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1.58b: Descendant limit checks added.

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Steve Pinkham 2010-08-21 15:56:47 -04:00
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5
ChangeLog
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@ -1,3 +1,8 @@
Version 1.58b:
--------------
- Descendant limit checks added.
Version 1.57b:
--------------

2
Makefile
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@ -20,7 +20,7 @@
#
PROGNAME = skipfish
VERSION = 1.57b
VERSION = 1.58b
OBJFILES = http_client.c database.c crawler.c analysis.c report.c
INCFILES = alloc-inl.h string-inl.h debug.h types.h http_client.h \

530
README
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@ -6,249 +6,259 @@ skipfish - web application security scanner
* Written and maintained by Michal Zalewski <lcamtuf@google.com>.
* Copyright 2009, 2010 Google Inc, rights reserved.
* Released under terms and conditions of the Apache License, version 2.0.
* Released under terms and conditions of the Apache License, version 2.0.
--------------------
1. What is skipfish?
--------------------
Skipfish is an active web application security reconnaissance tool. It prepares
an interactive sitemap for the targeted site by carrying out a recursive crawl
and dictionary-based probes. The resulting map is then annotated with the
output from a number of active (but hopefully non-disruptive) security checks.
The final report generated by the tool is meant to serve as a foundation for
professional web application security assessments.
Why should I bother with this particular tool?
Skipfish is an active web application security reconnaissance tool. It
prepares an interactive sitemap for the targeted site by carrying out a
recursive crawl and dictionary-based probes. The resulting map is then
annotated with the output from a number of active (but hopefully
non-disruptive) security checks. The final report generated by the tool is
meant to serve as a foundation for professional web application security
assessments.
-------------------------------------------------
2. Why should I bother with this particular tool?
-------------------------------------------------
A number of commercial and open source tools with analogous functionality is
readily available (e.g., Nikto, Nessus); stick to the one that suits you best.
That said, skipfish tries to address some of the common problems associated
with web security scanners. Specific advantages include:
readily available (e.g., Nikto, Nessus); stick to the one that suits you
best. That said, skipfish tries to address some of the common problems
associated with web security scanners. Specific advantages include:
* High performance: 500+ requests per second against responsive Internet
targets, 2000+ requests per second on LAN / MAN networks, and 7000+ requests
against local instances has been observed, with a very modest CPU, network,
against local instances have been observed, with a very modest CPU, network,
and memory footprint. This can be attributed to:
- Multiplexing single-thread, fully asynchronous network I/O and data
* Multiplexing single-thread, fully asynchronous network I/O and data
processing model that eliminates memory management, scheduling, and IPC
inefficiencies present in some multi-threaded clients.
- Advanced HTTP/1.1 features such as range requests, content
compression, and keep-alive connections, as well as forced response size
limiting, to keep network-level overhead in check.
* Advanced HTTP/1.1 features such as range requests, content compression,
and keep-alive connections, as well as forced response size limiting, to
keep network-level overhead in check.
- Smart response caching and advanced server behavior heuristics are
used to minimize unnecessary traffic.
* Smart response caching and advanced server behavior heuristics are used to
minimize unnecessary traffic.
- Performance-oriented, pure C implementation, including a custom
* Performance-oriented, pure C implementation, including a custom
HTTP stack.
* Ease of use: skipfish is highly adaptive and reliable. The scanner
features:
* Ease of use: skipfish is highly adaptive and reliable. The scanner features:
- Heuristic recognition of obscure path- and query-based parameter
handling schemes.
* Heuristic recognition of obscure path- and query-based parameter handling
schemes.
- Graceful handling of multi-framework sites where certain paths obey
a completely different semantics, or are subject to different filtering
* Graceful handling of multi-framework sites where certain paths obey
completely different semantics, or are subject to different filtering
rules.
- Automatic wordlist construction based on site content analysis.
* Automatic wordlist construction based on site content analysis.
- Probabilistic scanning features to allow periodic, time-bound
assessments of arbitrarily complex sites.
* Probabilistic scanning features to allow periodic, time-bound assessments
of arbitrarily complex sites.
* Well-designed security checks: the tool is meant to provide accurate and
meaningful results:
* Well-designed security checks: the tool is meant to provide accurate
and meaningful results:
- Three-step differential probes are preferred to signature checks
for detecting vulnerabilities.
* Handcrafted dictionaries offer excellent coverage and permit thorough
$keyword.$extension testing in a reasonable timeframe.
- Ratproxy-style logic is used to spot subtle security problems:
cross-site request forgery, cross-site script inclusion, mixed content,
issues MIME- and charset mismatches, incorrect caching directive, etc.
* Three-step differential probes are preferred to signature checks for
detecting vulnerabilities.
- Bundled security checks are designed to handle tricky scenarios:
stored XSS (path, parameters, headers), blind SQL or XML injection, or
blind shell injection.
* Ratproxy-style logic is used to spot subtle security problems:
cross-site request forgery, cross-site script inclusion, mixed content,
issues MIME- and charset mismatches, incorrect caching directives, etc.
- Report post-processing drastically reduces the noise caused by any
remaining false positives or server gimmicks by identifying repetitive
patterns.
* Bundled security checks are designed to handle tricky scenarios:
stored XSS (path, parameters, headers), blind SQL or XML injection,
or blind shell injection.
* Report post-processing drastically reduces the noise caused by any
remaining false positives or server gimmicks by identifying repetitive
