pyssh-client/app/key_manager.py

"""Gestion des cles SSH : generation, import, export, registre local."""
from __future__ import annotations

import base64
import hashlib
import shutil
import uuid
from dataclasses import dataclass, field, asdict
from pathlib import Path

import paramiko
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import rsa, ed25519, ec

from app.paths import DATA_DIR  # noqa: E402  (chemins valables aussi en .exe)
from app.storage.json_store import load_json_document, save_json_document
from app.security.key_protection import protect_private_key

KEYS_FILE = DATA_DIR / "keys.json"
DEFAULT_KEY_DIR = DATA_DIR / "keys"
SCHEMA_VERSION = 1


def compute_fingerprint(public_key_line: str) -> str:
    """Empreinte SHA256 canonique (format `SHA256:xxxx...`, comme `ssh-keygen -lf`),
    a partir d'une ligne de cle publique OpenSSH ("type base64 [commentaire]").

    Utilisee pour toute cle, qu'elle soit generee, importee ou relue depuis le
    registre : jamais un simple fragment du base64, qui ne serait pas un vrai
    condense cryptographique de la cle."""
    parts = (public_key_line or "").split()
    if len(parts) < 2:
        return ""
    try:
        raw = base64.b64decode(parts[1])
    except (ValueError, TypeError):
        return ""
    digest = hashlib.sha256(raw).digest()
    return "SHA256:" + base64.b64encode(digest).decode("utf-8").rstrip("=")


KEY_TYPE_ED25519 = "ed25519"
KEY_TYPE_RSA = "rsa"
KEY_TYPE_ECDSA_P256 = "ecdsa-p256"
KEY_TYPE_ECDSA_P384 = "ecdsa-p384"
KEY_TYPE_ECDSA_P521 = "ecdsa-p521"

# Courbes elliptiques NIST utilisees par ECDSA. Ed25519 est aussi une courbe
# elliptique (Curve25519) et reste le choix recommande : plus court, plus rapide,
# et sans les interrogations qui entourent le choix des parametres des courbes NIST.
ECDSA_CURVES = {
    KEY_TYPE_ECDSA_P256: ec.SECP256R1,
    KEY_TYPE_ECDSA_P384: ec.SECP384R1,
    KEY_TYPE_ECDSA_P521: ec.SECP521R1,
}

KEY_TYPE_LABELS = {
    KEY_TYPE_ED25519: "Ed25519 (recommande)",
    KEY_TYPE_ECDSA_P256: "ECDSA — courbe NIST P-256",
    KEY_TYPE_ECDSA_P384: "ECDSA — courbe NIST P-384",
    KEY_TYPE_ECDSA_P521: "ECDSA — courbe NIST P-521",
    KEY_TYPE_RSA: "RSA (compatibilite maximale)",
}

# Resume affiche dans le formulaire de generation, pour choisir en connaissance de cause.
# Les equivalences de robustesse suivent les recommandations du NIST (SP 800-57).
KEY_TYPE_DESCRIPTIONS = {
    KEY_TYPE_ED25519: (
        "Courbe Curve25519, de la famille des courbes d'Edwards.\n"
        "Robustesse equivalente a RSA 3072, pour une cle publique de 68 caracteres seulement.\n"
        "Signature rapide et concue pour resister aux erreurs d'implementation. Ses parametres\n"
        "sont justifies publiquement, contrairement aux courbes NIST.\n"
        "Compatible OpenSSH 6.5 et plus (2014) : tout serveur actuel l'accepte."
    ),
    KEY_TYPE_ECDSA_P256: (
        "Courbe NIST P-256 (aussi appelee secp256r1 ou prime256v1), 256 bits.\n"
        "Robustesse equivalente a RSA 3072, comme Ed25519.\n"
        "Tres repandue et souvent exigee par les politiques de conformite (FIPS).\n"
        "Reserve : le NIST n'a jamais explique publiquement le choix de ses parametres,\n"
        "ce qui lui vaut une mefiance persistante. A retenir surtout si une regle l'impose.\n"
        "Compatible OpenSSH 5.7 et plus (2011)."
    ),
    KEY_TYPE_ECDSA_P384: (
        "Courbe NIST P-384 (secp384r1), 384 bits.\n"
        "Robustesse equivalente a RSA 7680 : un cran au-dessus de P-256.\n"
        "Retenue dans les contextes qui exigent un niveau eleve (par exemple la suite CNSA).\n"
        "Memes reserves que P-256 sur l'origine des parametres."
    ),
    KEY_TYPE_ECDSA_P521: (
        "Courbe NIST P-521 (secp521r1), 521 bits — et non 512, ce n'est pas une coquille.\n"
        "Robustesse equivalente a RSA 15360, le maximum des courbes NIST.\n"
        "Sensiblement plus lente, et rarement necessaire en pratique.\n"
        "Memes reserves que P-256 sur l'origine des parametres."
    ),
    KEY_TYPE_RSA: (
        "Ce n'est pas une courbe : RSA repose sur la difficulte de factoriser de grands nombres.\n"
        "Cles nettement plus volumineuses et signatures plus lentes qu'une courbe elliptique.\n"
        "2048 bits = robustesse correcte, 3072 bits equivaut a Ed25519, 4096 bits par prudence.\n"
        "Son interet est la compatibilite : accepte absolument partout, y compris par des\n"
        "equipements anciens (vieux switchs, NAS, systemes embarques)."
    ),
}


