openiddict-documentation/configuration/proof-key-for-code-exchange.md
2022-01-07 18:10:45 +01:00

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# Proof Key for Code Exchange
Initially designed as a way to protect mobile applications from seeing their callback URIs hijacked by a malicious application installed on the same device,
the [Proof Key for Code Exchange (PKCE)](https://tools.ietf.org/html/rfc7636) mechanism has been extended to confidential clients to help mitigate authorization code leakages.
This mechanism is fully supported by all versions of OpenIddict and can be enforced globally or per-client to block authorization requests that don't send PKCE parameters.
## Enabling PKCE enforcement at the global level
Proof Key for Code Exchange can be enforced globally by calling `options.RequireProofKeyForCodeExchange()` in the server options:
```csharp
services.AddOpenIddict()
.AddServer(options =>
{
options.RequireProofKeyForCodeExchange();
});
```
## Enabling PKCE enforcement per client
Proof Key for Code Exchange can also be enforced per-client by adding it to the list of requirements attached to a client:
```csharp
await manager.CreateAsync(new OpenIddictApplicationDescriptor
{
ClientId = "mvc",
ClientSecret = "901564A5-E7FE-42CB-B10D-61EF6A8F3654",
ConsentType = ConsentTypes.Explicit,
PostLogoutRedirectUris =
{
new Uri("https://localhost:44381/signout-callback-oidc")
},
RedirectUris =
{
new Uri("https://localhost:44381/signin-oidc")
},
Permissions =
{
Permissions.Endpoints.Authorization,
Permissions.Endpoints.Logout,
Permissions.Endpoints.Token,
Permissions.GrantTypes.AuthorizationCode,
Permissions.GrantTypes.RefreshToken,
Permissions.ResponseTypes.Code,
Permissions.Scopes.Email,
Permissions.Scopes.Profile,
Permissions.Scopes.Roles,
Permissions.Prefixes.Scope + "demo_api"
},
Requirements =
{
Requirements.Features.ProofKeyForCodeExchange
}
});
```
## Enabling `code_challenge_method=plain` support
By default, OpenIddict only supports `code_challenge_method=S256`, which is the safest code challenge method and the only one required by the PKCE specification.
While not recommended, support for the `code_challenge_method=plain` method can be manually enabled by adding it to `OpenIddictServerOptions.CodeChallengeMethods`:
```csharp
services.AddOpenIddict()
.AddServer(options =>
{
options.Configure(options => options.CodeChallengeMethods.Add(CodeChallengeMethods.Plain));
});
```