The internal agent proxy now supports authentication credentials when forwarding to an upstream SOCKS proxy.
Details
Auth token is threaded through all proxy environment variables: HTTP_PROXY, HTTPS_PROXY, ALL_PROXY, GRPC_PROXY, FTP_PROXY, DOCKER_HTTP_PROXY, DOCKER_HTTPS_PROXY, CLOUDSDK_PROXY_*.
GIT_SSH_COMMAND on Linux includes proxyauth=srt:${token} in the socat command.
GIT_CONFIG_PARAMETERS='http.proxyAuthMethod=basic' is set automatically when a proxy auth token is present.
The SOCKS server validates credentials and logs "SOCKS auth rejected" on mismatch.
Evidence
Authentication token threading in sandbox environment setup (search for "SOCKS auth rejected" and "GIT_CONFIG_PARAMETERS='http.proxyAuthMethod=basic'")
Strings lifted out of the shipped bundle, so the claim above can be checked against them.
