chore: Tx Tips API audit (#11641)

## Description

ref: https://github.com/cosmos/cosmos-sdk/issues/11087



---

### Author Checklist

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please add links to any relevant follow up issues.*

I have...

- [x] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] added `!` to the type prefix if API or client breaking change
- [x] targeted the correct branch (see [PR Targeting](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#pr-targeting))
- [x] provided a link to the relevant issue or specification
- [ ] followed the guidelines for [building modules](https://github.com/cosmos/cosmos-sdk/blob/master/docs/building-modules)
- [ ] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#testing)
- [ ] added a changelog entry to `CHANGELOG.md`
- [ ] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [ ] updated the relevant documentation or specification
- [ ] reviewed "Files changed" and left comments if necessary
- [ ] confirmed all CI checks have passed

### Reviewers Checklist

*All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.*

I have...

- [ ] confirmed the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] confirmed `!` in the type prefix if API or client breaking change
- [ ] confirmed all author checklist items have been addressed 
- [ ] reviewed state machine logic
- [ ] reviewed API design and naming
- [ ] reviewed documentation is accurate
- [ ] reviewed tests and test coverage
- [ ] manually tested (if applicable)

api/cosmos/tx/signing/v1beta1/signing.pulsar.go

@@ -2738,7 +2738,13 @@ const (
 	// SIGN_MODE_EIP_191 specifies the sign mode for EIP 191 signing on the Cosmos
 	// SDK. Ref: https://eips.ethereum.org/EIPS/eip-191
 	//
-	// Since: cosmos-sdk 0.45
+	// Currently, SIGN_MODE_EIP_191 is registered as a SignMode enum variant,
+	// but is not implemented on the SDK by default. To enable EIP-191, you need
+	// to pass a custom `TxConfig` that has an implementation of
+	// `SignModeHandler` for EIP-191. The SDK may decide to fully support
+	// EIP-191 in the future.
+	//
+	// Since: cosmos-sdk 0.45.2
 	SignMode_SIGN_MODE_EIP_191 SignMode = 191
 )
 

api/cosmos/tx/v1beta1/tx.pulsar.go

@@ -8814,11 +8814,11 @@ type AuxSignerData struct {
 	// AuxSignerData across different chains, the bech32 prefix of the target
 	// chain (where the final transaction is broadcasted) should be used.
 	Address string `protobuf:"bytes,1,opt,name=address,proto3" json:"address,omitempty"`
-	// sign_doc is the SIGN_MOD_DIRECT_AUX sign doc that the auxiliary signer
+	// sign_doc is the SIGN_MODE_DIRECT_AUX sign doc that the auxiliary signer
 	// signs. Note: we use the same sign doc even if we're signing with
 	// LEGACY_AMINO_JSON.
 	SignDoc *SignDocDirectAux `protobuf:"bytes,2,opt,name=sign_doc,json=signDoc,proto3" json:"sign_doc,omitempty"`
-	// mode is the signing mode of the single signer
+	// mode is the signing mode of the single signer.
 	Mode v1beta1.SignMode `protobuf:"varint,3,opt,name=mode,proto3,enum=cosmos.tx.signing.v1beta1.SignMode" json:"mode,omitempty"`
 	// sig is the signature of the sign doc.
 	Sig []byte `protobuf:"bytes,4,opt,name=sig,proto3" json:"sig,omitempty"`

client/tx/aux_builder.go

@@ -121,14 +121,14 @@ func (b *AuxTxBuilder) SetSignMode(mode signing.SignMode) error {
 	return nil
 }
 
-// SetTip sets an optional tip.
+// SetTip sets an optional tip in the AuxSignerData.
 func (b *AuxTxBuilder) SetTip(tip *tx.Tip) {
 	b.checkEmptyFields()
 
 	b.auxSignerData.SignDoc.Tip = tip
 }
 
-// SetSignature sets the aux signer's signature.
+// SetSignature sets the aux signer's signature in the AuxSignerData.
 func (b *AuxTxBuilder) SetSignature(sig []byte) {
 	b.checkEmptyFields()
 

docs/core/tips.md

@@ -66,7 +66,7 @@ As we mentioned in the flow above, the tipper signs over the `SignDocDirectAux`,
 - The tipper MUST use `SIGN_MODE_DIRECT_AUX` or `SIGN_MODE_LEGACY_AMINO_JSON`. That is because the tipper needs to sign over the body, the tip, but not the other signers' information and not over the fee (which is unknown to the tipper).
 - The fee payer MUST use `SIGN_MODE_DIRECT` or `SIGN_MODE_LEGACY_AMINO_JSON`. The fee payer signs over the whole transaction.
 
-For example, if the fee payers signs the whole transaction with `SIGN_MODE_DIRECT_AUX`, it will be rejected by the node, as that would introduce malleability issues (`SIGN_MODE_DIRECT_AUX` doesn't sign over fees).
+For example, if the fee payer signs the whole transaction with `SIGN_MODE_DIRECT_AUX`, it will be rejected by the node, as that would introduce malleability issues (`SIGN_MODE_DIRECT_AUX` doesn't sign over fees).
 
