1. Response status encoded as part of the response body
* Key-value pairs encoded as a HTTP/1 headers block (without the terminating newline).
* Key-value pairs encoded as a HTTP/1 headers block (without the terminating newline), per https://tools.ietf.org/html/rfc7230#section-3.2
```
key1: foo\r\n
key2: bar\r\n
```
2. 8th (MSB) bit of the 1st gRPC frame byte
* 0: data
* 1: trailers
```
10000000b: an uncompressed trailer (as part of the body)
10000001b: a compressed trailer
```
3. Trailers must be the last message of the response, as enforced
by the implementation
4. Trailers-only responses: no change to the gRPC protocol spec.
@ -72,10 +81,9 @@ in the body.
---
User Agent and Server headers
User Agent
* U-A: grpc-web-javascript/0.1
* Server: grpc-web-gateway/0.1
* U-A: grpc-web-javascript
---
@ -86,14 +94,12 @@ the response stream needs to be text encoded e.g. when XHR is used or due
to security policies with XHR
* Accept: application/grpc-web-text
2. The default text encoding is base64
* Text encoding may be specified with Content-Type or Accept headers as
* application/grpc-web-text-base64
* Note that “Content-Transfer-Encoding: base64” should not be used.
Due to in-stream base64 padding when delimiting messages, the entire
response body is not necessarily a valid base64-encoded entity
* While the server runtime will always base64-encode and flush gRPC messages
atomically the client library should not assume base64 padding always
happens at the boundary of message frames.
happens at the boundary of message frames. That is, the implementation may send base64-encoded "chunks" with potential padding whenever the runtime needs to flush a byte buffer.
3. For binary trailers, when the content-type is set to
application/grpc-web-text, the extra base64 encoding specified
in [gRPC over HTTP2](http://www.grpc.io/docs/guides/wire.html)
@ -131,6 +137,10 @@ Security
CORS preflight
* Should follow the [CORS spec](https://developer.mozilla.org/en-US/docs/Web/HTTP/Server-Side_Access_Control)
* Access-Control-Allow-Credentials to allow Authorization headers
* Access-Control-Allow-Methods to allow POST and (preflight) OPTIONS only
* Access-Control-Allow-Headers to whatever the preflight request carries
* The client library may support header overwrites to avoid preflight
* https://github.com/whatwg/fetch/issues/210
* CSP support to be specified
@ -149,3 +159,10 @@ Bidi-streaming, with flow-control
* Pending on [whatwg fetch/streams](https://github.com/whatwg/fetch) to be
finalized and implemented in modern browsers
* gRPC-Web client will support the native gRPC protocol with modern browsers
---
Versioning
* Special headers may be introduced to support features that may break compatiblity.
As a universal RPC framework, gRPC needs to be fully usable within/across different international environments.
This document describes gRPC API and behavior specifics when used in a non-english environment.
## API Concepts
While some API elements need to be able to represent non-english content, some are intentionally left as ASCII-only
for simplicity & performance reasons.
### Method name (in RPC Invocation)
Method names are ASCII-only and may only contain characters allowed by HTTP/2 text header values. That should not
be very limiting as most gRPC services will use protobuf which only allows method names from an even more restricted ASCII subset.
Also, handling method names is a very hot code path so any additional encoding/decoding step is to be avoided.
Recommended representation in language-specific APIs: string type.
### Host name (in RPC Invocation)
Host names are punycode encoded, but the user is responsible for providing the punycode-encoded string if she wishes to use an internationalized host name.
Recommended representation in language-specific APIs: string/unicode string.
NOTE: overriding host name when invoking RPCs is only supported by C-core based gRPC implementations.
### Status detail/message (accompanies RPC status code)
Status messages are expected to contain national-alphabet characters.
Allowed values are unicode strings (content will be percent-encoded on the wire).
Recommended representation in language-specific APIs: unicode string.
### Metadata key
Allowed values are defined by HTTP/2 standard (metadata keys are represented as HTTP/2 header/trailer names).
Recommended representation in language-specific APIs: string.
### Metadata value (text-valued metadata)
Allowed values are defined by HTTP/2 standard (metadata values are represented as HTTP/2 header/trailer text values).
Recommended representation in language-specific APIs: string.
NOTE: This document describes how server-side authentication works in C-core based gRPC implementations only. In gRPC Java and Go, server side authentication is handled differently.
## AuthContext
To perform server-side authentication, gRPC exposes the *authentication context* for each call. The context exposes important authentication-related information about the RPC such as the type of security/authentication type being used and the peer identity.
The authentication context is structured as a multi-map of key-value pairs - the *auth properties*. In addition to that, for authenticated RPCs, the set of properties corresponding to a selected key will represent the verified identity of the caller - the *peer identity*.
The contents of the *auth properties* are populated by an *auth interceptor*. The interceptor also chooses which property key will act as the peer identity (e.g. for client certificate authentication this property will be `"x509_common_name"` or `"x509_subject_alternative_name"`).
WARNING: AuthContext is the only reliable source of truth when it comes to authenticating RPCs. Using any other call/context properties for authentication purposes is wrong and inherently unsafe.
####Example AuthContext contents
For secure channel using mutual TLS authentication with both client and server certificates (test certificates from this repository are used).
Populated auth properties:
```
"transport_security_type": "ssl" # connection is secured using TLS/SSL
"x509_common_name": "*.test.google.com" # from client's certificate
Auth properties are elements of the AuthContext. They have a name (a key of type string) and a value which can be a string or binary data.
## Auth Interceptors
Auth interceptors are gRPC components that populate contents of the auth context based on gRPC's internal state and/or call metadata.
gRPC comes with some basic "interceptors" already built-in.
WARNING: While there is a public API that allows anyone to write their own custom interceptor, please think twice before using it.
There are legitimate uses for custom interceptors but you should keep in mind that as auth interceptors essentially decide which RPCs are authenticated and which are not, their code is very sensitive from the security perspective and getting things wrong might have serious consequences. If unsure, we strongly recommend to rely on official & proven interceptors that come with gRPC.
####Available auth interceptors
- TLS/SSL certificate authentication (built into gRPC's security layer, automatically used whenever you use a secure connection)
- (coming soon) JWT auth token authentication
- more will be added over time
## Status (by language)
C-core exposes low level API to access auth context contents and to implement an auth interceptor.
In C++, the auth interceptor API is exposed as `AuthMetadataProcessor`.
A high level API to access AuthContext contents is available in these languages:
Mark D. Roth
8 years ago