Add a SECURITY.md

Move content from the Security Process[1] and Security Exceptions[2]
wiki documents into the repository so that it is in a standard place for
analysis tools to look for the glibc security policy.

This is a more or less verbatim port of the wiki document with some
restructuring for a more coherent layout since the two pages are now
merged.  There should be no change in messaging in this commit.

Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>

1 files changed, 209 insertions, 0 deletions

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+# The GNU C Library Security Process
+
+This document describes the process followed by the GNU C Library maintainers
+to handle bugs that may have a security impact.  This includes determining if a
+bug has a security impact, reporting such bugs to the community and handling
+such bugs all the way to resolution.  This process may evolve over time, so if
+you're reading this from a release tarball, be sure to check the latest copy of
+the [SECURITY.md in the
+repository](https://sourceware.org/git/?p=glibc.git;a=blob;f=SECURITY.md),
+especially for instructions on reporting issues privately.
+
+## What is a security bug?
+
+Most security vulnerabilities in the GNU C Library materialize only after an
+application uses functionality in a specific way.  Therefore, it is sometimes
+difficult to determine if a defect in the GNU C Library constitutes a
+vulnerability as such.  The follow guidelines can help with a decision.
+
+* Buffer overflows should be treated as security bugs if it is conceivable that
+  the data triggering them can come from an untrusted source.
+* Other 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.
+* Bugs that crash `nscd` are generally security bugs, except if they can only
+  be triggered by a trusted data source (DNS is not trusted, but NIS and LDAP
+  probably are).
+* The [Security Exceptions](#SecurityExceptions) section below describes
+  subsystems for which determining the security status of bugs is especially
+  complicated.
+* For consistency, if the bug has received a CVE name attributing it to the GNU
+  C library, it should be flagged `security+`.
+* Duplicates of security bugs (flagged with `security+`) should be flagged
+  `security-`, to avoid cluttering the reporting.
+
+In this context, _service breakage_ means client-side privilege escalation
+(code execution) or server-side denial of service or privilege escalation
+through actual, concrete, non-synthetic applications. Or put differently, if
+the GNU C Library causes a security bug in an application (and the application
+uses the library in a standard-conforming manner or according to the manual),
+the GNU C Library bug should be treated as security-relevant.
+
+### Security Exceptions
+
+It may be especially complicated to determine the security status of bugs in
+some subsystems in the GNU C Library.  This subsection describes such
+subsystems and the special considerations applicable during security bug
+classification in them.
+
+#### Regular expression processing
+
+Regular expression processing comes in two parts, compilation (through regcomp)
+and execution (through regexec).
+
+Implementing regular expressions efficiently, in a standard-conforming way, and
+without denial-of-service vulnerabilities is very difficult and impossible for
+Basic Regular Expressions. Most implementation strategies have issues dealing
+with certain classes of patterns.
+
+Consequently, certain issues which can be triggered only with crafted patterns
+(either during compilation or execution) are treated as regular bugs and not
+security issues.  Examples of such issues would include (but is not limited
+to):
+
+ * Running out of memory through valid use of malloc
+ * Quadratic or exponential behaviour resulting in slow execution time
+ * Stack overflows due to recursion when processing patterns
+
+Crashes, infinite loops (and not merely exponential behavior), buffer overflows
+and overreads, memory leaks and other bugs resulting from the regex
+implementation relying on undefined behavior should be treated as security
+vulnerabilities.
+
+#### wordexp patterns
+
+`wordexp` inherently has exponential memory consumption in terms of the input
+size.  This means that denial of service flaws from crafted patterns are not
+security issues (even if they lead to other issues, such as NULL pointer
+dereferences).
+
+#### Asynchronous I/O
+
+The GNU C Library tries to implement asynchronous I/O without kernel support,
+which means that several operations are not fully standard conforming.  Several
+known races can cause crashes and resource leaks.  Such bugs are only treated
+as security bugs if applications (as opposed to synthetic test cases) have
+security exposures due to these bugs.
+
+#### Asynchronous cancellation
+
+The implementation of asynchronous cancellation is not fully
+standard-conforming and has races and leaks.  Again, such bugs are only treated
