feat: private authwit with static call

docs/docs/guides/smart_contracts/writing_contracts/authwit.md

@@ -74,7 +74,7 @@ As part of `AuthWit` we are assuming that the `on_behalf_of` implements the priv
 
 ```rust
 #[aztec(private)]
-fn spend_private_authwit(inner_hash: Field) -> Field;
+fn verify_private_authwit(inner_hash: Field) -> Field;
 ```
 
 For public authwit, we have a shared registry that is used, there we are using a `consume` function.
@@ -101,10 +101,8 @@ To make it convenient to compute the message hashes in TypeScript, the `aztec.js
 
 For private calls where we allow execution on behalf of others, we generally want to check if the current call is authenticated by `on_behalf_of`. To easily do so, we can use the `assert_current_call_valid_authwit` which fetches information from the current context without us needing to provide much beyond the `on_behalf_of`.
 
-This function will then make a to `on_behalf_of` to execute the `spend_private_authwit` function which validates that the call is authenticated.
-The `on_behalf_of` should assert that we are indeed authenticated and then emit a nullifier when we are spending the authwit to prevent replay attacks.
-If the return value is not as expected, we throw an error.
-This is to cover the case where the `on_behalf_of` might implemented some function with the same selector as the `spend_private_authwit` that could be used to authenticate unintentionally.
+This function will then make a call to `on_behalf_of` to execute the `verify_private_authwit` function which validates that the call is authenticated.
+The `on_behalf_of` should assert that we are indeed authenticated and then return the `IS_VALID` selector. If the return value is not as expected, we throw an error. This is to cover the case where the `on_behalf_of` might implemented some function with the same selector as the `verify_private_authwit` that could be used to authenticate unintentionally.
 
 #### Example
 

docs/docs/guides/smart_contracts/writing_contracts/common_patterns/index.md

@@ -31,7 +31,7 @@ E.g. you don't want a user to subscribe once they have subscribed already. Or yo
 
 Emit a nullifier in your function. By adding this nullifier into the tree, you prevent another nullifier from being added again. This is also why in authwit, we emit a nullifier, to prevent someone from reusing their approval.
 
-#include_code spend_private_authwit /noir-projects/aztec-nr/authwit/src/account.nr rust
+#include_code verify_private_authwit /noir-projects/aztec-nr/authwit/src/account.nr rust
 
 Note be careful to ensure that the nullifier is not deterministic and that no one could do a preimage analysis attack. More in [the anti pattern section on deterministic nullifiers](#deterministic-nullifiers)
 

docs/docs/migration_notes.md

@@ -9,11 +9,11 @@ Aztec is in full-speed development. Literally every version breaks compatibility
 ## TBD
 
 ### [Aztec.nr] changes to `NoteInterface`
+
 `compute_nullifier` function was renamed to `compute_note_hash_and_nullifier` and now the function has to return not only the nullifier but also the note hash used to compute the nullifier.
 The same change was done to `compute_nullifier_without_context` function.
 These changes were done because having the note hash exposed allowed us to not having to re-compute it again in `destroy_note` function of Aztec.nr which led to significant decrease in gate counts (see the [optimization PR](https://github.com/AztecProtocol/aztec-packages/pull/7103) for more details).
 
-
 ```diff
 - impl NoteInterface<VALUE_NOTE_LEN, VALUE_NOTE_BYTES_LEN> for ValueNote {
 -    fn compute_nullifier(self, context: &mut PrivateContext) -> Field {
@@ -89,10 +89,46 @@ To further reduce gate count, you can iterate over `options.limit` instead of `m
 + for i in 0..options.limit {
 ```
 
