Generate JWT OAuth2 Access token without password

Question

My Spring Boot authorization service is able to create JWT tokens for users with correct credentials. It shall also be possible to get a token via social login (Facebook in this case). The Facebook authentication already works and I find myself redirected to the following endpoint after I get the users's Facebook data.

I could create the JWT token completely from scratch, but that is not what I want. I want to use the already configured (with key pair and so on) TokenServices from my authentication server.

The only way I found was via TokenEndpoint. The problem is that I need the user's password, which I don't have and shouldn't have at this point.

How can I generate the token from what I already configured?

This endpoint is where I end up after Facebook's redirect:

@GetMapping("/loginSuccess")
fun getLoginInfo(authentication: OAuth2AuthenticationToken): ResponseEntity<OAuth2AccessToken> {

    val client = authorizedClientService.loadAuthorizedClient<OAuth2AuthorizedClient>(authentication.authorizedClientRegistrationId, authentication.name)

    val userInfoEndpointUri = client.clientRegistration.providerDetails.userInfoEndpoint.uri

    if (!StringUtils.isEmpty(userInfoEndpointUri)) {
        val restTemplate = RestTemplate()
        val headers = HttpHeaders()
        headers.add(HttpHeaders.AUTHORIZATION, "Bearer " + client.accessToken.tokenValue)

        val entity = HttpEntity("", headers)
        val response = restTemplate.exchange(userInfoEndpointUri, HttpMethod.GET, entity, Map::class.java)

        // At this point I have the email address of the user and I am able to
        // map it to my own User Entity  
        // This is where I would like to create a token and return it  
        // However, the following generation process requires the user's password
        return authService.generateToken((response.body as Map<*, *>)["email"] as String)
    }

    throw AuthenticationException("Error")
}

I would like to use getAccessToken(OAuth2Authentication authentication) in JwtTokenStore but its implementation returns null:

@Override
public OAuth2AccessToken getAccessToken(OAuth2Authentication authentication) {
   // We don't want to accidentally issue a token, and we have no way to 
   // reconstruct the refresh token
   return null;
}