brew: Add ScpDownloadStrategy

Library/Homebrew/download_strategy.rb

@@ -594,6 +594,70 @@ class GitHubPrivateRepositoryReleaseDownloadStrategy < GitHubPrivateRepositoryDo
   end
 end
 
+# ScpDownloadStrategy downloads files using ssh via scp. To use it, add
+# ":using => ScpDownloadStrategy" to the URL section of your formula or
+# provide a URL starting with scp://. This strategy uses ssh credentials for
+# authentication. If a public/private keypair is configured, it will not
+# prompt for a password.
+#
+# Usage:
+#
+#   class Abc < Formula
+#     url "scp://example.com/src/abc.1.0.tar.gz"
+#     ...
+class ScpDownloadStrategy < AbstractFileDownloadStrategy
+  attr_reader :tarball_path, :temporary_path
+
+  def initialize(name, resource)
+    super
+    @tarball_path = HOMEBREW_CACHE/"#{name}-#{version}#{ext}"
+    @temporary_path = Pathname.new("#{cached_location}.incomplete")
+    parse_url_pattern
+  end
+
+  def parse_url_pattern
+    url_pattern = %r{scp://([^@]+@)?([^@:/]+)(:\d+)?/(\S+)}
+    if @url !~ url_pattern
+      raise ScpDownloadStrategyError, "Invalid URL for scp: #{@url}"
+    end
+
+    _, @user, @host, @port, @path = *@url.match(url_pattern)
+  end
+
+  def fetch
+    ohai "Downloading #{@url}"
+
+    if cached_location.exist?
+      puts "Already downloaded: #{cached_location}"
+    else
+      begin
+        safe_system "scp", scp_source, temporary_path.to_s
+      rescue ErrorDuringExecution
+        raise ScpDownloadStrategyError, "Failed to run scp #{scp_source}"
+      end
+
+      ignore_interrupts { temporary_path.rename(cached_location) }
+    end
+  end
+
+  def cached_location
+    tarball_path
+  end
+
+  def clear_cache
+    super
+    rm_rf(temporary_path)
+  end
+
+  private
+
+  def scp_source
+    path_prefix = "/" unless @path.start_with?("~")
+    port_arg = "-P #{@port[1..-1]} " if @port
+    "#{port_arg}#{@user}#{@host}:#{path_prefix}#{@path}"
+  end
+end
+
 class SubversionDownloadStrategy < VCSDownloadStrategy
   def initialize(name, resource)
     super
@@ -1140,6 +1204,8 @@ class DownloadStrategyDetector
     when %r{^s3://}
       require_aws_sdk
       S3DownloadStrategy
+    when %r{^scp://}
+      ScpDownloadStrategy
     else
       CurlDownloadStrategy
     end

Library/Homebrew/exceptions.rb

@@ -515,6 +515,13 @@ class CurlDownloadStrategyError < RuntimeError
   end
 end
 
+# raised in ScpDownloadStrategy.fetch
+class ScpDownloadStrategyError < RuntimeError
+  def initialize(cause)
+    super "Download failed: #{cause}"
+  end
+end
+
 # raised by safe_system in utils.rb
 class ErrorDuringExecution < RuntimeError
   def initialize(cmd, args = [])

Library/Homebrew/test/download_strategies_spec.rb

@@ -268,6 +268,90 @@ describe CurlDownloadStrategy do
   end
 end
 
+describe ScpDownloadStrategy do
+  def resource_for(url)
+    double(Resource, url: url, mirrors: [], specs: {}, version: nil)
+  end
+
+  subject { described_class.new(name, resource) }
+  let(:name) { "foo" }
+  let(:url) { "scp://example.com/foo.tar.gz" }
+  let(:resource) { resource_for(url) }
+
+  describe "#initialize" do
+    invalid_urls = %w[
+      http://example.com/foo.tar.gz
+      scp://@example.com/foo.tar.gz
+      scp://example.com:/foo.tar.gz
+      scp://example.com
+    ]
+
+    invalid_urls.each do |invalid_url|
+      context "with invalid URL #{invalid_url}" do
+        it "raises ScpDownloadStrategyError" do
+          expect {
+            described_class.new(name, resource_for(invalid_url))
+          }.to raise_error(ScpDownloadStrategyError)
+        end
+      end
+    end
+  end
+
+  describe "#fetch" do
+    before do
+      expect(subject.temporary_path).to receive(:rename).and_return(true)
+    end
+
+    context "when given a valid URL" do
+      let(:url) { "scp://example.com/foo.tar.gz" }
+      it "copies the file via scp" do
+        expect(subject)
+          .to receive(:safe_system)
+          .with("scp", "example.com:/foo.tar.gz", anything)
+          .and_return(true)
+
+        subject.fetch
+      end
+    end
+
+    context "when given a URL with a username" do
+      let(:url) { "scp://user@example.com/foo.tar.gz" }
+      it "copies the file via scp" do
+        expect(subject)
+          .to receive(:safe_system)
+          .with("scp", "user@example.com:/foo.tar.gz", anything)
+          .and_return(true)
+
+        subject.fetch
+      end
+    end
+
+    context "when given a URL with a port" do
+      let(:url) { "scp://example.com:1234/foo.tar.gz" }
+      it "copies the file via scp" do
+        expect(subject)
+          .to receive(:safe_system)
+          .with("scp", "-P 1234 example.com:/foo.tar.gz", anything)
+          .and_return(true)
+
+        subject.fetch
+      end
+    end
+
+    context "when given a URL with /~/" do
+      let(:url) { "scp://example.com/~/foo.tar.gz" }
+      it "treats the path as relative to the home directory" do
+        expect(subject)
+          .to receive(:safe_system)
+          .with("scp", "example.com:~/foo.tar.gz", anything)
+          .and_return(true)
+
+        subject.fetch
+      end
+    end
+  end
+end
+
 describe DownloadStrategyDetector do
   describe "::detect" do
     subject { described_class.detect(url, strategy) }
@@ -306,6 +390,11 @@ describe DownloadStrategyDetector do
       end
     end
 
+    context "when given an scp URL" do
+      let(:url) { "scp://example.com/brew.tar.gz" }
+      it { is_expected.to eq(ScpDownloadStrategy) }
+    end
+
     it "defaults to cURL" do
       expect(subject).to eq(CurlDownloadStrategy)
     end