+### [Aztec.nr] static private authwit
+
+The private authwit validation is now making a static call to the account contract instead of passing over control flow. This is to ensure that it cannot be used for re-entry.
+
+To make this change however, we cannot allow emitting a nullifier from the account contract, since that would break the static call. Instead, we will be changing the `spend_private_authwit` to a `verify_private_authwit` and in the `auth` library emit the nullifier. This means that the "calling" contract will now be emitting the nullifier, and not the account. For example, for a token contract, the nullifier is now emitted by the token contract. However, as this is done inside the `auth` library, the token contract doesn't need to change much.
+
+The biggest difference is related to "cancelling" an authwit. Since it is no longer in the account contract, you cannot just emit a nullifier from it anymore. Instead it must rely on the token contract providing functionality for cancelling.
+
+There are also a few general changes to how authwits are generated, namely to more easily support the data required for a validity lookup now. Previously we could lookup the `message_hash` directly at the account contract, now we instead need to use the `inner_hash` and the contract of the consumer to figure out if it have already been emitted.
+
+A minor extension have been made to the authwit creations to make it easier to sign a specific a hash with a specific caller, e.g., the `inner_hash` can be provided as `{consumer, inner_hash}` to the `createAuthWit` where it previously needed to do a couple of manual steps to compute the outer hash. The `computeOuterAuthWitHash` have been amde internal and the `computeAuthWitMessageHash` can instead be used to compute the values similarly to other authwit computations.
+
+```diff
+const innerHash = computeInnerAuthWitHash([Fr.ZERO, functionSelector.toField(), entrypointPackedArgs.hash]);
+-const outerHash = computeOuterAuthWitHash(
+-    this.dappEntrypointAddress,
+-    new Fr(this.chainId),
+-    new Fr(this.version),
+-    innerHash,
+-);
++const outerHash = computeAuthWitMessageHash(
++    { consumer: this.dappEntrypointAddress, innerHash },
++    { chainId: new Fr(this.chainId), version: new Fr(this.version) },
++);
+```
+
+If the wallet is used to compute the authwit, it will populate the chain id and version instead of requiring it to be provided by tha actor.
+
+```diff
+const innerHash = computeInnerAuthWitHash([Fr.fromString('0xdead')]);
+-const outerHash = computeOuterAuthWitHash(wallets[1].getAddress(), chainId, version, innerHash);
+-const witness = await wallets[0].createAuthWit(outerHash);
++ const witness = await wallets[0].createAuthWit({ comsumer: accounts[1].address, inner_hash });
+```
+
 ## 0.43.0
 
 ### [Aztec.nr] break `token.transfer()` into `transfer` and `transferFrom`
-Earlier we had just one function - `transfer()` which used authwits to handle the case where a contract/user wants to transfer funds on behalf of another user. 
+
+Earlier we had just one function - `transfer()` which used authwits to handle the case where a contract/user wants to transfer funds on behalf of another user.
 To reduce circuit sizes and proof times, we are breaking up `transfer` and introducing a dedicated `transferFrom()` function like in the ERC20 standard.
 
