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Add more info about fuzzing

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- Add counter-arg about how source improves fuzzing
- Add quote from Daniel Stenberg about fuzzing cURL.
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Rohan Kumar 2022-02-04 13:01:19 -08:00
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5
content/posts/floss-security.gmi
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@ -164,6 +164,10 @@ In fact, some types of fuzz tests (e.g. fuzzing an API for a web service) hardly
Fuzzing frequently catches bugs that are only apparent by running a program, not by reading source code. Even so, the biggest beneficiaries of fuzzing are open source projects. cURL, OpenSSL, web browsers, text rendering libraries (HarfBuzz, FreeType) and toolchains (GCC, Clang, the official Go toolchain, etc.) are some notable examples. Fuzzing frequently catches bugs that are only apparent by running a program, not by reading source code. Even so, the biggest beneficiaries of fuzzing are open source projects. cURL, OpenSSL, web browsers, text rendering libraries (HarfBuzz, FreeType) and toolchains (GCC, Clang, the official Go toolchain, etc.) are some notable examples.
> I've said it before but let me say it again: fuzzing is really the top method to find problems in curl once we've fixed all flaws that the static analyzers we use have pointed out. The primary fuzzing for curl is done by OSS-Fuzz, that tirelessly keeps hammering on the most recent curl code.
=> https://daniel.haxx.se/blog/2020/09/23/a-google-grant-for-libcurl-work --- Daniel Stenberg "A Google grant for libcurl work"
### Example: CVE-2022-0185 ### Example: CVE-2022-0185
A recent example of how fuzzing helps spot a vulnerability in an open-source project is CVE-2022-0185: a Linux 0-day found by the Crusaders of Rust a few weeks ago. It was discovered using the syzkaller kernel fuzzer. A recent example of how fuzzing helps spot a vulnerability in an open-source project is CVE-2022-0185: a Linux 0-day found by the Crusaders of Rust a few weeks ago. It was discovered using the syzkaller kernel fuzzer.
@ -187,6 +191,7 @@ I readily concede to several points in favor of source availability from a secur
* Patching vulnerabilities is important. Source availability makes it possible for the community, package maintainers, or reporters of a vulnerability to patch software. Package maintainers often blur the line between "packager" and "contributor" by helping projects migrate away from abandoned/insecure dependencies. One example that comes to mind is the Python 2 to Python 3 transition for projects like Calibre.¹² Being able to fix issues independent of upstream support is an important mitigation against user domestication. * Patching vulnerabilities is important. Source availability makes it possible for the community, package maintainers, or reporters of a vulnerability to patch software. Package maintainers often blur the line between "packager" and "contributor" by helping projects migrate away from abandoned/insecure dependencies. One example that comes to mind is the Python 2 to Python 3 transition for projects like Calibre.¹² Being able to fix issues independent of upstream support is an important mitigation against user domestication.
* Some developers/vendors don't distribute binaries that make use of modern toolchain-level exploit mitigations (e.g. PIE, RELRO, stack canaries, automatic variable initialization, control-flow integrity, etc.). In these cases, building software yourself with these mitigations (or delegating it to a distro that enforces them) requires source code availability (or at least some sort of intermediate representation). * Some developers/vendors don't distribute binaries that make use of modern toolchain-level exploit mitigations (e.g. PIE, RELRO, stack canaries, automatic variable initialization, control-flow integrity, etc.). In these cases, building software yourself with these mitigations (or delegating it to a distro that enforces them) requires source code availability (or at least some sort of intermediate representation).
* Closed-source software may or may not have builds available that include sanitizers and debug symbols. * Closed-source software may or may not have builds available that include sanitizers and debug symbols.
* Although fuzzing release binaries is possible, fuzzing is much easier to do when source code is available. Vendors of proprietary software seldom release special fuzz-friendly builds, and filtering out false-positives can be quite tedious without understanding high-level design.
* It is certainly possible to notice a vulnerability in source code. Excluding low-hanging fruit typically caught by static code analysis and peer review, it’s not the main way most vulnerabilities are found nowadays (thanks to X_Cli for reminding me about what source analysis does accomplish). * It is certainly possible to notice a vulnerability in source code. Excluding low-hanging fruit typically caught by static code analysis and peer review, it’s not the main way most vulnerabilities are found nowadays (thanks to X_Cli for reminding me about what source analysis does accomplish).
