OIDC exchange support

.pre-commit-config.yaml

@@ -105,11 +105,15 @@ repos:
     name: flake8 WPS-only
     args:
     - --ignore
+    # NOTE: WPS326: Found implicit string concatenation
+    # NOTE: WPS332: Found walrus operator
     - >-
       WPS102,
       WPS110,
       WPS111,
       WPS305,
+      WPS326,
+      WPS332,
       WPS347,
       WPS360,
       WPS421,

Dockerfile

@@ -25,6 +25,7 @@ WORKDIR /app
 COPY LICENSE.md .
 COPY twine-upload.sh .
 COPY print-hash.py .
+COPY oidc-exchange.py .
 
 RUN chmod +x twine-upload.sh
 ENTRYPOINT ["/app/twine-upload.sh"]

README.md

@@ -62,6 +62,51 @@ The secret used in `${{ secrets.PYPI_API_TOKEN }}` needs to be created on the
 settings page of your project on GitHub. See [Creating & using secrets].
 
 
+### Publishing with OpenID Connect
+
+> **IMPORTANT**: This functionality is in beta, and will not work for you
+> unless you're a member of the PyPI OIDC beta testers' group. For more
+> information, see [warehouse#12965].
+
+This action supports PyPI's [OpenID Connect publishing]
+implementation, which allows authentication to PyPI without a manually
+configured API token or username/password combination. To perform
+[OIDC publishing][OpenID Connect Publishing] with this action, your project's
+OIDC publisher must already be configured on PyPI.
+
+To enter the OIDC flow, configure this action's job with the `id-token: write`
+permission and **without** an explicit username or password:
+
+```yaml
+jobs:
+  pypi-publish:
+    name: Upload release to PyPI
+    runs-on: ubuntu-latest
+    permissions:
+      id-token: write  # IMPORTANT: this permission is mandatory for OIDC publishing
+    steps:
+    # retrieve your distributions here
+
+    - name: Publish package distributions to PyPI
+      uses: pypa/gh-action-pypi-publish@release/v1
+```
+
+Other indices that support OIDC publishing can also be used, like TestPyPI:
+
+```yaml
+- name: Publish package distributions to TestPyPI
+  uses: pypa/gh-action-pypi-publish@release/v1
+  with:
+    repository-url: https://test.pypi.org/legacy/
+```
+
+> **Pro tip**: only set the `id-token: write` permission in the job that does
+> publishing, not globally. Also, try to separate building from publishing
+> — this makes sure that any scripts maliciously injected into the build
+> or test environment won't be able to elevate privileges while flying under
+> the radar.
+
+
 ## Non-goals
 
 This GitHub Action [has nothing to do with _building package
@@ -221,3 +266,6 @@ https://packaging.python.org/glossary/#term-Distribution-Package
 https://raw.githubusercontent.com/vshymanskyy/StandWithUkraine/main/banner-direct-single.svg
 [SWUdocs]:
 https://github.com/vshymanskyy/StandWithUkraine/blob/main/docs/README.md
+
+[warehouse#12965]: https://github.com/pypi/warehouse/issues/12965
+[OpenID Connect Publishing]: https://pypi.org/help/#openid-connect

action.yml

@@ -20,6 +20,7 @@ inputs:
       The inputs have been normalized to use kebab-case.
       Use `repository-url` instead.
     required: false
+    default: https://pypi.org/legacy/
   packages-dir:  # Canonical alias for `packages_dir`
     description: The target directory for distribution
     required: false