 ### [Aztec.nr] `options.limit` has to be constant
@@ -909,9 +945,9 @@ After:
 
 ```rust
 #[aztec(private)]
-fn spend_private_authwit(inner_hash: Field) -> Field {
+fn verify_private_authwit(inner_hash: Field) -> Field {
     let actions = AccountActions::private(&mut context, ACCOUNT_ACTIONS_STORAGE_SLOT, is_valid_impl);
-    actions.spend_private_authwit(inner_hash)
+    actions.verify_private_authwit(inner_hash)
 }
 
 #[aztec(public)]

noir-projects/aztec-nr/authwit/src/account.nr

@@ -31,8 +31,8 @@ impl AccountActions<&mut PrivateContext> {
     }
     // docs:end:entrypoint
 
-    // docs:start:spend_private_authwit
-    pub fn spend_private_authwit(self, inner_hash: Field) -> Field {
+    // docs:start:verify_private_authwit
+    pub fn verify_private_authwit(self, inner_hash: Field) -> Field {
         // The `inner_hash` is "siloed" with the `msg_sender` to ensure that only it can 
         // consume the message.
         // This ensures that contracts cannot consume messages that are not intended for them.
@@ -44,8 +44,7 @@ impl AccountActions<&mut PrivateContext> {
         );
         let valid_fn = self.is_valid_impl;
         assert(valid_fn(self.context, message_hash) == true, "Message not authorized by account");
-        self.context.push_new_nullifier(message_hash, 0);
         IS_VALID_SELECTOR
     }
-    // docs:end:spend_private_authwit
+    // docs:end:verify_private_authwit
 }

noir-projects/aztec-nr/authwit/src/auth.nr

@@ -1,6 +1,9 @@
 use dep::aztec::protocol_types::{
     abis::function_selector::FunctionSelector, address::AztecAddress,
-    constants::{GENERATOR_INDEX__AUTHWIT_INNER, GENERATOR_INDEX__AUTHWIT_OUTER, CANONICAL_AUTH_REGISTRY_ADDRESS},
+    constants::{
+    GENERATOR_INDEX__AUTHWIT_INNER, GENERATOR_INDEX__AUTHWIT_OUTER, GENERATOR_INDEX__AUTHWIT_NULLIFIER,
+    CANONICAL_AUTH_REGISTRY_ADDRESS
+},
     hash::pedersen_hash
 };
 use dep::aztec::{prelude::Deserialize, context::{PrivateContext, PublicContext, gas::GasOpts}, hash::hash_args_array};
@@ -10,20 +13,36 @@ global IS_VALID_SELECTOR = 0xabf64ad4; // 4 first bytes of keccak256("IS_VALID()
 // docs:start:assert_current_call_valid_authwit
 // Assert that `on_behalf_of` have authorized the current call with a valid authentication witness
 pub fn assert_current_call_valid_authwit(context: &mut PrivateContext, on_behalf_of: AztecAddress) {
-    let function_selector = FunctionSelector::from_signature("spend_private_authwit(Field)");
     let inner_hash = compute_inner_authwit_hash([context.msg_sender().to_field(), context.selector().to_field(), context.args_hash]);
-    let result: Field = context.call_private_function(on_behalf_of, function_selector, [inner_hash]).unpack_into();
-    assert(result == IS_VALID_SELECTOR, "Message not authorized by account");
+    assert_inner_hash_valid_authwit(context, on_behalf_of, inner_hash);
 }
 // docs:end:assert_current_call_valid_authwit
 
+pub fn assert_inner_hash_valid_authwit(context: &mut PrivateContext, on_behalf_of: AztecAddress, inner_hash: Field) {
+    // We perform a static call here and not a standard one to ensure that the account contract cannot re-enter.
+    let result: Field = context.static_call_private_function(
+        on_behalf_of,
+        FunctionSelector::from_signature("verify_private_authwit(Field)"),
+        [inner_hash]
