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