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@MarcoPolo
MarcoPolo committed Oct 21, 2024
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Expand Up @@ -21,6 +21,7 @@ authenticate themselves to each other. The protocol works whether the Client
provides the first challenge, or the Server provides the first challenge.

Example Diagram of Server initiated handshake

```
┌─────────┐ ┌────────┐
│ Client │ │ Server │
Expand Down Expand Up @@ -48,6 +49,7 @@ Example Diagram of Server initiated handshake
```

Example Diagram of Client initiated handshake

```
┌────────┐ ┌────────┐
│ Client │ │ Server │
Expand All @@ -71,29 +73,29 @@ Example Diagram of Client initiated handshake

## Parameters

| Param Name | Description |
| ---------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| hostname | The server name used in the TLS connection (SNI). |
| challenge-server | The random quoted string value the client generates to challenge the server to prove its identity |
| challenge-client | The random quoted string value the server generates to challenge the client to prove its identity |
| sig | A base64 encoded signature. |
| public-key | A base64 encoded value of peer's public key. This MUST be the key used for the Peer's Peer ID. The key itself is encoded per the [Peer ID spec]. |
| opaque | A value opaque to the client blob generated by the server. If a client receives this it must return it. A server may use this to authenticate statelessly. For example, it could store the challenge-client and a expiry time. |
| Param Name | Description |
| ---------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------- |
| hostname | The server name used in the TLS connection (SNI). |
| challenge-server | The random quoted string value the client generates to challenge the server to prove its identity |
| challenge-client | The random quoted string value the server generates to challenge the client to prove its identity |
| sig | A base64 encoded signature. |
| public-key | A base64 encoded value of peer's public key. This MUST be the key used for the Peer's Peer ID. The key itself is encoded per the [Peer ID spec]. |
| opaque | A value opaque to the client blob generated by the server. If a client receives this it must return it. A server may use this to authenticate statelessly. |

Params are encoded per [RFC 9110 auth-param's ABNF](https://datatracker.ietf.org/doc/html/rfc9110#name-cmaollected-abnf). Generally it'll be something like: `hostname="example.com", challenge-server="challenge-string"`

## Signing

Signatures sign some set of parameters prefixed by the string `libp2p-PeerID`. The parameters are sorted
alphabetically, prepended with a varint length prefix, and concatenated together
to form the data to be signed. The parameter name and value is split with a `=`.
If the parameter value is appended directly after the `=`. Strings MUST be UTF-8
encoded. Byte Arrays MUST be appended as-is. The signing algorithm is defined by
the key type used. Refer to the [Peer ID spec] for specifics on the signing
algorithm. The set of parameters is prefixed with the auth scheme
"libp2p-PeerID"
Signatures sign some set of parameters prefixed by the string `libp2p-PeerID`.
The parameters are sorted alphabetically, prepended with a varint length
prefix, and concatenated together to form the data to be signed. The parameter
name and value is split with a `=`. The parameter value is appended directly
after the `=`. Strings MUST be UTF-8 encoded. Byte Arrays MUST be appended
as-is. The signing algorithm is defined by the key type used. Refer to the
[Peer ID spec] for specifics on the signing algorithm.

### Signing Example

| Parameter | Value |
| ------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| hostname | example.com |
Expand All @@ -104,7 +106,7 @@ algorithm. The set of parameters is prefixed with the auth scheme
| data to sign (hex encoded) | 6c69627032702d5065657249443d6368616c6c656e67652d7365727665723d455245524552455245524552455245524552455245524552455245524552455245524552455245524552453d36636c69656e742d7075626c69632d6b65793d080112208139770ea87d175f56a35466c34c7ecccb8d8a91b4ee37a25df60f5b8fc9b39414686f73746e616d653d6578616d706c652e636f6d |
| signature (base64 encoded) | UA88qZbLUzmAxrD9KECbDCgSKAUBAvBHrOCF2X0uPLR1uUCF7qGfLPc7dw3Olo-LaFCDpk5sXN7TkLWPVvuXAA== |

Note that the `=` after the libp2p-PeerID scheme is actually the varint length of the challenge-server parameter.
Note that the `=` after the libp2p-PeerID scheme is the varint length of the challenge-server parameter.

## Base64 Encoding

Expand All @@ -130,7 +132,8 @@ protocol operates as follows:

1. The client makes an HTTP request to an authenticated resource.

2. The server responds with status code 401 (Unauthorized) and set the header:
2. The server responds with status code 401 (Unauthorized) and sets the header:

