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docs: update go account management page (#25189)

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* update go accounts page

* refine draft

* apply suggestions from code review

rewords description of key encryption and adds links to Scrypt docs. Adds warning that best practise is to use Clef.
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  1. 271
      docs/_dapp/native-accounts.md

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@ -3,70 +3,48 @@ title: Go Account Management
sort_key: D
---
To provide Ethereum integration for your native applications, the very first thing you
should be interested in doing is account management.
Although all current leading Ethereum implementations provide account management built in,
it is ill advised to keep accounts in any location that is shared between multiple
applications and/or multiple people. The same way you do not entrust your ISP (who is
after all your gateway into the internet) with your login credentials; you should not
entrust an Ethereum node (who is your gateway into the Ethereum network) with your
credentials either.
The proper way to handle user accounts in your native applications is to do client side
account management, everything self-contained within your own application. This way you
can ensure as fine grained (or as coarse) access permissions to the sensitive data as
deemed necessary, without relying on any third party application's functionality and/or
vulnerabilities.
To support this, `go-ethereum` provides a simple, yet thorough accounts package that gives
you all the tools to do properly secured account management via encrypted keystores and
passphrase protected accounts. You can leverage all the security of the `go-ethereum`
crypto implementation while at the same time running everything in your own application.
Geth provides a simple, yet thorough accounts package that includes all the tools developers
need to leverage all the security of Geth's crypto implementation in a Go native application.
The account management is done client side with all sensitive data held inside the application.
This gives the user control over access permissions without relying on any third party.
## Encrypted keystores
**Note Geth's built-in account management is convenient and straightforward to use, but
best practise is to use the external tool *Clef* for key management.**
{:toc}
Although handling accounts locally to an application does provide certain security
guarantees, access keys to Ethereum accounts should never lay around in clear-text form.
As such, we provide an encrypted keystore that provides the proper security guarantees for
you without requiring a thorough understanding from your part of the associated
cryptographic primitives.
- this will be removed by the toc
The important thing to know when using the encrypted keystore is that the cryptographic
primitives used within can operate either in *standard* or *light* mode. The former
provides a higher level of security at the cost of increased computational burden and
resource consumption:
## Encrypted keystores
* *standard* needs 256MB memory and 1 second processing on a modern CPU to access a key
* *light* needs 4MB memory and 100 millisecond processing on a modern CPU to access a key
Access keys to Ethereum accounts should never be stored in plain-text. Instead, they should be
stored encrypted so that even if the mobile device is accessed by a malicious third party the
keys are still hidden under an additional layer of security. Geth provides a keystore that enables
developers to store keys securely. The Geth keystore uses [Scrypt][scrypt-docs] to store keys that are encoded
using the [`secp256k1`][secp256k1] elliptic curve. Accounts are stored on disk in the
[Web3 Secret Storage][wss] format. Developers should be aware of these implementation details
but are not required to deeply understand the cryptographic primitives in order to use the keystore.
As such, *standard* is more suitable for native applications, but you should be aware of
the trade-offs nonetheless in case you you're targeting more resource constrained
environments.
One thing that should be understood, though, is that the cryptographic primitives underpinning the
keystore can operate in light or standard mode. Light mode is computationally cheaper, while standard
mode has extra security. Light mode is appropriate for mobile devices, but developers should be
aware that there is a security trade-off.
*For those interested in the cryptographic and/or implementation details, the key-store
uses the `secp256k1` elliptic curve as defined in the [Standards for Efficient
Cryptography](https://www.secg.org/sec2-v2.pdf), implemented by the [`libsecp256k`](https://github.com/bitcoin-core/secp256k1) library and wrapped by
[`github.com/ethereum/go-ethereum/accounts`](https://godoc.org/github.com/ethereum/go-ethereum/accounts). Accounts are stored on disk in
the [Web3 Secret Storage](https://github.com/ethereum/wiki/wiki/Web3-Secret-Storage-Definition) format.*
* standard needs 256MB memory and 1 second processing on a modern CPU to access a key
* light needs 4MB memory and 100 millisecond processing on a modern CPU to access a key
### Keystores from Go
The encrypted keystore is implemented by the
[`accounts.Manager`](https://godoc.org/github.com/ethereum/go-ethereum/accounts#Manager)
struct from the
[`github.com/ethereum/go-ethereum/accounts`](https://godoc.org/github.com/ethereum/go-ethereum/accounts)
package, which also contains the configuration constants for the *standard* or *light*
security modes described above. Hence to do client side account management from Go, you'll
need to import only the `accounts` package into your code:
The encrypted keystore is implemented by the [`accounts.Manager`][accounts-manager] struct
from the [`accounts`][accounts-pkg] package, which also contains the configuration constants for the
*standard* or *light* security modes described above. Hence client side account management
simply requires importing the `accounts` package into the application code.
