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110 lines
4.7 KiB
Markdown
110 lines
4.7 KiB
Markdown
libscrypt
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=========
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Linux scrypt shared library.
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Full credit to algorithm designer and example code from Colin Percival here:
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http://www.tarsnap.com/scrypt.html
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Utilises BASE64 encoding library from ISC.
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Official project page, including stable tarballs found here:
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http://www.lolware.net/libscrypt.html
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Simple hashing interface
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The (reference) internal hashing function can be directly called as follows:
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int libscrypt_scrypt(const uint8_t *passwd, size_t passwdlen,
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const uint8_t *salt, size_t saltlen, uint64_t N, uint32_t r,
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uint32_t p, /*@out@*/ uint8_t *buf, size_t buflen);
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Libscrypt's easier to use interface wraps this up to deal with the salt and produce BASE64 output as so:
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int libscrypt_hash(char *dst, char *passphrase, uint32_t N, uint8_t r, uint8_t p);
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Sane constants have been created for N, r and p so you can create a hash like this:
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libscrypt_hash(outbuf, "My cats's breath smells like cat food", SCRYPT_N, SCRYPT_r, SCRYPT_p);
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This function sets errno as required for any error conditions.
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Output stored in "outbuf" is stored in a standardised MCF form, which means includes the randomly created, 128 bit salt, all N, r and p values, and a BASE64 encoded version of the hash. The entire MCF can be stored in a database, and compared for use as below:
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retval = libscrypt_check(mcf, "pleasefailme");
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retval < 0 error
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retval = 0 password incorrect
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retval > 0 pass
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mcf should be defined as at least SCRYPT_MCF_LEN in size.
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Note that libscrypt_check needs to modify the mcf string and will not return it
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to the original state. Pass it a copy if you need to keep the original mcf.
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A number of internal functions are exposed, and users wishing to create more complex use cases should consult the header file, which is aimed at documenting the API fully.
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The test reference is also aimed at providing a well documented use case.
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Building
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--------
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make
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make check
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Check the Makefile for advice on linking against your application.
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OSX
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-----
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Please compile and install with:
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make LDFLAGS= CFLAGS_EXTRA=
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make install-osx
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BUGS
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----
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SCRYPT_* constants are probably a little high for something like a Raspberry pi. Using '1' as SCRYPT_p is acceptable from a security and performance standpoint if needed.
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Experiments were performed with using memset() to zero out passwords as they were checked. This often caused issues with calling applications where the password based have been passed as a const*. We highly recommend implementing your own zeroing function the moment this library is called.
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There is apparently an issue when used on Samsung (and perhaps Android in general) devices. See [this issue](https://github.com/technion/libscrypt/issues/39) for more information.
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Notes on Code Development
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------------------------
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Code is now declared "stable", the master branch will always be "stable" and development will be done on branches.
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The reference machines are Fedora, CentOS, FreeBSD and Raspbian, and the code is expected to compile and run on all of these before being moved to stable branch.
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Full transparancy on the regular application of thorough testing can be found by reviewing recent test harness results here:
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http://www.lolware.net/libscrypttesting.txt
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Please, no more pull requests for Windows compatibility. If it's important to you - fork the project. I have no intention of pulling an OpenSSL and becoming a maze of ifdefs for platforms I don't even have a build environment for.
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I utilise Facebook's "infer" static analyser, in addition to clang's analyzer. Command to run is:
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infer -- make
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Contact
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-------
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I can be contacted at: technion@lolware.net
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If required, my GPG key can be found at: https://lolware.net/technion-GPG-KEY
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Future releases will have the Git tag signed.
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Changenotes
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-----------
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v1.1a: Single Makefile line change. I wouldn't ordinarily tag this as a new "release", but the purpose here is to assist with packaging in distributions.
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v1.12: The static library is built, but no longer installed by default. You can install it with "make install-static". This is because static libraries are not typically bundled in packages.
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v1.13: Minor packaging related update
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v1.15: Replaced the b64 libraries with more portable one from ISC. Now tested and verified on a wider variety of architectures. Note, libscrypt_b64_encrypt was originally an exported function. This is no longer the case as it is considered an internal function only.
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v1.18: God damnit Apple
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v1.19: Code safety cleanups. Now running Coverity.
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v1.20: Bigfixes involving large N values, return values on error
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<a href="https://scan.coverity.com/projects/2173">
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<img alt="Coverity Scan Build Status"
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src="https://scan.coverity.com/projects/2173/badge.svg"/>
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</a>
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