```
WWW-Authenticate: libp2p-PeerID challenge-client="<challenge-string>", public-key="<base64-encoded-public-key-bytes>", opaque="<opaque-value>"
```
Expand All @@ -153,31 +156,35 @@ protocol operates as follows:
key used to derive the client's peer id.

The `sig` param represents a signature over the parameters:
- `challenge-client`
- `server-public-key` the bytes of the server's public-key encoded per the [Peer ID spec].
- `hostname`

- `challenge-client`
- `server-public-key` the bytes of the server's public-key encoded per the [Peer ID spec].
- `hostname`

4. The server SHOULD verify the signature using the server name used in the TLS
session. The server MUST return 401 Unauthorized if the server fails to
validate the signature. If the signature is valid, the server has
authenticated the client's public key, and thus its PeerID. The server SHOULD
proceed to serve the HTTP request. The server MUST set the following response
headers:

```
Authentication-Info: libp2p-PeerID, sig="<base64-signature-bytes>" bearer="<base64-encoded-opaque-blob>"
```

The `sig` param represents a signature over the parameters:
- `challenge-server`
- `client-public-key` the bytes of the client's public-key encoded per the [Peer ID spec].
- `hostname`

- `challenge-server`
- `client-public-key` the bytes of the client's public-key encoded per the [Peer ID spec].
- `hostname`

The `bearer` token allows the client to make future Peer ID authenticated
requests. The value is opaque to the client, and the server may use it to
store authentication state such as:
- The client's Peer ID.
- The `hostname` parameter.
- The token creation date (to allow tokens to expire).

- The client's Peer ID.
- The `hostname` parameter.
- The token creation date (to allow tokens to expire).

5. The client MUST verify the signature. After verification the client has
authenticated the server's Peer ID. The client SHOULD send the `bearer`
Expand All @@ -200,14 +207,16 @@ The client initiated handshake is as follows
```

2. The server responds with status code 401 (Unauthorized) and set the header:

```
WWW-Authenticate: libp2p-PeerID challenge-client="<challenge-string>", public-key="<base64-encoded-public-key-bytes>", sig="<base64-signature-bytes>", opaque="<opaque-value>"
```

The `sig` param represents a signature over the parameters:
- `challenge-server`
- `client-public-key` the bytes of the client's public-key encoded per the [Peer ID spec].
- `hostname`

- `challenge-server`
- `client-public-key` the bytes of the client's public-key encoded per the [Peer ID spec].
- `hostname`

3. The client MUST verify the signature. After verification the client has
authenticated the server's Peer ID.
Expand All @@ -222,31 +231,33 @@ The client initiated handshake is as follows
The client MAY send application data in this request.

The `sig` param represents a signature over the parameters:
- `challenge-client`
- `server-public-key` the bytes of the server's public-key encoded per the [Peer ID spec].
- `hostname`

- `challenge-client`
- `server-public-key` the bytes of the server's public-key encoded per the [Peer ID spec].
- `hostname`

4. The server MUST verify the signature. The server SHOULD verify the signature
using the server name used in the TLS session. The server MUST return 401
Unauthorized if the server fails to validate the signature. If the signature
is valid, the server has authenticated the client's public key, and thus its
PeerID. The server SHOULD proceed to serve the HTTP request. The server MUST
set the following response headers:

```
Authentication-Info: libp2p-PeerID bearer="<base64-encoded-opaque-blob>"
```

The `bearer` token allows the client to make future Peer ID authenticated
requests. The value is opaque to the client, and the server MAY use it to
store authentication state such as:
- The client's Peer ID.
- The `hostname` parameter.
- The token creation date (to allow tokens to expire).

