gdanezis / petlib

A python library that implements a number of Privacy Enhancing Technolgies

petlib

A python library that implements a number of Privacy Enhancing Technologies (PETs).

• The full petlib documentation: http://petlib.readthedocs.org/en/latest/
• Package petlib on pypi: https://pypi.python.org/pypi/petlib/
• Git repository: https://github.com/gdanezis/petlib
• Travis CI report: https://travis-ci.org/gdanezis/petlib

Pre-requisites

On Ubuntu / debian use apt-get to install package libssl-dev. Ensure you also install libffi-dev and python-dev:

sudo apt-get install python-dev
sudo apt-get install libssl-dev
sudo apt-get install libffi-dev

On MacOS, install OpenSSL 1.1.x using homebrew:

brew install [email protected]

On Windows, install 32 bit or 64 bit OpenSSL binary edition matching your Python installation. Ensure libeay32.dll is on the system PATH (https://www.openssl.org/related/binaries.html). Configure the path variables of Microsoft VS compilers for 32 bit or 64 bit architectures, by executing the command vcvars32.bat or vcvarsx86_amd64.bat.

Quick install

If you have pip installed the following command should install petlib:

pip install petlib

Test your installation:

python -c "import petlib; petlib.run_tests()"

Build & Test

You may use setuptools and tox to build and test the library:

python setup.py build_ext

To run all tests simply do:

tox

petlib's Issues

Better doc formatting

See gist https://gist.github.com/Sidnioulz/c1bed98c196681e6095a

Invalid comparisons result in recursive exceptions

If you compare Bn to anything that is not a Bn...

Bn(42) == "something"

...petlib falls into a recursive death:

Output:
AttributeError                            Traceback (most recent call last)
~/Workspace/zkc/venv/lib/python3.6/site-packages/petlib/bn.py in __inner_cmp__(self, other)
    283         try:
--> 284             sig = int(_C.BN_cmp(self.bn, other.bn))
    285             return sig

AttributeError: 'NotImplementedType' object has no attribute 'bn'

During handling of the above exception, another exception occurred:

RecursionError                            Traceback (most recent call last)
<ipython-input-2-ea31e540b152> in <module>()
----> 1 Bn(42) == "statast"

~/Workspace/zkc/venv/lib/python3.6/site-packages/petlib/bn.py in __eq__(self, other)
    294
    295     def __eq__(self, other):
--> 296         return self.__inner_cmp__(other) == 0
    297
    298     def __ne__(self, other):

~/Workspace/zkc/venv/lib/python3.6/site-packages/petlib/bn.py in __inner_cmp__(self, other)
    285             return sig
    286         except AttributeError:
--> 287             return self.__inner_cmp__(Bn.from_num(other))
    288
    289     def __lt__(self, other):

... last 1 frames repeated, from the frame below ...

~/Workspace/zkc/venv/lib/python3.6/site-packages/petlib/bn.py in __inner_cmp__(self, other)
    285             return sig
    286         except AttributeError:
--> 287             return self.__inner_cmp__(Bn.from_num(other))
    288
    289     def __lt__(self, other):

RecursionError: maximum recursion depth exceeded while calling a Python object

ubuntu18.04 LTS pip install petlib

ubuntu18.04 LTS pip install petlib do not work, no mistake, just stop all the time

