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-# Specification for the fuzz testing tool
-#
-# Copyright (C) 2014 Maria Kustova <maria.k@catit.be>
-#
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program. If not, see <http://www.gnu.org/licenses/>.
-
-
-Image fuzzer
-============
-
-Description
------------
-
-The goal of the image fuzzer is to catch crashes of qemu-io/qemu-img
-by providing to them randomly corrupted images.
-Test images are generated from scratch and have valid inner structure with some
-elements, e.g. L1/L2 tables, having random invalid values.
-
-
-Test runner
------------
-
-The test runner generates test images, executes tests utilizing generated
-images, indicates their results and collects all test related artifacts (logs,
-core dumps, test images, backing files).
-The test means execution of all available commands under test with the same
-generated test image.
-By default, the test runner generates new tests and executes them until
-keyboard interruption. But if a test seed is specified via the '--seed' runner
-parameter, then only one test with this seed will be executed, after its finish
-the runner will exit.
-
-The runner uses an external image fuzzer to generate test images. An image
-generator should be specified as a mandatory parameter of the test runner.
-Details about interactions between the runner and fuzzers see "Module
-interfaces".
-
-The runner activates generation of core dumps during test executions, but it
-assumes that core dumps will be generated in the current working directory.
-For comprehensive test results, please, set up your test environment
-properly.
-
-Paths to binaries under test (SUTs) qemu-img and qemu-io are retrieved from
-environment variables. If the environment check fails the runner will
-use SUTs installed in system paths.
-qemu-img is required for creation of backing files, so it's mandatory to set
-the related environment variable if it's not installed in the system path.
-For details about environment variables see qemu-iotests/check.
-
-The runner accepts a JSON array of fields expected to be fuzzed via the
-'--config' argument, e.g.
-
- '[["feature_name_table"], ["header", "l1_table_offset"]]'
-
-Each sublist can have one or two strings defining image structure elements.
-In the latter case a parent element should be placed on the first position,
-and a field name on the second one.
-
-The runner accepts a list of commands under test as a JSON array via
-the '--command' argument. Each command is a list containing a SUT and all its
-arguments, e.g.
-
- runner.py -c '[["qemu-io", "$test_img", "-c", "write $off $len"]]'
- /tmp/test ../qcow2
-
-For variable arguments next aliases can be used:
- - $test_img for a fuzzed img
- - $off for an offset in the fuzzed image
- - $len for a data size
-
-Values for last two aliases will be generated based on a size of a virtual
-disk of the generated image.
-In case when no commands are specified the runner will execute commands from
-the default list:
- - qemu-img check
- - qemu-img info
- - qemu-img convert
- - qemu-io -c read
- - qemu-io -c write
- - qemu-io -c aio_read
- - qemu-io -c aio_write
- - qemu-io -c flush
- - qemu-io -c discard
- - qemu-io -c truncate
-
-
-Qcow2 image generator
----------------------
-
-The 'qcow2' generator is a Python package providing 'create_image' method as
-a single public API. See details in 'Test runner/image fuzzer' chapter of
-'Module interfaces'.
-
-Qcow2 contains two submodules: fuzz.py and layout.py.
-
-'fuzz.py' contains all fuzzing functions, one per image field. It's assumed
-that after code analysis every field will have own constraints for its value.
-For now only universal potentially dangerous values are used, e.g. type limits
-for integers or unsafe symbols as '%s' for strings. For bitmasks random amount
-of bits are set to ones. All fuzzed values are checked on non-equality to the
-current valid value of the field. In case of equality the value will be
-regenerated.
-
-'layout.py' creates a random valid image, fuzzes a random subset of the image
-fields by 'fuzz.py' module and writes a fuzzed image to the file specified.
-If a fuzzer configuration is specified, then it has the next interpretation:
-
- 1. If a list contains a parent image element only, then some random portion
- of fields of this element will be fuzzed every test.
- The same behavior is applied for the entire image if no configuration is
- used. This case is useful for the test specialization.
