Merge pull request #16941 from alebcay/elf-avoid-ldd

os/linux/elf: avoid using ldd for listing dynamic dependencies

Library/Homebrew/os/linux/elf.rb

@@ -1,6 +1,8 @@
 # typed: true
 # frozen_string_literal: true
 
+require "os/linux/ld"
+
 # {Pathname} extension for dealing with ELF files.
 # @see https://en.wikipedia.org/wiki/Executable_and_Linkable_Format#File_header
 #
@@ -130,19 +132,7 @@ def initialize(path)
  @dylib_id, needed = needed_libraries path
  return if needed.empty?
 
- ldd = DevelopmentTools.locate "ldd"
- ldd_output = Utils.popen_read(ldd, path.expand_path.to_s).split("\n")
- return unless $CHILD_STATUS.success?
-
- ldd_paths = ldd_output.filter_map do |line|
- match = line.match(/\t.+ => (.+) \(.+\)|\t(.+) => not found/)
- next unless match
-
- match.captures.compact.first
- end
- @dylibs = ldd_paths.select do |ldd_path|
- needed.include? File.basename(ldd_path)
- end
+ @dylibs = needed.map { |lib| find_full_lib_path(lib).to_s }
  end
 
  private
@@ -157,6 +147,52 @@ def needed_libraries_using_patchelf_rb(path)
  patcher = path.patchelf_patcher
  [patcher.soname, patcher.needed]
  end
+
+ def find_full_lib_path(basename)
+ local_paths = (path.patchelf_patcher.runpath || path.patchelf_patcher.rpath)&.split(":")
+
+ # Search for dependencies in the runpath/rpath first
+ local_paths&.each do |local_path|
+ candidate = Pathname(local_path)/basename
+ return candidate if candidate.exist? && candidate.elf?
+ end
+
+ # Check if DF_1_NODEFLIB is set
+ dt_flags_1 = path.patchelf_patcher.elf.segment_by_type(:dynamic)&.tag_by_type(:flags_1)
+ nodeflib_flag = if dt_flags_1.nil?
+ false
+ else
+ dt_flags_1.value & ELFTools::Constants::DF::DF_1_NODEFLIB != 0
+ end
+
+ linker_library_paths = OS::Linux::Ld.library_paths
+ linker_system_dirs = OS::Linux::Ld.system_dirs
+
+ # If DF_1_NODEFLIB is set, exclude any library paths that are subdirectories
+ # of the system dirs
+ if nodeflib_flag
+ linker_library_paths = linker_library_paths.reject do |lib_path|
+ linker_system_dirs.any? { |system_dir| Utils::Path.child_of? system_dir, lib_path }
+ end
+ end
+
+ # If not found, search recursively in the paths listed in ld.so.conf (skipping
+ # paths that are subdirectories of the system dirs if DF_1_NODEFLIB is set)
+ linker_library_paths.each do |linker_library_path|
+ candidate = Pathname(linker_library_path)/basename
+ return candidate if candidate.exist? && candidate.elf?
+ end
+
+ # If not found, search in the system dirs, unless DF_1_NODEFLIB is set
+ unless nodeflib_flag
+ linker_system_dirs.each do |linker_system_dir|
+ candidate = Pathname(linker_system_dir)/basename
+ return candidate if candidate.exist? && candidate.elf?
+ end
+ end
+
+ basename
+ end
  end
  private_constant :Metadata
 

Library/Homebrew/os/linux/ld.rb

@@ -0,0 +1,74 @@
+# typed: strict
+# frozen_string_literal: true
+
+module OS
+ module Linux
+ # Helper functions for querying `ld` information.
+ #
+ # @api private
+ module Ld
+ sig { returns(String) }
+ def self.brewed_ld_so_diagnostics
+ brewed_ld_so = HOMEBREW_PREFIX/"lib/ld.so"
+ return "" unless brewed_ld_so.exist?
+
+ ld_so_output = Utils.popen_read(brewed_ld_so, "--list-diagnostics")
+ return "" unless $CHILD_STATUS.success?
+
+ ld_so_output
+ end
+
+ sig { returns(String) }
+ def self.sysconfdir
+ fallback_sysconfdir = "/etc"
+
+ match = brewed_ld_so_diagnostics.match(/path.sysconfdir="(.+)"/)
+ return fallback_sysconfdir unless match
+
+ match.captures.compact.first || fallback_sysconfdir
+ end
+
+ sig { returns(T::Array[String]) }
+ def self.system_dirs
+ dirs = []
+
+ brewed_ld_so_diagnostics.split("\n").each do |line|
+ match = line.match(/path.system_dirs\[0x.*\]="(.*)"/)
+ next unless match
+
+ dirs << match.captures.compact.first
+ end
+
+ dirs
+ end
+
+ sig { params(conf_path: T.any(Pathname, String)).returns(T::Array[String]) }
+ def self.library_paths(conf_path = Pathname(sysconfdir)/"ld.so.conf")
+ conf_file = Pathname(conf_path)
+ paths = Set.new
+ directory = conf_file.realpath.dirname
+
+ conf_file.readlines.each do |line|
+ # Remove comments and leading/trailing whitespace
+ line.strip!
+ line.sub!(/\s*#.*$/, "")
+
+ if line.start_with?(/\s*include\s+/)
+ include_path = Pathname(line.sub(/^\s*include\s+/, "")).expand_path
+ wildcard = include_path.absolute? ? include_path : directory/include_path
+
+ Dir.glob(wildcard.to_s).each do |include_file|
+ paths += library_paths(include_file)
+ end
+ elsif line.empty?
+ next
+ else
+ paths << line
+ end
+ end
+
+ paths.to_a
+ end
+ end
+ end
+end

