Bind to pgcrypto from python

Question

I'd like to call some pgcrypto functions from python. Namely px_crypt. I can't seem to figure out the right object files to link it seems.

Here's my code:

#include <Python.h>

#include "postgres.h"

#include "pgcrypto/px-crypt.h"


static PyObject*
pgcrypt(PyObject* self, PyObject* args)
{
    const char* key;
    const char* setting;

    if (!PyArg_ParseTuple(args, "ss", &key, &setting))
        return NULL;

    return Py_BuildValue("s", px_crypt(key, setting, "", 0));
}

static PyMethodDef PgCryptMethods[] =
{
     {"pgcrypt", pgcrypt, METH_VARARGS, "Call pgcrypto's crypt"},
     {NULL, NULL, 0, NULL}
};

PyMODINIT_FUNC
initpypgcrypto(void)
{
     (void) Py_InitModule("pypgcrypto", PgCryptMethods);
}

and gcc commands and output:

x86_64-linux-gnu-gcc -pthread -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fno-strict-aliasing -D_FORTIFY_SOURCE=2 -g -fstack-protector-strong -Wformat -Werror=format-security -fPIC -I/home/ionut/github/postgres/contrib/ -I/usr/include/postgresql/9.4/server/ -I/usr/include/python2.7 -c pypgcrypto.c -o build/temp.linux-x86_64-2.7/pypgcrypto.o
x86_64-linux-gnu-gcc -pthread -shared -Wl,-O1 -Wl,-Bsymbolic-functions -Wl,-z,relro -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -D_FORTIFY_SOURCE=2 -g -fstack-protector-strong -Wformat -Werror=format-security -Wl,-z,relro -D_FORTIFY_SOURCE=2 -g -fstack-protector-strong -Wformat -Werror=format-security build/temp.linux-x86_64-2.7/pypgcrypto.o /usr/lib/postgresql/9.4/lib/pgcrypto.so -lpgport -lpq -o build/lib.linux-x86_64-2.7/pypgcrypto.so

Error is:

python -c "import pypgcrypto; print pypgcrypto.pgcrypt('foo', 'bar')"

Traceback (most recent call last):
  File "<string>", line 1, in <module>
ImportError: /usr/lib/postgresql/9.4/lib/pgcrypto.so: undefined symbol: InterruptPending

Answer 1

From one of your comments I got this...

I want to replicate pgcrypto's behavior in order to be able to generate password hashes that match the ones already in my database.

You can use python to do this already. I don't know what algorithm you're using, nor should I, here are two different methods using python to generate the exact same hash as Postgresql's pgcrypto

Crypt

=# select crypt('12345678', gen_salt('xdes')), md5('test');
        crypt         |               md5                
----------------------+----------------------------------
 _J9..b8FIoskMdlHvKjk | 098f6bcd4621d373cade4e832627b4f6

Here's the Python to check the password...

#!/usr/bin/env python
import crypt
from hmac import compare_digest as compare_hash

def login():
    hash_ = '_J9..OtC82a6snTAAqWg'
    print(compare_hash(crypt.crypt('123456789', hash_), hash_))
    #return True

if __name__ == '__main__':
  login()

MD5

For md5 you can use passlib's md5_crypt as follows...

=# select crypt('12345678', gen_salt('md5')), md5('test');
               crypt                |               md5                
------------------------------------+----------------------------------
 $1$UUVXoPbO$JMA7yhrKvaZcKqoFoi9jl. | 098f6bcd4621d373cade4e832627b4f6

Python would look something like...

#!/usr/bin/env python
from passlib.hash import md5_crypt

def login():
    hash_ = '$1$kOFl2EuX$QhhnPMAdx2/j2Tsk15nfQ0'
    print(md5_crypt.verify("12345678", hash_))

if __name__ == '__main__':
  login()

Blowfish

select crypt('12345678', gen_salt('bf')), md5('test');
                            crypt                             |               md5                
--------------------------------------------------------------+----------------------------------
 $2a$06$HLZUXMgqFhi/sl1D697il.lN8OMQFBWR2VBuZ5nTCd59jvGLU9pQ2 | 098f6bcd4621d373cade4e832627b4f6

Python code...

#!/usr/bin/env python
from passlib.hash import md5_crypt
from passlib.hash import bcrypt

def blowfish():
    hash_ = '$2a$06$HLZUXMgqFhi/sl1D697il.lN8OMQFBWR2VBuZ5nTCd59jvGLU9pQ2'
    print(bcrypt.verify("12345678", hash_))

if __name__ == '__main__':
  blowfish()