#!/usr/bin/env python3
"""CASAN H4 — Suspicious base64/hex decoder (Track A, V4 encoding smuggling).

Reads text on stdin. Finds embedded base64 and hex blobs, decodes them, and
prints the decoded plaintext (one blob per line) on stdout so the caller can
re-run its injection/secret pattern scan on the *decoded* content.

Safety / no-false-positive design:
  * Only blobs >= MIN_LEN characters are considered (short words are ignored).
  * A decoded blob is emitted ONLY if it is mostly printable text. Random
    base64-looking words (e.g. "objectives", DER key bytes) decode to
    non-printable garbage and are dropped, so they can never trigger a match.
  * Output is advisory: the caller decides a decoded blob is malicious only if
    the decoded text itself matches a block/secret pattern.

Deterministic: same input always yields the same output.
"""
import base64
import binascii
import re
import sys

MIN_LEN = 16
PRINTABLE_RATIO = 0.8

B64_RE = re.compile(r"[A-Za-z0-9+/]{%d,}={0,2}" % MIN_LEN)
HEX_RE = re.compile(r"\b[0-9a-fA-F]{%d,}\b" % MIN_LEN)


def _mostly_printable(text: str) -> bool:
    if not text:
        return False
    ok = sum(1 for c in text if c.isprintable() or c.isspace())
    return ok >= PRINTABLE_RATIO * len(text)


def decode_blobs(data: str):
    out = []
    for m in B64_RE.findall(data):
        pad = m + "=" * ((4 - len(m) % 4) % 4)
        try:
            dec = base64.b64decode(pad, validate=True)
        except (binascii.Error, ValueError):
            continue
        txt = dec.decode("utf-8", "ignore")
        if _mostly_printable(txt):
            out.append(txt)
    for m in HEX_RE.findall(data):
        if len(m) % 2 != 0:
            continue
        try:
            dec = bytes.fromhex(m)
        except ValueError:
            continue
        txt = dec.decode("utf-8", "ignore")
        if _mostly_printable(txt):
            out.append(txt)
    return out


if __name__ == "__main__":
    blobs = decode_blobs(sys.stdin.read())
    if blobs:
        sys.stdout.write("\n".join(blobs))