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ssh: reject RekeyThresholds over MaxInt64

This fixes weirdness when users use int64(-1) as sentinel value.

Also, really use cipher specific default thresholds. These were added
in a59c127, but weren't taking
effect. Add a test.

Fixes golang/go#19639

Change-Id: Ie9518a0ff12fded2fca35465abb427d7a9f84340
Reviewed-on: https://go-review.googlesource.com/39431
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
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hanwen committed Apr 4, 2017
1 parent 573951c commit c78caca803c95773f48a844d3dcab04b9bc4d6dd
Showing with 35 additions and 5 deletions.
  1. +7 −5 ssh/common.go
  2. +28 −0 ssh/handshake_test.go
View
@@ -9,6 +9,7 @@ import (
"crypto/rand"
"fmt"
"io"
"math"
"sync"
_ "crypto/sha1"
@@ -186,7 +187,7 @@ type Config struct {
// The maximum number of bytes sent or received after which a
// new key is negotiated. It must be at least 256. If
// unspecified, 1 gigabyte is used.
// unspecified, a size suitable for the chosen cipher is used.
RekeyThreshold uint64
// The allowed key exchanges algorithms. If unspecified then a
@@ -230,11 +231,12 @@ func (c *Config) SetDefaults() {
}
if c.RekeyThreshold == 0 {
// RFC 4253, section 9 suggests rekeying after 1G.
c.RekeyThreshold = 1 << 30
}
if c.RekeyThreshold < minRekeyThreshold {
// cipher specific default
} else if c.RekeyThreshold < minRekeyThreshold {
c.RekeyThreshold = minRekeyThreshold
} else if c.RekeyThreshold >= math.MaxInt64 {
// Avoid weirdness if somebody uses -1 as a threshold.
c.RekeyThreshold = math.MaxInt64
}
}
View
@@ -526,3 +526,31 @@ func TestDisconnect(t *testing.T) {
t.Errorf("readPacket 3 succeeded")
}
}
func TestHandshakeRekeyDefault(t *testing.T) {
clientConf := &ClientConfig{
Config: Config{
Ciphers: []string{"aes128-ctr"},
},
HostKeyCallback: InsecureIgnoreHostKey(),
}
trC, trS, err := handshakePair(clientConf, "addr", false)
if err != nil {
t.Fatalf("handshakePair: %v", err)
}
defer trC.Close()
defer trS.Close()
trC.writePacket([]byte{msgRequestSuccess, 0, 0})
trC.Close()
rgb := (1024 + trC.readBytesLeft) >> 30
wgb := (1024 + trC.writeBytesLeft) >> 30
if rgb != 64 {
t.Errorf("got rekey after %dG read, want 64G", rgb)
}
if wgb != 64 {
t.Errorf("got rekey after %dG write, want 64G", wgb)
}
}

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