allow changing curve

README.md

@@ -137,6 +137,15 @@ You can send with your own code phrase (must be more than 4 characters).
 croc send --code [code-phrase] [file(s)-or-folder]
 ```
 
+### Allow overwriting without prompt
+
+By default, croc will prompt whether to overwrite a file. You can automatically overwrite files by using the `--overwrite` flag (recipient only). For example, receive a file to automatically overwrite:
+
+```
+croc --yes --overwrite <code>
+```
+
+
 ### Use pipes - stdin and stdout
 
 You can pipe to `croc`:
@@ -173,6 +182,14 @@ You can use a proxy as your connection to the relay by adding a proxy address wi
 croc --socks5 "127.0.0.1:9050" send SOMEFILE
 ```
 
+### Change encryption curve
+
+You can choose from several different elliptic curves to use for encryption by using the `--curve` flag. Only the recipient can choose the curve. For example, receive a file using the P-521 curve:
+
+```
+croc --curve p521 <codephrase>
+```
+
 ### Self-host relay
 
 The relay is needed to staple the parallel incoming and outgoing connections. By default, `croc` uses a public relay but you can also run your own relay:

go.mod

@@ -1,9 +1,6 @@
 module github.com/schollz/croc/v8
-
 go 1.13
-
 replace github.com/schollz/pake3 => ../pake3
-
 require (
 github.com/OneOfOne/xxhash v1.2.5 // indirect
 github.com/cespare/xxhash v1.1.0

src/cli/cli.go

@@ -20,6 +20,7 @@ import (
 	"github.com/schollz/croc/v8/src/tcp"
 	"github.com/schollz/croc/v8/src/utils"
 	log "github.com/schollz/logger"
+	pake "github.com/schollz/pake3"
 )
 
 // Version specifies the version
@@ -87,6 +88,7 @@ func Run() (err error) {
 		&cli.BoolFlag{Name: "local", Usage: "force to use only local connections"},
 		&cli.BoolFlag{Name: "ignore-stdin", Usage: "ignore piped stdin"},
 		&cli.BoolFlag{Name: "overwrite", Usage: "do not prompt to overwrite"},
+		&cli.StringFlag{Name: "curve", Value: "siec", Usage: "choose an encryption curve (" + strings.Join(pake.AvailableCurves(), ", ") + ")"},
 		&cli.StringFlag{Name: "ip", Value: "", Usage: "set sender ip if known e.g. 10.0.0.1:9009, [::1]:9009"},
 		&cli.StringFlag{Name: "relay", Value: models.DEFAULT_RELAY, Usage: "address of the relay", EnvVars: []string{"CROC_RELAY"}},
 		&cli.StringFlag{Name: "relay6", Value: models.DEFAULT_RELAY6, Usage: "ipv6 address of the relay", EnvVars: []string{"CROC_RELAY6"}},
@@ -195,6 +197,7 @@ func send(c *cli.Context) (err error) {
 		SendingText:    c.String("text") != "",
 		NoCompress:     c.Bool("no-compress"),
 		Overwrite:      c.Bool("overwrite"),
+		Curve:          c.String("curve"),
 	}
 	if crocOptions.RelayAddress != models.DEFAULT_RELAY {
 		crocOptions.RelayAddress6 = ""
@@ -391,6 +394,7 @@ func receive(c *cli.Context) (err error) {
 		OnlyLocal:     c.Bool("local"),
 		IP:            c.String("ip"),
 		Overwrite:     c.Bool("overwrite"),
+		Curve:         c.String("curve"),
 	}
 	if crocOptions.RelayAddress != models.DEFAULT_RELAY {
 		crocOptions.RelayAddress6 = ""

src/croc/croc.go

@@ -66,6 +66,7 @@ type Options struct {
 	NoCompress     bool
 	IP             string
 	Overwrite      bool
+	Curve          string
 }
 
 // Client holds the state of the croc transfer
@@ -165,11 +166,9 @@ func New(ops Options) (c *Client, err error) {
 
 	c.conn = make([]*comm.Comm, 16)
 
-	// initialize pake
+	// initialize pake for recipient
-	if c.Options.IsSender {
+	if !c.Options.IsSender {
-		c.Pake, err = pake.InitCurve([]byte(c.Options.SharedSecret[5:]), 1, "siec")
+		c.Pake, err = pake.InitCurve([]byte(c.Options.SharedSecret[5:]), 0, c.Options.Curve)
-	} else {
-		c.Pake, err = pake.InitCurve([]byte(c.Options.SharedSecret[5:]), 0, "siec")
 	}
 	if err != nil {
 		return
@@ -696,6 +695,7 @@ func (c *Client) transfer(options TransferOptions) (err error) {
 		err = message.Send(c.conn[0], c.Key, message.Message{
 			Type:   "pake",
 			Bytes:  c.Pake.Bytes(),
+			Bytes2: []byte(c.Options.Curve),
 		})
 		if err != nil {
 			return
@@ -825,12 +825,23 @@ func (c *Client) processMessageFileInfo(m message.Message) (done bool, err error
 func (c *Client) processMessagePake(m message.Message) (err error) {
 	log.Debug("received pake payload")
 
+	var salt []byte
+	if c.Options.IsSender {
+		// initialize curve based on the recipient's choice
+		log.Debugf("using curve %s", string(m.Bytes2))
+		c.Pake, err = pake.InitCurve([]byte(c.Options.SharedSecret[5:]), 1, string(m.Bytes2))
+		if err != nil {
+			log.Error(err)
+			return
+		}
+
+		// update the pake
 		err = c.Pake.Update(m.Bytes)
 		if err != nil {
 			return
 		}
-	var salt []byte
+
-	if c.Options.IsSender {
+		// generate salt and send it back to recipient
 		log.Debug("generating salt")
 		salt = make([]byte, 8)
 		if _, rerr := rand.Read(salt); err != nil {
@@ -844,6 +855,10 @@ func (c *Client) processMessagePake(m message.Message) (err error) {
 			Bytes2: salt,
 		})
 	} else {
+		err = c.Pake.Update(m.Bytes)
+		if err != nil {
+			return
+		}
 		salt = m.Bytes2
 	}
 	// generate key