add oidc workload identity federation flow to github action

updates

.github/workflows/tailscale.yml

@@ -1,5 +1,8 @@
 name: tailscale
 
+permissions:
+  id-token: write # This is required for requesting the JWT
+
 on:
   workflow_dispatch:
   push:
@@ -15,12 +18,25 @@ jobs:
       matrix:
         os: [ubuntu-latest, windows-latest, macos-latest, windows-11-arm]
         cache: ['false', 'true']
+        auth: ['oauth', 'oauth-legacy', 'oidc']
     runs-on: ${{ matrix.os }}
     steps:
       - name: Check out code
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
 
-      - name: Tailscale Action
+      - name: Tailscale Action (OAuth)
+        if: matrix.auth == 'oauth'
+        uses: ./
+        with:
+          oauth-client-id: ${{ secrets.TS_OAUTH_GRANULAR_CLIENT_ID }}
+          oauth-secret: ${{ secrets.TS_OAUTH_GRANULAR_SECRET }}
+          tags: tag:ci
+          use-cache: ${{ matrix.cache }}
+
+      # This job runs as a sanity check to ensure we have not broken the ability for OAuth clients using
+      # our legacy scopes to successfully connect to tailnets using this action.
+      - name: Tailscale Action (OAuth legacy)
+        if: matrix.auth == 'oauth-legacy'
         uses: ./
         with:
           oauth-client-id: ${{ secrets.TS_OAUTH_CLIENT_ID }}
@@ -28,6 +44,16 @@ jobs:
           tags: tag:ci
           use-cache: ${{ matrix.cache }}
 
+      - name: Tailscale Action (OIDC)
+        if: matrix.auth == 'oidc'
+        uses: ./
+        with:
+          oidc-client-id: ${{ secrets.TS_OIDC_CLIENT_ID }}
+          oidc-aud-claim: ${{ secrets.TS_OIDC_AUD_CLAIM }}
+          tags: tag:ci
+          tailnet: ${{ secrets.TS_TAILNET_NAME }}
+          use-cache: ${{ matrix.cache }}
+
       - name: check for tailscale connection
         shell: bash
         run:
@@ -41,4 +67,4 @@ jobs:
             echo "::error::Unexpected extra files: $extra_files"
             exit 1
           fi
-
+          

README.md

@@ -29,6 +29,19 @@ be automatically removed by the coordination server a short time after they
 finish their run. The nodes are also [marked Preapproved](https://tailscale.com/kb/1085/auth-keys/)
 on tailnets which use [Device Approval](https://tailscale.com/kb/1099/device-approval/)
 
+## Authenticate with GitHub's OIDC provider (alpha)
+
+The Tailscale GitHub action can use an OIDC token provided by GitHub to authenticate the workflow to your tailnet. This functionality is currently available as a private alpha. To join the alpha program, contact your account rep or email `sam@tailscale.com`.
+
+```yaml
+  - name: Tailscale
+    uses: tailscale/github-action@v3
+    with:
+      oidc-client-id: ${{ secrets.TS_OIDC_CLIENT_ID }}
+      oidc-aud-claim: ${{ secrets.TS_OIDC_AUD_CLAIM }}
+      tags: tag:ci
+```
+
 ## Tailnet Lock
 
 If you are using this Action in a [Tailnet
@@ -92,4 +105,4 @@ You can opt in to caching Tailscale binaries by passing `'true'` to the `use-cac
       oauth-client-id: ${{ secrets.TS_OAUTH_CLIENT_ID }}
       oauth-secret: ${{ secrets.TS_OAUTH_SECRET }}
       use-cache: 'true'
-```
+```

action.yml

@@ -17,6 +17,15 @@ inputs:
   oauth-secret:
     description: 'Your Tailscale OAuth Client Secret.'
     required: false
+  oidc-client-id:
+    description: 'Your Tailscale OIDC Client ID.'
+    required: false
+  oidc-aud-claim:
+    description: 'Your Tailscale OIDC audience claim'
+    required: false
+  tailnet:
+    description: 'Your Tailscale tailnet name (e.g., example.com)'
+    required: false
   tags:
     description: 'Comma separated list of Tags to be applied to nodes. The OAuth client must have permission to apply these tags.'
     required: false
@@ -66,12 +75,82 @@ runs:
           echo "::error title=⛔ error hint::Support Linux, Windows, and macOS Only"
           exit 1
       - name: Check Auth Info Empty
-        if: ${{ inputs.authkey == '' && (inputs['oauth-secret'] == '' || inputs.tags == '') }}
+        if: ${{ inputs.authkey == '' && (inputs['oauth-secret'] == '' || inputs.tags == '') && (inputs['oidc-client-id'] == '' || inputs['oidc-aud-claim'] == '') }}
         shell: bash
         run: |
-          echo "::error title=⛔ error hint::OAuth identity empty, Maybe you need to populate it in the Secrets for your workflow, see more in https://docs.github.com/en/actions/security-guides/encrypted-secrets and https://tailscale.com/s/oauth-clients"
+          echo "::error title=⛔ error hint::OAuth and OIDC identity are empty, Maybe you need to populate it in the Secrets for your workflow, see more in https://docs.github.com/en/actions/security-guides/encrypted-secrets and https://tailscale.com/s/oauth-clients"
           exit 1
 