```go
import "github.com/ethereum/go-ethereum/accounts"
import "github.com/ethereum/go-ethereum/accounts/keystore"
import "github.com/ethereum/go-ethereum/common"
```
Afterwards you can create a new encrypted account manager via:
Afterwards a new encrypted account manager can be created via:
```go
ks := keystore.NewKeyStore("/path/to/keystore", keystore.StandardScryptN, keystore.StandardScryptP)
@ -74,69 +52,60 @@ am := accounts.NewManager(&accounts.Config{InsecureUnlockAllowed: false}, ks)
```
The path to the keystore folder needs to be a location that is writable by the local user
but non-readable for other system users (for security reasons obviously), so we'd
recommend placing it either inside your user's home directory or even more locked down for
backend applications.
The last two arguments of
[`keystore.NewKeyStore`](https://godoc.org/github.com/ethereum/go-ethereum/accounts/keystore#NewKeyStore)
are the crypto parameters defining how resource-intensive the keystore encryption should
be. You can choose between [`accounts.StandardScryptN, accounts.StandardScryptP`,
`accounts.LightScryptN,
accounts.LightScryptP`](https://godoc.org/github.com/ethereum/go-ethereum/accounts#pkg-constants)
or specify your own numbers (please make sure you understand the underlying cryptography
for this). We recommend using the *standard* version.
but non-readable for other system users, such as inside the user's home directory.
The last two arguments of [`keystore.NewKeyStore`][keystore] are the crypto parameters defining
how resource-intensive the keystore encryption should be. The options are
[`accounts.StandardScryptN, accounts.StandardScryptP`, `accounts.LightScryptN,
accounts.LightScryptP`][pkg-constants] or custom values (requiring understanding of the underlying
cryptography). The *standard* version is recommended.
## Account lifecycle
Having created an encrypted keystore for your Ethereum accounts, you can use this account
manager for the entire account lifecycle requirements of your native application. This
includes the basic functionality of creating new accounts and deleting existing ones; as
well as the more advanced functionality of updating access credentials, exporting existing
accounts, and importing them on another device.
Once an encrypted keystore for Ethereum accounts exists it, it can be used to manage accounts for the
entire account lifecycle requirements of a Go native application. This includes the basic functionality
of creating new accounts and deleting existing ones as well as updating access credentials,
exporting existing accounts, and importing them on other devices.
Although the keystore defines the encryption strength it uses to store your accounts,
there is no global master password that can grant access to all of them. Rather each
account is maintained individually, and stored on disk in its [encrypted
format](https://github.com/ethereum/wiki/wiki/Web3-Secret-Storage-Definition)
individually, ensuring a much cleaner and stricter separation of credentials.
Although the keystore defines the encryption strength it uses to store accounts, there is no global master
password that can grant access to all of them. Rather each account is maintained individually, and stored on
disk in its [encrypted format][wss] individually, ensuring a much cleaner and stricter separation of
credentials.
This individuality however means that any operation requiring access to an account will
need to provide the necessary authentication credentials for that particular account in
the form of a passphrase:
This individuality means that any operation requiring access to an account will need to provide the
necessary authentication credentials for that particular account in the form of a passphrase:
* When creating a new account, the caller must supply a passphrase to encrypt the account
with. This passphrase will be required for any subsequent access, the lack of which
will forever forfeit using the newly created account.
* When deleting an existing account, the caller must supply a passphrase to verify
ownership of the account. This isn't cryptographically necessary, rather a protective
measure against accidental loss of accounts.
* When updating an existing account, the caller must supply both current and new
passphrases. After completing the operation, the account will not be accessible via the
old passphrase any more.
* When exporting an existing account, the caller must supply both the current passphrase
to decrypt the account, as well as an export passphrase to re-encrypt it with before
returning the key-file to the user. This is required to allow moving accounts between
machines and applications without sharing original credentials.
* When importing a new account, the caller must supply both the encryption passphrase of
the key-file being imported, as well as a new passhprase with which to store the
account. This is required to allow storing account with different credentials than used
for moving them around.
*Please note, there is no recovery mechanisms for losing the passphrases. The
cryptographic properties of the encrypted keystore (if using the provided parameters)
guarantee that account credentials cannot be brute forced in any meaningful time.*
### Accounts from Go
***Please note, there are no recovery mechanisms for lost passphrases. The
cryptographic properties of the encrypted keystore (using the provided parameters)
guarantee that account credentials cannot be brute forced in any meaningful time.***
An Ethereum account is implemented by the
[`accounts.Account`](https://godoc.org/github.com/ethereum/go-ethereum/accounts#Account)
struct from the
[`github.com/ethereum/go-ethereum/accounts`](https://godoc.org/github.com/ethereum/go-ethereum/accounts)
package. Assuming we already have an instance of an
[`accounts.Manager`](https://godoc.org/github.com/ethereum/go-ethereum/accounts#Manager)
called `am` from the previous section, we can easily execute all of the described
lifecycle operations with a handful of function calls (error handling omitted).
