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0f6e11c35f
This commit checks that the size of the bech32 encoded invoice is not
greater than 7092 bytes, which is the maximum number of bytes that can
fit into a QR code. This mitigates a potential DoS vector where an attacker
could craft a very large bech32 invoice string containing an absurd amount
of route and/or hop hints. If sent to an application that processes
payment requests, this would allocate a burdensome amount of memory
due to the public key parsing for each route/hop hint.
For a 1.7MB payment request, this yielded about 38MB in allocations
from just parsing public keys:
```
45.51MB 7.31% 92.07% 45.51MB 7.31% math/big.nat.make
25.50MB 4.09% 96.16% 25.50MB 4.09% github.com/lightningnetwork/lnd/zpay32.bech32VerifyChecksum
1MB 0.16% 96.32% 39.50MB 6.34% github.com/lightningnetwork/lnd/zpay32.parseRouteHint
1MB 0.16% 96.48% 33.50MB 5.38% github.com/btcsuite/btcd/btcec.decompressPoint
0.50MB 0.08% 96.56% 7.50MB 1.20% crypto/elliptic.(*CurveParams).doubleJacobian
0.50MB 0.08% 96.64% 38MB 6.10% github.com/btcsuite/btcd/btcec.ParsePubKey
0 0% 96.64% 12MB 1.93% crypto/ecdsa.Verify
0 0% 96.64% 8MB 1.28% crypto/elliptic.(*CurveParams).ScalarBaseMult
0 0% 96.64% 12MB 1.93% crypto/elliptic.(*CurveParams).ScalarMult
```
With this change, memory usage will be far lower as decoding will exit
early with an error if the invoice is too large.
zpay32
The zpay32 package implements a basic scheme for the encoding of payment
requests between two lnd nodes within the Lightning Network. The zpay32
encoding scheme uses the
zbase32
scheme along with a checksum to encode a serialized payment request.
The payment request serialized by the package consist of: the destination's public key, the payment hash to use for the payment, and the value of payment to send.
Installation and Updating
$ go get -u github.com/lightningnetwork/lnd/zpay32