Pavol Rusnak
3 years ago
committed by
Jakob Unterwurzacher
parent
6a9c49e9cf
commit
1e624a4cc3
@ -0,0 +1,110 @@
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package fido2
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import (
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"bytes"
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"encoding/base64"
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"fmt"
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"io"
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"os"
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"os/exec"
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"strings"
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"github.com/rfjakob/gocryptfs/internal/cryptocore"
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"github.com/rfjakob/gocryptfs/internal/exitcodes"
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"github.com/rfjakob/gocryptfs/internal/tlog"
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)
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type fidoCommand int
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const (
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cred fidoCommand = iota
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assert fidoCommand = iota
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assertWithPIN fidoCommand = iota
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)
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const relyingPartyID = "gocryptfs"
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func callFidoCommand(command fidoCommand, device string, stdin []string) ([]string, error) {
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var cmd *exec.Cmd
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switch command {
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case cred:
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cmd = exec.Command("fido2-cred", "-M", "-h", "-v", device)
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case assert:
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cmd = exec.Command("fido2-assert", "-G", "-h", device)
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case assertWithPIN:
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cmd = exec.Command("fido2-assert", "-G", "-h", "-v", device)
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}
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tlog.Debug.Printf("callFidoCommand: executing %q with args %v", cmd.Path, cmd.Args)
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cmd.Stderr = os.Stderr
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in, err := cmd.StdinPipe()
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if err != nil {
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return nil, err
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}
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for _, s := range stdin {
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// This does not deadlock because the pipe buffer is big enough (64kiB on Linux)
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io.WriteString(in, s+"\n")
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}
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in.Close()
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out, err := cmd.Output()
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if err != nil {
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return nil, fmt.Errorf("%s failed with %v", cmd.Args[0], err)
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}
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return strings.Split(string(out), "\n"), nil
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}
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// Register registers a credential using a FIDO2 token
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func Register(device string, userName string) (credentialID []byte) {
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tlog.Info.Printf("FIDO2 Register: interact with your device ...")
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cdh := base64.StdEncoding.EncodeToString(cryptocore.RandBytes(32))
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userID := base64.StdEncoding.EncodeToString(cryptocore.RandBytes(32))
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stdin := []string{cdh, relyingPartyID, userName, userID}
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out, err := callFidoCommand(cred, device, stdin)
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if err != nil {
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tlog.Fatal.Println(err)
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os.Exit(exitcodes.FIDO2Error)
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}
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credentialID, err = base64.StdEncoding.DecodeString(out[4])
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if err != nil {
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tlog.Fatal.Println(err)
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os.Exit(exitcodes.FIDO2Error)
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}
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return credentialID
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}
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// Secret generates a HMAC secret using a FIDO2 token
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func Secret(device string, credentialID []byte, salt []byte) (secret []byte) {
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tlog.Info.Printf("FIDO2 Secret: interact with your device ...")
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cdh := base64.StdEncoding.EncodeToString(cryptocore.RandBytes(32))
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crid := base64.StdEncoding.EncodeToString(credentialID)
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hmacsalt := base64.StdEncoding.EncodeToString(salt)
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stdin := []string{cdh, relyingPartyID, crid, hmacsalt}
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// try asserting without PIN first
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out, err := callFidoCommand(assert, device, stdin)
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if err != nil {
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// if that fails, let's assert with PIN
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out, err = callFidoCommand(assertWithPIN, device, stdin)
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if err != nil {
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tlog.Fatal.Println(err)
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os.Exit(exitcodes.FIDO2Error)
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}
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}
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secret, err = base64.StdEncoding.DecodeString(out[4])
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if err != nil {
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tlog.Fatal.Println(err)
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os.Exit(exitcodes.FIDO2Error)
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}
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// sanity checks
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secretLen := len(secret)
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if secretLen < 32 {
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tlog.Fatal.Printf("FIDO2 HMACSecret too short (%d)!\n", secretLen)
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os.Exit(exitcodes.FIDO2Error)
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}
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zero := make([]byte, secretLen)
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if bytes.Equal(zero, secret) {
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tlog.Fatal.Printf("FIDO2 HMACSecret is all zero!")
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os.Exit(exitcodes.FIDO2Error)
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}
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return secret
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}
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