A documentation for using ssh key from github secret to `--ssh` variable

[flexchar]

It'd be incredibly helpful to have an example of how to use the --ssh option when one has a private key stored as a secret on the repository.

[crazy-max]

Here's an example to load a SSH key in your workflow and use it in your Dockerfile to fetch Go modules from private repos:

      -
        name: Checkout
        uses: actions/checkout@v3
      -
        name: Set up SSH
        uses: MrSquaare/ssh-setup-action@c86f64bc308405a10f3c9f2ef6124fdf4370e677 # v2.0.0
        with:
          host: github.com
          private-key: ${{ secrets.SSH_GITHUB_PPK }}
          private-key-name: github-ppk
      -
        name: Build and push
        uses: docker/build-push-action@v4
        with:
          context: .
          ssh: default
          push: true
          tags: user/app:latest

# syntax=docker/dockerfile:1

ARG GO_VERSION="1.20"

FROM golang:${GO_VERSION}-alpine AS base
ENV CGO_ENABLED=0
ENV GOPRIVATE="github.com/foo/*"
RUN apk add --no-cache file git rsync openssh-client
RUN mkdir -p -m 0700 ~/.ssh && ssh-keyscan github.com >> ~/.ssh/known_hosts
WORKDIR /src

FROM base AS vendor
# this step configure git and checks the ssh key is loaded
RUN --mount=type=ssh <<EOT
  set -e
  echo "Setting Git SSH protocol"
  git config --global url."git@github.com:".insteadOf "https://github.com/"
  (
    set +e
    ssh -T git@github.com
    if [ ! "$?" = "1" ]; then
      echo "No GitHub SSH key loaded exiting..."
      exit 1
    fi
  )
EOT
# this one download go modules
RUN --mount=type=bind,target=. \
    --mount=type=cache,target=/go/pkg/mod \
    --mount=type=ssh \
    go mod download -x

FROM vendor AS build
RUN --mount=type=bind,target=. \
    --mount=type=cache,target=/go/pkg/mod \
    --mount=type=cache,target=/root/.cache \
    go build ...

[na-jakobs]

I found that you need to specify ssh default equals the agent socket:

- name: Build and push
  uses: docker/build-push-action@v5
  with:
    ssh: |
      default=${{ env.SSH_AUTH_SOCK }}
    context: .
    push: true
    tags: |
      myimage:latest

[crazy-max]

This should be enough:

  with:
    ssh: default

@dvdksn Maybe we could make some docs for ssh using #714 (comment)

[will4j]

This works for me: just save ssh private key to a temporary file and use it in ssh variable.

# .github/workflows/image-build.yaml
jobs:
  build-image:
    steps:
      - name: Save ssh private key file
        run: echo "${{ secrets.DEPLOY_SSH_PRIVATE_KEY }}" > deploy-ssh-key
      - name: Build and push app image
        uses: docker/build-push-action@v5
        with:
          context: .
          push: true
          file: Dockerfile
          ssh: |
            default=deploy-ssh-key

# Dockerfile
...
RUN --mount=type=ssh conda env create -f environment.yml
...