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package main
import (
"encoding/json"
"errors"
"fmt"
"io"
"log"
"log/slog"
"net"
"net/http"
"regexp"
"github.com/TecharoHQ/anubis/cmd/anubis/internal/config"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promauto"
"github.com/yl2chen/cidranger"
)
var (
policyApplications = promauto.NewCounterVec(prometheus.CounterOpts{
Name: "anubis_policy_results",
Help: "The results of each policy rule",
}, []string{"rule", "action"})
)
type ParsedConfig struct {
orig config.Config
Bots []Bot
DNSBL bool
}
type Bot struct {
Name string
UserAgent *regexp.Regexp
Path *regexp.Regexp
Action config.Rule `json:"action"`
Challenge *config.ChallengeRules
Ranger cidranger.Ranger
}
func (b Bot) Hash() (string, error) {
var pathRex string
if b.Path != nil {
pathRex = b.Path.String()
}
var userAgentRex string
if b.UserAgent != nil {
userAgentRex = b.UserAgent.String()
}
return sha256sum(fmt.Sprintf("%s::%s::%s", b.Name, pathRex, userAgentRex)), nil
}
func parseConfig(fin io.Reader, fname string, defaultDifficulty int) (*ParsedConfig, error) {
var c config.Config
if err := json.NewDecoder(fin).Decode(&c); err != nil {
return nil, fmt.Errorf("can't parse policy config JSON %s: %w", fname, err)
}
if err := c.Valid(); err != nil {
return nil, err
}
var err error
result := &ParsedConfig{
orig: c,
}
for _, b := range c.Bots {
if berr := b.Valid(); berr != nil {
err = errors.Join(err, berr)
continue
}
var botParseErr error
parsedBot := Bot{
Name: b.Name,
Action: b.Action,
}
if b.RemoteAddr != nil && len(b.RemoteAddr) > 0 {
parsedBot.Ranger = cidranger.NewPCTrieRanger()
for _, cidr := range b.RemoteAddr {
_, rng, err := net.ParseCIDR(cidr)
if err != nil {
return nil, fmt.Errorf("[unexpected] range %s not parsing: %w", cidr, err)
}
parsedBot.Ranger.Insert(cidranger.NewBasicRangerEntry(*rng))
}
}
if b.UserAgentRegex != nil {
userAgent, err := regexp.Compile(*b.UserAgentRegex)
if err != nil {
botParseErr = errors.Join(botParseErr, fmt.Errorf("while compiling user agent regexp: %w", err))
continue
} else {
parsedBot.UserAgent = userAgent
}
}
if b.PathRegex != nil {
path, err := regexp.Compile(*b.PathRegex)
if err != nil {
botParseErr = errors.Join(botParseErr, fmt.Errorf("while compiling path regexp: %w", err))
continue
} else {
parsedBot.Path = path
}
}
if b.Challenge == nil {
parsedBot.Challenge = &config.ChallengeRules{
Difficulty: defaultDifficulty,
ReportAs: defaultDifficulty,
Algorithm: config.AlgorithmFast,
}
} else {
parsedBot.Challenge = b.Challenge
if parsedBot.Challenge.Algorithm == config.AlgorithmUnknown {
parsedBot.Challenge.Algorithm = config.AlgorithmFast
}
}
result.Bots = append(result.Bots, parsedBot)
}
if err != nil {
return nil, fmt.Errorf("errors validating policy config JSON %s: %w", fname, err)
}
result.DNSBL = c.DNSBL
return result, nil
}
type CheckResult struct {
Name string
Rule config.Rule
}
func (cr CheckResult) LogValue() slog.Value {
return slog.GroupValue(
slog.String("name", cr.Name),
slog.String("rule", string(cr.Rule)))
}
func cr(name string, rule config.Rule) CheckResult {
return CheckResult{
Name: name,
Rule: rule,
}
}
func (s *Server) checkRemoteAddress(b Bot, addr net.IP) bool {
if b.Ranger == nil {
return false
}
ok, err := b.Ranger.Contains(addr)
if err != nil {
log.Panicf("[unexpected] something very funky is going on, %q does not have a calculable network number: %v", addr.String(), err)
}
return ok
}
// Check evaluates the list of rules, and returns the result
func (s *Server) check(r *http.Request) (CheckResult, *Bot, error) {
host := r.Header.Get("X-Real-Ip")
if host == "" {
return zilch[CheckResult](), nil, fmt.Errorf("[misconfiguration] X-Real-Ip header is not set")
}
addr := net.ParseIP(host)
if addr == nil {
return zilch[CheckResult](), nil, fmt.Errorf("[misconfiguration] %q is not an IP address", host)
}
for _, b := range s.policy.Bots {
if b.UserAgent != nil {
if uaMatch := b.UserAgent.MatchString(r.UserAgent()); uaMatch || (uaMatch && s.checkRemoteAddress(b, addr)) {
return cr("bot/"+b.Name, b.Action), &b, nil
}
}
if b.Path != nil {
if pathMatch := b.Path.MatchString(r.URL.Path); pathMatch || (pathMatch && s.checkRemoteAddress(b, addr)) {
return cr("bot/"+b.Name, b.Action), &b, nil
}
}
if b.Ranger != nil {
if s.checkRemoteAddress(b, addr) {
return cr("bot/"+b.Name, b.Action), &b, nil
}
}
}
return cr("default/allow", config.RuleAllow), &Bot{
Challenge: &config.ChallengeRules{
Difficulty: defaultDifficulty,
ReportAs: defaultDifficulty,
Algorithm: config.AlgorithmFast,
},
}, nil
}
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