Getting error unsupported grant type when trying to get a JWT by calling an OWIN OAuth secured Web Api via Postman

Question

I have followed this article to implement an OAuth Authorization server  However when I use post man to get a token  I get an error in the response       error    unsupported grant type    I read somewhere that the data in Postman needs to be posted using Content-type application x-www-form-urlencoded  I have prepped the required settings in Postman     and yet my headers are like this     Here is my code  public class CustomOAuthProvider   OAuthAuthorizationServerProvider       public override Task ValidateClientAuthentication OAuthValidateClientAuthenticationContext context                context Validated            return Task FromResult lt object gt  null              public override Task MatchEndpoint OAuthMatchEndpointContext context                if  context OwinContext Request Method     OPTIONS   amp  amp  context IsTokenEndpoint                        context OwinContext Response Headers Add  Access-Control-Allow-Methods   new      POST                  context OwinContext Response Headers Add  Access-Control-Allow-Headers   new      accept    authorization    content-type                  context OwinContext Response StatusCode   200              context RequestCompleted                return Task FromResult lt object gt  null                     return base MatchEndpoint context                     public override async Task GrantResourceOwnerCredentials OAuthGrantResourceOwnerCredentialsContext context                string allowedOrigin                 context OwinContext Response Headers Add  Access-Control-Allow-Origin   new     allowedOrigin             context OwinContext Response Headers Add  Access-Control-Allow-Headers   new      Content-Type               Models TheUser user   new Models TheUser            user UserName   context UserName          user FirstName    Sample first name           user LastName    Dummy Last name            ClaimsIdentity identity   new ClaimsIdentity  JWT             identity AddClaim new Claim ClaimTypes Name  context UserName            foreach  string claim in user Claims                        identity AddClaim new Claim  Claim   claim                           var ticket   new AuthenticationTicket identity  null           context Validated ticket            public class CustomJwtFormat   ISecureDataFormat lt AuthenticationTicket gt        private readonly string  issuer   string Empty       public CustomJwtFormat string issuer                 issuer   issuer             public string Protect AuthenticationTicket data                string audienceId   ConfigurationManager AppSettings  AudienceId            string symmetricKeyAsBase64   ConfigurationManager AppSettings  AudienceSecret            var keyByteArray   TextEncodings Base64Url Decode symmetricKeyAsBase64           var signingKey   new HmacSigningCredentials keyByteArray           var issued   data Properties IssuedUtc          var expires   data Properties ExpiresUtc          var token   new JwtSecurityToken  issuer  audienceId  data Identity Claims  issued Value UtcDateTime  expires Value UtcDateTime  signingKey           var handler   new JwtSecurityTokenHandler            var jwt   handler WriteToken token           return jwt             public AuthenticationTicket Unprotect string protectedText                throw new NotImplementedException              In the CustomJWTFormat class above only the breakpoint in the constructor gets hit  In the CustomOauth class  the breakpoint in the GrantResourceOwnerCredentials method never gets hit  The others do    The Startup class   public class Startup       public void Configuration IAppBuilder app                app UseCors Microsoft Owin Cors CorsOptions AllowAll            HttpConfiguration config   new HttpConfiguration            WebApiConfig Register config            ConfigureOAuthTokenGeneration app           ConfigureOAuthTokenConsumption app            app UseWebApi config              private void ConfigureOAuthTokenGeneration IAppBuilder app                var OAuthServerOptions   new OAuthAuthorizationServerOptions                           For Dev enviroment only  on production should be AllowInsecureHttp   false              AllowInsecureHttp   true              TokenEndpointPath   new PathString   oauth token                AccessTokenExpireTimeSpan   TimeSpan FromDays 1               Provider   new CustomOAuthProvider                AccessTokenFormat   new CustomJwtFormat ConfigurationManager AppSettings  Issuer                           OAuth 2 0 Bearer Access Token Generation         app UseOAuthAuthorizationServer OAuthServerOptions              private void ConfigureOAuthTokenConsumption IAppBuilder app                string issuer   ConfigurationManager AppSettings  Issuer             string audienceId   ConfigurationManager AppSettings  AudienceId            byte   audienceSecret   TextEncodings Base64Url Decode ConfigurationManager AppSettings  AudienceSecret                 Api controllers with an  Authorize  attribute will be validated with JWT         app UseJwtBearerAuthentication              new JwtBearerAuthenticationOptions                               AuthenticationMode   AuthenticationMode Active                  AllowedAudiences   new     audienceId                    IssuerSecurityTokenProviders   new IIssuerSecurityTokenProvider                                         new SymmetricKeyIssuerSecurityTokenProvider issuer  audienceSecret                                              Do I need to set up Content-type application x-www-form-urlencoded somewhere else in the web api code  What could be wrong  Please help

User · Answer

Note the URL  localhost 55828 token  not localhost 55828 API token  Note the request data  Its not in json format  its just plain data without double quotes  userName xxx gmail com amp password Test123  amp grant type password Note the content type  Content-Type   application x-www-form-urlencoded   not Content-Type   application json   When you use JavaScript to make post request  you may use following    http post  localhost 55828 token       userName     encodeURIComponent email          amp password     encodeURIComponent password          amp grant type password      headers     Content-Type    application x-www-form-urlencoded       success function  data            See screenshots below from Postman

User · Answer

Use grant type   Your password

User · Answer

try to add this in your payload  grant type password amp username pippo amp password pluto

User · Answer

Old Question  but for angular 6  this needs to be done when you are using HttpClient I am exposing token data publicly here but it would be good if accessed via read-only properties   import   Injectable   from   angular core   import   HttpClient   from   angular common http   import   Observable  of   from  rxjs   import   delay  tap   from  rxjs operators   import   Router   from   angular router      Injectable   export class AuthService       isLoggedIn  boolean   false      url    token        tokenData           username           AccessToken            constructor private http  HttpClient  private router  Router           login username  string  password  string   Observable lt object gt            let model    username     username     amp password     password     amp grant type      password            return this http post this url  model  pipe              tap                  data   gt                        console log  Log In succesful                         console log response                       this isLoggedIn   true                      this tokenData   data                      this username   data  username                        this AccessToken   data  access token                        console log this tokenData                       return true                                      error   gt                        console log error                       return false

User · Answer

The response is a bit late - but in case anyone has the issue in the future     From the screenshot above - it seems that you are adding the url data  username  password  grant type  to the header and not to the body element   Clicking on the body tab  and then select  x-www-form-urlencoded  radio button  there should be a key-value list below that where you can enter the request data

User · Answer

If you are using AngularJS you need to pass the body params as string       factory getToken   function person username        console log  Getting DI Token        var url   diUrl     token        return  http           method   POST           url  url          data   grant type password amp username myuser user com amp password mypass           responseType  json           headers     Content-Type    application x-www-form-urlencoded

User · Answer

I was getting this error too and the reason ended up being wrong call url  I am leaving this answer here  if someone else happens to mix the urls and getting this error  Took me hours to realize I had wrong URL   Error I got  HTTP code 400           error    unsupported grant type        error description    grant type not supported      I was calling   https   MY INSTANCE lightning force com  While the correct URL would have been   https   MY INSTANCE cs110 my salesforce com

User · Answer

With Postman  select Body tab and choose the raw option and type the following   grant type password amp username yourusername amp password yourpassword

[c#] Getting "error": "unsupported_grant_type" when trying to get a JWT by calling an OWIN OAuth secured Web Api via Postman

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