patterns.
That said, skipfish is not a silver bullet, and may be unsuitable for certain
purposes. For example, it does not satisfy most of the requirements outlined in
WASC Web Application Security Scanner Evaluation Criteria (some of them on
purposes. For example, it does not satisfy most of the requirements outlined
in WASC Web Application Security Scanner Evaluation Criteria (some of them on
purpose, some out of necessity); and unlike most other projects of this type,
it does not come with an extensive database of known vulnerabilities for
banner-type checks.
-----------------------------------------------------
2. Most curious! What specific tests are implemented?
3. Most curious! What specific tests are implemented?
-----------------------------------------------------
A rough list of the security checks offered by the tool is outlined below.
* High risk flaws (potentially leading to system compromise):
- Server-side SQL injection (including blind vectors, numerical
parameters).
- Explicit SQL-like syntax in GET or POST parameters.
- Server-side shell command injection (including blind vectors).
- Server-side XML / XPath injection (including blind vectors).
- Format string vulnerabilities.
- Integer overflow vulnerabilities.
- Locations accepting HTTP PUT.
* Server-side SQL injection (including blind vectors, numerical parameters).
* Explicit SQL-like syntax in GET or POST parameters.
* Server-side shell command injection (including blind vectors).
* Server-side XML / XPath injection (including blind vectors).
* Format string vulnerabilities.
* Integer overflow vulnerabilities.
* Locations accepting HTTP PUT.
* Medium risk flaws (potentially leading to data compromise):
- Stored and reflected XSS vectors in document body (minimal JS XSS
support present).
- Stored and reflected XSS vectors via HTTP redirects.
- Stored and reflected XSS vectors via HTTP header splitting.
- Directory traversal (including constrained vectors).
- Assorted file POIs (server-side sources, configs, etc).
- Attacker-supplied script and CSS inclusion vectors (stored and
reflected).
- External untrusted script and CSS inclusion vectors.
- Mixed content problems on script and CSS resources (optional).
- Incorrect or missing MIME types on renderables.
- Generic MIME types on renderables.
- Incorrect or missing charsets on renderables.
- Conflicting MIME / charset info on renderables.
- Bad caching directives on cookie setting responses.
* Stored and reflected XSS vectors in document body (minimal JS XSS support).
* Stored and reflected XSS vectors via HTTP redirects.
* Stored and reflected XSS vectors via HTTP header splitting.
* Directory traversal (including constrained vectors).
* Assorted file POIs (server-side sources, configs, etc).
* Attacker-supplied script and CSS inclusion vectors (stored and reflected).
* External untrusted script and CSS inclusion vectors.
* Mixed content problems on script and CSS resources (optional).
* Incorrect or missing MIME types on renderables.
* Generic MIME types on renderables.
* Incorrect or missing charsets on renderables.
* Conflicting MIME / charset info on renderables.
* Bad caching directives on cookie setting responses.
* Low risk issues (limited impact or low specificity):
- Directory listing bypass vectors.
- Redirection to attacker-supplied URLs (stored and reflected).
- Attacker-supplied embedded content (stored and reflected).
- External untrusted embedded content.
- Mixed content on non-scriptable subresources (optional).
- HTTP credentials in URLs.
- Expired or not-yet-valid SSL certificates.
- HTML forms with no XSRF protection.
- Self-signed SSL certificates.
- SSL certificate host name mismatches.
- Bad caching directives on less sensitive content.
* Directory listing bypass vectors.
* Redirection to attacker-supplied URLs (stored and reflected).
* Attacker-supplied embedded content (stored and reflected).
* External untrusted embedded content.
* Mixed content on non-scriptable subresources (optional).
* HTTP credentials in URLs.
* Expired or not-yet-valid SSL certificates.
* HTML forms with no XSRF protection.
* Self-signed SSL certificates.
* SSL certificate host name mismatches.
* Bad caching directives on less sensitive content.
* Internal warnings:
- Failed resource fetch attempts.
- Exceeded crawl limits.
- Failed 404 behavior checks.
- IPS filtering detected.
- Unexpected response variations.
- Seemingly misclassified crawl nodes.
* Failed resource fetch attempts.
* Exceeded crawl limits.
* Failed 404 behavior checks.
* IPS filtering detected.
* Unexpected response variations.
* Seemingly misclassified crawl nodes.
* Non-specific informational entries:
- General SSL certificate information.
- Significantly changing HTTP cookies.
- Changing Server, Via, or X-... headers.
- New 404 signatures.
- Resources that cannot be accessed.
- Resources requiring HTTP authentication.
- Broken links.
- Server errors.
- All external links not classified otherwise (optional).
- All external e-mails (optional).
- All external URL redirectors (optional).
- Links to unknown protocols.
- Form fields that could not be autocompleted.
- Password entry forms (for external brute-force).
- File upload forms.
- All other HTML forms detected.
- Numerical file names (for external brute-force).
- User-supplied links otherwise rendered on a page.
- Incorrect or missing MIME type on less significant content.
- Generic MIME type on less significant content.
- Incorrect or missing charset on less significant content.
- Conflicting MIME / charset information on less significant content.
- OGNL-like parameter passing conventions.
* General SSL certificate information.
* Significantly changing HTTP cookies.
* Changing Server, Via, or X-... headers.
* New 404 signatures.
* Resources that cannot be accessed.
* Resources requiring HTTP authentication.
* Broken links.
* Server errors.
* All external links not classified otherwise (optional).
* All external e-mails (optional).
* All external URL redirectors (optional).
* Links to unknown protocols.
* Form fields that could not be autocompleted.
* Password entry forms (for external brute-force).
* File upload forms.
* Other HTML forms (not classified otherwise).
* Numerical file names (for external brute-force).
* User-supplied links otherwise rendered on a page.
* Incorrect or missing MIME type on less significant content.
* Generic MIME type on less significant content.
* Incorrect or missing charset on less significant content.
