# Dl when $SAFE = 1

**URL:** <https://www.ruby-forum.com/t/dl-when-safe-1/89176>\
**Category:** Development\
**Created:** [March 18, 2007, 5:03am UTC](https://www.ruby-forum.com/t/dl-when-safe-1/89176 "2007-03-18T05:03:38Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![sheepman](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/d07c76/32.png) [@sheepman](https://www.ruby-forum.com/u/sheepman)\
**Post date:** [March 18, 2007, 5:03am UTC](https://www.ruby-forum.com/t/dl-when-safe-1/89176/1 "2007-03-18T05:03:38Z")

</div>

こんにちは、sheepman です。

$SAFE=1のときの dl ライブラリの振る舞いに関してです。

require ‘dl’  
$SAFE = 1  
h = DL.dlopen(nil)  
sys = h.sym(‘system’, ‘IP’)  
uname = ‘uname -rs’.taint  
sys[uname]

という感じで、汚染されている文字列を引数として system を呼べてしまいます。  
というわけで、パッチを書いてみました。

DL.dlopen の引数も SafeStringValue でチェックするようにしました。

dl のコードを読むと、String#to\_ptr はもとの文字列が汚染されていなくても、常に汚染された  
PtrData を返すので、 PtrData.new も常に汚染されたオブジェクトを返すようにしています。

このパッチは後方互換がないので、検討が必要だと思います。

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<div class="post-metadata">

**Author:** ![sheepman](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/d07c76/32.png) [@sheepman](https://www.ruby-forum.com/u/sheepman)\
**Post date:** [March 18, 2007, 8:00pm UTC](https://www.ruby-forum.com/t/dl-when-safe-1/89176/2 "2007-03-18T20:00:06Z")

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sheepman wrote:

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---

<div class="post-metadata">

**Author:** ![sheepman](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/d07c76/32.png) [@sheepman](https://www.ruby-forum.com/u/sheepman)\
**Post date:** [March 19, 2007, 12:43am UTC](https://www.ruby-forum.com/t/dl-when-safe-1/89176/3 "2007-03-19T00:43:34Z")

</div>

e$B$3$s$K$A$O!"e(Bsheepman e$B$G$9!#e(B

On Mon, 19 Mar 2007 03:59:37 +0900  
Takaaki T. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

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