KeyError: 'OPENSSL_CONF

When I installing petlib on win,there is an error:
ERROR: Command errored out with exit status 1: command: 'd:\python3\python3.exe' -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'C:\\Users\\12711\\AppData\\Local\\Temp\\pip-install-_5s5ibkx\\petlib\\setup.py'"'"'; __file__='"'"'C:\\Users\\12711\\AppData\\Local\\Temp\\pip-install-_5s5ibkx\\petlib\\setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' egg_info --egg-base 'C:\Users\12711\AppData\Local\Temp\pip-install-_5s5ibkx\petlib\pip-egg-info' cwd: C:\Users\12711\AppData\Local\Temp\pip-install-_5s5ibkx\petlib\ Complete output (27 lines): Traceback (most recent call last): File "<string>", line 1, in <module> File "C:\Users\12711\AppData\Local\Temp\pip-install-_5s5ibkx\petlib\setup.py", line 40, in <module> zip_safe=False, File "d:\python3\lib\site-packages\setuptools\__init__.py", line 145, in setup return distutils.core.setup(**attrs) File "d:\python3\lib\distutils\core.py", line 108, in setup _setup_distribution = dist = klass(attrs) File "d:\python3\lib\site-packages\setuptools\dist.py", line 448, in __init__ k: v for k, v in attrs.items() File "d:\python3\lib\distutils\dist.py", line 281, in __init__ self.finalize_options() File "d:\python3\lib\site-packages\setuptools\dist.py", line 740, in finalize_options ep.load()(self) File "d:\python3\lib\site-packages\setuptools\dist.py", line 747, in _finalize_setup_keywords ep.load()(self, ep.name, value) File "d:\python3\lib\site-packages\cffi\setuptools_ext.py", line 211, in cffi_modules add_cffi_module(dist, cffi_module) File "d:\python3\lib\site-packages\cffi\setuptools_ext.py", line 49, in add_cffi_module execfile(build_file_name, mod_vars) File "d:\python3\lib\site-packages\cffi\setuptools_ext.py", line 25, in execfile exec(code, glob, glob) File "petlib/compile.py", line 34, in <module> openssl_conf = os.environ["OPENSSL_CONF"] File "d:\python3\lib\os.py", line 669, in __getitem__ raise KeyError(key) from None KeyError: 'OPENSSL_CONF' ---------------------------------------- ERROR: Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.

Clean-up the install, build and test docs.

Returns int, instead of bool?

I'm stubbing petlib at the moment and noticed that https://github.com/gdanezis/petlib/blob/master/petlib/bn.py#L763 doesn't return a bool. Is that intentional?

errors uring "pip install petlib"

Very long error output when I follow the instruction of readme to install petlib（Ubuntu 14.04.6 LTS， python 2.7.6) The end of the error msg is :

error: command 'i686-linux-gnu-gcc' failed with exit status 1
----------------------------------------

ERROR: Command "/usr/bin/python -u -c 'import setuptools, tokenize;file='"'"'/tmp/pip-install-H3NHgN/petlib/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(file);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, file, '"'"'exec'"'"'))' install --record /tmp/pip-record-4D7FJ1/install-record.txt --single-version-externally-managed --compile" failed with error code 1 in /tmp/pip-install-H3NHgN/petlib/

Any one can help figure it out?

Bn's constructor does not check its parameter is a number

Which results in Bn.__init__ serving arbitrary objects to abs(). According to the doc, the following types are acceptable:

"The argument may be a plain or long integer or a floating point number. If the argument is a complex number, its magnitude is returned."

You could either make Bn be an int or float, make its constructor explicitely reject wrong input types, or build a copy constructor (is that even a thing in Python!?).