+as security bugs if applications (as opposed to synthetic test cases) have
+security exposures due to these bugs.
+
+#### Crafted binaries and ldd
+
+The `ldd` tool is not expected to be used with untrusted executables.
+
+#### Post-exploitation countermeasures
+
+Certain features have been added to the library only to make exploitation of
+security bugs (mainly for code execution) more difficult.  Examples includes
+the stack smashing protector, function pointer obfuscation, vtable validation
+for stdio stream handles, and various heap consistency checks.  Failure of such
+countermeasures to stop exploitation of a different vulnerability is not a
+security vulnerability in itself.  By their nature, these countermeasures are
+based on heuristics and will never offer complete protection, so the original
+vulnerability needs to be fixed anyway.
+
+## Reporting private security bugs
+
+**IMPORTANT: All bugs reported in Bugzilla are public.**
+
+As a rule of thumb, security vulnerabilities which are exposed over the network
+or can be used for local privilege escalation (through existing applications,
+not synthetic test cases) should be reported privately.  We expect that such
+critical security bugs are rare, and that most security bugs can be reported in
+Bugzilla, thus making them public immediately.  If in doubt, you can file a
+private bug, as explained in the next paragraph.
+
+If you want to report a _private_ security bug that is not immediately
+public, please contact _one_ of our downstream distributions with security
+teams.  The follow teams have volunteered to handle such bugs:
+
+* Debian: security@debian.org
+* Red Hat: secalert@redhat.com
+* SUSE: security@suse.de
+
+Please report the bug to _just one_ of these teams.  It will be shared with
+other teams as necessary.
+
+The team you 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
+
+We expect that critical security bugs are rare, and that most security bugs can
+be reported in Bugzilla, thus making them public immediately. When reporting
+public security bugs the reporter should provide rationale for their choice of
+public disclosure.
+
+## Triaging security bugs
+
+This section is aimed at developers, not reporters.
+
+Security-relevant bugs should be marked with `security+`, as per the [Bugzilla
+security flag
+documentation](https://sourceware.org/glibc/wiki/Bugzilla%20Procedures#security),
+following the guidelines above.  If you set the `security+` flag, you should
+make sure the following information is included in the bug (usually in a bug
+comment):
+
+* The first glibc version which includes the vulnerable code.  If the
+  vulnerability was introduced before glibc 2.4 (released in 2006), this
+  information is not necessary.
+* The commit or commits (identified by hash) that fix this vulnerability in the
+  master branch, and (for historic security bugs) the first release that
+  includes this fix.
+* The summary should include the CVE names (if any), in parentheses at the end.
+* If there is a single CVE name assigned to this bug, it should be set as an
+  alias.
+
+The following links are helpful for finding untriaged bugs:
+
+* [Unprocessed bugs](https://sourceware.org/bugzilla/buglist.cgi?f1=flagtypes.name&o1=notsubstring&product=glibc&query_format=advanced&v1=security)
+* [`security?` review requests](https://sourceware.org/bugzilla/buglist.cgi?f1=flagtypes.name&o1=substring&product=glibc&query_format=advanced&v1=security%3f)
+* [Open `security+` bugs](https://sourceware.org/bugzilla/buglist.cgi?bug_status=UNCONFIRMED&bug_status=NEW&bug_status=ASSIGNED&bug_status=SUSPENDED&bug_status=WAITING&bug_status=REOPENED&bug_status=VERIFIED&f1=flagtypes.name&o1=substring&product=glibc&query_format=advanced&v1=security%2B)
+
+## Fixing security bugs
+
+For changes to master, the regular [consensus-driven
+process](https://sourceware.org/glibc/wiki/Consensus) must be followed.  It
+makes sense to obtain consensus in private, to ensure that the patch is likely
+in a committable state, before disclosing an emboargoed vulnerability.
+
+Security backports to release branches need to follow the
+[release process](https://sourceware.org/glibc/wiki/Release#General_policy).
+
+Contact the [website
+maintainers](https://sourceware.org/glibc/wiki/MAINTAINERS#Maintainers_for_the_website)
+and have them draft a news entry for the website frontpage to direct users to
+the bug, the fix, or the mailing list discussions.
+
+## CVE assignment
+
+Security bugs flagged with `security+` should have [CVE identifiers](http://cve.mitre.org/about/).
+
+For bugs which are public (thus all bugs in Bugzilla), CVE assignment has to
+happen through the [oss-security mailing
+list](http://oss-security.openwall.org/wiki/mailing-lists/oss-security).
+(Downstreams will eventually request CVE assignment through their public
+Bugzilla monitoring processes.)
+
+For initially private security bugs, CVEs will be assigned as needed by the
+downstream security teams.  Once a public bug is filed, the name should be
+included in Bugzilla.