.commit()
+
+
+@rangeban.command()
+def list():
+    with app.app_context():
+        bans = models.RangeBan.query.all()
+        if len(bans) == 0:
+            click.echo('No bans.')
+        else:
+            click.secho('ID     CIDR Range         Enabled Temp', bold=True)
+            for b in bans:
+                click.echo('{0: <6} {1: <18} {2: <7} {3: <4}'
+                           .format(b.id, b.cidr_string,
+                                   check_str(b.enabled),
+                                   check_str(b.temp is not None)))
+
+@rangeban.command()
+@click.argument('banid', type=int)
+@click.argument('status')
+def enabled(banid, status):
+    yeses = ['true', '1', 'yes', '\u2713']
+    noses = ['false', '0', 'no', '\u2717']
+    if status.lower() in yeses:
+        set_to = True
+    elif status.lower() in noses:
+        set_to = False
+    else:
+        click.secho('Please choose one of {} or {}.'
+                    .format(yeses, noses), err=True, fg='red')
+        sys.exit(1)
+    with app.app_context():
+        ban = models.RangeBan.query.get(banid)
+        if not ban:
+            click.secho('No ban with id {} found.'
+                        .format(banid), err=True, fg='red')
+            sys.exit(1)
+        ban.enabled = set_to
+        db.session.add(ban)
+        db.session.commit()
+        click.echo('{} ban {} on {}.'.format('Enabled' if set_to else 'Disabled',
+                                             banid, ban._cidr_string))
+
+
+
+if __name__ == '__main__':
+    rangeban()