* Conflicting MIME / charset information on less significant content.
* OGNL-like parameter passing conventions.
Along with a list of identified issues, skipfish also provides summary
overviews of document types and issue types found; and an interactive sitemap,
with nodes discovered through brute-force denoted in a distinctive way.
overviews of document types and issue types found; and an interactive
sitemap, with nodes discovered through brute-force denoted in a distinctive
way.
NOTE: As a conscious design decision, skipfish will not redundantly complain
NOTE: As a conscious design decision, skipfish will not redundantly complain
about highly non-specific issues, including but not limited to:
* Non-`httponly` cookies,
* Non-HTTPS or `autocomplete`-enabled forms,
* Non-httponly or non-secure cookies,
* Non-HTTPS or autocomplete-enabled forms,
* HTML comments detected on a page,
* Filesystem path disclosure in error messages,
* Server of framework version disclosure,
* Mere presence of certain technologies, such as WebDAV.
* Servers supporting TRACE or OPTIONS requests,
* Mere presence of certain technologies, such as WebDAV.
Most of these aspects are easy to inspect in a report if so desired - for
example, all the HTML forms are listed separately, so are new cookies or
interesting HTTP headers - and the expectation is that the auditor may opt to
make certain design recommendations based on this data where appropriate. That
said, these occurrences are not highlighted as a specific security flaw.
Most of these aspects are easy to inspect in a report if so desired - for
example, all the HTML forms are listed separately, so are new cookies or
interesting HTTP headers - and the expectation is that the auditor may opt to
make certain design recommendations based on this data where appropriate.
That said, these occurrences are not highlighted as a specific security flaw.
-----------------------------------------------------------
3. All right, I want to try it out. What do I need to know?
4. All right, I want to try it out. What do I need to know?
-----------------------------------------------------------
First and foremost, please do not be evil. Use skipfish only against services
you own, or have a permission to test.
Keep in mind that all types of security testing can be disruptive. Although the
scanner is designed not to carry out malicious attacks, it may accidentally
interfere with the operations of the site. You must accept the risk, and plan
accordingly. Run the scanner against test instances where feasible, and be
prepared to deal with the consequences if things go wrong.
Keep in mind that all types of security testing can be disruptive. Although
the scanner is designed not to carry out malicious attacks, it may
accidentally interfere with the operations of the site. You must accept the
risk, and plan accordingly. Run the scanner against test instances where
feasible, and be prepared to deal with the consequences if things go wrong.
Also note that the tool is meant to be used by security professionals, and is
experimental in nature. It may return false positives or miss obvious security
problems - and even when it operates perfectly, it is simply not meant to be a
point-and-click application. Do not rely on its output at face value.
experimental in nature. It may return false positives or miss obvious
security problems - and even when it operates perfectly, it is simply not
meant to be a point-and-click application. Do not take its output at face
value.
Running the tool against vendor-supplied demo sites is not a good way to
evaluate it, as they usually approximate vulnerabilities very imperfectly; we
Running the tool against vendor-supplied demo sites is not a good way to
evaluate it, as they usually approximate vulnerabilities very imperfectly; we
made no effort to accommodate these cases.
Lastly, the scanner is simply not designed for dealing with rogue and
misbehaving HTTP servers - and offers no guarantees of safe (or sane) behavior
there.
Lastly, the scanner is simply not designed for dealing with rogue and
misbehaving HTTP servers - and offers no guarantees of safe (or sane)
behavior there.
--------------------------
4. How to run the scanner?
5. How to run the scanner?
--------------------------
To compile it, simply unpack the archive and try make. Chances are, you will
need to install libidn first.
Next, you need to copy the desired dictionary file from dictionaries/ to
skipfish.wl. Please read dictionaries/README-FIRST carefully to make the right
choice. This step has a profound impact on the quality of scan results later on.
skipfish.wl. Please read dictionaries/README-FIRST carefully to make the
right choice. This step has a profound impact on the quality of scan results
later on.
Once you have the dictionary selected, you can try:
$ ./skipfish -o output_dir http://www.example.com/some/starting/path.txt
Note that you can provide more than one starting URL if so desired; all of them
will be crawled.
Note that you can provide more than one starting URL if so desired; all of
them will be crawled.
The tool will display some helpful stats while the scan is in progress. You
The tool will display some helpful stats while the scan is in progress. You
can also switch to a list of in-flight HTTP requests by pressing return.
In the example above, skipfish will scan the entire www.example.com (including
services on other ports, if linked to from the main page), and write a report
to output_dir/index.html. You can then view this report with your favorite
browser (JavaScript must be enabled). The index.html file is static; actual
results are stored as a hierarchy of JSON files, suitable for machine
processing if needs be.
In the example above, skipfish will scan the entire www.example.com
(including services on other ports, if linked to from the main page), and
write a report to output_dir/index.html. You can then view this report with
your favorite browser (JavaScript must be enabled; and because of recent
file:/// security improvements in certain browsers, you might need to access
results over HTTP). The index.html file is static; actual results are stored
as a hierarchy of JSON files, suitable for machine processing or different
presentation frontends if needs be.
Some sites may require authentication; for simple HTTP credentials, you can try:
Some sites may require authentication; for simple HTTP credentials, you can
try:
$ ./skipfish -A user:pass ...other parameters...
Alternatively, if the site relies on HTTP cookies instead, log in in your