oidc-exchange.py

@@ -0,0 +1,156 @@
+import os
+import sys
+from http import HTTPStatus
+from pathlib import Path
+from typing import NoReturn
+from urllib.parse import urlparse
+
+import id  # pylint: disable=redefined-builtin
+import requests
+
+_GITHUB_STEP_SUMMARY = Path(os.getenv("GITHUB_STEP_SUMMARY"))
+
+# Rendered if OIDC identity token retrieval fails for any reason.
+_TOKEN_RETRIEVAL_FAILED_MESSAGE = """
+OIDC token retrieval failed: {identity_error}
+
+This generally indicates a workflow configuration error, such as insufficient
+permissions. Make sure that your workflow has `id-token: write` configured
+at the job level, e.g.:
+
+```yaml
+permissions:
+  id-token: write
+```
+
+Learn more at https://docs.github.com/en/actions/deployment/security-hardening-your-deployments/about-security-hardening-with-openid-connect#adding-permissions-settings.
+"""
+
+# Rendered if the package index refuses the given OIDC token.
+_SERVER_REFUSED_TOKEN_EXCHANGE_MESSAGE = """
+Token request failed: the server refused the request for the following reasons:
+
+{reasons}
+"""
+
+# Rendered if the package index's token response isn't valid JSON.
+_SERVER_TOKEN_RESPONSE_MALFORMED_JSON = """
+Token request failed: the index produced an unexpected
+{status_code} response.
+
+This strongly suggests a server configuration or downtime issue; wait
+a few minutes and try again.
+"""
+
+# Rendered if the package index's token response isn't a valid API token payload.
+_SERVER_TOKEN_RESPONSE_MALFORMED_MESSAGE = """
+Token response error: the index gave us an invalid response.
+
+This strongly suggests a server configuration or downtime issue; wait
+a few minutes and try again.
+"""
+
+
+def die(msg: str) -> NoReturn:
+    with _GITHUB_STEP_SUMMARY.open("a", encoding="utf-8") as io:
+        print(msg, file=io)
+
+    # NOTE: `msg` is Markdown formatted, so we emit only the header line to
+    # avoid clogging the console log with a full Markdown formatted document.
+    header = msg.splitlines()[0]
+    print(f"::error::OIDC exchange failure: {header}", file=sys.stderr)
+    sys.exit(1)
+
+
+def debug(msg: str):
+    print(f"::debug::{msg.title()}", file=sys.stderr)
+
+
+def get_normalized_input(name: str) -> str | None:
+    name = f"INPUT_{name.upper()}"
+    if val := os.getenv(name):
+        return val
+    return os.getenv(name.replace("-", "_"))
+
+
+def assert_successful_audience_call(resp: requests.Response, domain: str):
+    if resp.ok:
+        return
+
+    match resp.status_code:
+        case HTTPStatus.FORBIDDEN:
+            # This index supports OIDC, but forbids the client from using
+            # it (either because it's disabled, limited to a beta group, etc.)
+            die(f"audience retrieval failed: repository at {domain} has OIDC disabled")
+        case HTTPStatus.NOT_FOUND:
+            # This index does not support OIDC.
+            die(
+                "audience retrieval failed: repository at "
+                f"{domain} does not indicate OIDC support",
+            )
+        case other:
+            status = HTTPStatus(other)
+            # Unknown: the index may or may not support OIDC, but didn't respond with
+            # something we expect. This can happen if the index is broken, in maintenance mode,
+            # misconfigured, etc.
+            die(
+                "audience retrieval failed: repository at "
+                f"{domain} responded with unexpected {other}: {status.phrase}",
+            )
+
+
+repository_url = get_normalized_input("repository-url")
+repository_domain = urlparse(repository_url).netloc
+token_exchange_url = f"https://{repository_domain}/_/oidc/github/mint-token"
+
+# Indices are expected to support `https://{domain}/_/oidc/audience`,
+# which tells OIDC exchange clients which audience to use.
+audience_url = f"https://{repository_domain}/_/oidc/audience"
+audience_resp = requests.get(audience_url)
+assert_successful_audience_call(audience_resp, repository_domain)
+
+oidc_audience = audience_resp.json()["audience"]
+
+debug(f"selected OIDC token exchange endpoint: {token_exchange_url}")
+
+try:
+    oidc_token = id.detect_credential(audience=oidc_audience)
+except id.IdentityError as identity_error:
+    die(_TOKEN_RETRIEVAL_FAILED_MESSAGE.format(identity_error=identity_error))
+
+# Now we can do the actual token exchange.
+mint_token_resp = requests.post(
+    token_exchange_url,
+    json={"token": oidc_token},
+)
+
+try:
+    mint_token_payload = mint_token_resp.json()
+except requests.JSONDecodeError:
+    # Token exchange failure normally produces a JSON error response, but
+    # we might have hit a server error instead.
+    die(
+        _SERVER_TOKEN_RESPONSE_MALFORMED_JSON.format(
+            status_code=mint_token_resp.status_code,
+        ),
+    )
+
+# On failure, the JSON response includes the list of errors that
+# occurred during minting.
+if not mint_token_resp.ok:
+    reasons = "\n".join(
+        f"* `{error['code']}`: {error['description']}"
+        for error in mint_token_payload["errors"]
+    )
+
+    die(_SERVER_REFUSED_TOKEN_EXCHANGE_MESSAGE.format(reasons=reasons))
+
+pypi_token = mint_token_payload.get("token")
+if pypi_token is None:
+    die(_SERVER_TOKEN_RESPONSE_MALFORMED_MESSAGE)
+
+# Mask the newly minted PyPI token, so that we don't accidentally leak it in logs.
+print(f"::add-mask::{pypi_token}", file=sys.stderr)
+
+# This final print will be captured by the subshell in `twine-upload.sh`.
+print(pypi_token)

