validate reactor messages (#2711)

* validate reactor messages

Refs #2683

* validate blockchain messages

Refs #2683

* validate evidence messages

Refs #2683

* todo

* check ProposalPOL and signature sizes

* add a changelog entry

* check addr is valid when we add it to the addrbook

* validate incoming netAddr (not just nil check!)

* fixes after Bucky's review

* check timestamps

* beef up block#ValidateBasic

* move some checks into bcBlockResponseMessage

* update Gopkg.lock

Fix

```
grouped write of manifest, lock and vendor: failed to export github.com/tendermint/go-amino: fatal: failed to unpack tree object 6dcc6ddc143e116455c94b25c1004c99e0d0ca12
```

by running `dep ensure -update`

* bump year since now we check it

* generate test/p2p/data on the fly using tendermint testnet

* allow sync chains older than 1 year

* use full path when creating a testnet

* move testnet gen to test/docker/Dockerfile

* relax LastCommitRound check

Refs #2737

* fix conflicts after merge

* add small comment

* some ValidateBasic updates

* fixes

* AppHash length is not fixed

types/validation.go

@@ -0,0 +1,40 @@
+package types
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/tendermint/tendermint/crypto/tmhash"
+	tmtime "github.com/tendermint/tendermint/types/time"
+)
+
+// ValidateTime does a basic time validation ensuring time does not drift too
+// much: +/- one year.
+// TODO: reduce this to eg 1 day
+// NOTE: DO NOT USE in ValidateBasic methods in this package. This function
+// can only be used for real time validation, like on proposals and votes
+// in the consensus. If consensus is stuck, and rounds increase for more than a day,
+// having only a 1-day band here could break things...
+// Can't use for validating blocks because we may be syncing years worth of history.
+func ValidateTime(t time.Time) error {
+	var (
+		now     = tmtime.Now()
+		oneYear = 8766 * time.Hour
+	)
+	if t.Before(now.Add(-oneYear)) || t.After(now.Add(oneYear)) {
+		return fmt.Errorf("Time drifted too much. Expected: -1 < %v < 1 year", now)
+	}
+	return nil
+}
+
+// ValidateHash returns an error if the hash is not empty, but its
+// size != tmhash.Size.
+func ValidateHash(h []byte) error {
+	if len(h) > 0 && len(h) != tmhash.Size {
+		return fmt.Errorf("Expected size to be %d bytes, got %d bytes",
+			tmhash.Size,
+			len(h),
+		)
+	}
+	return nil
+}