-
- 2. If a list contains a parent element and a field name, then a field
- will be always fuzzed for every test. This case is useful for regression
- testing.
-
-The generator can create header fields, header extensions, L1/L2 tables and
-refcount table and blocks.
-
-Module interfaces
------------------
-
-* Test runner/image fuzzer
-
-The runner calls an image generator specifying the path to a test image file,
-path to a backing file and its format and a fuzzer configuration.
-An image generator is expected to provide a
-
- 'create_image(test_img_path, backing_file_path=None,
- backing_file_format=None, fuzz_config=None)'
-
-method that creates a test image, writes it to the specified file and returns
-the size of the virtual disk.
-The file should be created if it doesn't exist or overwritten otherwise.
-fuzz_config has a form of a list of lists. Every sublist can have one
-or two elements: first element is a name of a parent image element, second one
-if exists is a name of a field in this element.
-Example,
- [['header', 'l1_table_offset'],
- ['header', 'nb_snapshots'],
- ['feature_name_table']]
-
-Random seed is set by the runner at every test execution for the regression
-purpose, so an image generator is not recommended to modify it internally.
-
-
-Overall fuzzer requirements
-===========================
-
-Input data:
-----------
-
- - image template (generator)
- - work directory
- - action vector (optional)
- - seed (optional)
- - SUT and its arguments (optional)
-
-
-Fuzzer requirements:
--------------------
-
-1. Should be able to inject random data
-2. Should be able to select a random value from the manually pregenerated
- vector (boundary values, e.g. max/min cluster size)
-3. Image template should describe a general structure invariant for all
- test images (image format description)
-4. Image template should be autonomous and other fuzzer parts should not
- rely on it
-5. Image template should contain reference rules (not only block+size
- description)
-6. Should generate the test image with the correct structure based on an image
- template
-7. Should accept a seed as an argument (for regression purpose)
-8. Should generate a seed if it is not specified as an input parameter.
-9. The same seed should generate the same image for the same action vector,
- specified or generated.
-10. Should accept a vector of actions as an argument (for test reproducing and
- for test case specification, e.g. group of tests for header structure,
- group of test for snapshots, etc)
-11. Action vector should be randomly generated from the pool of available
- actions, if it is not specified as an input parameter
-12. Pool of actions should be defined automatically based on an image template
-13. Should accept a SUT and its call parameters as an argument or select them
- randomly otherwise. As far as it's expected to be rarely changed, the list
- of all possible test commands can be available in the test runner
- internally.
-14. Should support an external cancellation of a test run
-15. Seed should be logged (for regression purpose)
-16. All files related to a test result should be collected: a test image,
- SUT logs, fuzzer logs and crash dumps
-17. Should be compatible with python version 2.4-2.7
-18. Usage of external libraries should be limited as much as possible.
-
-
-Image formats:
--------------
-
-Main target image format is qcow2, but support of image templates should
-provide an ability to add any other image format.
-
-
-Effectiveness:
--------------
-
-The fuzzer can be controlled via template, seed and action vector;
-it makes the fuzzer itself invariant to an image format and test logic.
-It should be able to perform rather complex and precise tests, that can be
-specified via an action vector. Otherwise, knowledge about an image structure
-allows the fuzzer to generate the pool of all available areas can be fuzzed
-and randomly select some of them and so compose its own action vector.
-Also complexity of a template defines complexity of the fuzzer, so its
-functionality can be varied from simple model-independent fuzzing to smart
-model-based one.
-
-
-Glossary:
---------
-
-Action vector is a sequence of structure elements retrieved from an image
-format, each of them will be fuzzed for the test image. It's a subset of
-elements of the action pool. Example: header, refcount table, etc.
-Action pool is all available elements of an image structure that generated
-automatically from an image template.
-Image template is a formal description of an image structure and relations
-between image blocks.
-Test image is an output image of the fuzzer defined by the current seed and
-action vector.