R4R: Support adding offline pubkeys to gaiacli keys

PENDING.md

@@ -51,6 +51,8 @@ IMPROVEMENTS
 * Gaia REST API (`gaiacli advanced rest-server`)
 
 * Gaia CLI  (`gaiacli`)
+  *[\#3203](https://github.com/cosmos/cosmos-sdk/pull/3202) Support adding offline public keys to the keystore
+
 
 * Gaia
   * [\#3158](https://github.com/cosmos/cosmos-sdk/pull/3158) Validate slashing genesis

client/keys/add.go

@@ -7,7 +7,6 @@ import (
 	"net/http"
 	"os"
 
-	"github.com/cosmos/go-bip39"
 	"github.com/gorilla/mux"
 	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
@@ -18,9 +17,11 @@ import (
 	ccrypto "github.com/cosmos/cosmos-sdk/crypto"
 	"github.com/cosmos/cosmos-sdk/crypto/keys"
 	"github.com/cosmos/cosmos-sdk/crypto/keys/hd"
+	sdk "github.com/cosmos/cosmos-sdk/types"
 )
 
 const (
+	flagPublicKey   = "pubkey"
 	flagInteractive = "interactive"
 	flagBIP44Path   = "bip44-path"
 	flagRecover     = "recover"
@@ -36,16 +37,18 @@ func addKeyCommand() *cobra.Command {
 		Short: "Add an encrypted private key (either newly generated or recovered), encrypt it, and save to disk",
 		Long: `Derive a new private key and encrypt to disk.
 Optionally specify a BIP39 mnemonic, a BIP39 passphrase to further secure the mnemonic,
-and a bip32 HD path to derive a specific account. The key will be stored under the given name 
+and a bip32 HD path to derive a specific account. The key will be stored under the given name
 and encrypted with the given password. The only input that is required is the encryption password.
 
 If run with -i, it will prompt the user for BIP44 path, BIP39 mnemonic, and passphrase.
 The flag --recover allows one to recover a key from a seed passphrase.
 If run with --dry-run, a key would be generated (or recovered) but not stored to the local keystore.
+Use the --pubkey flag to add arbitrary public keys to the keystore for constructing multisig transactions
 `,
 		Args: cobra.ExactArgs(1),
 		RunE: runAddCmd,
 	}
+	cmd.Flags().String(FlagPublicKey, "", "Store only a public key (useful for constructing multisigs e.g.  cosmospub1...)")
 	cmd.Flags().BoolP(flagInteractive, "i", false, "Interactively prompt user for BIP39 passphrase and mnemonic")
 	cmd.Flags().Bool(client.FlagUseLedger, false, "Store a local reference to a private key on a Ledger device")
 	cmd.Flags().String(flagBIP44Path, "44'/118'/0'/0/0", "BIP44 path from which to derive a private key")
@@ -73,6 +76,9 @@ func runAddCmd(cmd *cobra.Command, args []string) error {
 
 	buf := client.BufferStdin()
 	name := args[0]
+
+	interactive := viper.GetBool(flagInteractive)
+
 	if viper.GetBool(flagDryRun) {
 		// we throw this away, so don't enforce args,
 		// we want to get a new random seed phrase quickly
@@ -94,7 +100,7 @@ func runAddCmd(cmd *cobra.Command, args []string) error {
 		}
 
 		// ask for a password when generating a local key
-		if !viper.GetBool(client.FlagUseLedger) {
+		if viper.GetString(flagPublicKey) == "" && !viper.GetBool(client.FlagUseLedger) {
 			encryptPassword, err = client.GetCheckPassword(
 				"Enter a passphrase to encrypt your key to disk:",
 				"Repeat the passphrase:", buf)
@@ -104,10 +110,16 @@ func runAddCmd(cmd *cobra.Command, args []string) error {
 		}
 	}
 
-	interactive := viper.GetBool(flagInteractive)
-	flags := cmd.Flags()
-	bipFlag := flags.Lookup(flagBIP44Path)
+	if viper.GetString(flagPublicKey) != "" {
+		pk, err := sdk.GetAccPubKeyBech32(viper.GetString(flagPublicKey))
+		if err != nil {
+			return err
+		}
+		kb.CreateOffline(name, pk)
+		return nil
+	}
 
+	bipFlag := cmd.Flags().Lookup(flagBIP44Path)
 	bip44Params, err := getBIP44ParamsAndPath(bipFlag.Value.String(), bipFlag.Changed || !interactive)
 	if err != nil {
 		return err