browser or using a simple curl script, and then provide skipfish with a session
cookie:
browser or using a simple curl script, and then provide skipfish with a
session cookie:
$ ./skipfish -C name=val ...other parameters...
@ -263,20 +273,20 @@ $ ./skipfish -X /logout/logout.aspx ...other parameters...
The -X option is also useful for speeding up your scans by excluding /icons/,
/doc/, /manuals/, and other standard, mundane locations along these lines. In
general, you can use -X, plus -I (only spider URLs matching a substring) and -S
(ignore links on pages where a substring appears in response body) to limit the
scope of a scan any way you like - including restricting it only to a specific
protocol and port:
general, you can use -X, plus -I (only spider URLs matching a substring) and
-S (ignore links on pages where a substring appears in response body) to
limit the scope of a scan any way you like - including restricting it only to
a specific protocol and port:
$ ./skipfish -I http://example.com:1234/ ...other parameters...
A related function, -K, allows you to specify parameter names not to fuzz
A related function, -K, allows you to specify parameter names not to fuzz
(useful for applications that put session IDs in the URL, to minimize noise).
Another useful scoping option is -D - allowing you to specify additional hosts
or domains to consider in-scope for the test. By default, all hosts appearing
in the command-line URLs are added to the list - but you can use -D to broaden
these rules, for example:
Another useful scoping option is -D - allowing you to specify additional
hosts or domains to consider in-scope for the test. By default, all hosts
appearing in the command-line URLs are added to the list - but you can use -D
to broaden these rules, for example:
$ ./skipfish -D test2.example.com -o output-dir http://test1.example.com/
@ -284,120 +294,124 @@ $ ./skipfish -D test2.example.com -o output-dir http://test1.example.com/
$ ./skipfish -D .example.com -o output-dir http://test1.example.com/
In some cases, you do not want to actually crawl a third-party domain, but you
trust the owner of that domain enough not to worry about cross-domain content
inclusion from that location. To suppress warnings, you can use the -B option,
for example:
In some cases, you do not want to actually crawl a third-party domain, but
you trust the owner of that domain enough not to worry about cross-domain
content inclusion from that location. To suppress warnings, you can use the
-B option, for example:
$ ./skipfish -B .google-analytics.com -B .googleapis.com ...other parameters...
$ ./skipfish -B .google-analytics.com -B .googleapis.com ...other
parameters...
By default, skipfish sends minimalistic HTTP headers to reduce the amount of
data exchanged over the wire; some sites examine User-Agent strings or header
ordering to reject unsupported clients, however. In such a case, you can use -b
ie or -b ffox to mimic one of the two popular browsers.
ordering to reject unsupported clients, however. In such a case, you can use
-b ie or -b ffox to mimic one of the two popular browsers.
When it comes to customizing your HTTP requests, you can also use the -H option
to insert any additional, non-standard headers; or -F to define a custom
mapping between a host and an IP (bypassing the resolver). The latter feature
is particularly useful for not-yet-launched or legacy services.
When it comes to customizing your HTTP requests, you can also use the -H
option to insert any additional, non-standard headers; or -F to define a
custom mapping between a host and an IP (bypassing the resolver). The latter
feature is particularly useful for not-yet-launched or legacy services.
Some sites may be too big to scan in a reasonable timeframe. If the site
features well-defined tarpits - for example, 100,000 nearly identical user
profiles as a part of a social network - these specific locations can be
excluded with -X or -S. In other cases, you may need to resort to other
settings: -d limits crawl depth to a specified number of subdirectories; -c
limits the number of children per directory; and -r limits the total number of
requests to send in a scan.
limits the number of children per directory; -x limits the total number of
descendants per crawl tree branch; and -r limits the total number of requests
to send in a scan.
An interesting option is available for repeated assessments: -p. By specifying
a percentage between 1 and 100%, it is possible to tell the crawler to follow
fewer than 100% of all links, and try fewer than 100% of all dictionary
entries. This - naturally - limits the completeness of a scan, but unlike most
other settings, it does so in a balanced, non-deterministic manner. It is
extremely useful when you are setting up time-bound, but periodic assessments
of your infrastructure. Another related option is -q, which sets the initial
random seed for the crawler to a specified value. This can be used to exactly
reproduce a previous scan to compare results. Randomness is relied upon most
heavily in the -p mode, but also for making a couple of other scan management
decisions elsewhere.
An interesting option is available for repeated assessments: -p. By
specifying a percentage between 1 and 100%, it is possible to tell the
crawler to follow fewer than 100% of all links, and try fewer than 100% of
all dictionary entries. This - naturally - limits the completeness of a scan,
but unlike most other settings, it does so in a balanced, non-deterministic
manner. It is extremely useful when you are setting up time-bound, but
periodic assessments of your infrastructure. Another related option is -q,
which sets the initial random seed for the crawler to a specified value. This
can be used to exactly reproduce a previous scan to compare results.
Randomness is relied upon most heavily in the -p mode, but also for making a
couple of other scan management decisions elsewhere.
Some particularly complex (or broken) services may involve a very high number
of identical or nearly identical pages. Although these occurrences are by
default grayed out in the report, they still use up some screen estate and take
a while to process on JavaScript level. In such extreme cases, you may use the
-Q option to suppress reporting of duplicate nodes altogether, before the
report is written. This may give you a less comprehensive understanding of how
the site is organized, but has no impact on test coverage.
default grayed out in the report, they still use up some screen estate and