* Software as a Service can be incredibly difficult to analyze, as we typically have little more than the ability to query a server. Servers don't send core dumps, server-side binaries, or trace logs for analysis. Furthermore, it's difficult to verify which software a server is running.¹⁴ For services that require trusting a server, access to the server-side software is important from both a security and a user-freedom perspective * Software as a Service can be incredibly difficult to analyze, as we typically have little more than the ability to query a server. Servers don't send core dumps, server-side binaries, or trace logs for analysis. Furthermore, it's difficult to verify which software a server is running.¹⁴ For services that require trusting a server, access to the server-side software is important from both a security and a user-freedom perspective

11
content/posts/floss-security.md
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@ -128,7 +128,13 @@ Manual invocation of a program paired with a tracer like `strace` won't always e
Fuzzing doesn't necessarily depend on access to source code, as it is a black-box technique. Fuzzers like [American Fuzzy Loop (AFL)](https://lcamtuf.coredump.cx/afl/) normally use [special builds](#special-builds), but [other fuzzing setups](https://aflplus.plus/docs/binaryonly_fuzzing/) can work with just about any binaries. In fact, some types of fuzz tests (e.g. [fuzzing an API](https://github.com/KissPeter/APIFuzzer/) for a web service) hardly need to know any implementation details. Fuzzing doesn't necessarily depend on access to source code, as it is a black-box technique. Fuzzers like [American Fuzzy Loop (AFL)](https://lcamtuf.coredump.cx/afl/) normally use [special builds](#special-builds), but [other fuzzing setups](https://aflplus.plus/docs/binaryonly_fuzzing/) can work with just about any binaries. In fact, some types of fuzz tests (e.g. [fuzzing an API](https://github.com/KissPeter/APIFuzzer/) for a web service) hardly need to know any implementation details.
Fuzzing frequently catches bugs that are only apparent by running a program, not by reading source code. Even so, the biggest beneficiaries of fuzzing are open source projects. [cURL](https://github.com/curl/curl-fuzzer), [OpenSSL](https://github.com/openssl/openssl/tree/master/fuzz), web browsers, text rendering libraries (HarfBuzz, FreeType) and toolchains (GCC, Clang, the official Go toolchain, etc.) are some notable examples. Fuzzing frequently catches bugs that are only apparent by running a program, not by reading source code. Even so, the biggest beneficiaries of fuzzing are open source projects. [cURL](https://github.com/curl/curl-fuzzer), [OpenSSL](https://github.com/openssl/openssl/tree/master/fuzz), web browsers, text rendering libraries (HarfBuzz, FreeType) and toolchains (GCC, Clang, the official Go toolchain, etc.) are some notable examples. <cite><span class="h-card vcard"><a class="p-name url fn n" href="https://daniel.haxx.se/"><span class="p-given-name given-name">Daniel</span> <span class="p-family-name family-name">Stenberg</span></a></span></cite> wrote about <a href="https://daniel.haxx.se/blog/2020/09/23/a-google-grant-for-libcurl-work/" rel="cite">fuzzing curl</a>:
<blockquote cite="https://daniel.haxx.se/blog/2020/09/23/a-google-grant-for-libcurl-work/">
<p>
I've said it before but let me say it again: fuzzing is really the top method to find problems in curl once we've fixed all flaws that the static analyzers we use have pointed out. The primary fuzzing for curl is done by OSS-Fuzz, that tirelessly keeps hammering on the most recent curl code.
</p>
</blockquote>
If you want to get started with fuzzing, I recommend checking out [the quick-start guide for American Fuzzy Loop](https://github.com/google/AFL/blob/master/docs/QuickStartGuide.txt). Some languages like Go 1.18 also have fuzzing tools available right in the standard library. If you want to get started with fuzzing, I recommend checking out [the quick-start guide for American Fuzzy Loop](https://github.com/google/AFL/blob/master/docs/QuickStartGuide.txt). Some languages like Go 1.18 also have fuzzing tools available right in the standard library.
@ -151,6 +157,7 @@ I readily concede to several points in favor of source availability from a secur
- Patching vulnerabilities is important. Source availability makes it possible for the community, package maintainers, or reporters of a vulnerability to patch software. Package maintainers often blur the line between "packager" and "contributor" by helping projects migrate away from abandoned/insecure dependencies. One example that comes to mind is the Python 2 to Python 3 transition for projects like Calibre.[^12] Being able to fix issues independent of upstream support is an important mitigation against [user domestication](./../../../2021/01/27/whatsapp-and-the-domestication-of-users.html). - Patching vulnerabilities is important. Source availability makes it possible for the community, package maintainers, or reporters of a vulnerability to patch software. Package maintainers often blur the line between "packager" and "contributor" by helping projects migrate away from abandoned/insecure dependencies. One example that comes to mind is the Python 2 to Python 3 transition for projects like Calibre.[^12] Being able to fix issues independent of upstream support is an important mitigation against [user domestication](./../../../2021/01/27/whatsapp-and-the-domestication-of-users.html).
