Validates whether an image is acceptable through mime type

image/jpeg, image/png & image/gif are considered the allowed mime types
for an image. mimemagic gem is added as dependency in order to do the
checking.

Added tests to check against three supported mime types. A fake jpg
fixture (created with 'touch' command) has been added to test that
extension is no longer used.

5 files changed, 14 insertions, 8 deletions

diff --git a/axlsx.gemspec b/axlsx.gemspec
index 9fc19285..8e3cd9ca 100644
--- a/axlsx.gemspec
+++ b/axlsx.gemspec
@@ -20,6 +20,7 @@ Gem::Specification.new do |s|
   s.add_runtime_dependency 'nokogiri', '>= 1.4.1'
   s.add_runtime_dependency 'rubyzip', '~> 1.1.7'
   s.add_runtime_dependency "htmlentities", "~> 4.3.1"
+  s.add_runtime_dependency "mimemagic", "~> 0.3"
 
   s.add_development_dependency 'yard'
   s.add_development_dependency 'kramdown'
diff --git a/examples/image1_fake.jpg b/examples/image1_fake.jpg
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/examples/image1_fake.jpg
diff --git a/lib/axlsx.rb b/lib/axlsx.rb
index c6f01b19..14456024 100644
--- a/lib/axlsx.rb
+++ b/lib/axlsx.rb
@@ -1,6 +1,7 @@
 # encoding: UTF-8
 require 'htmlentities'
 require 'axlsx/version.rb'
+require 'mimemagic'
 
 require 'axlsx/util/simple_typed_list.rb'
 require 'axlsx/util/constants.rb'
diff --git a/lib/axlsx/drawing/pic.rb b/lib/axlsx/drawing/pic.rb
index 571e9047..b090c661 100644
--- a/lib/axlsx/drawing/pic.rb
+++ b/lib/axlsx/drawing/pic.rb
@@ -25,8 +25,8 @@ module Axlsx
       @picture_locking = PictureLocking.new(options)
     end
 
-    # allowed file extenstions
-    ALLOWED_EXTENSIONS = ['gif', 'jpeg', 'png', 'jpg']
+    # allowed mime types
+    ALLOWED_MIME_TYPES = %w(image/jpeg image/png image/gif)
 
     # The name to use for this picture
     # @return [String]
@@ -67,7 +67,7 @@ module Axlsx
 
     def image_src=(v)
       Axlsx::validate_string(v)
-      RestrictionValidator.validate 'Pic.image_src', ALLOWED_EXTENSIONS, File.extname(v.downcase).delete('.')
+      RestrictionValidator.validate 'Pic.image_src', ALLOWED_MIME_TYPES, MimeMagic.by_magic(File.open(v)).to_s
       raise ArgumentError, "File does not exist" unless File.exist?(v)
       @image_src = v
     end
diff --git a/test/drawing/tc_pic.rb b/test/drawing/tc_pic.rb
index 3cea49c0..066d9962 100644
--- a/test/drawing/tc_pic.rb
+++ b/test/drawing/tc_pic.rb
@@ -5,7 +5,10 @@ class TestPic < Test::Unit::TestCase
   def setup
     @p = Axlsx::Package.new
     ws = @p.workbook.add_worksheet
-    @test_img =  File.dirname(__FILE__) + "/../../examples/image1.jpeg"
+    @test_img = @test_img_jpg =  File.dirname(__FILE__) + "/../../examples/image1.jpeg"
+    @test_img_png =  File.dirname(__FILE__) + "/../../examples/image1.png"
+    @test_img_gif =  File.dirname(__FILE__) + "/../../examples/image1.gif"
+    @test_img_fake =  File.dirname(__FILE__) + "/../../examples/image1_fake.jpg"
     @test_img_up = File.dirname(__FILE__) + "/../../examples/IMAGE1UP.JPEG"
     @image = ws.add_image :image_src => @test_img, :hyperlink => 'https://github.com/randym', :tooltip => "What's up doc?"
   end
@@ -70,11 +73,12 @@ class TestPic < Test::Unit::TestCase
   end
 
   def test_image_src
-    assert_raise(ArgumentError) { @image.image_src = 49 }
-    assert_raise(ArgumentError) { @image.image_src = 'Unknown' }
     assert_raise(ArgumentError) { @image.image_src = __FILE__ }
-    assert_nothing_raised { @image.image_src = @test_img }
-    assert_equal(@image.image_src, @test_img)
+    assert_raise(ArgumentError) { @image.image_src = @test_img_fake }
+    assert_nothing_raised { @image.image_src = @test_img_gif }
+    assert_nothing_raised { @image.image_src = @test_img_png }
+    assert_nothing_raised { @image.image_src = @test_img_jpg }
+    assert_equal(@image.image_src, @test_img_jpg)
   end
 
   def test_image_src_downcase