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+What is a GCC security bug?
+===========================
+
+ A security bug is one that threatens the security of a system or
+ network, or might compromise the security of data stored on it.
+ In the context of GCC there are multiple ways in which this might
+ happen and some common scenarios are detailed below.
+
+ If you're reporting a security issue and feel like it does not fit
+ into any of the descriptions below, you're encouraged to reach out
+ through the GCC bugzilla or if needed, privately by following the
+ instructions in the last two sections of this document.
+
+Compiler drivers, programs, libgccjit and support libraries
+-----------------------------------------------------------
+
+ The compiler driver processes source code, invokes other programs
+ such as the assembler and linker and generates the output result,
+ which may be assembly code or machine code. Compiling untrusted
+ sources can result in arbitrary code execution and unconstrained
+ resource consumption in the compiler. As a result, compilation of
+ such code should be done inside a sandboxed environment to ensure
+ that it does not compromise the development environment.
"... the host environment" seems more appropriate.
+
+ The libgccjit library can, despite the name, be used both for
+ ahead-of-time compilation and for just-in-compilation. In both
+ cases it can be used to translate input representations (such as
+ source code) in the application context; in the latter case the
+ generated code is also run in the application context.
+
+ Limitations that apply to the compiler driver, apply here too in
+ terms of sanitizing inputs and it is recommended that both the
s/sanitizing inputs/trusting inputs/ (I suggested it earlier, just unsure
if you don't agree or it simply fell through the cracks)
+ compilation *and* execution context of the code are appropriately
+ sandboxed to contain the effects of any bugs in libgccjit, the
+ application code using it, or its generated code to the sandboxed
+ environment.
+
+ Libraries such as libiberty, libcc1 and libcpp are not distributed
+ for runtime support and have similar challenges to compiler drivers.
+ While they are expected to be robust against arbitrary input, they
+ should only be used with trusted inputs when linked into the
+ compiler.
+
+ Libraries such as zlib that bundled into GCC to build it will be
'are bundled with' (missing 'are', s/into/with/)
+ treated the same as the compiler drivers and programs as far as
+ security coverage is concerned. However if you find an issue in
+ these libraries independent of their use in GCC, you should reach
+ out to their upstream projects to report them.
+
+ As a result, the only case for a potential security issue in the
+ compiler is when it generates vulnerable application code for
+ trusted input source code that is conforming to the relevant
+ programming standard or extensions documented as supported by GCC
+ and the algorithm expressed in the source code does not have the
+ vulnerability. The output application code could be considered
+ vulnerable if it produces an actual vulnerability in the target
+ application, specifically in the following cases:
It seems ambiguous if the list that follows is meant to be an exhaustive
enumeration. I think it is meant to give examples without covering all
possibilities; if that's the case, I would suggest
s/specifically in the following cases/for example/
If I misunderstood and the list is really meant to be exhaustive,
it would be nice to make that clear and perhaps refer the reader
to the second paragraph when their scenario does not fit.
+
+ - The application dereferences an invalid memory location despite
+ the application sources being valid.
+ - The application reads from or writes to a valid but incorrect
+ memory location, resulting in an information integrity issue or an
+ information leak.
+ - The application ends up running in an infinite loop or with
+ severe degradation in performance despite the input sources having
+ no such issue, resulting in a Denial of Service. Note that
+ correct but non-performant code is not a security issue candidate,
+ this only applies to incorrect code that may result in performance
+ degradation severe enough to amount to a denial of service.
+ - The application crashes due to the generated incorrect code,
+ resulting in a Denial of Service.
+
+Language runtime libraries
+--------------------------
+
+ GCC also builds and distributes libraries that are intended to be
+ used widely to implement runtime support for various programming
+ languages. These include the following:
+
+ * libada
+ * libatomic
+ * libbacktrace
+ * libcc1
+ * libcody
+ * libcpp
+ * libdecnumber
+ * libffi
+ * libgcc
+ * libgfortran
+ * libgm2
+ * libgo
+ * libgomp
+ * libitm
+ * libobjc
+ * libphobos
+ * libquadmath
+ * libssp
+ * libstdc++
+
+ These libraries are intended to be used in arbitrary contexts and as
+ a result, bugs in these libraries may be evaluated for security
+ impact. However, some of these libraries, e.g. libgo, libphobos,
+ etc. are not maintained in the GCC project, due to which the GCC
+ project may not be the correct point of contact for them. You are
+ encouraged to look at README files within those library directories
+ to locate the canonical security contact point for those projects
+ and include them in the report. Once the issue is fixed in the
+ upstream project, the fix will be synced into GCC in a future
+ release.