Library/Homebrew/test/os/linux/ld_spec.rb

@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+require "os/linux/ld"
+require "tmpdir"
+
+RSpec.describe OS::Linux::Ld do
+ describe "::library_paths" do
+ ld_etc = Pathname("")
+ before do
+ ld_etc = Pathname(Dir.mktmpdir("homebrew-tests-ld-etc-", Dir.tmpdir))
+ FileUtils.mkdir [ld_etc/"subdir1", ld_etc/"subdir2"]
+ (ld_etc/"ld.so.conf").write <<~EOS
+ # This line is a comment
+
+ include #{ld_etc}/subdir1/*.conf # This is an end-of-line comment, should be ignored
+
+ # subdir2 is an empty directory
+ include #{ld_etc}/subdir2/*.conf
+
+ /a/b/c
+ /d/e/f # Indentation on this line should be ignored
+ /a/b/c # Duplicate entry should be ignored
+ EOS
+
+ (ld_etc/"subdir1/1-1.conf").write <<~EOS
+ /foo/bar
+ /baz/qux
+ EOS
+
+ (ld_etc/"subdir1/1-2.conf").write <<~EOS
+ /g/h/i
+ EOS
+
+ # Empty files (or files containing only whitespace) should be ignored
+ (ld_etc/"subdir1/1-3.conf").write "\n\t\n\t\n"
+ (ld_etc/"subdir1/1-4.conf").write ""
+ end
+
+ after do
+ FileUtils.rm_rf ld_etc
+ end
+
+ it "parses library paths successfully" do
+ expect(described_class.library_paths(ld_etc/"ld.so.conf")).to eq(%w[/foo/bar /baz/qux /g/h/i /a/b/c /d/e/f])
+ end
+ end
+end

Library/Homebrew/test/utils/path_spec.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+require "utils/path"
+
+RSpec.describe Utils::Path do
+ describe "::child_of?" do
+ it "recognizes a path as its own child" do
+ expect(described_class.child_of?("/foo/bar", "/foo/bar")).to be(true)
+ end
+
+ it "recognizes a path that is a child of the parent" do
+ expect(described_class.child_of?("/foo", "/foo/bar")).to be(true)
+ end
+
+ it "recognizes a path that is a grandchild of the parent" do
+ expect(described_class.child_of?("/foo", "/foo/bar/baz")).to be(true)
+ end
+
+ it "does not recognize a path that is not a child" do
+ expect(described_class.child_of?("/foo", "/bar/baz")).to be(false)
+ end
+
+ it "handles . and .. in paths correctly" do
+ expect(described_class.child_of?("/foo", "/foo/./bar")).to be(true)
+ expect(described_class.child_of?("/foo/bar", "/foo/../foo/bar/baz")).to be(true)
+ end
+
+ it "handles relative paths correctly" do
+ expect(described_class.child_of?("foo", "./bar/baz")).to be(false)
+ expect(described_class.child_of?("../foo", "./bar/baz/../../../foo/bar/baz")).to be(true)
+ end
+ end
+end

Library/Homebrew/utils/path.rb

@@ -0,0 +1,14 @@
+# typed: strict
+# frozen_string_literal: true
+
+module Utils
+ module Path
+ sig { params(parent: T.any(Pathname, String), child: T.any(Pathname, String)).returns(T::Boolean) }
+ def self.child_of?(parent, child)
+ parent_pathname = Pathname(parent).expand_path
+ child_pathname = Pathname(child).expand_path
+ child_pathname.ascend { |p| return true if p == parent_pathname }
+ false
+ end
+ end
+end