Module: PgPipeline::SessionGuard

Defined in:
lib/pg_pipeline/session_guard.rb

Constant Summary collapse

VALID_MODES = 
%i[default strict].freeze
ALLOWED_LEADING = 
%w[select insert update delete merge values with].freeze
FORBIDDEN_PATTERNS = 
{
  "set_config" => /\bset_config\s*\(/i,
  "setseed" => /\bsetseed\s*\(/i,
  "currval" => /\bcurrval\s*\(/i,
  "lastval" => /\blastval\s*\(/i,
  "session-advisory-lock" => /\bpg_(?:try_)?advisory_lock(?:_shared)?\s*\(/i,
  "session-advisory-unlock" => /\bpg_advisory_unlock(?:_shared|_all)?\s*\(/i,
  "select-into-temp" => /\binto\s+(?:(?:global|local)\s+)?temp(?:orary)?\b/i,
  "select-into-pg-temp" => /\binto\s+(?:table\s+)?pg_temp(?:_\d+)?\s*\./i
}.freeze
STRICT_FORBIDDEN = 
{
  "nextval" => /\bnextval\s*\(/i,
  "setval" => /\bsetval\s*\(/i,
  "setseed" => /\bsetseed\s*\(/i,
  "set_config" => /\bset_config\s*\(/i,
  "session-advisory-lock" => /\bpg_(?:try_)?advisory_lock(?:_shared)?\s*\(/i,
  "session-advisory-unlock" => /\bpg_advisory_unlock(?:_shared|_all)?\s*\(/i,
  "pg_export_snapshot" => /\bpg_export_snapshot\s*\(/i
}.freeze
PATTERN_PREFILTER = 
/\binto\b/i
NEEDS_MASK = 
/['"]|--|\/\*|\$[A-Za-z_0-9]*\$/
LEADING_KEYWORD = 
/\A\s*([a-zA-Z_]+)/
WHITESPACE_BYTES = 
[9, 10, 11, 12, 13, 32].freeze
GUARD_CACHE_LIMIT = 
2048
SAFE = 
:safe

Class Method Summary collapse

Class Method Details

.assert_multiplexable!(sql, mode: :default) ⇒ Object 



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# File 'lib/pg_pipeline/session_guard.rb', line 37

def assert_multiplexable!(sql, mode: :default)
  assert_multiplexable_normalized!(sql, mode: normalize_mode!(mode))
end

.assert_multiplexable_normalized!(sql, mode:) ⇒ Object

Raises:



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# File 'lib/pg_pipeline/session_guard.rb', line 41

def assert_multiplexable_normalized!(sql, mode:)
  reason = unsafe_reason_normalized(sql, mode: mode)
  return true unless reason

  raise UnsafeMultiplexError,
        "refusing to multiplex SQL (#{reason}); the shared path only accepts " \
        "session-neutral operations. Use Client#session for session work or " \
        "Client#transaction for an explicit transaction.\n" \
        "  offending SQL: #{sql.to_s.strip[0, 160]}"
end

.code_only(sql) ⇒ Object 



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# File 'lib/pg_pipeline/session_guard.rb', line 104

def code_only(sql)
  source = sql.to_s.b
  size = source.bytesize
  output = String.new(capacity: size, encoding: Encoding::BINARY)
  index = 0
  block_depth = 0

  while index < size
    byte = source.getbyte(index)
    nxt = index + 1 < size ? source.getbyte(index + 1) : nil

    if block_depth.positive?
      if byte == 47 && nxt == 42
        block_depth += 1
        output << "  "
        index += 2
      elsif byte == 42 && nxt == 47
        block_depth -= 1
        output << "  "
        index += 2
      else
        output << (byte == 10 ? 10 : 32)
        index += 1
      end
      next
    end

    if byte == 45 && nxt == 45
      newline = source.index("\n", index + 2)
      if newline
        output << (" " * (newline - index)) << "\n"
        index = newline + 1
      else
        output << (" " * (size - index))
        break
      end
      next
    end

    if byte == 47 && nxt == 42
      block_depth = 1
      output << "  "
      index += 2
      next
    end

    if byte == 39
      index = mask_quoted(source, output, index, 39, escape_backslash: escape_string_prefix?(source, index))
      next
    end

    if byte == 34
      index = mask_quoted(source, output, index, 34, escape_backslash: false)
      next
    end

    if byte == 36
      remainder = source.byteslice(index, size - index)
      tag = remainder.match(/\A\$(?:[A-Za-z_][A-Za-z0-9_]*)?\$/)&.[](0)
      if tag
        closing = source.index(tag, index + tag.bytesize)
        finish = closing ? closing + tag.bytesize : size
        output << (" " * (finish - index))
        index = finish
        next
      end
    end

    output << byte
    index += 1
  end

  output
end

.compute_unsafe_reason(sql, mode) ⇒ Object 



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# File 'lib/pg_pipeline/session_guard.rb', line 75

def compute_unsafe_reason(sql, mode)
  code = NEEDS_MASK.match?(sql) ? code_only(sql) : sql
  lead = code[LEADING_KEYWORD, 1]&.downcase

  return "empty" unless lead
  return "leading:#{lead}" unless ALLOWED_LEADING.include?(lead)
  return "multiple-statements" if multiple_statements?(code)
  return nil unless code.include?("(") || code.match?(PATTERN_PREFILTER)

  FORBIDDEN_PATTERNS.each do |name, pattern|
    return name if code.match?(pattern)
  end

  if mode == :strict
    STRICT_FORBIDDEN.each do |name, pattern|
      return "strict:#{name}" if code.match?(pattern)
    end
  end

  nil
end

.guard_cache ⇒ Object 



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# File 'lib/pg_pipeline/session_guard.rb', line 71

def guard_cache
  @guard_cache ||= { default: {}, strict: {} }
end

.multiple_statements?(code) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/pg_pipeline/session_guard.rb', line 222

def multiple_statements?(code)
  first = code.index(";")
  return false unless first

  index = first + 1
  size = code.bytesize
  while index < size
    return true unless WHITESPACE_BYTES.include?(code.getbyte(index))

    index += 1
  end
  false
end

.normalize_mode!(mode) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/pg_pipeline/session_guard.rb', line 97

def normalize_mode!(mode)
  normalized = mode.respond_to?(:to_sym) ? mode.to_sym : mode
  return normalized if VALID_MODES.include?(normalized)

  raise ArgumentError, "guard must be one of: #{VALID_MODES.map(&:inspect).join(", ")}"
end

.unsafe_reason(sql, mode: :default) ⇒ Object 



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# File 'lib/pg_pipeline/session_guard.rb', line 55

def unsafe_reason(sql, mode: :default)
  unsafe_reason_normalized(sql, mode: normalize_mode!(mode))
end

.unsafe_reason_normalized(sql, mode:) ⇒ Object 



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# File 'lib/pg_pipeline/session_guard.rb', line 59

def unsafe_reason_normalized(sql, mode:)
  key = sql.to_s
  cache = guard_cache.fetch(mode)
  cached = cache[key]
  return (cached.equal?(SAFE) ? nil : cached) if cached

  reason = compute_unsafe_reason(key, mode)
  cache.shift if cache.size >= GUARD_CACHE_LIMIT
  cache[key] = reason || SAFE
  reason
end