ZEBRA is a Zcash node written entirely in Rust. Prior to zebrad version 4.3.1 and prior to zebra-chain version 6.0.2, Orchard transactions contain a rk field which is a randomized validating key and also an elliptic curve point. The Zcash specification allows the field to be the identity (a "zero" value), however, the orchard crate which is used to verify Orchard proofs would panic when fed a rk with the identity value. Thus an attacker could send a crafted transaction that would make a Zebra node crash. This issue has been patched in zebrad version 4.3.1 and zebra-chain version 6.0.2.

Affected: crates.io: zebrad, crates.io: zebra-chain

# rk Identity Point Panic in Transaction Verification

## Summary

Orchard transactions contain a `rk` field which is a randomized validating key and also an elliptic curve point. The Zcash specification allows the field to be the identity (a "zero" value), however, the `orchard` crate which is used to verify Orchard proofs would panic when fed a `rk` with the identity value. Thus an attacker could send a crafted transaction that would make a Zebra node crash.

## Severity

**Critical** - This is a Denial of Service Vulnerability that could allow an attacker to crash Zebra nodes.

## Affected Versions

All Zebra versions prior to **version 4.3.1**.

## Description

The vulnerability exists in the `circuits.rs` file of the `orchard` crate; it attempts to get the coordinates of the `rk` value and calls `unwrap()` on the results, which causes a panic if `rk` is the identity.

Zebra parses `rk` as a byte vector; it creates an Orchard "bundle" using the `orchard` crate and then calls the same crate to verify it, triggering the panic.

An attacker could exploit this by: 1. Creating a transaction with a identity `rk` 2. Submitting it to a Zebra node, making it crash

## Impact

**Denial of Service**

* **Attack Vector:** Network. * **Effect:** Node crash. * **Scope:** Any impacted Zebra node.

## Fixed Versions

This issue is fixed in **Zebra 4.3.1**.

The fix was agreed with `zcashd` developers (which has the same issue) to not allow the identity `rk` anymore and change the speci…