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canaries.go
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canaries.go
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package generate
/*
Sliver Implant Framework
Copyright (C) 2019 Bishop Fox
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
import (
"encoding/json"
"fmt"
insecureRand "math/rand"
"strings"
"time"
clientpb "github.com/bishopfox/sliver/protobuf/client"
"github.com/bishopfox/sliver/server/db"
)
const (
// CanaryBucketName - DNS Canary bucket name
CanaryBucketName = "canaries"
canaryPrefix = "can://"
canarySize = 6
)
var (
dnsCharSet = []rune("abcdefghijklmnopqrstuvwxyz0123456789-_")
)
// DNSCanary - DNS canary
type DNSCanary struct {
SliverName string `json:"sliver_name"`
Domain string `json:"domain"`
Triggered bool `json:"triggered"`
FirstTrigger string `json:"first_trigger"`
LatestTrigger string `json:"latest_trigger"`
Count int `json:"count"`
}
// ToProtobuf - Return a protobuf version of the struct
func (c *DNSCanary) ToProtobuf() *clientpb.DNSCanary {
return &clientpb.DNSCanary{
SliverName: c.SliverName,
Domain: c.Domain,
Triggered: c.Triggered,
FristTriggered: c.FirstTrigger,
LatestTrigger: c.LatestTrigger,
Count: uint32(c.Count),
}
}
func canarySubDomain() string {
subdomain := []rune{}
index := insecureRand.Intn(len(dnsCharSet) - 12) // ensure first char is alphabetic
subdomain = append(subdomain, dnsCharSet[index])
for i := 0; i < canarySize; i++ {
index := insecureRand.Intn(len(dnsCharSet))
subdomain = append(subdomain, dnsCharSet[index])
}
return string(subdomain)
}
// ListCanaries - List of all embedded canaries
func ListCanaries() ([]*DNSCanary, error) {
bucket, err := db.GetBucket(CanaryBucketName)
if err != nil {
return nil, err
}
rawCanaries, err := bucket.Map("")
canaries := []*DNSCanary{}
for _, rawCanary := range rawCanaries {
canary := &DNSCanary{}
err := json.Unmarshal(rawCanary, canary)
if err != nil {
buildLog.Errorf("Failed to parse canary")
continue
}
canaries = append(canaries, canary)
}
return canaries, nil
}
// CheckCanary - Check if a canary exists
func CheckCanary(domain string) (*DNSCanary, error) {
bucket, err := db.GetBucket(CanaryBucketName)
if err != nil {
return nil, err
}
data, err := bucket.Get(domain)
if err != nil {
return nil, err
}
canary := &DNSCanary{}
err = json.Unmarshal(data, canary)
return canary, err
}
// UpdateCanary - Update an existing canary
func UpdateCanary(canary *DNSCanary) error {
bucket, err := db.GetBucket(CanaryBucketName)
if err != nil {
return err
}
canaryData, err := json.Marshal(canary)
if err != nil {
return err
}
return bucket.Set(canary.Domain, canaryData)
}
// CanaryGenerator - Holds data related to canary generation
type CanaryGenerator struct {
SliverName string
ParentDomains []string
}
// GenerateCanary - Generate a canary domain and save it to the db
// currently this gets called by template engine
func (g *CanaryGenerator) GenerateCanary() string {
bucket, err := db.GetBucket(CanaryBucketName)
if err != nil {
buildLog.Warnf("Failed to fetch canary bucket")
return ""
}
if len(g.ParentDomains) < 1 {
buildLog.Warnf("No parent domains")
return ""
}
// Don't need secure random here
insecureRand.Seed(time.Now().UnixNano())
index := insecureRand.Intn(len(g.ParentDomains))
parentDomain := g.ParentDomains[index]
if strings.HasPrefix(parentDomain, ".") {
parentDomain = parentDomain[1:]
}
if !strings.HasSuffix(parentDomain, ".") {
parentDomain += "." // Ensure we have the FQDN
}
subdomain := canarySubDomain()
canaryDomain := fmt.Sprintf("%s.%s", subdomain, parentDomain)
buildLog.Infof("Generated new canary domain %s", canaryDomain)
canary, err := json.Marshal(&DNSCanary{
SliverName: g.SliverName,
Domain: canaryDomain,
Triggered: false,
Count: 0,
})
if err != nil {
return ""
}
err = bucket.Set(canaryDomain, canary)
if err != nil {
buildLog.Errorf("Failed to save canary %s", err)
return ""
}
return fmt.Sprintf("%s%s", canaryPrefix, canaryDomain)
}