Python Snowflake Private Key: Fix the 'from_buffer' TypeError with Bytes Literals and Full PEM

Learn why a Unicode string Snowflake private key fails in Python with TypeError: from_buffer, and fix it by supplying bytes and a full PEM BEGIN/END headers.

Embedding a Snowflake private key directly in Python code looks straightforward until Python reminds you that bytes and text are not the same thing. A common pitfall is replacing file-backed binary reads with a plain Unicode string, which immediately triggers a TypeError. Below is a concise walk-through of why it happens and how to fix it correctly.

Problem statement

The working approach reads a private key from a file and passes the raw bytes to the cryptography loader. That succeeds because the loader expects a bytes-like input.

with open("rsa_key_1.p8", "rb") as fh:
    priv_obj = serialization.load_pem_private_key(
        fh.read(),
        password=None,
        backend=default_backend()
    )

Swapping the file read for a literal string looks tempting, but fails with TypeError: from_buffer() cannot return the address of a unicode object.

with open("rsa_key_1.p8", "rb") as fh:
    priv_obj = serialization.load_pem_private_key(
        'MIIE...rZ+x8ZcfhhLj+lyWLhDfA8feg/vYlV+gLDKsZfQLN9JDRMGgffN3EE7vM9WBO/msB8fpo5g==',
        password=None,
        backend=default_backend()
    )

What actually goes wrong

The loader expects a bytes object. Reading from a file opened with mode rb returns bytes, which is why the first snippet works. A quoted literal without a b prefix is a Unicode str, so when it’s handed to the loader, Python raises a TypeError. There is a second issue: the loader expects a proper PEM payload, including the BEGIN/END lines, not just the Base64 body.

If you are unsure what the function receives from disk, printing the file content makes it obvious that you get a bytes object and that it includes the header and footer lines.

The fix

Provide the full PEM block as bytes. That means adding the correct BEGIN/END delimiters and making the literal a bytes literal. This matches what the file-based approach feeds into the loader.

priv_obj = serialization.load_pem_private_key(
    b'''-----BEGIN ENCRYPTED PRIVATE KEY-----
MIIE...rZ+x8ZcfhhLj+lyWLhDfA8feg/vYlV+gLDKsZfQLN9JDRMGgffN3EE7vM9WBO/msB8fpo5g==
-----END ENCRYPTED PRIVATE KEY-----''',
    password=None,
    backend=default_backend()
)

This mirrors the file content byte-for-byte: the data type is bytes and the format is full PEM, which is exactly what the loader consumes.

Why you should care

Understanding the difference between str and bytes in Python avoids brittle authentication code and frustrating type errors. It also forces you to respect the input format that crypto tooling expects, including the PEM header and footer. On the security side, if any part of a private key was shared publicly, you should generate a new key rather than trying to salvage the exposed one.

Takeaways

If you move from reading a private key file to embedding it in code, keep two rules in mind. First, pass bytes, not a Unicode string; a b prefix on the literal is mandatory. Second, include the complete PEM block, with BEGIN/END lines and the Base64 content. Following these rules brings the in-code approach in line with the file-backed version and eliminates the TypeError.