+    ).unpack_into();
+    assert(result == IS_VALID_SELECTOR, "Message not authorized by account");
+    // Compute the nullifier, similar computation to the outer hash, but without the chain_id and version.
+    // Those should already be handled in the verification, so we just need something to nullify, that allow same inner_hash for multiple actors.
+    let nullifier = compute_authwit_nullifier(on_behalf_of, inner_hash);
+    context.push_new_nullifier(nullifier, 0);
+}
+
 // docs:start:assert_current_call_valid_authwit_public
 // Assert that `on_behalf_of` have authorized the current call in a public context
 pub fn assert_current_call_valid_authwit_public(context: &mut PublicContext, on_behalf_of: AztecAddress) {
     let inner_hash = compute_inner_authwit_hash(
         [(*context).msg_sender().to_field(), (*context).selector().to_field(), (*context).get_args_hash()]
     );
+    assert_inner_hash_valid_authwit_public(context, on_behalf_of, inner_hash);
+}
+// docs:end:assert_current_call_valid_authwit_public
 
+pub fn assert_inner_hash_valid_authwit_public(context: &mut PublicContext, on_behalf_of: AztecAddress, inner_hash: Field) {
     let result: Field = context.call_public_function(
         AztecAddress::from_field(CANONICAL_AUTH_REGISTRY_ADDRESS),
         FunctionSelector::from_signature("consume((Field),Field)"),
@@ -32,7 +51,6 @@ pub fn assert_current_call_valid_authwit_public(context: &mut PublicContext, on_
     ).deserialize_into();
     assert(result == IS_VALID_SELECTOR, "Message not authorized by account");
 }
-// docs:end:assert_current_call_valid_authwit_public
 
 // docs:start:compute_call_authwit_hash
 // Compute the message hash to be used by an authentication witness 
@@ -54,6 +72,13 @@ pub fn compute_inner_authwit_hash<N>(args: [Field; N]) -> Field {
     pedersen_hash(args, GENERATOR_INDEX__AUTHWIT_INNER)
 }
 
+pub fn compute_authwit_nullifier(on_behalf_of: AztecAddress, inner_hash: Field) -> Field {
+    pedersen_hash(
+        [on_behalf_of.to_field(), inner_hash],
+        GENERATOR_INDEX__AUTHWIT_NULLIFIER
+    )
+}
+
 pub fn compute_outer_authwit_hash(
     consumer: AztecAddress,
     chain_id: Field,

noir-projects/aztec-nr/aztec/src/context/unconstrained_context.nr

@@ -2,7 +2,9 @@ use dep::protocol_types::address::AztecAddress;
 
 struct UnconstrainedContext {
     block_number: u32,
-    contract_address: AztecAddress,    
+    contract_address: AztecAddress,
+    version: Field,
+    chain_id: Field,
 }
 
 impl UnconstrainedContext {
@@ -13,7 +15,9 @@ impl UnconstrainedContext {
         // available.
         let block_number = block_number_oracle();
         let contract_address = contract_address_oracle();
-        Self { block_number, contract_address }
+        let chain_id = chain_id_oracle();
+        let version = version_oracle();
+        Self { block_number, contract_address, version, chain_id }
     }
 
     fn block_number(self) -> u32 {
@@ -23,10 +27,24 @@ impl UnconstrainedContext {
     fn this_address(self) -> AztecAddress {
         self.contract_address
     }
+
+    fn version(self) -> Field {
+        self.version
+    }
+
+    fn chain_id(self) -> Field {
+        self.chain_id
+    }
 }
 
 #[oracle(getContractAddress)]
 unconstrained fn contract_address_oracle() -> AztecAddress {}
 
 #[oracle(getBlockNumber)]
