@actions/artifact: BlobClient upload fails with "Bad Request" through HTTPS proxy — no proxy transport configured

Description

When a GitHub Actions self-hosted runner is configured with HTTPS_PROXY, the upload-artifact action fails with Error: Bad Request during the blob upload step. The @actions/artifact package creates a BlobClient from @azure/storage-blob without configuring proxy transport, causing the Azure SDK's HTTP pipeline to handle the CONNECT tunnel incorrectly.

Root cause

In packages/artifact/src/internal/upload/blob-upload.ts:

const blobClient = new BlobClient(authenticatedUploadURL)
const blockBlobClient = blobClient.getBlockBlobClient()

The BlobClient is created with only a URL — no StoragePipelineOptions with proxy configuration. The @azure/storage-blob SDK creates its own internal HTTP pipeline which may not correctly handle HTTPS CONNECT tunnels even though HTTPS_PROXY is set in the environment.

Suggested fix

Pass pipeline options with proxy configuration:

import { ProxyPolicy } from '@azure/core-rest-pipeline'

const blobClient = new BlobClient(authenticatedUploadURL, undefined, {
  proxyOptions: {
    host: process.env.HTTPS_PROXY || process.env.https_proxy,
  }
})

Or use newPipeline with the StorageSharedKeyCredential and configure the proxy in the pipeline options.

Evidence

Proxy logs confirm the CONNECT tunnel succeeds but the upload stalls:

CONNECT productionresultssa6.blob.core.windows.net:443 → status=200 (ALLOWED)
  requestSize=17259    (only ~17 KB sent)
  responseSize=8828    (error response)
  latency=74.999634s   (stalled for 75 seconds)
  user-agent: azsdk-net-Storage.Blobs/12.27.0 (.NET 8.0.25; Ubuntu 24.04.4 LTS)

Curl and Python upload 1 MB to the same blob endpoint through the same proxy in <1 second:

curl PUT 1MB to blob → HTTP 409 in 0.3s
Python PUT 1MB to blob → HTTP 409 in 0.6s

Standalone .NET HttpClient.PutAsync() also works fine (1.1s) — the issue is in how the Azure SDK BlobClient is instantiated without proxy configuration.

Workflow output

Run actions/upload-artifact@bbbca2ddaa5d8feaa63e36b76fdaad77386f024f
With the provided path, there will be 1 file uploaded
Artifact name is valid!
Root directory input is valid!
Uploading artifact: trivy-scan-results--skaffold-build-24347418057-1-1776089109.zip
Beginning upload of artifact content to blob storage
Error: Bad Request

Related

• actions/runner#4351 — same root cause in the runner's .NET ResultsHttpClient.cs which also creates BlobClient without proxy transport. The runner's step log/summary/diagnostic uploads stall in the same way.

Environment

• Runner: GitHubActionsRunner-linux-x64/2.333.1 (self-hosted on GKE via actions-runner-controller v0.13.1)
• Action: actions/upload-artifact@v4 (SHA bbbca2ddaa5d8feaa63e36b76fdaad77386f024f)
• Package: @actions/artifact v6.2.0 → @azure/storage-blob v12.30.0
• Proxy: GCP Secure Web Proxy (HTTPS forward proxy, CONNECT tunnel, no TLS inspection)
• Config: HTTPS_PROXY=http://<proxy-ip>:443
• Platform: Ubuntu 24.04.4 LTS on GKE

Workaround

Add .blob.core.windows.net to NO_PROXY:

NO_PROXY=.blob.core.windows.net

This bypasses the proxy for Azure Blob traffic, but defeats the purpose of hostname-based egress control through the proxy.

Start in packages/artifact/src/internal/upload/blob-upload.ts and inspect how BlobClient is constructed from authenticatedUploadURL, then review the @azure/storage-blob pipeline options used by the package. Reproduce the upload with HTTPS_PROXY configured and confirm that the artifact upload completes without the Bad Request or stall seen in the issue.