feat: grpc-web add CORS handler (#9493)

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## Description

Closes: #9467 

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---

### Author Checklist

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- [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
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- [ ] 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

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- [ ] 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 
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- [ ] manually tested (if applicable)

CHANGELOG.md

@@ -131,6 +131,7 @@ if input key is empty, or input data contains empty key.
 
 ### Improvements
 
+* (gRPC-Web) [\#9493](https://github.com/cosmos/cosmos-sdk/pull/9493) Add `EnableUnsafeCORS` flag to grpc-web config.
 * (store) [\#9403](https://github.com/cosmos/cosmos-sdk/pull/9403) Add `RefundGas` function to `GasMeter` interface
 * (baseapp, types) [\#9390](https://github.com/cosmos/cosmos-sdk/pull/9390) Add current block header hash to `Context`
 * (x/staking) [\#9423](https://github.com/cosmos/cosmos-sdk/pull/9423) Staking delegations now returns empty list instead of rpc error when no records found.

server/config/config.go

@@ -140,6 +140,9 @@ type GRPCWebConfig struct {
 
 	// Address defines the gRPC-web server to listen on
 	Address string `mapstructure:"address"`
+
+	// EnableUnsafeCORS defines if CORS should be enabled (unsafe - use it at your own risk)
+	EnableUnsafeCORS bool `mapstructure:"enable-unsafe-cors"`
 }
 
 // StateSyncConfig defines the state sync snapshot configuration.
@@ -297,8 +300,9 @@ func GetConfig(v *viper.Viper) Config {
 			Address: v.GetString("grpc.address"),
 		},
 		GRPCWeb: GRPCWebConfig{
-			Enable:  v.GetBool("grpc-web.enable"),
-			Address: v.GetString("grpc-web.address"),
+			Enable:           v.GetBool("grpc-web.enable"),
+			Address:          v.GetString("grpc-web.address"),
+			EnableUnsafeCORS: v.GetBool("grpc-web.enable-unsafe-cors"),
 		},
 		StateSync: StateSyncConfig{
 			SnapshotInterval:   v.GetUint64("state-sync.snapshot-interval"),

server/config/toml.go

@@ -184,6 +184,9 @@ enable = {{ .GRPCWeb.Enable }}
 # Address defines the gRPC-web server address to bind to.
 address = "{{ .GRPCWeb.Address }}"
 
+# EnableUnsafeCORS defines if CORS should be enabled (unsafe - use it at your own risk).
+enable-unsafe-cors = {{ .GRPCWeb.EnableUnsafeCORS }}
+
 ###############################################################################
 ###                        State Sync Configuration                         ###
 ###############################################################################

server/grpc/grpc_web.go

@@ -11,7 +11,16 @@ import (
 
 // StartGRPCWeb starts a gRPC-Web server on the given address.
 func StartGRPCWeb(grpcSrv *grpc.Server, config config.Config) (*http.Server, error) {
-	wrappedServer := grpcweb.WrapServer(grpcSrv)
+	var options []grpcweb.Option
+	if config.GRPCWeb.EnableUnsafeCORS {
+		options = append(options,
+			grpcweb.WithOriginFunc(func(origin string) bool {
+				return true
+			}),
+		)
+	}
+
+	wrappedServer := grpcweb.WrapServer(grpcSrv, options...)
 	handler := func(resp http.ResponseWriter, req *http.Request) {
 		wrappedServer.ServeHTTP(resp, req)
 	}