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Add first version of lab oob1 (ossf#468)
Signed-off-by: David A. Wheeler <[email protected]>
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| <!DOCTYPE html> | ||
| <html> | ||
| <head> | ||
| <meta http-equiv="X-UA-Compatible" content="IE=edge"> | ||
| <meta name="viewport" content="width=device-width, initial-scale=1"> | ||
| <link rel="stylesheet" href="https://best.openssf.org/assets/css/style.css"> | ||
| <link rel="stylesheet" href="checker.css"> | ||
| <script src="js-yaml.min.js"></script> | ||
| <script src="checker.js"></script> | ||
| <link rel="license" href="https://creativecommons.org/licenses/by/4.0/"> | ||
|
|
||
| <!-- See create_labs.md for how to create your own lab! --> | ||
|
|
||
| <!-- Sample expected answer --> | ||
| <script id="expected0" type="plain/text"> | ||
| if (1 + 2 + 16 > s->s3->rrec.length) | ||
| return 0; | ||
| </script> | ||
| <!-- | ||
| --> | ||
| <script id="expected1" type="plain/text"> | ||
| if (1 + 2 + payload + 16 > s->s3->rrec.length) | ||
| return 0; | ||
| </script> | ||
|
|
||
| <!-- Full pattern of correct answer --> | ||
| <script id="correct0" type="plain/text"> | ||
| \s* | ||
| if \s+ \( | ||
| (1 \+ 2 \+ 16|19) > s -> s3 -> rrec \. length \) | ||
| \s+ return \s+ 0 ; | ||
| \s* | ||
| </script> | ||
| <script id="correct1" type="plain/text"> | ||
| \s* | ||
| if \s+ \( (1 \+ 2|3) \+ payload \+ 16 > s -> s3 -> rrec \. length \) | ||
| \s+ return \s+ 0 ; | ||
| \s* | ||
| </script> | ||
| <!-- | ||
| \s* app \. use \( helmet \( \{ | ||
| contentSecurityPolicy: \{ | ||
| directives: \{ | ||
| "script-src": \[ "'self'" , | ||
| (["'`])https://example\.com\1 \] , | ||
| "style-src": \[ "'self'" \] | ||
| \} , | ||
| \} | ||
| \} \) \) ; | ||
| --> | ||
|
|
||
| <script id="info" type="application/yaml"> | ||
| --- | ||
| hints: | ||
| - absent: "if" | ||
| text: Begin with "if" as we will return 0 when there is a problem. | ||
| - absent: | | ||
| \( | ||
| text: Need "(...)" around the condition after an if statement. | ||
| # - present: "import" | ||
| # text: Yes, many JavaScript implementations support an import statement. | ||
| # However, in this exercise we will use a require form. Please use that | ||
| # instead. | ||
| # examples: | ||
| # - - 'import express from "express";' | ||
| # - absent: "const" | ||
| # text: Start with const. | ||
| # - absent: 'const\s+helmet =' | ||
| # text: Create a constant name named helmet using the form const helmet = ... | ||
| # examples: | ||
| # - - 'const' | ||
| # - - 'consthelmet = ' | ||
| # - present: 'require \( helmet \)' | ||
| # text: The parameter of a requirement statement must be string. | ||
| # Surround the term helment with double-quotes. | ||
| # examples: | ||
| # - - ' const helmet = require(helmet);' | ||
| # - absent: "; $" | ||
| # text: JavaScript doesn''t require semicolon terminators, but the rest of | ||
| # the code uses them. You should try to match a coding style when modifying | ||
| # existing code unless there''s an important reason not to. | ||
| # Please update the first statment. | ||
| # examples: | ||
| # - - ' const helmet = require("helmet")' | ||
| # - absent: '\s* app \. use \( helmet \( \{' | ||
| # index: 1 | ||
| # text: Your code should begin with app.use(helmet({ | ||
| # - absent: | | ||
| # \s* app \. use \( helmet \( \{ | ||
| # contentSecurityPolicy: \{ \s* | ||
| # index: 1 | ||
| # text: | | ||
| # Your code should begin with: | ||
| # app.use(helmet({ | ||
| # contentSecurityPolicy: { | ||
| # - absent: | | ||
| # \s* app \. use \( helmet \( \{ | ||
| # contentSecurityPolicy: \{ | ||
| # directives: \{ \s* | ||
| # index: 1 | ||
| # text: | | ||
| # Your code should begin with: | ||
| # app.use(helmet({ | ||
| # contentSecurityPolicy: { | ||
| # directives: { | ||
| # - absent: | | ||
| # \s* app \. use \( helmet \( \{ | ||
| # contentSecurityPolicy: \{ | ||
| # directives: \{ | ||
| # "script-src": \[ "'self'" , ["']https://example.com["'] \] , \s* | ||
