Example script for creating an idjag token with Keycloak

idjag-test.sh

#!/usr/bin/env zsh
# Manual end-to-end test for the Identity Assertion JWT (ID-JAG) token-exchange flow.
#
# Prereq: start Keycloak with the experimental feature enabled, e.g.
#   bin/kc.sh start-dev --features=identity-assertion-jwt,token-exchange
#
# Requires: curl, jq, openssl (all standard on macOS).
set -u

BASE=${BASE:-http://localhost:8081}
REALM=${REALM:-master}
ADMIN_USER=${ADMIN_USER:-admin}
ADMIN_PASS=${ADMIN_PASS:-admin}
CLIENT_ID=mcp-client
CLIENT_SECRET=secret

# --- helpers ---------------------------------------------------------------

# Portable base64url decode (macOS/BSD openssl, no GNU-only flags).
b64url_decode() {
  local data="${1//-/+}"; data="${data//_//}"
  local pad=$(( ${#data} % 4 ))
  (( pad )) && data="${data}$(printf '=%.0s' {1..$((4 - pad))})"
  printf '%s' "$data" | openssl base64 -d -A
}

# Decode a JWT segment: jwt_decode <jwt> <1=header|2=payload>
jwt_decode() {
  b64url_decode "$(printf '%s' "$1" | cut -d. -f"$2")" | jq .
}

die() { print -u2 "ERROR: $*"; exit 1; }

# --- admin token (cached) --------------------------------------------------

print "== getting admin token =="
ADMIN_TOKEN=$(curl -s "$BASE/realms/master/protocol/openid-connect/token" \
  -d grant_type=password -d client_id=admin-cli \
  -d username="$ADMIN_USER" -d password="$ADMIN_PASS" | jq -r '.access_token // empty')
[[ -n "$ADMIN_TOKEN" ]] || die "could not get admin token (check $ADMIN_USER/$ADMIN_PASS creds)"
print "admin token OK"

AUTH=(-H "Authorization: Bearer $ADMIN_TOKEN")

# --- (re)create the mcp-client ---------------------------------------------

print "\n== (re)creating client '$CLIENT_ID' =="
CID=$(curl -s "${AUTH[@]}" \
  "$BASE/admin/realms/$REALM/clients?clientId=$CLIENT_ID" | jq -r '.[0].id // empty')
if [[ -n "$CID" ]]; then
  curl -s -X DELETE "${AUTH[@]}" "$BASE/admin/realms/$REALM/clients/$CID" >/dev/null
  print "deleted existing client ($CID)"
fi

HTTP=$(curl -s -o /dev/null -w '%{http_code}' \
  -X POST "$BASE/admin/realms/$REALM/clients" \
  "${AUTH[@]}" -H "Content-Type: application/json" -d @- <<JSON
{
  "clientId": "$CLIENT_ID",
  "enabled": true,
  "protocol": "openid-connect",
  "publicClient": false,
  "secret": "$CLIENT_SECRET",
  "directAccessGrantsEnabled": true,
  "standardFlowEnabled": false,
  "attributes": {
    "id.jag.issuance.enabled": "true",
    "id.jag.allowed.audiences": "https://auth.chat.example",
    "id.jag.client.id": "mcp-client-at-resource-as",
    "id.jag.allowed.scopes": "chat.read##chat.history"
  }
}
JSON
)
[[ "$HTTP" == "201" ]] || die "create client failed (HTTP $HTTP)"
print "create client: 201"

# Resolve the actual secret (in case the server overrode it).
CID=$(curl -s "${AUTH[@]}" \
  "$BASE/admin/realms/$REALM/clients?clientId=$CLIENT_ID" | jq -r '.[0].id')
SECRET=$(curl -s "${AUTH[@]}" \
  "$BASE/admin/realms/$REALM/clients/$CID/client-secret" | jq -r '.value')
print "client secret: $SECRET"

# --- get an ID token for the user ------------------------------------------

print "\n== getting ID token =="
ID_TOKEN=$(curl -s "$BASE/realms/$REALM/protocol/openid-connect/token" \
  -d grant_type=password -d username="$ADMIN_USER" -d password="$ADMIN_PASS" \
  -d client_id="$CLIENT_ID" -d client_secret="$SECRET" \
  -d scope="openid email" | jq -r '.id_token // empty')
[[ -n "$ID_TOKEN" ]] || die "login failed (no id_token; is 'openid' scope mapped?)"
print "ID token OK"

# --- happy path: exchange ID token -> ID-JAG -------------------------------

print "\n== exchanging ID token for an ID-JAG =="
RESP=$(curl -s -u "$CLIENT_ID:$SECRET" "$BASE/realms/$REALM/protocol/openid-connect/token" \
  -d grant_type=urn:ietf:params:oauth:grant-type:token-exchange \
  -d requested_token_type=urn:ietf:params:oauth:token-type:id-jag \
  -d subject_token="$ID_TOKEN" \
  -d subject_token_type=urn:ietf:params:oauth:token-type:id_token \
  -d audience=https://auth.chat.example \
  -d resource=https://mcp.chat.example/mcp \
  -d scope="chat.read chat.history")
print "$RESP" | jq .

JAG=$(print "$RESP" | jq -r '.access_token // empty')
[[ -n "$JAG" ]] || die "no ID-JAG returned (is the 'identity-assertion-jwt' feature enabled?)"

print "\n-- ID-JAG header --"
jwt_decode "$JAG" 1
print -- "-- ID-JAG payload --"
jwt_decode "$JAG" 2

print "\n== advertised grant profiles =="
curl -s "$BASE/realms/$REALM/.well-known/openid-configuration" \
  | jq '.authorization_grant_profiles_supported'

# --- negative: audience not allow-listed -> 403 ----------------------------

print "\n== negative: non-allow-listed audience (expect 403) =="
curl -s -o /dev/null -w 'not-allowed audience: %{http_code}\n' \
  -u "$CLIENT_ID:$SECRET" "$BASE/realms/$REALM/protocol/openid-connect/token" \
  -d grant_type=urn:ietf:params:oauth:grant-type:token-exchange \
  -d requested_token_type=urn:ietf:params:oauth:token-type:id-jag \
  -d subject_token="$ID_TOKEN" \
  -d subject_token_type=urn:ietf:params:oauth:token-type:id_token \
  -d audience=evil.example

# --- negative: wrong subject_token_type -> 400 invalid_request -------------

print "\n== negative: wrong subject_token_type (expect 400 invalid_request) =="
curl -s -u "$CLIENT_ID:$SECRET" "$BASE/realms/$REALM/protocol/openid-connect/token" \
  -d grant_type=urn:ietf:params:oauth:grant-type:token-exchange \
  -d requested_token_type=urn:ietf:params:oauth:token-type:id-jag \
  -d subject_token="$ID_TOKEN" \
  -d subject_token_type=urn:ietf:params:oauth:token-type:access_token \
  -d audience=auth.chat.example | jq '{error, error_description}'

# --- negative: scope outside the allow-list -> 400 invalid_scope -----------

print "\n== negative: non-allow-listed scope (expect 400 invalid_scope) =="
curl -s -u "$CLIENT_ID:$SECRET" "$BASE/realms/$REALM/protocol/openid-connect/token" \
  -d grant_type=urn:ietf:params:oauth:grant-type:token-exchange \
  -d requested_token_type=urn:ietf:params:oauth:token-type:id-jag \
  -d subject_token="$ID_TOKEN" \
  -d subject_token_type=urn:ietf:params:oauth:token-type:id_token \
  -d audience=auth.chat.example \
  -d scope="chat.read chat.delete" | jq '{error, error_description}'

print "\nDone."