- The client's Peer ID.
- The `hostname` parameter.
- The token creation date (to allow tokens to expire).

5. The client SHOULD send the `bearer` token for future Peer ID authenticated
requests.


## libp2p bearer token

The libp2p bearer token is a token given to the client from the server that
Expand All @@ -259,6 +270,7 @@ authentication protocol when it wants the client to request a new libp2p
bearer token.

To use the bearer token, the client MUST set the Authorization header as follows:

```
Authorization: libp2p-PeerID bearer="<base64-encoded-opaque-blob>"
```
Expand All @@ -273,36 +285,36 @@ but it only does the authentication flow. The client and server SHOULD NOT send
any data besides what is defined in the above authentication flow. The protocol
id for the authentication endpoint is `/http-peer-id-auth/1.0.0`.


## Considerations for Implementations

* Implementations MUST only authenticate over a secured connection (i.e. TLS).
* Implementations SHOULD limit the maximum length of any variable length field.
* The suggested Maximum length of the Authentication related header should is
2048 bytes.
- Implementations SHOULD only authenticate over a secured connection (i.e. TLS).
- Implementations SHOULD limit the maximum length of any variable length field.
- The suggested Maximum length of the Authentication related header should is
2048 bytes.

## Security Considerations

Protection against man-in-the-middle (mitm) type attacks is through Web PKI. If
Protection against man-in-the-middle (MITM) type attacks is through Web PKI. If
the client is in an environment where Web PKI can not be fully trusted (e.g. an
enterprise network with a custom enterprise root CA installed on the client),
then this authentication scheme can not protect the client from a mitm attack.
then this authentication scheme can not protect the client from a MITM attack.

This authentication scheme is also not secure in cases where you do not own your
domain name or the certificate. If someone else can get a valid certificate for
your domain, you may be vulnerable to a mitm attack.
This authentication scheme is also not secure in cases where you do not own
your domain name or the TLS certificate. If someone else can get a valid
certificate for your domain, you may be vulnerable to a MITM attack.

## Complete Server Initiated Handshake Example

The following is a complete and reproducible handshake. Generated by the current
implementation of this spec in go-libp2p. This is a server-initiated handshake.

Understanding the opaque value is not necessary in order to understand this
Understanding the opaque value is not necessary in order to understand the
spec. Servers are free to do whatever they want with the opaque field. The
opaque value represents encoded server state authenticated with an HMAC. The
details can be found in the go-libp2p source.

### Parameters

| Parameter | Value |
| -------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------- |
| hostname | example.com |
Expand All @@ -314,6 +326,7 @@ details can be found in the go-libp2p source.
| "Now" time | 1970-01-01 00:00:00 +0000 UTC |

### Handshake Diagram

```mermaid
sequenceDiagram
Client->>Server: Initial request
Expand All @@ -329,9 +342,10 @@ Client->>Server: Authorization=libp2p-PeerID bearer="YhlYjHWTMOkTleROtjMiChL7Mx1

## Complete Client Initiated Handshake Example

Below is the same as above, but using the client initated handshake.
Below is the same as above, but using the client initiated handshake.

### Parameters

| Parameter | Value |
| -------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------- |
| hostname | example.com |
Expand All @@ -343,6 +357,7 @@ Below is the same as above, but using the client initated handshake.
| "Now" time | 1970-01-01 00:00:00 +0000 UTC |

### Handshake Diagram

```mermaid
sequenceDiagram
Client->>Server: Authorization=libp2p-PeerID challenge-server="MzMzMzMzMzMzMzMzMzMzMzMzMzMzMzMz", public-key="CAESIIE5dw6ofRdfVqNUZsNMfszLjYqRtO43ol32D1uPybOU"
Expand All @@ -356,7 +371,6 @@ Note over Client: Future requests use the bearer token
```

[Peer ID spec]: https://github.com/libp2p/specs/blob/master/peer-ids/peer-ids.md

[@MarcoPolo]: https://github.com/MarcoPolo
[@sukunrt]: https://github.com/sukunrt
[@achingbrain]: https://github.com/achingbrain

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