requirements/runtime.in

@@ -1,5 +1,13 @@
 twine
 
+# NOTE: Used to detect an ambient OIDC credential for OIDC publishing.
+id ~= 1.0
+
+# NOTE: This is pulled in transitively through `twine`, but we also declare
+# NOTE: it explicitly here because `oidc-exchange.py` uses it.
+# Ref: https://github.com/di/id
+requests
+
 # NOTE: `pkginfo` is a transitive dependency for us that is coming from Twine.
 # NOTE: It is declared here only to avoid installing a broken combination of
 # NOTE: the distribution packages. This should be removed once a fixed version

requirements/runtime.txt

@@ -18,6 +18,8 @@ cryptography==39.0.1
     # via secretstorage
 docutils==0.19
     # via readme-renderer
+id==1.0.0
+    # via -r requirements/runtime.in
 idna==3.4
     # via requests
 importlib-metadata==5.1.0
@@ -36,10 +38,12 @@ more-itertools==9.0.0
     # via jaraco-classes
 pkginfo==1.9.2
     # via
-    #   -r runtime.in
+    #   -r requirements/runtime.in
     #   twine
 pycparser==2.21
     # via cffi
+pydantic==1.10.6
+    # via id
 pygments==2.13.0
     # via
     #   readme-renderer
@@ -48,6 +52,8 @@ readme-renderer==37.3
     # via twine
 requests==2.28.1
     # via
+    #   -r requirements/runtime.in
+    #   id
     #   requests-toolbelt
     #   twine
 requests-toolbelt==0.10.1
@@ -61,7 +67,9 @@ secretstorage==3.3.3
 six==1.16.0
     # via bleach
 twine==4.0.1
-    # via -r runtime.in
+    # via -r requirements/runtime.in
+typing-extensions==4.5.0
+    # via pydantic
 urllib3==1.26.13
     # via
     #   requests

twine-upload.sh

@@ -40,6 +40,12 @@ INPUT_VERIFY_METADATA="$(get-normalized-input 'verify-metadata')"
 INPUT_SKIP_EXISTING="$(get-normalized-input 'skip-existing')"
 INPUT_PRINT_HASH="$(get-normalized-input 'print-hash')"
 
+if [[ "${INPUT_USER}" == "__token__" && -z "${INPUT_PASSWORD}" ]] ; then
+    # No password supplied by the user implies that we're in the OIDC flow;
+    # retrieve the OIDC credential and exchange it for a PyPI API token.
+    echo "::notice::In OIDC flow"
+    INPUT_PASSWORD="$(python /app/oidc-exchange.py)"
+fi
 
 if [[
     "$INPUT_USER" == "__token__" &&