 unconstrained fn block_number_oracle() -> u32 {}
+
+#[oracle(getChainId)]
+unconstrained fn chain_id_oracle() -> Field {}
+
+#[oracle(getVersion)]
+unconstrained fn version_oracle() -> Field {}

noir-projects/aztec-nr/aztec/src/encrypted_logs/header.nr

@@ -44,7 +44,7 @@ fn test_encrypted_log_header() {
     let ciphertext = header.compute_ciphertext(secret, point);
 
     let expected_header_ciphertext = [
-        131, 119, 105, 129, 244, 32, 151, 205, 12, 99, 93, 62, 10, 180, 72, 21, 179, 36, 250, 95, 56, 167, 171, 16, 195, 164, 223, 57, 75, 5, 24, 119, 198, 34, 99, 189, 193, 183, 227, 43, 79, 204, 214, 89, 221, 153, 246, 64
+        228, 9, 65, 81, 62, 59, 249, 207, 90, 196, 206, 72, 39, 199, 82, 196, 23, 131, 32, 226, 26, 176, 43, 39, 239, 177, 177, 192, 85, 216, 17, 15, 18, 187, 35, 225, 135, 192, 63, 88, 29, 173, 232, 46, 72, 82, 187, 139
     ];
 
     assert_eq(ciphertext, expected_header_ciphertext);

noir-projects/aztec-nr/aztec/src/encrypted_logs/incoming_body.nr

@@ -131,7 +131,7 @@ mod test {
         let ciphertext = body.compute_ciphertext(eph_sk, ivpk_app);
 
         let expected_note_body_ciphertext = [
-            131, 119, 105, 129, 244, 32, 151, 205, 12, 99, 93, 62, 10, 180, 72, 21, 47, 232, 95, 17, 240, 230, 80, 129, 174, 158, 23, 76, 114, 185, 43, 18, 254, 148, 147, 230, 66, 216, 167, 62, 180, 213, 238, 33, 108, 29, 84, 139, 99, 206, 212, 253, 92, 116, 137, 31, 0, 104, 45, 91, 250, 109, 141, 114, 189, 53, 35, 60, 108, 156, 170, 206, 150, 114, 150, 187, 198, 13, 62, 153, 133, 13, 169, 167, 242, 221, 40, 168, 186, 203, 104, 82, 47, 238, 142, 179, 90, 37, 9, 70, 245, 176, 122, 247, 42, 87, 75, 7, 20, 89, 166, 123, 14, 26, 230, 156, 49, 94, 0, 94, 72, 58, 171, 239, 115, 174, 155, 7, 151, 17, 60, 206, 193, 134, 70, 87, 215, 88, 21, 194, 63, 26, 106, 105, 124, 213, 252, 152, 192, 71, 115, 13, 181, 5, 169, 15, 170, 196, 174, 228, 170, 192, 91, 76, 110, 220, 89, 47, 248, 144, 189, 251, 167, 149, 248, 226
+            228, 9, 65, 81, 62, 59, 249, 207, 90, 196, 206, 72, 39, 199, 82, 196, 63, 127, 188, 251, 150, 188, 238, 205, 3, 86, 102, 164, 175, 12, 137, 158, 163, 111, 205, 10, 229, 230, 46, 202, 110, 107, 156, 180, 67, 192, 161, 201, 48, 153, 169, 1, 25, 182, 93, 39, 39, 207, 251, 218, 234, 147, 156, 13, 110, 180, 190, 199, 41, 6, 211, 203, 176, 110, 165, 186, 110, 127, 199, 22, 201, 149, 92, 249, 219, 68, 145, 68, 179, 29, 233, 34, 98, 123, 197, 234, 169, 53, 44, 14, 81, 60, 92, 27, 250, 134, 49, 248, 57, 119, 236, 118, 158, 104, 82, 243, 98, 164, 60, 72, 74, 27, 177, 194, 221, 225, 193, 150, 67, 235, 205, 106, 150, 24, 126, 186, 220, 178, 199, 189, 113, 54, 181, 55, 46, 15, 236, 236, 9, 159, 5, 172, 237, 154, 110, 50, 241, 64, 92, 13, 37, 53, 20, 140, 42, 146, 229, 63, 97, 25, 159, 63, 235, 104, 68, 100
         ];
 
         assert_eq(expected_note_body_ciphertext.len(), ciphertext.len());
@@ -206,7 +206,7 @@ mod test {
         let ciphertext = body.compute_ciphertext(eph_sk, ivpk_app);
 
         let expected_event_body_ciphertext = [
