[ruby/resolv] Tighten argument check in Resolv::LOC::Alt.create

Limit the range from -100 km to the upper limit of the 32-bit
representation.

ruby/resolv@e6dfbe7cb0

Author: nobu

lib/resolv.rb

@@ -3428,7 +3428,10 @@ class Alt
 
       # Regular expression LOC Alt must match.
 
-      Regex = /^([+-]*\d+\.*\d*)[m]$/
+      Regex = /\A([+-]?0*\d{1,8}(?:\.\d+)?)m\z/
+
+      # Bias to a base of 100,000m below the WGS 84 reference spheroid.
+      Bias = 100_000_00
 
       ##
       # Creates a new LOC::Alt from +arg+ which may be:
@@ -3444,8 +3447,11 @@ def self.create(arg)
           unless Regex =~ arg
             raise ArgumentError.new("not a properly formed Alt string: " + arg)
           end
-          altitude = [($1.to_f*(1e2))+(1e7)].pack("N")
-          return Alt.new(altitude)
+          altitude = ($1.to_f * 100).to_i + Bias
+          unless (0...0x1_0000_0000) === altitude
+            raise ArgumentError.new("out of raise as Alt: #{arg}")
+          end
+          return new([altitude].pack("N"))
         else
           raise ArgumentError.new("cannot interpret as Alt: #{arg.inspect}")
         end

test/resolv/test_resource.rb

@@ -75,6 +75,27 @@ def test_coord
     assert_equal([coordinate].pack("N"), coord.coordinates)
     assert_equal(coord, Resolv::LOC::Coord.create(coord.to_s))
   end
+
+  def test_alt
+    assert_alt("0.0m", 0)
+    assert_alt("+0.0m", 0)
+    assert_alt("-0.0m", 0)
+    assert_alt("+0.01m", 1)
+    assert_alt("1.0m", 100)
+    assert_alt("+1.0m", 100)
+    assert_alt("100000.0m", +10000000)
+    assert_alt("+100000.0m", +10000000)
+    assert_alt("-100000.0m", -10000000)
+    assert_alt("+42849672.95m", 0xffff_ffff-100_000_00)
+    assert_raise(ArgumentError) {Resolv::LOC::Alt.create("-100000.01m")}
+    assert_raise(ArgumentError) {Resolv::LOC::Alt.create("+42849672.96m")}
+  end
+
+  private def assert_alt(input, altitude)
+    alt = Resolv::LOC::Alt.create(input)
+
+    assert_equal([altitude + 1e7].pack("N"), alt.altitude)
+  end
 end
 
 class TestResolvResourceCAA < Test::Unit::TestCase