petlib fails to compile with openssl 1.1

 Running setup.py develop for petlib
    Complete output from command /home/kali/Virtualenvs/petlib/bin/python2 -c "import setuptools, tokenize;__file__='/home/kali/leap/petlib/setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" develop --no-deps:
    running develop
    running egg_info
    writing requirements to petlib.egg-info/requires.txt
    writing petlib.egg-info/PKG-INFO
    writing top-level names to petlib.egg-info/top_level.txt
    writing dependency_links to petlib.egg-info/dependency_links.txt
    reading manifest file 'petlib.egg-info/SOURCES.txt'
    writing manifest file 'petlib.egg-info/SOURCES.txt'
    running build_ext
    generating cffi module 'build/temp.linux-x86_64-2.7/petlib._petlib.c'
    creating build
    creating build/temp.linux-x86_64-2.7
    building 'petlib._petlib' extension
    creating build/temp.linux-x86_64-2.7/build
    creating build/temp.linux-x86_64-2.7/build/temp.linux-x86_64-2.7
    x86_64-linux-gnu-gcc -pthread -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fno-strict-aliasing -Wdate-time -D_FORTIFY_SOURCE=2 -g -fdebug-prefix-map=/build/python2.7-HVkOs2/python2.7-2.7.13=. -fstack-protector-strong -Wformat -Werror=format-security -fPIC -I/usr/include/python2.7 -c build/temp.linux-x86_64-2.7/petlib._petlib.c -o build/temp.linux-x86_64-2.7/build/temp.linux-x86_64-2.7/petlib._petlib.o -Wno-deprecated-declarations
    build/temp.linux-x86_64-2.7/petlib._petlib.c: In function ‘hmac_ctx_size’:
    build/temp.linux-x86_64-2.7/petlib._petlib.c:462:19: error: invalid application of ‘sizeof’ to incomplete type ‘HMAC_CTX {aka struct hmac_ctx_st}’
         return sizeof(HMAC_CTX);
                       ^~~~~~~~
    build/temp.linux-x86_64-2.7/petlib._petlib.c: At top level:
    build/temp.linux-x86_64-2.7/petlib._petlib.c:466:41: error: macro "ERR_load_crypto_strings" passed 1 arguments, but takes just 0
     extern void ERR_load_crypto_strings(void);
                                             ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c:468:34: error: macro "ERR_free_strings" passed 1 arguments, but takes just 0
     extern void ERR_free_strings(void);
                                      ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c:535:5: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
     int setup_ssl_threads() {
         ^~~~~~~~~~~~~~~~~
    build/temp.linux-x86_64-2.7/petlib._petlib.c:1037:56: error: field ‘y’ has incomplete type
     struct _cffi_align_typedef_HMAC_CTX { char x; HMAC_CTX y; };
                                                            ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c: In function ‘_cffi_d_BN_init’:
    build/temp.linux-x86_64-2.7/petlib._petlib.c:1882:3: warning: implicit declaration of function ‘BN_init’ [-Wimplicit-function-declaration]
       BN_init(x0);
       ^~~~~~~
    build/temp.linux-x86_64-2.7/petlib._petlib.c: In function ‘_cffi_d_CRYPTO_lock’:
    build/temp.linux-x86_64-2.7/petlib._petlib.c:3013:3: warning: implicit declaration of function ‘CRYPTO_lock’ [-Wimplicit-function-declaration]
       CRYPTO_lock(x0, x1, x2, x3);
       ^~~~~~~~~~~
    build/temp.linux-x86_64-2.7/petlib._petlib.c: In function ‘_cffi_d_HMAC_CTX_cleanup’:
    build/temp.linux-x86_64-2.7/petlib._petlib.c:7195:3: warning: implicit declaration of function ‘HMAC_CTX_cleanup’ [-Wimplicit-function-declaration]
       HMAC_CTX_cleanup(x0);
       ^~~~~~~~~~~~~~~~
    build/temp.linux-x86_64-2.7/petlib._petlib.c: In function ‘_cffi_d_HMAC_CTX_init’:
    build/temp.linux-x86_64-2.7/petlib._petlib.c:7231:3: warning: implicit declaration of function ‘HMAC_CTX_init’ [-Wimplicit-function-declaration]
       HMAC_CTX_init(x0);
       ^~~~~~~~~~~~~
    build/temp.linux-x86_64-2.7/petlib._petlib.c: In function ‘_cffi_checkfld__ECDSA_SIG’:
    build/temp.linux-x86_64-2.7/petlib._petlib.c:7897:23: error: dereferencing pointer to incomplete type ‘ECDSA_SIG {aka struct ECDSA_SIG_st}’
       { BIGNUM * *tmp = &p->r; (void)tmp; }
                           ^~
    build/temp.linux-x86_64-2.7/petlib._petlib.c: At top level:
    build/temp.linux-x86_64-2.7/petlib._petlib.c:7900:51: error: field ‘y’ has incomplete type
     struct _cffi_align__ECDSA_SIG { char x; ECDSA_SIG y; };
                                                       ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c: In function ‘_cffi_checkfld__EVP_CIPHER_CTX’:
    build/temp.linux-x86_64-2.7/petlib._petlib.c:7907:33: error: dereferencing pointer to incomplete type ‘EVP_CIPHER_CTX {aka struct evp_cipher_ctx_st}’
       { EVP_CIPHER const * *tmp = &p->cipher; (void)tmp; }
                                     ^~
    build/temp.linux-x86_64-2.7/petlib._petlib.c: At top level:
    build/temp.linux-x86_64-2.7/petlib._petlib.c:7916:61: error: field ‘y’ has incomplete type