take a while to process on JavaScript level. In such extreme cases, you may
use the -Q option to suppress reporting of duplicate nodes altogether, before
the report is written. This may give you a less comprehensive understanding
of how the site is organized, but has no impact on test coverage.
In certain quick assessments, you might also have no interest in paying any
particular attention to the desired functionality of the site - hoping to
explore non-linked secrets only. In such a case, you may specify -P to inhibit
all HTML parsing. This limits the coverage and takes away the ability for the
scanner to learn new keywords by looking at the HTML, but speeds up the test
dramatically. Another similarly crippling option that reduces the risk of
persistent effects of a scan is -O, which inhibits all form parsing and
submission steps.
explore non-linked secrets only. In such a case, you may specify -P to
inhibit all HTML parsing. This limits the coverage and takes away the ability
for the scanner to learn new keywords by looking at the HTML, but speeds up
the test dramatically. Another similarly crippling option that reduces the
risk of persistent effects of a scan is -O, which inhibits all form parsing
and submission steps.
By default, skipfish complains loudly about all MIME or character set
mismatches on renderable documents, and classifies many of them as "medium
risk"; this is because, if any user-controlled content is returned, the
situation could lead to cross-site scripting attacks in certain browsers. On
some poorly designed and maintained sites, this may contribute too much noise;
if so, you may use -J to mark these issues as "low risk" unless the scanner can
explicitly sees its own user input being echoed back on the resulting page.
This may miss many subtle attack vectors, though.
some poorly designed and maintained sites, this may contribute too much
noise; if so, you may use -J to mark these issues as "low risk" unless the
scanner can explicitly sees its own user input being echoed back on the
resulting page. This may miss many subtle attack vectors, though.
Some sites that handle sensitive user data care about SSL - and about getting
it right. Skipfish may optionally assist you in figuring out problematic mixed
content scenarios - use the -M option to enable this. The scanner will complain
about situations such as http:// scripts being loaded on https:// pages - but
will disregard non-risk scenarios such as images.
it right. Skipfish may optionally assist you in figuring out problematic
mixed content scenarios - use the -M option to enable this. The scanner will
complain about situations such as http:// scripts being loaded on https://
pages - but will disregard non-risk scenarios such as images.
Likewise, certain pedantic sites may care about cases where caching is
restricted on HTTP/1.1 level, but no explicit HTTP/1.0 caching directive is
given on specifying -E in the command-line causes skipfish to log all such
cases carefully.
Lastly, in some assessments that involve self-contained sites without extensive
user content, the auditor may care about any external e-mails or HTTP links
seen, even if they have no immediate security impact. Use the -U option to have
these logged.
Lastly, in some assessments that involve self-contained sites without
extensive user content, the auditor may care about any external e-mails or
HTTP links seen, even if they have no immediate security impact. Use the -U
option to have these logged.
Dictionary management is a special topic, and - as mentioned - is covered in
more detail in dictionaries/README-FIRST. Please read that file before
proceeding. Some of the relevant options include -W to specify a custom
wordlist, -L to suppress auto-learning, -V to suppress dictionary updates, -G
to limit the keyword guess jar size, -R to drop old dictionary entries, and -Y
to inhibit expensive $keyword.$extension fuzzing.
to limit the keyword guess jar size, -R to drop old dictionary entries, and
-Y to inhibit expensive $keyword.$extension fuzzing.
Skipfish also features a form auto-completion mechanism in order to maximize
scan coverage. The values should be non-malicious, as they are not meant to
implement security checks - but rather, to get past input validation logic. You
can define additional rules, or override existing ones, with the -T option (-T
form_field_name=field_value, e.g. -T login=test123 -T password=test321 -
although note that -C and -A are a much better method of logging in).
implement security checks - but rather, to get past input validation logic.
You can define additional rules, or override existing ones, with the -T
option (-T form_field_name=field_value, e.g. -T login=test123 -T
password=test321 - although note that -C and -A are a much better method of
logging in).
There is also a handful of performance-related options. Use -g to set the
maximum number of connections to maintain, globally, to all targets (it is
sensible to keep this under 50 or so to avoid overwhelming the TCP/IP stack on
your system or on the nearby NAT / firewall devices); and -m to set the per-IP
limit (experiment a bit: 2-4 is usually good for localhost, 4-8 for local
networks, 10-20 for external targets, 30+ for really lagged or non-keep-alive
hosts). You can also use -w to set the I/O timeout (i.e., skipfish will wait
only so long for an individual read or write), and -t to set the total request
timeout, to account for really slow or really fast sites.
sensible to keep this under 50 or so to avoid overwhelming the TCP/IP stack
on your system or on the nearby NAT / firewall devices); and -m to set the
per-IP limit (experiment a bit: 2-4 is usually good for localhost, 4-8 for
local networks, 10-20 for external targets, 30+ for really lagged or
non-keep-alive hosts). You can also use -w to set the I/O timeout (i.e.,
skipfish will wait only so long for an individual read or write), and -t to
set the total request timeout, to account for really slow or really fast
sites.
Lastly, -f controls the maximum number of consecutive HTTP errors you are
willing to see before aborting the scan; and -s sets the maximum length of a
response to fetch and parse (longer responses will be truncated).
Further rate-limiting is available through third-party user mode tools such as
trickle, or kernel-level traffic shaping.
Further rate-limiting is available through third-party user mode tools such
as trickle, or kernel-level traffic shaping.
Oh, and runtime stats can be suppressed with -u to run skipfish in quiet mode.
