Module: Pwnbus::Configdb::Files

Defined in:
lib/pwnbus/configdb/files.rb

Overview

Handling procedures for database files.

Class Method Summary collapse

Class Method Details

.can_access_path?(db_path, options) ⇒ Boolean

True if the file is accessible with the desired Configdb#open options.

Args:

db_path:: path to a database file
options:: same as for Configdb#new

Returns:

  • (Boolean) 


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# File 'lib/pwnbus/configdb/files.rb', line 74

def self.can_access_path?(db_path, options)
  db_stat = File.stat(db_path)
  options[:read] ? db_stat.readable? : db_stat.writable?
end

.crash_recovery_db_path(db_path, options) ⇒ Object

Peforms crash recovery on a database.

Args:

db_path:: path to a file containing a configuration database
options:: same as for Configdb#new

Returns the path to the recovered database. Most of the time, this will be



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# File 'lib/pwnbus/configdb/files.rb', line 28

def self.crash_recovery_db_path(db_path, options)
  new_db_path = db_path + '.new'
  if !File.exist?(db_path)
    # Crashed during rename.
    if options[:read]        
      # Writing to the .new copy completed. The copy will be locked.
      return new_db_path
    else
      # Do the rename.
      File.rename new_db_path, db_path
      return db_path
    end
  end
        
  if File.exist?(new_db_path) && !options[:read]
    # Crashed during new version write. The new version is probably corrupted.
    File.unlink new_db_path
  end
  db_path
end

.create_db(name, options) ⇒ Object

Creates a new database. The database must not exist.

Args:

name:: the database name
options:: same as for Configdb#open

Returns the path to the database file.



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# File 'lib/pwnbus/configdb/files.rb', line 98

def self.create_db(name, options)
  db_path = File.join ensure_db_dir_exists, name + '.yml'
  File.open(db_path, 'w') do |f|
    f.flock File::LOCK_EX
    YAML.dump empty_db_data(name), f
  end
  permissions = public_db_name?(name) ? 0644 : 0600
  File.chmod permissions, db_path
  db_path
end

.db_dir_global_path ⇒ Object

Path to the computer-global databases.



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# File 'lib/pwnbus/configdb/files.rb', line 147

def self.db_dir_global_path
  '/etc/pwnbus'
end

.db_dir_paths ⇒ Object

Paths to the directory containing database files for the current user.



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# File 'lib/pwnbus/configdb/files.rb', line 133

def self.db_dir_paths
  if superuser?
    [db_dir_global_path]
  else
    [db_dir_user_path, db_dir_global_path]
  end
end

.db_dir_user_path ⇒ Object

Path to the directory holding per-user databases.



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# File 'lib/pwnbus/configdb/files.rb', line 142

def self.db_dir_user_path
  File.expand_path('~/.pwnbus')
end

.empty_db_data(name) ⇒ Object

The contents of a empty (newly created) database.

Args:

name:: the database's name



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# File 'lib/pwnbus/configdb/files.rb', line 113

def self.empty_db_data(name)
  {}
end

.ensure_db_dir_exists ⇒ Object

Returns the the database directory. Creates it if it doesn’t exist.



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# File 'lib/pwnbus/configdb/files.rb', line 123

def self.ensure_db_dir_exists
  dir_path = db_dir_paths.first
  unless File.exist? dir_path    
    FileUtils.mkdir_p dir_path
    File.chmod 0755, dir_path
  end
  dir_path
end

.find_db(name) ⇒ Object

The path to a database, or nil if the database doesn’t exist.

Args:

name:: the database name



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# File 'lib/pwnbus/configdb/files.rb', line 83

def self.find_db(name)
  db_dir_paths.each do |dir_path|
    db_path = File.join dir_path, name + '.yml'
    return db_path if File.exist?(db_path) || File.exist?(db_path + '.new')
  end
  nil
end

.open_db(db_path, options) ⇒ Object

Opens the file for a configuration database. The file must exist.

Returns a File instance.



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# File 'lib/pwnbus/configdb/files.rb', line 14

def self.open_db(db_path, options)
  db_path = crash_recovery_db_path db_path, options
  f = File.open db_path, 'r'
  f.flock options[:read] ? File::LOCK_SH : File::LOCK_EX
  f
end

.public_db_name?(name) ⇒ Boolean

Databases whose names start with . are public (global-read, author-write).

Returns:

  • (Boolean) 


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# File 'lib/pwnbus/configdb/files.rb', line 118

def self.public_db_name?(name)
  name[0] != ?.
end

.superuser? ⇒ Boolean

True if running as the root user.

Returns:

  • (Boolean) 


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# File 'lib/pwnbus/configdb/files.rb', line 152

def self.superuser?
  Process.euid == 0
end

.write_db(db_path, options) ⇒ Object

Writes a new database version atomically.

Args:

db_path:: path to a file containing a configuration database
options:: same as for Configdb#new

Returns db_path.



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# File 'lib/pwnbus/configdb/files.rb', line 56

def self.write_db(db_path, options)
  new_db_path = db_path + '.new'
  File.open(new_db_path, 'w') do |f|
    f.flock File::LOCK_EX
    permissions = public_db_name?(File.basename(db_path)) ? 0644 : 0600
    File.chmod permissions, new_db_path      
    yield f
  end
  File.unlink db_path
  File.rename new_db_path, db_path
  db_path
end