 In both cases, using `SIGN_MODE_LEGACY_AMINO_JSON` is recommended only if hardware wallet signing is needed.
 
@@ -98,7 +98,7 @@ If you are using the Cosmos SDK's default middleware stack `NewDefaultTxHandler(
 
 The Cosmos SDK also provides some CLI tooling for the transaction tips flow, both for the tipper and for the feepayer.
 
-For the tipper, the CLI `tx` subcommand has two new flags: `--aux` and `--tip`. The `--aux` flag is used to denote that we are creating a `AuxSignerData` instead of a , and the `--tip` is used to populate its `Tip` field.
+For the tipper, the CLI `tx` subcommand has two new flags: `--aux` and `--tip`. The `--aux` flag is used to denote that we are creating an `AuxSignerData` instead of a `Tx`, and the `--tip` is used to populate its `Tip` field.
 
 ```bash
 $ simd tx gov vote 16 yes --from <tipper_address> --aux --tip 50ibcdenom
@@ -110,7 +110,7 @@ $ simd tx gov vote 16 yes --from <tipper_address> --aux --tip 50ibcdenom
 
 It is useful to pipe the JSON output to a file, `> aux_signed_tx.json`
 
-For the fee payer, the Cosmos SDK added a `tx aux-to-fee` subcommand to include a `AuxSignerData` into a transaction, add fees to it, and broadcast it.
+For the fee payer, the Cosmos SDK added a `tx aux-to-fee` subcommand to include an `AuxSignerData` into a transaction, add fees to it, and broadcast it.
 
 ```bash
 $ simd tx aux-to-fee aux_signed_tx.json --from <fee_payer_address> --fees 30atom

proto/cosmos/tx/v1beta1/tx.proto

@@ -238,11 +238,11 @@ message AuxSignerData {
   // AuxSignerData across different chains, the bech32 prefix of the target
   // chain (where the final transaction is broadcasted) should be used.
   string address = 1 [(cosmos_proto.scalar) = "cosmos.AddressString"];
-  // sign_doc is the SIGN_MOD_DIRECT_AUX sign doc that the auxiliary signer
+  // sign_doc is the SIGN_MODE_DIRECT_AUX sign doc that the auxiliary signer
   // signs. Note: we use the same sign doc even if we're signing with
   // LEGACY_AMINO_JSON.
   SignDocDirectAux sign_doc = 2;
-  // mode is the signing mode of the single signer
+  // mode is the signing mode of the single signer.
   cosmos.tx.signing.v1beta1.SignMode mode = 3;
   // sig is the signature of the sign doc.
   bytes sig = 4;

types/tx/signing/signing.pb.go

@@ -58,7 +58,13 @@ const (
 	// SIGN_MODE_EIP_191 specifies the sign mode for EIP 191 signing on the Cosmos
 	// SDK. Ref: https://eips.ethereum.org/EIPS/eip-191
 	//
-	// Since: cosmos-sdk 0.45
+	// Currently, SIGN_MODE_EIP_191 is registered as a SignMode enum variant,
+	// but is not implemented on the SDK by default. To enable EIP-191, you need
+	// to pass a custom `TxConfig` that has an implementation of
+	// `SignModeHandler` for EIP-191. The SDK may decide to fully support
+	// EIP-191 in the future.
+	//
+	// Since: cosmos-sdk 0.45.2
 	SignMode_SIGN_MODE_EIP_191 SignMode = 191
 )
 

types/tx/tx.pb.go

@@ -922,11 +922,11 @@ type AuxSignerData struct {
 	// AuxSignerData across different chains, the bech32 prefix of the target
 	// chain (where the final transaction is broadcasted) should be used.
 	Address string `protobuf:"bytes,1,opt,name=address,proto3" json:"address,omitempty"`
-	// sign_doc is the SIGN_MOD_DIRECT_AUX sign doc that the auxiliary signer
+	// sign_doc is the SIGN_MODE_DIRECT_AUX sign doc that the auxiliary signer
 	// signs. Note: we use the same sign doc even if we're signing with
 	// LEGACY_AMINO_JSON.
 	SignDoc *SignDocDirectAux `protobuf:"bytes,2,opt,name=sign_doc,json=signDoc,proto3" json:"sign_doc,omitempty"`
-	// mode is the signing mode of the single signer
+	// mode is the signing mode of the single signer.
 	Mode signing.SignMode `protobuf:"varint,3,opt,name=mode,proto3,enum=cosmos.tx.signing.v1beta1.SignMode" json:"mode,omitempty"`
 	// sig is the signature of the sign doc.
 	Sig []byte `protobuf:"bytes,4,opt,name=sig,proto3" json:"sig,omitempty"`