Oh, and real-time scan statistics can be suppressed with -u.
--------------------------------
5. But seriously, how to run it?
6. But seriously, how to run it?
--------------------------------
A standard, authenticated scan of a well-designed and self-contained site
@ -407,52 +421,53 @@ issues):
$ ./skipfish -MEU -C "AuthCookie=value" -X /logout.aspx -o output_dir \
http://www.example.com/
Five-connection crawl, but no brute-force; pretending to be MSIE, caring
less about ambiguous MIME or character set mismatches, and trusting
Five-connection crawl, but no brute-force; pretending to be MSIE and caring
less about ambiguous MIME or character set mismatches, and trusting
example.com links:
$ ./skipfish -m 5 -LVJ -W /dev/null -o output_dir -b ie -B example.com \
http://www.example.com/
Brute force only (no HTML link extraction), limited to a specific
directory, timing out after 5 seconds:
Brute force only (no HTML link extraction), limited to a single directory and
timing out after 5 seconds:
$ ./skipfish -P -I http://www.example.com/dir1/ -O -o output_dir -t 5 \
$ ./skipfish -P -I http://www.example.com/dir1/ -o output_dir -t 5 -I \
http://www.example.com/dir1/
For a short list of all command-line options, try ./skipfish -h.
----------------------------------------------------
6. How to interpret and address the issues reported?
7. How to interpret and address the issues reported?
----------------------------------------------------
Most of the problems reported by skipfish should self-explanatory, assuming you
have a good gasp of the fundamentals of web security. If you need a quick
refresher on some of the more complicated topics, such as MIME sniffing, you
Most of the problems reported by skipfish should self-explanatory, assuming you
have a good gasp of the fundamentals of web security. If you need a quick
refresher on some of the more complicated topics, such as MIME sniffing, you
may enjoy our comprehensive Browser Security Handbook as a starting point:
http://code.google.com/p/browsersec/
If you still need assistance, there are several organizations that put a
considerable effort into documenting and explaining many of the common web
security threats, and advising the public on how to address them. I encourage
you to refer to the materials published by OWASP and Web Application Security
If you still need assistance, there are several organizations that put a
considerable effort into documenting and explaining many of the common web
security threats, and advising the public on how to address them. I encourage
you to refer to the materials published by OWASP and Web Application Security
Consortium, amongst others:
* http://www.owasp.org/index.php/Category:Principle
* http://www.owasp.org/index.php/Category:OWASP_Guide_Project
* http://www.webappsec.org/projects/articles/
Although I am happy to diagnose problems with the scanner itself, I regrettably
cannot offer any assistance with the inner wokings of third-party web
Although I am happy to diagnose problems with the scanner itself, I regrettably
cannot offer any assistance with the inner wokings of third-party web
applications.
---------------------------------------
7. Known limitations / feature wishlist
8. Known limitations / feature wishlist
---------------------------------------
Below is a list of features currently missing in skipfish. If you wish to
improve the tool by contributing code in one of these areas, please let me know:
improve the tool by contributing code in one of these areas, please let me
know:
* Buffer overflow checks: after careful consideration, I suspect there is
no reliable way to test for buffer overflows remotely. Much like the actual
@ -468,24 +483,24 @@ improve the tool by contributing code in one of these areas, please let me know:
problems seem to be largely addressed on browser level at this point, so
they were much lower priority at the time of this writing.
* Security checks and link extraction for third-party, plugin-based content
(Flash, Java, PDF, etc).
* Security checks and link extraction for third-party, plugin-based
content (Flash, Java, PDF, etc).
* Password brute-force and numerical filename brute-force probes.
* Search engine integration (vhosts, starting paths).
* More specific PHP tests (eval injection, RFI).
* VIEWSTATE decoding.
* VIEWSTATE decoding.
* NTLM and digest authentication.
* Proxy support: somewhat incompatible with performance control features
currently employed by skipfish; but in the long run, should be provided as
a last-resort option.
* More specific PHP tests (eval injection, RFI).
* Scan resume option.
* Proxy support: somewhat incompatible with performance control features
currently employed by skipfish; but in the long run, should be provided
as a last-resort option.
* Scan resume option.
* Option to limit document sampling or save samples directly to disk.
@ -493,16 +508,17 @@ improve the tool by contributing code in one of these areas, please let me know:
* Config file support.
* A database for banner / version checks?
* A database for banner / version checks?
-------------------------------------
8. Oy! Something went horribly wrong!
9. Oy! Something went horribly wrong!
-------------------------------------
There is no web crawler so good that there wouldn't be a web framework to one
day set it on fire. If you encounter what appears to be bad behavior (e.g., a
scan that takes forever and generates too many requests, completely bogus nodes
in scan output, or outright crashes), please first check this page:
scan that takes forever and generates too many requests, completely bogus
nodes in scan output, or outright crashes), please first check our known
issues page:
http://code.google.com/p/skipfish/wiki/KnownIssues
@ -526,12 +542,12 @@ $ gdb --batch -ex back ./skipfish core
...and be sure to send the author the output of that last command as well.
-----------------------
9. Credits and feedback
-----------------------
------------------------
10. Credits and feedback
------------------------
Skipfish is made possible thanks to the contributions of, and valuable feedback
from, Google's information security engineering team.
Skipfish is made possible thanks to the contributions of, and valuable
feedback from, Google's information security engineering team.
If you have any bug reports, questions, suggestions, or concerns regarding the
application, the author can be reached at lcamtuf@google.com.
If you have any bug reports, questions, suggestions, or concerns regarding
the application, the author can be reached at lcamtuf@google.com.