An Ethereum account is implemented by the [`accounts.Account`][accounts-account] struct from
the Geth [accounts][accounts-pkg] package. Assuming an instance of an
[`accounts.Manager`][accounts-manager] called `am` exists, all of the described lifecycle
operations can be executed with a handful of function calls (error handling omitted).
```go
// Create a new account with the specified encryption passphrase.
@ -158,58 +127,47 @@ _ = ks.Delete(newAcc, "Update password")
impAcc, _ := ks.Import(jsonAcc, "Export password", "Import password")
```
*Although instances of
[`accounts.Account`](https://godoc.org/github.com/ethereum/go-ethereum/accounts#Account)
can be used to access various information about specific Ethereum accounts, they do not
contain any sensitive data (such as passphrases or private keys), rather act solely as
identifiers for client code and the keystore.*
*Although instances of [`accounts.Account`][accounts-account] can be used to access various information about
specific Ethereum accounts, they do not contain any sensitive data (such as passphrases or private keys),
rather they act solely as identifiers for client code and the keystore.*
## Signing authorization
As mentioned above, account objects do not hold the sensitive private keys of the
associated Ethereum accounts, but are merely placeholders to identify the cryptographic
keys with. All operations that require authorization (e.g. transaction signing) are
performed by the account manager after granting it access to the private keys.
Account objects do not hold the sensitive private keys of the associated Ethereum accounts.
Account objects are placeholders that identify the cryptographic keys. All operations that
require authorization (e.g. transaction signing) are performed by the account manager after
granting it access to the private keys.
There are a few different ways one can authorize the account manager to execute signing
There are a few different ways to authorize the account manager to execute signing
operations, each having its advantages and drawbacks. Since the different methods have
wildly different security guarantees, it is essential to be clear on how each works:
* **Single authorization**: The simplest way to sign a transaction via the account
manager is to provide the passphrase of the account every time something needs to be
signed, which will ephemerally decrypt the private key, execute the signing operation
and immediately throw away the decrypted key. The drawbacks are that the passphrase
needs to be queried from the user every time, which can become annoying if done
frequently; or the application needs to keep the passphrase in memory, which can have
security consequences if not done properly; and depending on the keystore's configured
strength, constantly decrypting keys can result in non-negligible resource
requirements.
* **Multiple authorizations**: A more complex way of signing transactions via the account
manager is to unlock the account via its passphrase once, and allow the account manager
to cache the decrypted private key, enabling all subsequent signing requests to
complete without the passphrase. The lifetime of the cached private key may be managed
manually (by explicitly locking the account back up) or automatically (by providing a
timeout during unlock). This mechanism is useful for scenarios where the user may need
to sign many transactions or the application would need to do so without requiring user
input. The crucial aspect to remember is that **anyone with access to the account
manager can sign transactions while a particular account is unlocked** (e.g.
application running untrusted code).
*Note, creating transactions is out of scope here, so the remainder of this section will
assume we already have a transaction hash to sign, and will focus only on creating a
cryptographic signature authorizing it. Creating an actual transaction and injecting the
authorization signature into it will be covered later.*
### Signing from Go
Assuming we already have an instance of an
[`accounts.Manager`](https://godoc.org/github.com/ethereum/go-ethereum/accounts#Manager)
called `am` from the previous sections, we can create a new account to sign transactions
with via it's already demonstrated
[`NewAccount`](https://godoc.org/github.com/ethereum/go-ethereum/accounts#Manager.NewAccount)
method; and to avoid going into transaction creation for now, we can hard-code a random
[`common.Hash`](https://godoc.org/github.com/ethereum/go-ethereum/common#Hash) to sign
instead.
* **Single authorization**: The simplest way to sign a transaction via the account
manager is to provide the passphrase of the account every time something needs to be
signed, which will ephemerally decrypt the private key, execute the signing operation
and immediately throw away the decrypted key. The drawbacks are that the passphrase
needs to be queried from the user every time, which can become annoying if done
frequently or the application needs to keep the passphrase in memory, which can have
security consequences if not done properly. Depending on the keystore's configured
strength, constantly decrypting keys can result in non-negligible resource
requirements.