+      - name: get OIDC token from GitHub Actions
+        if: ${{ inputs['oidc-client-id'] != '' && inputs['oidc-aud-claim'] != '' && inputs['oauth-secret'] == '' }}
+        shell: bash
+        run: |
+          JWT=$(curl -H "Authorization: Bearer $ACTIONS_ID_TOKEN_REQUEST_TOKEN" "${ACTIONS_ID_TOKEN_REQUEST_URL}&audience=${{ inputs['oidc-aud-claim'] }}" | jq -r '.value')
+          if [ -z "$JWT" ]; then
+            echo "::error title=⛔ error hint::Failed to get JWT from GitHub Actions OIDC provider"
+            exit 1
+          fi
+          echo "::add-mask::$JWT" # Mask the JWT in the logs
+          echo "JWT=$JWT" >> $GITHUB_ENV
+
+      - name: Exchange JWT OIDC token and get authkey
+        if: ${{ inputs['oidc-client-id'] != '' && inputs['oidc-aud-claim'] != '' }}
+        shell: bash
+        run: |
+          echo "Exchanging JWT OIDC token for short-lived API token..."
+          RESPONSE=$(curl -X POST https://api.tailscale.com/api/v2/oauth/token-exchange \
+            -H "Content-Type: application/x-www-form-urlencoded" \
+            -d "client_id=${{ inputs['oidc-client-id'] }}" \
+            -d "jwt=$JWT")
+          export ACCESS_TOKEN=$(echo $RESPONSE | jq -r '.access_token')
+          echo "::add-mask::$ACCESS_TOKEN" # Mask the access token in the logs
+          if [ -z "$ACCESS_TOKEN" ] || [ "$ACCESS_TOKEN" = "null" ]; then
+            echo "::error title=⛔ error hint::Failed to get ACCESS_TOKEN from OIDC token exchange, response: $RESPONSE"
+            exit 1
+          fi
+
+          echo "Retrieving authkey from Tailscale API"
+          
+          # Convert comma-separated tags to JSON array format
+          TAGS_JSON=$(echo "${{ inputs.tags }}" | sed 's/,/","/g' | sed 's/^/["/' | sed 's/$/"]/')
+          
+          # Make the API call and capture both the response and curl info
+          CURL_OUTPUT=$(curl -s -w "\n%{http_code}" -X POST https://api.tailscale.com/api/v2/tailnet/${{ inputs.tailnet }}/keys \
+            --header 'Content-Type: application/json' \
+            --header "Authorization: Bearer ${ACCESS_TOKEN}" \
+            --data "{
+            \"keyType\": \"auth\",
+            \"capabilities\": {
+              \"devices\": {
+                \"create\": {
+                  \"reusable\": false,
+                  \"ephemeral\": true,
+                  \"preauthorized\": true,
+                  \"tags\": $TAGS_JSON
+                }
+              }
+            },
+            \"expirySeconds\": 3600
+          }")
+          
+          # Extract HTTP status code (last line) and JSON response (everything else)
+          HTTP_STATUS=$(echo "$CURL_OUTPUT" | tail -n1)
+          JSON_RESPONSE=$(echo "$CURL_OUTPUT" | sed '$d')
+          echo "::add-mask::$JSON_RESPONSE" # Mask the JSON response in the logs
+          
+          if [ "$HTTP_STATUS" != "200" ]; then
+            echo "::error title=⛔ error hint::Tailscale API returned HTTP $HTTP_STATUS"
+            exit 1
+          fi
+          
+          export AUTHKEY=$(echo "$JSON_RESPONSE" | jq -r '.key')
+          echo "::add-mask::$AUTHKEY" # Mask the auth key in the logs
+          if [ -z "$AUTHKEY" ] || [ "$AUTHKEY" = "null" ]; then
+            echo "::error title=⛔ error hint::Failed to get AUTHKEY from Tailscale API"
+            exit 1
+          fi
+          echo "AUTHKEY=$AUTHKEY" >> $GITHUB_ENV
+
       - name: Set Resolved Version
         shell: bash
         run: |
@@ -310,6 +389,15 @@ runs:
             TAILSCALE_AUTHKEY="${{ inputs['oauth-secret'] }}?preauthorized=true&ephemeral=true"
             TAGS_ARG="--advertise-tags=${{ inputs.tags }}"
           fi
+
+          if [ -n "${{ inputs['oidc-aud-claim'] }}" ] && [ -n "${{ inputs['oidc-client-id'] }}" ]; then
+            if [ -z "$AUTHKEY" ]; then
+              echo "::error title=⛔ error hint::Failed to get AUTHKEY from OIDC token exchange"
+              exit 1
+            fi
+            TAILSCALE_AUTHKEY="$AUTHKEY"
+            TAGS_ARG="--advertise-tags=${{ inputs.tags }}"
+          fi
           if [ "${{ runner.os }}" != "Windows" ]; then
             MAYBE_SUDO="sudo -E"
           fi