3
config.h
View File

@ -70,7 +70,8 @@
/* Configurable settings for crawl database (cmdline override): */
#define MAX_DEPTH 16 /* Maximum crawl tree depth */
#define MAX_CHILDREN 1024 /* Maximum children per tree node */
#define MAX_CHILDREN 512 /* Maximum children per tree node */
#define MAX_DESCENDANTS 8192 /* Maximum descendants per branch */
#define MAX_SAMENAME 3 /* Identically named path nodes */
/* Crawl / analysis constants: */

22
crawler.c
View File

@ -1654,7 +1654,7 @@ static void crawl_par_numerical_init(struct pivot_desc* pv) {
DEBUG_HELPER(pv);
if (pv->child_cnt >= max_children) goto schedule_next;
if (!descendants_ok(pv)) goto schedule_next;
/* Skip to the first digit, then to first non-digit. */
@ -1754,7 +1754,7 @@ static u8 par_numerical_callback(struct http_request* req,
!((is_c_sens(req->pivot) ? strcmp : strcasecmp)((char*)TPAR(req),
(char*)req->pivot->child[i]->name))) goto schedule_next;
if (req->pivot->child_cnt >= max_children) goto schedule_next;
if (!descendants_ok(req->pivot)) goto schedule_next;
/* Hmm, looks like we're onto something. Let's manually create a dummy
pivot and attach it to current node, without any activity planned.
@ -1777,6 +1777,8 @@ static u8 par_numerical_callback(struct http_request* req,
req->pivot->child[req->pivot->child_cnt++] = n;
add_descendant(req->pivot);
req->pivot = n;
RESP_CHECKS(req, res);
@ -1814,7 +1816,7 @@ static void crawl_par_dict_init(struct pivot_desc* pv) {
restart_dict:
if (pv->child_cnt >= max_children) {
if (!descendants_ok(pv)) {
crawl_par_trylist_init(pv);
return;
}
@ -1945,7 +1947,7 @@ static u8 par_dict_callback(struct http_request* req,
!((is_c_sens(req->pivot) ? strcmp : strcasecmp)((char*)TPAR(req),
(char*)req->pivot->child[i]->name))) goto schedule_next;
if (req->pivot->child_cnt >= max_children) goto schedule_next;
if (!descendants_ok(req->pivot)) goto schedule_next;
n = ck_alloc(sizeof(struct pivot_desc));
@ -1963,6 +1965,9 @@ static u8 par_dict_callback(struct http_request* req,
* sizeof(struct pivot_desc*));
req->pivot->child[req->pivot->child_cnt++] = n;
add_descendant(req->pivot);
req->pivot = n;
keep = 1;
@ -1992,7 +1997,7 @@ void crawl_par_trylist_init(struct pivot_desc* pv) {
no point in going through the try list if restarted. */
if (pv->fuzz_par == -1 || pv->bogus_par || pv->res_varies
|| pv->child_cnt >= max_children) {
|| !descendants_ok(pv)) {
pv->state = PSTATE_DONE;
return;
} else
@ -2078,7 +2083,7 @@ static u8 par_trylist_callback(struct http_request* req,
!((is_c_sens(req->pivot) ? strcmp : strcasecmp)((char*)TPAR(req),
(char*)req->pivot->child[i]->name))) goto schedule_next;
if (req->pivot->child_cnt >= max_children) goto schedule_next;
if (!descendants_ok(req->pivot)) goto schedule_next;
n = ck_alloc(sizeof(struct pivot_desc));
@ -2096,6 +2101,9 @@ static u8 par_trylist_callback(struct http_request* req,
* sizeof(struct pivot_desc*));
req->pivot->child[req->pivot->child_cnt++] = n;
add_descendant(req->pivot);
req->pivot = n;
RESP_CHECKS(req, res);
@ -2634,7 +2642,7 @@ static void crawl_dir_dict_init(struct pivot_desc* pv) {
if (in_dict_init || pv->pending > DICT_BATCH || pv->state != PSTATE_CHILD_DICT)
return;
if (pv->child_cnt >= max_children) {
if (!descendants_ok(pv)) {
crawl_parametric_init(pv);
return;
}