-            131, 119, 105, 129, 244, 32, 151, 205, 12, 99, 93, 62, 10, 180, 72, 21, 47, 232, 95, 17, 240, 230, 80, 129, 174, 158, 23, 76, 114, 185, 43, 18, 254, 148, 147, 230, 66, 216, 167, 62, 180, 213, 238, 33, 108, 29, 84, 139, 157, 165, 187, 138, 35, 3, 236, 75, 197, 105, 102, 247, 224, 253, 13, 217, 145, 62, 96, 167, 93, 23, 18, 198, 187, 91, 8, 3, 197, 195, 127, 9, 218, 111, 125, 97, 141, 129, 142, 1, 230, 108, 35, 211, 170, 170, 170, 249, 249, 104, 68, 191, 245, 207, 182, 245, 248, 82, 175, 83, 155, 138, 208, 65, 31, 129, 251, 242, 219, 76, 17, 61, 178, 187, 108, 114, 177, 215, 175, 189, 166, 221, 94, 9, 22, 57, 151, 204, 57, 220, 129, 243, 217, 18, 101, 128, 229, 40, 254, 175, 2, 21, 31, 198, 18, 152, 169, 32, 113, 92, 37, 65, 169, 119, 95, 149, 239, 8, 23, 182, 22, 209, 207, 120, 133, 90, 252, 106
+            228, 9, 65, 81, 62, 59, 249, 207, 90, 196, 206, 72, 39, 199, 82, 196, 63, 127, 188, 251, 150, 188, 238, 205, 3, 86, 102, 164, 175, 12, 137, 158, 163, 111, 205, 10, 229, 230, 46, 202, 110, 107, 156, 180, 67, 192, 161, 201, 66, 122, 29, 35, 42, 33, 153, 216, 199, 208, 103, 207, 126, 153, 189, 136, 19, 220, 238, 15, 169, 29, 255, 11, 123, 107, 70, 192, 53, 40, 36, 93, 187, 32, 123, 136, 104, 23, 229, 245, 152, 90, 84, 2, 136, 112, 42, 27, 82, 214, 104, 14, 250, 48, 199, 245, 88, 22, 200, 77, 38, 51, 127, 56, 138, 255, 16, 46, 179, 129, 215, 185, 185, 116, 148, 16, 133, 62, 56, 180, 10, 132, 109, 77, 206, 199, 21, 167, 7, 163, 171, 158, 244, 23, 18, 121, 108, 42, 107, 7, 48, 84, 212, 104, 39, 16, 109, 7, 108, 129, 60, 80, 112, 241, 223, 140, 186, 158, 38, 74, 230, 213, 159, 175, 142, 228, 128, 160
         ];
 
         assert_eq(expected_event_body_ciphertext.len(), ciphertext.len());

noir-projects/aztec-nr/aztec/src/encrypted_logs/outgoing_body.nr

@@ -99,7 +99,7 @@ mod test {
         let ciphertext = body.compute_ciphertext(sender_ovsk_app, eph_pk);
 
         let expected_outgoing_body_ciphertext = [
-            126, 10, 214, 39, 130, 143, 96, 143, 79, 143, 22, 36, 55, 41, 234, 255, 226, 26, 138, 236, 91, 188, 204, 216, 172, 133, 134, 69, 161, 237, 134, 5, 75, 192, 10, 6, 229, 54, 194, 56, 103, 243, 57, 248, 147, 237, 4, 3, 39, 28, 226, 30, 237, 228, 212, 115, 246, 244, 105, 39, 129, 119, 126, 207, 176, 14, 75, 134, 241, 23, 2, 187, 239, 86, 47, 56, 239, 20, 92, 176, 70, 12, 219, 226, 150, 70, 192, 43, 125, 53, 230, 153, 135, 228, 210, 197, 76, 123, 185, 190, 61, 172, 29, 168, 241, 191, 205, 71, 136, 72, 52, 115, 232, 246, 87, 42, 50, 150, 134, 108, 225, 90, 191, 191, 182, 150, 124, 147, 78, 249, 144, 111, 122, 187, 187, 5, 249, 167, 186, 14, 228, 128, 158, 138, 55, 99, 228, 46, 219, 187, 248, 122, 70, 31, 39, 209, 127, 23, 244, 84, 14, 93, 86, 208, 155, 151, 238, 70, 63, 3, 137, 59, 206, 230, 4, 20
+            127, 84, 96, 176, 101, 107, 236, 57, 68, 8, 53, 202, 138, 74, 186, 54, 74, 193, 245, 7, 109, 59, 218, 33, 1, 31, 205, 225, 241, 209, 64, 222, 94, 245, 4, 150, 47, 241, 187, 64, 152, 20, 102, 158, 200, 217, 213, 82, 1, 240, 170, 185, 51, 80, 27, 109, 63, 231, 235, 120, 174, 44, 133, 248, 10, 97, 60, 40, 222, 190, 147, 76, 187, 48, 91, 206, 48, 106, 56, 118, 38, 127, 82, 4, 182, 188, 44, 224, 31, 129, 47, 107, 134, 252, 20, 25, 122, 191, 158, 69, 35, 255, 215, 171, 196, 45, 91, 184, 83, 80, 238, 201, 1, 233, 235, 159, 171, 130, 158, 64, 176, 165, 132, 30, 84, 81, 71, 195, 145, 47, 82, 247, 210, 192, 23, 4, 220, 90, 56, 109, 46, 105, 79, 251, 165, 141, 185, 233, 191, 118, 219, 153, 191, 162, 99, 238, 241, 249, 9, 74, 210, 241, 54, 28, 126, 226, 85, 235, 174, 75, 239, 207, 100, 184, 248, 194
         ];
 
         for i in 0..expected_outgoing_body_ciphertext.len() {