feat: add dig command

Other changes:
- use middleware for permission checking
- able to respond with emoji
- log incoming requests

cmds/dig.go

@@ -0,0 +1,172 @@
+package cmds
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"net"
+	"os/exec"
+	"regexp"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/go-errors/errors"
+
+	"git.gensokyo.cafe/kkyy/tgbot_misaka_5882f7/utils"
+)
+
+var (
+	// According to wikipedia
+	digValidDnsTypes = utils.ToLookupMap([]string{
+		"A", "AAAA", "AFSDB", "APL", "CAA", "CDNSKEY", "CDS", "CERT", "CNAME", "CSYNC", "DHCID", "DLV", "DNAME",
+		"DNSKEY", "DS", "EUI48", "EUI64", "HINFO", "HIP", "HTTPS", "IPSECKEY", "KEY", "KX", "LOC", "MX", "NAPTR", "NS",
+		"NSEC", "NSEC3", "NSEC3PARAM", "OPENPGPKEY", "PTR", "RRSIG", "RP", "SIG", "SMIMEA", "SOA", "SRV", "SSHFP",
+		"SVCB", "TA", "TKEY", "TLSA", "TSIG", "TXT", "URI", "ZONEMD",
+	})
+
+	digErrInvalidArgs = fmt.Errorf("invalid request")
+
+	digDnsNameRe = regexp.MustCompile(`^([a-z0-9_-]+\.?)+|\.$`)
+)
+
+type DigRequest struct {
+	Name    string
+	Type    string
+	Reverse bool
+}
+
+func NewDigRequest(req string) (*DigRequest, error) {
+	ret := &DigRequest{}
+
+	args := strings.Fields(req)
+	nArgs := len(args)
+	if nArgs == 0 || nArgs > 2 {
+		return nil, digErrInvalidArgs
+	}
+
+	if nArgs > 1 {
+		typ := strings.ToUpper(args[1])
+		if _, ok := digValidDnsTypes[typ]; !ok {
+			return nil, digErrInvalidArgs
+		}
+		ret.Type = typ
+	}
+
+	ip := net.ParseIP(args[0])
+	if ip != nil {
+		ret.Name = ip.String()
+		ret.Reverse = true
+		ret.Type = ""
+		return ret, nil
+	}
+
+	name := strings.ToLower(args[0])
+	if !digDnsNameRe.Match([]byte(name)) {
+		return nil, digErrInvalidArgs
+	}
+	ret.Name = name
+	return ret, nil
+}
+
+func (r *DigRequest) ToCmdArgs() []string {
+	args := make([]string, 0, 4)
+	args = append(args, "-u")
+
+	if r.Reverse {
+		args = append(args, "-x")
+	}
+	args = append(args, r.Name)
+
+	if r.Type != "" {
+		args = append(args, r.Type)
+	}
+	return args
+}
+
+type DigDnsRecord struct {
+	Name  string
+	TTL   int
+	Class string
+	Type  string
+	Data  string
+}
+
+type DigResponse struct {
+	Status    string
+	QueryTime time.Duration
+	Records   []DigDnsRecord
+}
+
+var (
+	digRespDnsRecordLineRe = regexp.MustCompile(`^([^;\s]\S*)\s+(\d+)\s+([A-Z]+)\s+([A-Z]+)\s+(.*)$`)
+	digRespHeaderLineRe    = regexp.MustCompile(`^;;.*HEADER.*status: ([A-Z]+),.*$`)
+	digResqQueryTimeLineRe = regexp.MustCompile(`^;; Query time: (\d+) usec$`)
+)
+
+func buildDigResponse(buf []byte) (*DigResponse, error) {
+	sc := bufio.NewScanner(bytes.NewReader(buf))
+	ret := &DigResponse{}
+
+	for sc.Scan() {
+		line := sc.Text()
+		if line == "" {
+			continue
+		}
+		if line[0] == ';' {
+			if ret.Status == "" {
+				m := digRespHeaderLineRe.FindStringSubmatch(line)
+				if len(m) == 2 {
+					ret.Status = m[1]
+					continue
+				}
+			}
+
+			m := digResqQueryTimeLineRe.FindStringSubmatch(line)
+			if len(m) == 2 {
+				usec, err := strconv.ParseInt(m[1], 10, 64)
+				if err != nil {
+					return nil, errors.WrapPrefix(err, "failed to parse query time", 0)
+				}
+				ret.QueryTime = time.Microsecond * time.Duration(usec)
+				continue
+			}
+		}
+
+		m := digRespDnsRecordLineRe.FindStringSubmatch(line)
+		if len(m) == 6 {
+			ttl, err := strconv.Atoi(m[2])
+			if err != nil {
+				return nil, errors.WrapPrefix(err, "failed to parse ttl", 0)
+			}
+			ret.Records = append(ret.Records, DigDnsRecord{
+				Name:  m[1],
+				TTL:   ttl,
+				Class: m[3],
+				Type:  m[4],
+				Data:  m[5],
+			})
+		}
+	}
+	if ret.Status == "" {
+		return nil, errors.New("failed to parse response: \"status\" is unknown")
+	}
+
+	return ret, nil
+}
+
+func Dig(req *DigRequest) (*DigResponse, error) {
+	cmd := exec.Command("/usr/bin/dig", req.ToCmdArgs()...)
+	cmd.Stdin = nil
+
+	buf, err := cmd.Output()
+	if err != nil {
+		return nil, errors.WrapPrefix(err, "failed to run dig command", 0)
+	}
+
+	ret, err := buildDigResponse(buf)
+	if err != nil {
+		return nil, errors.WrapPrefix(err, "failed to parse dig response", 0)
+	}
+	return ret, nil
+}