     struct _cffi_align__EVP_CIPHER_CTX { char x; EVP_CIPHER_CTX y; };
                                                                 ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c: In function ‘_cffi_checkfld__EVP_CIPHER’:
    build/temp.linux-x86_64-2.7/petlib._petlib.c:7923:12: error: dereferencing pointer to incomplete type ‘EVP_CIPHER {aka struct evp_cipher_st}’
       (void)((p->nid) | 0);  /* check that 'EVP_CIPHER.nid' is an integer */
                ^~
    build/temp.linux-x86_64-2.7/petlib._petlib.c: At top level:
    build/temp.linux-x86_64-2.7/petlib._petlib.c:7929:53: error: field ‘y’ has incomplete type
     struct _cffi_align__EVP_CIPHER { char x; EVP_CIPHER y; };
                                                         ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8090:3: error: invalid use of incomplete typedef ‘ECDSA_SIG {aka struct ECDSA_SIG_st}’
       { "r", offsetof(ECDSA_SIG, r),
       ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8093:3: error: invalid use of incomplete typedef ‘ECDSA_SIG {aka struct ECDSA_SIG_st}’
       { "s", offsetof(ECDSA_SIG, s),
       ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8096:3: error: invalid use of incomplete typedef ‘EVP_CIPHER_CTX {aka struct evp_cipher_ctx_st}’
       { "cipher", offsetof(EVP_CIPHER_CTX, cipher),
       ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8099:3: error: invalid use of incomplete typedef ‘EVP_CIPHER_CTX {aka struct evp_cipher_ctx_st}’
       { "encrypt", offsetof(EVP_CIPHER_CTX, encrypt),
       ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8102:3: error: invalid use of incomplete typedef ‘EVP_CIPHER_CTX {aka struct evp_cipher_ctx_st}’
       { "buf_len", offsetof(EVP_CIPHER_CTX, buf_len),
       ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8105:3: error: invalid use of incomplete typedef ‘EVP_CIPHER_CTX {aka struct evp_cipher_ctx_st}’
       { "num", offsetof(EVP_CIPHER_CTX, num),
       ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8108:3: error: invalid use of incomplete typedef ‘EVP_CIPHER_CTX {aka struct evp_cipher_ctx_st}’
       { "key_len", offsetof(EVP_CIPHER_CTX, key_len),
       ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8111:3: error: invalid use of incomplete typedef ‘EVP_CIPHER_CTX {aka struct evp_cipher_ctx_st}’
       { "flags", offsetof(EVP_CIPHER_CTX, flags),
       ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8114:3: error: invalid use of incomplete typedef ‘EVP_CIPHER_CTX {aka struct evp_cipher_ctx_st}’
       { "final_used", offsetof(EVP_CIPHER_CTX, final_used),
       ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8117:3: error: invalid use of incomplete typedef ‘EVP_CIPHER_CTX {aka struct evp_cipher_ctx_st}’
       { "block_mask", offsetof(EVP_CIPHER_CTX, block_mask),
       ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8120:3: error: invalid use of incomplete typedef ‘EVP_CIPHER {aka struct evp_cipher_st}’
       { "nid", offsetof(EVP_CIPHER, nid),
       ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8123:3: error: invalid use of incomplete typedef ‘EVP_CIPHER {aka struct evp_cipher_st}’
       { "block_size", offsetof(EVP_CIPHER, block_size),
       ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8126:3: error: invalid use of incomplete typedef ‘EVP_CIPHER {aka struct evp_cipher_st}’
       { "key_len", offsetof(EVP_CIPHER, key_len),
       ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8129:3: error: invalid use of incomplete typedef ‘EVP_CIPHER {aka struct evp_cipher_st}’
       { "iv_len", offsetof(EVP_CIPHER, iv_len),
       ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8132:3: error: invalid use of incomplete typedef ‘EVP_CIPHER {aka struct evp_cipher_st}’
       { "flags", offsetof(EVP_CIPHER, flags),
       ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8157:12: error: invalid application of ‘sizeof’ to incomplete type ‘HMAC_CTX {aka struct hmac_ctx_st}’
         sizeof(HMAC_CTX), offsetof(struct _cffi_align_typedef_HMAC_CTX, y), 2, 0 },
                ^~~~~~~~
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8157:5: error: initializer element is not constant
         sizeof(HMAC_CTX), offsetof(struct _cffi_align_typedef_HMAC_CTX, y), 2, 0 },
         ^~~~~~
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8157:5: note: (near initialization for ‘_cffi_struct_unions[9].size’)
    In file included from /usr/include/sched.h:28:0,
                     from /usr/include/pthread.h:23,
                     from /usr/include/openssl/crypto.h:406,
                     from /usr/include/openssl/bio.h:20,
                     from /usr/include/openssl/err.h:21,
                     from build/temp.linux-x86_64-2.7/petlib._petlib.c:435:
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8157:23: error: initializer element is not constant
         sizeof(HMAC_CTX), offsetof(struct _cffi_align_typedef_HMAC_CTX, y), 2, 0 },
                           ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8157:23: note: (near initialization for ‘_cffi_struct_unions[9].alignment’)
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8159:12: error: invalid application of ‘sizeof’ to incomplete type ‘ECDSA_SIG {aka struct ECDSA_SIG_st}’
         sizeof(ECDSA_SIG), offsetof(struct _cffi_align__ECDSA_SIG, y), 2, 2 },
                ^~~~~~~~~
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8159:5: error: initializer element is not constant
         sizeof(ECDSA_SIG), offsetof(struct _cffi_align__ECDSA_SIG, y), 2, 2 },
         ^~~~~~
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8159:5: note: (near initialization for ‘_cffi_struct_unions[10].size’)
    In file included from /usr/include/sched.h:28:0,
                     from /usr/include/pthread.h:23,
                     from /usr/include/openssl/crypto.h:406,
                     from /usr/include/openssl/bio.h:20,
                     from /usr/include/openssl/err.h:21,
                     from build/temp.linux-x86_64-2.7/petlib._petlib.c:435:
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8159:24: error: initializer element is not constant
         sizeof(ECDSA_SIG), offsetof(struct _cffi_align__ECDSA_SIG, y), 2, 2 },
                            ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8159:24: note: (near initialization for ‘_cffi_struct_unions[10].alignment’)
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8161:12: error: invalid application of ‘sizeof’ to incomplete type ‘EVP_CIPHER_CTX {aka struct evp_cipher_ctx_st}’
         sizeof(EVP_CIPHER_CTX), offsetof(struct _cffi_align__EVP_CIPHER_CTX, y), 4, 8 },
                ^~~~~~~~~~~~~~
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8161:5: error: initializer element is not constant
         sizeof(EVP_CIPHER_CTX), offsetof(struct _cffi_align__EVP_CIPHER_CTX, y), 4, 8 },
         ^~~~~~
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8161:5: note: (near initialization for ‘_cffi_struct_unions[11].size’)
    In file included from /usr/include/sched.h:28:0,
                     from /usr/include/pthread.h:23,
                     from /usr/include/openssl/crypto.h:406,
                     from /usr/include/openssl/bio.h:20,
                     from /usr/include/openssl/err.h:21,
                     from build/temp.linux-x86_64-2.7/petlib._petlib.c:435:
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8161:29: error: initializer element is not constant
         sizeof(EVP_CIPHER_CTX), offsetof(struct _cffi_align__EVP_CIPHER_CTX, y), 4, 8 },
                                 ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8161:29: note: (near initialization for ‘_cffi_struct_unions[11].alignment’)
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8163:12: error: invalid application of ‘sizeof’ to incomplete type ‘EVP_CIPHER {aka struct evp_cipher_st}’
         sizeof(EVP_CIPHER), offsetof(struct _cffi_align__EVP_CIPHER, y), 12, 5 },
                ^~~~~~~~~~
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8163:5: error: initializer element is not constant
         sizeof(EVP_CIPHER), offsetof(struct _cffi_align__EVP_CIPHER, y), 12, 5 },
         ^~~~~~
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8163:5: note: (near initialization for ‘_cffi_struct_unions[12].size’)
    In file included from /usr/include/sched.h:28:0,
                     from /usr/include/pthread.h:23,
                     from /usr/include/openssl/crypto.h:406,
                     from /usr/include/openssl/bio.h:20,
                     from /usr/include/openssl/err.h:21,
                     from build/temp.linux-x86_64-2.7/petlib._petlib.c:435:
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8163:25: error: initializer element is not constant
         sizeof(EVP_CIPHER), offsetof(struct _cffi_align__EVP_CIPHER, y), 12, 5 },
                             ^
    build/temp.linux-x86_64-2.7/petlib._petlib.c:8163:25: note: (near initialization for ‘_cffi_struct_unions[12].alignment’)
    build/temp.linux-x86_64-2.7/petlib._petlib.c: In function ‘hmac_ctx_size’:
    build/temp.linux-x86_64-2.7/petlib._petlib.c:463:1: warning: control reaches end of non-void function [-Wreturn-type]
     }
     ^
    At top level:
    build/temp.linux-x86_64-2.7/petlib._petlib.c:507:13: warning: ‘_ssl_thread_locking_function’ defined but not used [-Wunused-function]
     static void _ssl_thread_locking_function(int mode, int n, const char *file,
                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
    error: command 'x86_64-linux-gnu-gcc' failed with exit status 1
    
