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<a href="../../en-US/index.html">Defensive Coding Guide </a>
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<li><a class="" href="../../en-US/tasks/Tasks-Processes.html">Processes</a></li>
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<li><a class="" href="../../en-US/tasks/Tasks-Serialization.html">Serialization and Deserialization</a></li>
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<span id="sgSpan-0-3" class="fa fa-caret-right"></span> Implementing Security Features
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<div class="page-header">
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<h2>The Go Programming Language</h2>
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</div>
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<div id="preamble">
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<div class="sectionbody">
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<div class="paragraph">
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<p>This chapter contains language-specific recommendations for Go.</p>
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</div>
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</div>
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</div>
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<div class="sect1">
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<h2 id="chap-Defensive_Coding-Go-Memory_Safety"><a class="anchor" href="#chap-Defensive_Coding-Go-Memory_Safety"></a>Memory Safety</h2>
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<div class="sectionbody">
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<div class="paragraph">
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<p>Go provides memory safety, but only if the program is not executed
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in parallel (that is, <code>GOMAXPROCS</code> is not larger than
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<code>1</code>). The reason is that interface values and
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slices consist of multiple words are not updated atomically.
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Another thread of execution can observe an inconsistent pairing
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between type information and stored value (for interfaces) or
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pointer and length (for slices), and such inconsistency can lead
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to a memory safety violation.</p>
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</div>
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<div class="paragraph">
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<p>Code which does not run in parallel and does not use the
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<code>unsafe</code> package (or other packages which expose
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unsafe constructs) is memory-safe. For example, invalid casts and
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out-of-range subscripting cause panics at run time.</p>
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</div>
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<div class="paragraph">
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<p>Keep in mind that finalization can introduce parallelism because
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finalizers are executed concurrently, potentially interleaved with
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the rest of the program.</p>
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</div>
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</div>
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</div>
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<div class="sect1">
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<h2 id="chap-Defensive_Coding-Go-Error_Handling"><a class="anchor" href="#chap-Defensive_Coding-Go-Error_Handling"></a>Error Handling</h2>
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<div class="sectionbody">
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<div class="paragraph">
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<p>Only a few common operations (such as pointer dereference, integer
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division, array subscripting) trigger exceptions in Go, called
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<strong>panics</strong>. Most interfaces in the standard
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library use a separate return value of type
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<code>error</code> to signal error.</p>
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</div>
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<div class="paragraph">
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<p>Not checking error return values can lead to incorrect operation
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and data loss (especially in the case of writes, using interfaces
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such as <code>io.Writer</code>).</p>
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</div>
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<div class="paragraph">
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<p>The correct way to check error return values depends on the
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function or method being called. In the majority of cases, the
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first step after calling a function should be an error check
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against the <code>nil</code> value, handling any encountered
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error. See <a href="#ex-Defensive_Coding-Go-Error_Handling-Regular">Regular error handling in Go</a> for
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details.</p>
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</div>
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<div id="ex-Defensive_Coding-Go-Error_Handling-Regular" class="exampleblock">
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<div class="title">Example 1. Regular error handling in Go</div>
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<div class="content">
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<div class="listingblock">
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<div class="content">
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<pre class="CodeRay highlight"><code data-lang="go">Unresolved directive in <stdin> - include::../snippets/Go-Error_Handling-Regular.adoc[]</code></pre>
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</div>
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</div>
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</div>
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</div>
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<div class="paragraph">
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<p>However, with <code>io.Reader</code>,
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<code>io.ReaderAt</code> and related interfaces, it is
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necessary to check for a non-zero number of read bytes first, as
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shown in <a href="#ex-Defensive_Coding-Go-Error_Handling-IO">Read error handling in Go</a>. If this
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pattern is not followed, data loss may occur. This is due to the
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fact that the <code>io.Reader</code> interface permits
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returning both data and an error at the same time.</p>
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</div>
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<div id="ex-Defensive_Coding-Go-Error_Handling-IO" class="exampleblock">
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<div class="title">Example 2. Read error handling in Go</div>
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<div class="content">
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<div class="listingblock">
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<div class="content">
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<pre class="CodeRay highlight"><code data-lang="go">Unresolved directive in <stdin> - include::../snippets/Go-Error_Handling-IO.adoc[]</code></pre>
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</div>
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</div>
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</div>
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</div>
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</div>
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</div>
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<div class="sect1">
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<h2 id="chap-Defensive_Coding-Go-Garbage_Collector"><a class="anchor" href="#chap-Defensive_Coding-Go-Garbage_Collector"></a>Garbage Collector</h2>
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<div class="sectionbody">
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<div class="paragraph">
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<p>Older Go releases (before Go 1.3) use a conservative garbage
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collector without blacklisting. This means that data blobs can
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cause retention of unrelated data structures because the data is
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conservatively interpreted as pointers. This phenomenon can be
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triggered accidentally on 32-bit architectures and is more likely
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to occur if the heap grows larger. On 64-bit architectures, it
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may be possible to trigger it deliberately—it is unlikely to occur
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spontaneously.</p>
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</div>
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</div>
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</div>
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<div class="sect1">
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<h2 id="chap-Defensive_Coding-Go-Marshaling"><a class="anchor" href="#chap-Defensive_Coding-Go-Marshaling"></a>Marshaling and Unmarshaling</h2>
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<div class="sectionbody">
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<div class="paragraph">
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<p>Several packages in the <code>encoding</code> hierarchy
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provide support for serialization and deserialization. The usual
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caveats apply (see
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<a href="#chap-Defensive_Coding-Tasks-Serialization">[chap-Defensive_Coding-Tasks-Serialization]</a>).</p>
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</div>
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<div class="paragraph">
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<p>As an additional precaution, the <code>Unmarshal</code>
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and <code>Decode</code> functions should only be used with
|
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fresh values in the <code>interface{}</code> argument. This
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is due to the way defaults for missing values are implemented:
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During deserialization, missing value do not result in an error,
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but the original value is preserved. Using a fresh value (with
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suitable default values if necessary) ensures that data from a
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previous deserialization operation does not leak into the current
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one. This is especially relevant when structs are deserialized.</p>
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</div>
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