| # index: 1 | ||
| # text: | | ||
| # Your code should continue with: | ||
| # app.use(helmet({ | ||
| # contentSecurityPolicy: { | ||
| # directives: { | ||
| # "script-src": ["'self'", "https://example.com"], | ||
| # - absent: | | ||
| # "style-src": \[ "'self'" \] | ||
| # index: 1 | ||
| # text: | | ||
| # Don't forget to include "style-src": ["'self'"] | ||
| # - absent: '; $' | ||
| # index: 1 | ||
| # text: JavaScript doesn''t require semicolon terminators, but the rest of | ||
| # the code uses them. You should try to match a coding style when modifying | ||
| # existing code unless there''s an important reason not to. | ||
| # Please update the second statment. | ||
| # - text: I do not have more specific hints to provide. Please ensure that | ||
| # the parentheses, braces, and brackets pair correctly. | ||
| # # debug: true | ||
| </script> | ||
| </head> | ||
| <body> | ||
| <!-- For GitHub Pages formatting: --> | ||
| <div class="container-lg px-3 my-5 markdown-body"> | ||
| <h1>Lab Exercise oob1</h1> | ||
| <p> | ||
| This is a lab exercise on developing secure software. | ||
| For more information, see the <a href="introduction.html" target="_blank">introduction to | ||
| the labs</a>. | ||
|
|
||
| <p> | ||
| <h2>Task</h2> | ||
| <p> | ||
| <b>Please change the code below to fix this simplified version | ||
| of the "Heartbleed" bug in OpenSSL, an example of a buffer overread.</b> | ||
|
|
||
| <p> | ||
| <h2>Background</h2> | ||
| <p> | ||
| In almost all programming languages, the default response a program | ||
| attempts to read or write outside | ||
| of a buffer is either an attempt to resize the buffer or | ||
| an error of some kind (e.g., raising an exception). | ||
| That's because it's extremely easy to accidentally attempt to read | ||
| or write outside of a buffer. | ||
| <p> | ||
| However, C and the built-in arrays of C++ are different. | ||
| In C and C++, attempting to read or write outside a buffer is | ||
| <i>undefined behavior</i> and <i>anything</i> is allowed to happen | ||
| without any kind of protection. | ||
| In practice, what often happens is a read or write (respectively) of | ||
| other data. | ||
| <p> | ||
| The 2014 revelation of the Heartbleed vulnerability | ||
| (CVE-2014-0160) is an example of a buffer overread vulnerability. | ||
| Heartbleed was a vulnerability in OpenSSL, a widely-used toolkit | ||
| that implements the cryptographic protocol Secure Sockets Layer | ||
| (SSL) and its successor the Transport Layer Security (TLS). | ||
| Heartbleed affected a huge number of popular websites, including | ||
| Google, YouTube, Yahoo!, Pinterest, Blogspot, Instagram, Tumblr, | ||
| Reddit, Netflix, Stack Overflow, Slate, GitHub, Yelp, Etsy, the | ||
| U.S. Postal Service (USPS), Blogger, Dropbox, Wikipedia, and the | ||
| Washington Post. | ||
| See <a href="https://dwheeler.com/essays/heartbleed.html">here</a> for more. | ||
|
|
||
| <p> | ||
| <h2>Task Information</h2> | ||
| <p> | ||
| We're going re-create the fix in OpenSSF for the Heartbleed vulnerability | ||
| by modifying function <tt>dtls1_process_heartbeat</tt>. | ||
| <p> | ||
| At this point in the code, the construct | ||
| <tt>s->s3->rrec.length</tt> | ||
| indicates how many bytes are available. | ||
| Modify the code below in two places. | ||
| <p> | ||
| First, modify the code so that | ||
| if the minimum length of a response <tt>(1 + 2 + 16)</tt> is more than | ||
| the length claimed by | ||
| <tt>s->s3->rrec.length</tt>, | ||
| return return 0 without sending a heartbeat, | ||
| This will prevent trying to create a heartbeat when there's not enough | ||
| room to create one. | ||
| <p> | ||
| Second, modify the code so that | ||
| if the minimum length of a response with a payload | ||
| <tt>(1 + 2 + payload + 16</tt> | ||
| is more than the total length for a response given in | ||
| <tt>s->s3->rrec.length</tt> then again | ||
| return return 0 without sending a heartbeat, | ||
| <p> | ||
| This will prevent trying to create a heartbeat when there's not enough | ||
