Add sshchat dependencies in vendor

vendor/github.com/shazow/ssh-chat/sshd/ratelimit.go

@@ -0,0 +1,71 @@
+package sshd
+
+import (
+	"io"
+	"net"
+	"time"
+
+	"github.com/shazow/rateio"
+)
+
+type limitedConn struct {
+	net.Conn
+	io.Reader // Our rate-limited io.Reader for net.Conn
+}
+
+func (r *limitedConn) Read(p []byte) (n int, err error) {
+	return r.Reader.Read(p)
+}
+
+// ReadLimitConn returns a net.Conn whose io.Reader interface is rate-limited by limiter.
+func ReadLimitConn(conn net.Conn, limiter rateio.Limiter) net.Conn {
+	return &limitedConn{
+		Conn:   conn,
+		Reader: rateio.NewReader(conn, limiter),
+	}
+}
+
+// Count each read as 1 unless it exceeds some number of bytes.
+type inputLimiter struct {
+	// TODO: Could do all kinds of fancy things here, like be more forgiving of
+	// connections that have been around for a while.
+
+	Amount    int
+	Frequency time.Duration
+
+	remaining int
+	readCap   int
+	numRead   int
+	timeRead  time.Time
+}
+
+// NewInputLimiter returns a rateio.Limiter with sensible defaults for
+// differentiating between humans typing and bots spamming.
+func NewInputLimiter() rateio.Limiter {
+	grace := time.Second * 3
+	return &inputLimiter{
+		Amount:    2 << 14, // ~16kb, should be plenty for a high typing rate/copypasta/large key handshakes.
+		Frequency: time.Minute * 1,
+		readCap:   128,          // Allow up to 128 bytes per read (anecdotally, 1 character = 52 bytes over ssh)
+		numRead:   -1024 * 1024, // Start with a 1mb grace
+		timeRead:  time.Now().Add(grace),
+	}
+}
+
+// Count applies 1 if n<readCap, else n
+func (limit *inputLimiter) Count(n int) error {
+	now := time.Now()
+	if now.After(limit.timeRead) {
+		limit.numRead = 0
+		limit.timeRead = now.Add(limit.Frequency)
+	}
+	if n <= limit.readCap {
+		limit.numRead += 1
+	} else {
+		limit.numRead += n
+	}
+	if limit.numRead > limit.Amount {
+		return rateio.ErrRateExceeded
+	}
+	return nil
+}