Oob1 simplify (#471)

* Simplify lab oob1

Signed-off-by: David A. Wheeler <[email protected]>

* Add some hints

Signed-off-by: David A. Wheeler <[email protected]>

* Add oob1 to README

Signed-off-by: David A. Wheeler <[email protected]>

---------

Signed-off-by: David A. Wheeler <[email protected]>

Author: david-a-wheeler

docs/labs/README.md

@@ -19,6 +19,7 @@ Here are the labs available:
 * [regex1](regex1.html) - regular expressions (regexes)
 * [input2](input2.html) - input validation (more complex situations)
 * [csp1](csp1.html) - Content Security Policy (CSP)
+* [oob1](oob1.html) - Out-of-bounds (OOB)
 
 ## Please contribute labs
 
@@ -76,7 +77,7 @@ The items marked "PLANNED-1" are those we intend to do first;
     * Avoid Default & Hardcoded Credentials - PLANNED-1
     * Avoid Incorrect Conversion or Cast - PLANNED-2
   * Processing Data Securely: Undefined Behavior / Memory Safety
-    * Countering Out-of-Bounds Reads and Writes (Buffer Overflow) - PLANNED-1
+    * Countering Out-of-Bounds Reads and Writes (Buffer Overflow) - [oob1](oob1.html)
     * Double-free, Use-after-free, and Missing Release - PLANNED-1
     * Avoid Undefined Behavior - PLANNED-2
   * Processing Data Securely: Calculate Correctly

docs/labs/oob1.html

@@ -57,6 +57,11 @@
 - absent: |
     \(
   text: Need "(...)" around the condition after an if statement.
+- absent: |
+    >
+  text: Need comparison "if ( ... > ....)"
+- absent: return
+  text: Need "return 0;" to skip attempts to send a too-long response.
 definitions:
 - term: RETURN0
   value: |
@@ -232,10 +237,8 @@ <h2>Interactive Lab (<span id="grade"></span>)</h2>
   unsigned char *p = &s->s3->rrec.data[0], *pl;
   unsigned short hbtype;
   unsigned int payload;
-  unsigned int padding = 16; /* Use minimum padding */
 
   // ... Some details omitted here
- 
 <textarea id="attempt0" rows="3" cols="60" spellcheck="false">
   if ()
     ;
@@ -246,17 +249,10 @@ <h2>Interactive Lab (<span id="grade"></span>)</h2>
   if ()
     ;
 </textarea>
-
-  // ... Later on there are these lines, which create a buffer
-  // with enough room for a response, but uses a "memcpy" to
-  // copy the payload data. At this point in the code it's assumed
-  // that the payload's asserted length will fit in its created buffer.
-  //   buffer = OPENSSL_malloc(write_length);
-  //   bp = buffer;
-  //   *bp++ = TLS1_HB_RESPONSE;
-  //   s2n(payload, bp);
+  // ... Later on there will be a memory copy ("memcpy")
+  // to copy the payload data into a new buffer. If we
+  // had not checked, it would not be long enough:
   //   memcpy(bp, pl, payload);
-
 </code></pre>
 <button type="button" class="hintButton">Hint</button>
 <button type="button" class="resetButton">Reset</button>