| room to create one. | ||
| <p> | ||
| Note that this is not terribly difficult to fix. | ||
| The problem is that reading and writing buffers is extremely common, | ||
| but by default such accesses are unsafe in C and C++. | ||
| In practice it is difficult to <i>always</i> check all ranges | ||
| in all possible cases. | ||
| <!-- | ||
| if (1 + 2 + 16 > s->s3->rrec.length) | ||
| return 0; /* silently discard */ | ||
| --> | ||
|
|
||
| <p> | ||
| <h2>Interactive Lab (<span id="grade"></span>)</h2> | ||
| <p> | ||
| <form id="lab"> | ||
| <pre><code | ||
| >int | ||
| dtls1_process_heartbeat(SSL *s) | ||
| { | ||
| 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 () | ||
| ; | ||
| </textarea> | ||
| hbtype = *p++; | ||
| n2s(p, payload); | ||
| <textarea id="attempt1" rows="3" cols="60" spellcheck="false"> | ||
| 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); | ||
| // memcpy(bp, pl, payload); | ||
|
|
||
| </code></pre> | ||
| <button type="button" class="hintButton">Hint</button> | ||
| <button type="button" class="resetButton">Reset</button> | ||
| <button type="button" class="giveUpButton">Give up</button> | ||
| <br><br> | ||
| <p> | ||
| <details> | ||
| <summary>Source: This example was extracted from | ||
| <a href="https://github.com/openssl/openssl/blob/731f431497f463f3a2a97236fe0187b11c44aead/ssl/d1_both.c">OpenSSL file <tt>ssl/d1_both.c</tt> | ||
| commit 731f431497f4</a>; you can see its full header by | ||
| expanding details here.</summary> | ||
| <pre> | ||
| /* ssl/d1_both.c */ | ||
| /* | ||
| * DTLS implementation written by Nagendra Modadugu | ||
| * ([email protected]) for the OpenSSL project 2005. | ||
| */ | ||
| /* ==================================================================== | ||
| * Copyright (c) 1998-2005 The OpenSSL Project. All rights reserved. | ||
| * | ||
| * Redistribution and use in source and binary forms, with or without | ||
| * modification, are permitted provided that the following conditions | ||
| * are met: | ||
| * | ||
| * 1. Redistributions of source code must retain the above copyright | ||
| * notice, this list of conditions and the following disclaimer. | ||
| * | ||
| * 2. Redistributions in binary form must reproduce the above copyright | ||
| * notice, this list of conditions and the following disclaimer in | ||
| * the documentation and/or other materials provided with the | ||
| * distribution. | ||
| * | ||
| * 3. All advertising materials mentioning features or use of this | ||
| * software must display the following acknowledgment: | ||
| * "This product includes software developed by the OpenSSL Project | ||
| * for use in the OpenSSL Toolkit. (http://www.openssl.org/)" | ||
| * | ||
| * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to | ||
| * endorse or promote products derived from this software without | ||
| * prior written permission. For written permission, please contact | ||
| * [email protected]. | ||
| * | ||
| * 5. Products derived from this software may not be called "OpenSSL" | ||
| * nor may "OpenSSL" appear in their names without prior written | ||
| * permission of the OpenSSL Project. | ||
| * | ||
| * 6. Redistributions of any form whatsoever must retain the following | ||
| * acknowledgment: | ||
| * "This product includes software developed by the OpenSSL Project | ||
| * for use in the OpenSSL Toolkit (http://www.openssl.org/)" | ||
| * | ||
| * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY | ||
| * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | ||
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR | ||
| * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR | ||
| * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | ||
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT | ||
| * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; | ||
| * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | ||
| * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, | ||
| * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) | ||
| * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED | ||
| * OF THE POSSIBILITY OF SUCH DAMAGE. | ||
| * ==================================================================== | ||
| * | ||
| * This product includes cryptographic software written by Eric Young | ||
| * ([email protected]). This product includes software written by Tim | ||
| * Hudson ([email protected]). | ||
| * | ||
| */ | ||
| /* Copyright (C) 1995-1998 Eric Young ([email protected]) | ||
| * All rights reserved. | ||
| * | ||
| * This package is an SSL implementation written | ||
| * by Eric Young ([email protected]). | ||
| * The implementation was written so as to conform with Netscapes SSL. | ||
| * | ||
| * This library is free for commercial and non-commercial use as long as | ||
| * the following conditions are aheared to. The following conditions | ||
| * apply to all code found in this distribution, be it the RC4, RSA, | ||
| * lhash, DES, etc., code; not just the SSL code. The SSL documentation | ||
| * included with this distribution is covered by the same copyright terms | ||
| * except that the holder is Tim Hudson ([email protected]). | ||
| * | ||
| * Copyright remains Eric Young's, and as such any Copyright notices in | ||
| * the code are not to be removed. | ||
| * If this package is used in a product, Eric Young should be given attribution | ||
| * as the author of the parts of the library used. | ||
| * This can be in the form of a textual message at program startup or | ||
| * in documentation (online or textual) provided with the package. | ||
| * | ||
| * Redistribution and use in source and binary forms, with or without | ||
| * modification, are permitted provided that the following conditions | ||
| * are met: | ||
| * 1. Redistributions of source code must retain the copyright | ||
| * notice, this list of conditions and the following disclaimer. | ||
| * 2. Redistributions in binary form must reproduce the above copyright | ||
| * notice, this list of conditions and the following disclaimer in the | ||
| * documentation and/or other materials provided with the distribution. | ||
| * 3. All advertising materials mentioning features or use of this software | ||
| * must display the following acknowledgement: | ||
| * "This product includes cryptographic software written by | ||
| * Eric Young ([email protected])" | ||
| * The word 'cryptographic' can be left out if the rouines from the library | ||
| * being used are not cryptographic related :-). | ||
| * 4. If you include any Windows specific code (or a derivative thereof) from | ||
| * the apps directory (application code) you must include an acknowledgement: | ||
| * "This product includes software written by Tim Hudson ([email protected])" | ||
| * | ||
| * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND | ||
| * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | ||
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | ||
| * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE | ||
| * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | ||
| * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS | ||
| * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | ||
| * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | ||
| * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | ||
| * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | ||
| * SUCH DAMAGE. | ||
| * | ||
| * The licence and distribution terms for any publically available version or | ||
| * derivative of this code cannot be changed. i.e. this code cannot simply be | ||
| * copied and put under another distribution licence | ||
| * [including the GNU Public Licence.] | ||
| */ | ||
| </pre> | ||
| </details> | ||
| <br><br> | ||
| <p id="correctStamp" class="small"> | ||
| <textarea id="debugData" class="displayNone" rows="20" cols="65" readonly> | ||
| </textarea> | ||
| </form> | ||
| </div><!-- End GitHub pages formatting --> | ||
| </body> | ||
| </html> |
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