libcrypto not found using oscrypto library in Alpine-based Docker image - python-3.x

Question

I am getting exactly the same error as mentioned in ->
The library libcrypto could not be found
I understood the issue, however, I could not figure out the resolution. Do I need to update my lambda configuration or do I need to upgrade my Python libraries?
PFB my requriements.txt files
cryptography==36.0.2
botocore==1.20.0
azure-storage-blob==2.1.0
azure-storage-common==2.1.0
boto3==1.17.0
asn1crypto==1.5.1
certifi==2022.9.14
cffi==1.15.1
charset-normalizer==2.1.1
filelock==3.8.0
idna==3.4
oscrypto==1.3.0
pycparser==2.21
pycryptodomex==3.15.0
PyJWT==2.5.0
pyOpenSSL==22.0.0
pytz==2022.2.1
requests==2.28.1
typing_extensions==4.3.0
urllib3==1.26.12
My docker file -
FROM python:3.9-alpine3.16
COPY requirements.txt requirements.txt
RUN apk --update --no-cache add --virtual build-dependencies gcc python3-dev musl-dev libc-dev linux-headers libxslt-dev libxml2-dev py-pip ca-certificates wget libffi-dev openssl-dev python3-dev expat==2.4.9-r0 py-pip build-base zlib zlib-dev libressl libressl-dev \
&& apk add python3 make g++ \
&& pip install --upgrade pip \
&& pip install --upgrade pip setuptools \
&& pip install -r requirements.txt \
&& apk del build-dependencies
RUN pip install snowflake-connector-python==2.8.0 --no-use-pep517
RUN python -c 'from oscrypto import asymmetric'
Attempting docker build with the Dockerfile above results in a failure with:
Step 4/4 : RUN python -c 'from oscrypto import asymmetric'
---> Running in dc8f8b8920ac
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "/usr/local/lib/python3.9/site-packages/oscrypto/asymmetric.py", line 19, in <module>
from ._asymmetric import _unwrap_private_key_info
File "/usr/local/lib/python3.9/site-packages/oscrypto/_asymmetric.py", line 27, in <module>
from .kdf import pbkdf1, pbkdf2, pkcs12_kdf
File "/usr/local/lib/python3.9/site-packages/oscrypto/kdf.py", line 9, in <module>
from .util import rand_bytes
File "/usr/local/lib/python3.9/site-packages/oscrypto/util.py", line 14, in <module>
from ._openssl.util import rand_bytes
File "/usr/local/lib/python3.9/site-packages/oscrypto/_openssl/util.py", line 6, in <module>
from ._libcrypto import libcrypto, libcrypto_version_info, handle_openssl_error
File "/usr/local/lib/python3.9/site-packages/oscrypto/_openssl/_libcrypto.py", line 9, in <module>
from ._libcrypto_cffi import (
File "/usr/local/lib/python3.9/site-packages/oscrypto/_openssl/_libcrypto_cffi.py", line 27, in <module>
raise LibraryNotFoundError('The library libcrypto could not be found')
oscrypto.errors.LibraryNotFoundError: The library libcrypto could not be found
The command '/bin/sh -c python -c 'from oscrypto import asymmetric'' returned a non-zero code: 1

Answer 1

The exception is taking place at https://github.com/wbond/oscrypto/blob/1.3.0/oscrypto/_openssl/_libcrypto_cffi.py
Tracking through oscrypto._ffi, the problem comes down to an issue opening libcrypto with the ctypes library:
>>> import ctypes.util
>>> ctypes.util.find_library('crypto')
>>>
Why? Because /usr/lib has only libcrypto.so.1.1, and not a libcrypto.so symlink pointing to it. Easily fixed by adding an extra line to your Dockerfile:
RUN ln -s libcrypto.so.1.1 /usr/lib/libcrypto.so
...after which Python's ctypes behaves:
>>> from ctypes.util import find_library
>>> find_library('crypto')
'libcrypto.so.1.1'
...and so does oscrypto:
>>> from oscrypto import asymmetric
>>>