+
+ Most security vulnerabilities in these runtime libraries arise when
+ an application uses functionality in a specific way. As a result,
+ not all bugs qualify as security relevant. The following guidelines
+ can help with the decision:
+
+ - Buffer overflows and integer overflows should be treated as
+ security issues if it is conceivable that the data triggering them
+ can come from an untrusted source.
+ - Bugs that cause memory corruption which is likely exploitable
+ should be treated as security bugs.
+ - Information disclosure can be security bugs, especially if
+ exposure through applications can be determined.
+ - Memory leaks and races are security bugs if they cause service
+ breakage.
+ - Stack overflow through unbounded alloca calls or variable-length
+ arrays are security bugs if it is conceivable that the data
+ triggering the overflow could come from an untrusted source.
+ - Stack overflow through deep recursion and other crashes are
+ security bugs if they cause service breakage.
+ - Bugs that cripple the whole system (so that it doesn't even boot
+ or does not run most applications) are not security bugs because
+ they will not be exploitable in practice, due to general system
+ instability.
+
+Diagnostic libraries
+--------------------
+
+ Libraries like libvtv and the sanitizers are intended to be used in
+ diagnostic cases and not intended for use in sensitive environments.
+ As a result, bugs in these libraries will not be considered security
+ sensitive.
+
+GCC plugins
+-----------
+
+ It should be noted that GCC may execute arbitrary code loaded by a
+ user through the GCC plugin mechanism or through system preloading
+ mechanism. Such custom code should be vetted by the user for safety
+ as bugs exposed through such code will not be considered security
+ issues.
+
+Security features implemented in GCC
+------------------------------------
+
+ GCC implements a number of security features that reduce the impact
+ of security issues in applications, such as -fstack-protector,
+ -fstack-clash-protection, _FORTIFY_SOURCE and so on. A failure in
s/in/of/ together with...
+ these features functioning perfectly in all situations is not an
s/functioning/to function/
+ exploitable vulnerability in itself since it does not affect the
+ correctness of programs. Further, they're dependent on heuristics
+ and may not always have full coverage for protection.
+
+ Similarly, GCC may transform code in a way that the correctness of
+ the expressed algorithm is preserved, but supplementary properties
+ that are not specifically expressible in a high-level language
+ are not preserved. Examples of such supplementary properties
+ include absence of sensitive data in the program's address space
+ after an attempt to wipe it, or data-independent timing of code.
+ When the source code attempts to express such properties, failure
+ to preserve them in resulting machine code is not a security issue
+ in GCC.
+
+Reporting private security bugs
+===============================
+
+ *All bugs reported in the GCC Bugzilla are public.*
+
+ In order to report a private security bug that is not immediately
+ public, please contact one of the downstream distributions with
+ security teams. The following teams have volunteered to handle
+ such bugs:
+
+ Debian: secur...@debian.org
+ Red Hat: secal...@redhat.com
+ SUSE: secur...@suse.de
+ AdaCore: product-secur...@adacore.com
+
+ Please report the bug to just one of these teams. It will be shared
+ with other teams as necessary.
+
+ The team contacted will take care of details such as vulnerability
+ rating and CVE assignment (http://cve.mitre.org/about/). It is likely
+ that the team will ask to file a public bug because the issue is
+ sufficiently minor and does not warrant an embargo. An embargo is not
+ a requirement for being credited with the discovery of a security
+ vulnerability.
+
+Reporting public security bugs
+==============================
+
+ It is expected that critical security bugs will be rare, and that most
+ security bugs can be reported in GCC, thus making
+ them public immediately. The system can be found here:
+
+ https://gcc.gnu.org/bugzilla/
Thanks.
Alexander