* **Multiple authorizations**: A more complex way of signing transactions via the account
manager is to unlock the account via its passphrase once, and allow the account manager
to cache the decrypted private key, enabling all subsequent signing requests to
complete without the passphrase. The lifetime of the cached private key may be managed
manually (by explicitly locking the account back up) or automatically (by providing a
timeout during unlock). This mechanism is useful for scenarios where the user may need
to sign many transactions or the application would need to do so without requiring user
input. The crucial aspect to remember is that **anyone with access to the account
manager can sign transactions while a particular account is unlocked** (e.g.
application running untrusted code).
Assuming an instance of an [`accounts.Manager`][accounts-manager] called `am` exists, a new
account can be created to sign transactions using [`NewAccount`][new-account]. Creating transactions
is out of scope for this page so instead a random [`common.Hash`][common-hash] will be signed instead.
For information on creating transactions in Go native applications see the [Go API page](/docs/dapp/native).
```go
// Create a new account to sign transactions with
@ -217,7 +175,7 @@ signer, _ := ks.NewAccount("Signer password")
txHash := common.HexToHash("0x0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef")
```
With the boilerplate out of the way, we can now sign transaction using the authorization
With the boilerplate out of the way, the transaction can be signed using the authorization
mechanisms described above:
```go
@ -234,19 +192,32 @@ _ = ks.TimedUnlock(signer, "Signer password", time.Second)
signature, _ = ks.SignHash(signer, txHash.Bytes())
```
You may wonder why
[`SignWithPassphrase`](https://godoc.org/github.com/ethereum/go-ethereum/accounts#Manager.SignWithPassphrase)
takes an
[`accounts.Account`](https://godoc.org/github.com/ethereum/go-ethereum/accounts#Account)
as the signer, whereas
[`Sign`](https://godoc.org/github.com/ethereum/go-ethereum/accounts#Manager.Sign) takes
only a
[`common.Address`](https://godoc.org/github.com/ethereum/go-ethereum/common#Address). The
reason is that an
[`accounts.Account`](https://godoc.org/github.com/ethereum/go-ethereum/accounts#Account)
object may also contain a custom key-path, allowing
[`SignWithPassphrase`](https://godoc.org/github.com/ethereum/go-ethereum/accounts#Manager.SignWithPassphrase)
to sign using accounts outside of the keystore; however
[`Sign`](https://godoc.org/github.com/ethereum/go-ethereum/accounts#Manager.Sign) relies
on accounts already unlocked within the keystore, so it cannot specify custom paths.
Note that [`SignWithPassphrase`][sign-w-phrase] takes an [`accounts.Account`][accounts-account] as the
signer, whereas [`Sign`][accounts-sign] takes only a [`common.Address`][common-address]. The reason
for this is that an [`accounts.Account`][accounts-account] object may also contain a custom key-path, allowing
[`SignWithPassphrase`][sign-w-phrase] to sign using accounts outside of the keystore; however
[`Sign`][accounts-sign] relies on accounts already unlocked within the keystore, so it cannot specify custom paths.
## Summary
Account management is a fundamental pillar of Ethereum development. Geth's Go API provides the tools required
to integrate best-practise account security into Go native applications using a simple set of Go functions.
[accounts-sign]: (https://godoc.org/github.com/ethereum/go-ethereum/accounts#Manager.Sign)
[common-address]: https://godoc.org/github.com/ethereum/go-ethereum/common#Address
[accounts-sign]: https://godoc.org/github.com/ethereum/go-ethereum/accounts#Manager.Sign
[sign-w-phrase]: https://godoc.org/github.com/ethereum/go-ethereum/accounts#Manager.SignWithPassphrase
[secp256k1]: https://www.secg.org/sec2-v2.pdf
[libsecp256k1]: https://github.com/bitcoin-core/secp256k1
[wss]:https://github.com/ethereum/wiki/wiki/Web3-Secret-Storage-Definition
[go-accounts]:https://godoc.org/github.com/ethereum/go-ethereum/accounts
[accounts-manager]: https://godoc.org/github.com/ethereum/go-ethereum/accounts#Manager
[accounts-pkg]: https://godoc.org/github.com/ethereum/go-ethereum/accounts
[keystore]: https://godoc.org/github.com/ethereum/go-ethereum/accounts/keystore#NewKeyStore
[pkg-constants]: https://godoc.org/github.com/ethereum/go-ethereum/accounts#pkg-constants
[accounts-account]:https://godoc.org/github.com/ethereum/go-ethereum/accounts#Account
[new-account]: https://godoc.org/github.com/ethereum/go-ethereum/accounts#Manager.NewAccount
[common-hash]: https://godoc.org/github.com/ethereum/go-ethereum/common#Hash
[scrypt-docs]: https://pkg.go.dev/golang.org/x/crypto/scrypt

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