- Some developers/vendors don't distribute binaries that make use of modern toolchain-level exploit mitigations (e.g. <abbr title="Position-Independent Executables">PIE</abbr>, <abbr title="ReLocation Read-Only">RELRO</abbr>, stack canaries, automatic variable initialization, [<abbr title="Control-Flow Integrity">CFI</abbr>](https://clang.llvm.org/docs/ControlFlowIntegrity.html), etc.[^13]). In these cases, building software yourself with these mitigations (or delegating it to a distro that enforces them) requires source code availability (or at least some sort of intermediate representation). - Some developers/vendors don't distribute binaries that make use of modern toolchain-level exploit mitigations (e.g. <abbr title="Position-Independent Executables">PIE</abbr>, <abbr title="ReLocation Read-Only">RELRO</abbr>, stack canaries, automatic variable initialization, [<abbr title="Control-Flow Integrity">CFI</abbr>](https://clang.llvm.org/docs/ControlFlowIntegrity.html), etc.[^13]). In these cases, building software yourself with these mitigations (or delegating it to a distro that enforces them) requires source code availability (or at least some sort of intermediate representation).
- Closed-source software may or may not have builds available that include sanitizers and debug symbols. - Closed-source software may or may not have builds available that include sanitizers and debug symbols.
- Although fuzzing release binaries is possible, fuzzing is much easier to do when source code is available. Vendors of proprietary software seldom release special fuzz-friendly builds, and filtering out false-positives can be quite tedious without understanding high-level design.
- It is certainly possible to notice a vulnerability in source code. Excluding low-hanging fruit typically caught by static code analysis and peer review, it's not the main way most vulnerabilities are found nowadays (thanks to <span class="h-card vcard"><a class="p-name url n" href="https://www.broken-by-design.fr/"><span class="p-nickname nickname">X_Cli</span></a></span> for [reminding me about what source analysis does accomplish](https://lemmy.ml/post/167321/comment/117774)). - It is certainly possible to notice a vulnerability in source code. Excluding low-hanging fruit typically caught by static code analysis and peer review, it's not the main way most vulnerabilities are found nowadays (thanks to <span class="h-card vcard"><a class="p-name url n" href="https://www.broken-by-design.fr/"><span class="p-nickname nickname">X_Cli</span></a></span> for [reminding me about what source analysis does accomplish](https://lemmy.ml/post/167321/comment/117774)).
- Software as a Service can be incredibly difficult to analyze, as we typically have little more than the ability to query a server. Servers don't send core dumps, server-side binaries, or trace logs for analysis. Furthermore, it's difficult to verify which software a server is running.[^14] For services that require trusting a server, access to the server-side software is important from both a security and a user-freedom perspective - Software as a Service can be incredibly difficult to analyze, as we typically have little more than the ability to query a server. Servers don't send core dumps, server-side binaries, or trace logs for analysis. Furthermore, it's difficult to verify which software a server is running.[^14] For services that require trusting a server, access to the server-side software is important from both a security and a user-freedom perspective
@ -163,7 +170,7 @@ I've gone over some examples of how analyzing a software's security properties n
Likewise, don't assume software is safer than proprietary alternatives just because its source is visible. There are lots of great reasons to switch from macOS or Windows to Linux (it's been my main OS for years), but security is [low on that list](https://madaidans-insecurities.github.io/linux.html). Likewise, don't assume software is safer than proprietary alternatives just because its source is visible. There are lots of great reasons to switch from macOS or Windows to Linux (it's been my main OS for years), but security is [low on that list](https://madaidans-insecurities.github.io/linux.html).
I'm _not_ arguing that source code is useless from a security perspective. Releasing source code is just one thing vendors can do to improve audits; other options include releasing test builds with debug symbols/sanitizers, publishing docs describing their architecture, and/or just keeping software small and simple. My main point is that source unavailability does not imply insecurity, and source availability does not imply security. No matter the source model, we should evaluate software security through *study* rather than development model. Support the right things for the right reasons, and help others make informed choices with accurate information. There are enough good reasons to support software freedom; we don't need to rely on bad ones. I'm _not_ arguing that source code is useless from a security perspective. Releasing source code is just one thing vendors can do to improve audits; other options include releasing test builds with debug symbols/sanitizers, publishing docs describing their architecture, and/or just keeping software small and simple. My main point is that source unavailability does not imply insecurity, and source availability does not imply security. No matter the source model, we should evaluate software security through _study_ rather than development model. Support the right things for the right reasons, and help others make informed choices with accurate information. There are enough good reasons to support software freedom; we don't need to rely on bad ones.
[^1]: Writing an alternative or re-implementation doesn't require access to the original's source code, as is evidenced by a plethora of clean-room re-implementations of existing software written to circumvent the need to comply with license terms. [^1]: Writing an alternative or re-implementation doesn't require access to the original's source code, as is evidenced by a plethora of clean-room re-implementations of existing software written to circumvent the need to comply with license terms.