    ----------------------------------------

Petlib cannot be installed systemwide, else it tries to create cache files in /usr/lib/python3.4/site-packages/petlib/...

Petlib crashes when installed systewide, because it tries to create cache files in /usr/lib/python3.4/site-packages/petlib/... Please ensure that petlib identifies a read-write area to create cache files into, rather than in its install location which should be treated as read-only.

Suggested locations:
$XDG_CACHE_HOME/petlib
$HOME/.cache/petlib
/tmp/petlib

Attribute Error when trying to import petlib.pack

When attempting to import petlib.pack I get the following error:

Support not loading the library to build docs without compiling.
Traceback (most recent call last):
File "", line 1, in
File "/usr/local/lib/python2.7/dist-packages/petlib-0.0.43-py2.7-linux-armv7l.egg/petlib/pack.py", line 32, in
from .ec import EcGroup, EcPt
File "/usr/local/lib/python2.7/dist-packages/petlib-0.0.43-py2.7-linux-armv7l.egg/petlib/ec.py", line 2, in
from .bn import Bn, force_Bn, get_ctx
File "/usr/local/lib/python2.7/dist-packages/petlib-0.0.43-py2.7-linux-armv7l.egg/petlib/bn.py", line 794, in
zero = Bn(0)
File "/usr/local/lib/python2.7/dist-packages/petlib-0.0.43-py2.7-linux-armv7l.egg/petlib/bn.py", line 222, in init
self.bn = _C.BN_new()
AttributeError: 'NoneType' object has no attribute 'BN_new'

I tried following the error put was left puzzled when it came down to /usr/local/lib/python2.7/dist-packages/petlib-0.0.43-py2.7-linux-armv7l.egg/petlib/

Can provide debug information as needed.

Return type of `get_tag` should be `bytes`

Example (quick_gcm_enc uses get_tag and in here tag is the return value of get_tag):

>>> from os import urandom
>>> from petlib.cipher import Cipher
>>> message = "hello"
>>> plaintext = message.encode("utf8")
>>> aes = Cipher("aes-128-gcm")
>>> iv = urandom(16)
>>> key = urandom(16)
>>> ciphertext, tag = aes.quick_gcm_enc(key, iv, plaintext)
>>> type(tag)
<type '_cffi_backend.CDataOwn'>
>>> tag is str
False
>>> tag is bytes
False

"pip install petlib" error on Windows

When runnung
pip install petlib
under Windows, installation fails with the following error
OSError: ctypes.util.find_library() did not manage to locate a library called 'crypto'
Error occurs with all available 64bit OpenSSL versions 1.1.1d, 1.10L and 1.0.2t.

Linux installation works fine though!

AttributeError: 'NoneType' object has no attribute 'EC_GROUP_new_by_curve_name'

He,

just installed petlib and now trying to create a new EcGroup instance the following exception occurs.
Any recommendations to make it work?

Python 2.7.10 (default, Oct 23 2015, 19:19:21) 
[GCC 4.2.1 Compatible Apple LLVM 7.0.0 (clang-700.0.59.5)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import petlib
>>> from petlib.ec import EcGroup
Support not loading the library to build docs without compiling.
>>> G = EcGroup()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/sebastian/Developer/.envs/pet/lib/python2.7/site-packages/petlib/ec.py", line 62, in __init__
    self.ecg = _C.EC_GROUP_new_by_curve_name(nid)
AttributeError: 'NoneType' object has no attribute 'EC_GROUP_new_by_curve_name'

Little typo in the doc

I think there is little typo in the documentation of the function do_ecdsa_verify in petlib.ecdsa: it is a copy-paste of do_ecdsa_sign (see attached screenshot)