47
database.c
View File

@ -52,9 +52,10 @@ u32 num_deny_urls,
num_trust_domains,
num_skip_params;
u32 max_depth = MAX_DEPTH,
max_children = MAX_CHILDREN,
max_guesses = MAX_GUESSES;
u32 max_depth = MAX_DEPTH,
max_children = MAX_CHILDREN,
max_descendants = MAX_DESCENDANTS,
max_guesses = MAX_GUESSES;
u8 dont_add_words; /* No auto dictionary building */
@ -84,6 +85,31 @@ static u32 cur_xss_id, scan_id; /* Stored XSS manager IDs */
static struct http_request** xss_req; /* Stored XSS manager req cache */
/* Checks descendant counts. */
u8 descendants_ok(struct pivot_desc* pv) {
if (pv->child_cnt > max_children) return 0;
while (pv) {
if (pv->desc_cnt > max_descendants) return 0;
pv = pv->parent;
}
return 1;
}
void add_descendant(struct pivot_desc* pv) {
while (pv) {
pv->desc_cnt++;
pv = pv->parent;
}
}
/* Maps a parsed URL (in req) to the pivot tree, creating or modifying nodes
as necessary, and scheduling them for crawl. This should be called only
on requests that were *not* yet retrieved. */
@ -167,6 +193,8 @@ void maybe_add_pivot(struct http_request* req, struct http_response* res,
root_pivot.child[root_pivot.child_cnt++] = cur;
add_descendant(&root_pivot);
cur->type = PIVOT_SERV;
cur->state = PSTATE_FETCH;
cur->linked = 2;
@ -234,7 +262,7 @@ void maybe_add_pivot(struct http_request* req, struct http_response* res,
/* Enforce user limits. */
if ((i + 1) >= max_depth || cur->child_cnt > max_children) {
if ((i + 1) >= max_depth || !descendants_ok(cur)) {
problem(PROB_LIMITS, req, res, (u8*)"Child node limit exceeded", cur,
0);
return;
@ -261,6 +289,8 @@ void maybe_add_pivot(struct http_request* req, struct http_response* res,
cur->child[cur->child_cnt++] = n;
add_descendant(cur);
n->parent = cur;
n->linked = via_link;
n->name = ck_strdup(pname);
@ -427,7 +457,7 @@ void maybe_add_pivot(struct http_request* req, struct http_response* res,
/* Enforce user limits. */
if (cur->child_cnt > max_children) {
if (!descendants_ok(cur)) {
problem(PROB_LIMITS, req, res, (u8*)"Child node limit exceeded", cur, 0);
return;
}
@ -441,6 +471,8 @@ void maybe_add_pivot(struct http_request* req, struct http_response* res,
cur->child[cur->child_cnt++] = n;
add_descendant(cur);
n->parent = cur;
n->type = PIVOT_PARAM;
n->linked = via_link;
@ -1236,8 +1268,9 @@ void dump_pivots(struct pivot_desc* cur, u8 nest) {
}
SAY(cGRA "%sFlags : " cNOR "linked %u, case %u/%u, fuzz_par %d, ips %u, "
"sigs %u, reqs %u\n", indent, cur->linked, cur->csens, cur->c_checked,
cur->fuzz_par, cur->uses_ips, cur->r404_cnt, cur->pending);
"sigs %u, reqs %u, desc %u/%u\n", indent, cur->linked, cur->csens, cur->c_checked,
cur->fuzz_par, cur->uses_ips, cur->r404_cnt, cur->pending, cur->child_cnt,
cur->desc_cnt);
if (cur->req) {
url = serialize_path(cur->req, 1, 0);

10
database.h
View File

@ -96,6 +96,7 @@ struct pivot_desc {
struct pivot_desc* parent; /* Parent pivot, if any */
struct pivot_desc** child; /* List of children */
u32 child_cnt; /* Number of children */
u32 desc_cnt; /* Number of descendants */
struct issue_desc* issue; /* List of issues found */
u32 issue_cnt; /* Number of issues */
@ -153,6 +154,14 @@ struct pivot_desc {
extern struct pivot_desc root_pivot;
/* Checks child / descendant limits. */
u8 descendants_ok(struct pivot_desc* pv);
/* Increases descendant count. */
void add_descendant(struct pivot_desc* pv);
/* Maps a parsed URL (in req) to the pivot tree, creating or modifying nodes
as necessary, and scheduling them for crawl; via_link should be 1 if the
URL came from an explicit link or user input, 0 if brute-forced.
@ -332,6 +341,7 @@ extern u32 num_deny_urls,
extern u32 max_depth,
max_children,
max_descendants,
max_trylist,
max_guesses;

5
skipfish.1
View File

@ -40,7 +40,10 @@ do not accept any new cookies
maximum crawl tree depth (default: 16)
.TP
.B \-c max_child
maximum children to index per node (default: 1024)
maximum children to index per node (default: 512)
.TP
.B \-x max_desc
maximum descendants to index per crawl tree branch (default: 8192)
.TP
.B \-r r_limit
max total number of requests to send (default: 100000000)

14
skipfish.c
View File

@ -89,6 +89,7 @@ static void usage(char* argv0) {
" -d max_depth - maximum crawl tree depth (%u)\n"
" -c max_child - maximum children to index per node (%u)\n"
" -x max_desc - maximum descendants to index per branch (%u)\n"
" -r r_limit - max total number of requests to send (%u)\n"
" -p crawl%% - node and link crawl probability (100%%)\n"
" -q hex - repeat probabilistic scan with given seed\n"
@ -133,9 +134,9 @@ static void usage(char* argv0) {
" -s s_limit - response size limit (%u B)\n\n"
"Send comments and complaints to <lcamtuf@google.com>.\n", argv0,
max_depth, max_children, max_requests, DEF_WORDLIST, MAX_GUESSES,
max_connections, max_conn_host, max_fail, resp_tmout, rw_tmout,
idle_tmout, size_limit);
max_depth, max_children, max_descendants, max_requests, DEF_WORDLIST,
MAX_GUESSES, max_connections, max_conn_host, max_fail, resp_tmout,
rw_tmout, idle_tmout, size_limit);
exit(1);
}
@ -214,7 +215,7 @@ int main(int argc, char** argv) {
SAY("skipfish version " VERSION " by <lcamtuf@google.com>\n");
while ((opt = getopt(argc, argv,
"+A:F:C:H:b:Nd:c:r:p:I:X:S:D:PJOYQMZUEK:W:LVT:G:R:B:q:g:m:f:t:w:i:s:o:hu")) > 0)
"+A:F:C:H:b:Nd:c:x:r:p:I:X:S:D:PJOYQMZUEK:W:LVT:G:R:B:q:g:m:f:t:w:i:s:o:hu")) > 0)
switch (opt) {
@ -362,6 +363,11 @@ int main(int argc, char** argv) {
if (!max_children) FATAL("Invalid value '%s'.", optarg);
break;
case 'x':
max_descendants = atoi(optarg);
if (!max_descendants) FATAL("Invalid value '%s'.", optarg);
break;
case 'p':
crawl_prob = atoi(optarg);
if (!crawl_prob) FATAL("Invalid value '%s'.", optarg);