@dataclass
class KeyEntry:
    id: str = field(default_factory=lambda: str(uuid.uuid4()))
    name: str = ""
    key_type: str = KEY_TYPE_ED25519
    private_path: str = ""
    public_path: str = ""
    fingerprint: str = ""
    public_key_text: str = ""

    def to_dict(self) -> dict:
        return asdict(self)

    @staticmethod
    def from_dict(data: dict) -> "KeyEntry":
        e = KeyEntry()
        for k in KeyEntry.__dataclass_fields__:
            if k in data:
                setattr(e, k, data[k])
        return e


class KeyManager:
    def __init__(self, registry_path: Path = KEYS_FILE):
        self.registry_path = registry_path
        self.keys: list[KeyEntry] = []
        self.load_warning: str | None = None
        self.load()

    # ---------- registre ----------
    def load(self) -> None:
        DEFAULT_KEY_DIR.mkdir(parents=True, exist_ok=True)
        was_missing = not self.registry_path.exists()
        document, warning = load_json_document(
            self.registry_path,
            default={"schema_version": SCHEMA_VERSION, "keys": []},
            current_version=SCHEMA_VERSION,
        )
        self.load_warning = warning
        self.keys = [KeyEntry.from_dict(k) for k in document.get("keys", [])]

        # Uniformise le format des empreintes : les cles importees avant l'ajout de
        # compute_fingerprint() portaient un simple fragment du base64 plutot qu'un
        # vrai condense SHA256. On les corrige silencieusement au chargement.
        changed = False
        for entry in self.keys:
            if not entry.public_key_text:
                continue
            correct = compute_fingerprint(entry.public_key_text)
            if correct and entry.fingerprint != correct:
                entry.fingerprint = correct
                changed = True

        if was_missing or changed:
            self.save()

    def save(self) -> None:
        payload = {"schema_version": SCHEMA_VERSION, "keys": [k.to_dict() for k in self.keys]}
        save_json_document(self.registry_path, payload)

    def remove(self, key_id: str, delete_files: bool = False) -> None:
        entry = next((k for k in self.keys if k.id == key_id), None)
        if entry and delete_files:
            for p in (entry.private_path, entry.public_path):
                try:
                    if p and Path(p).exists():
                        Path(p).unlink()
                except OSError:
                    pass
        self.keys = [k for k in self.keys if k.id != key_id]
        self.save()

    # ---------- generation ----------
    def generate_key(
        self,
        name: str,
        key_type: str = KEY_TYPE_ED25519,
        rsa_bits: int = 4096,
        passphrase: str | None = None,
        save_dir: Path | None = None,
        comment: str = "",
    ) -> KeyEntry:
        save_dir = save_dir or DEFAULT_KEY_DIR
        save_dir.mkdir(parents=True, exist_ok=True)
        safe_name = "".join(c for c in name if c.isalnum() or c in ("-", "_")) or "id_key"
        filename = f"id_{key_type}_{safe_name}"
        priv_path = save_dir / filename
        pub_path = save_dir / f"{filename}.pub"

        if key_type == KEY_TYPE_ED25519:
            private_key = ed25519.Ed25519PrivateKey.generate()
        elif key_type in ECDSA_CURVES:
            private_key = ec.generate_private_key(ECDSA_CURVES[key_type]())
        else:
            private_key = rsa.generate_private_key(public_exponent=65537, key_size=rsa_bits)

        encryption = (
            serialization.BestAvailableEncryption(passphrase.encode("utf-8"))
            if passphrase
            else serialization.NoEncryption()
        )
        priv_bytes = private_key.private_bytes(
            encoding=serialization.Encoding.PEM,
            format=serialization.PrivateFormat.OpenSSH,
            encryption_algorithm=encryption,
        )
        pub_bytes = private_key.public_key().public_bytes(
            encoding=serialization.Encoding.OpenSSH,
            format=serialization.PublicFormat.OpenSSH,
        )
        comment_suffix = f" {comment}".rstrip() if comment else ""
        pub_text = pub_bytes.decode("utf-8") + comment_suffix + "\n"

        priv_path.write_bytes(priv_bytes)
        pub_path.write_text(pub_text, encoding="utf-8")
        protect_private_key(priv_path)

        fingerprint = compute_fingerprint(pub_text)
        entry = KeyEntry(
            name=name,
            key_type=key_type,
            private_path=str(priv_path),
            public_path=str(pub_path),
            fingerprint=fingerprint,
            public_key_text=pub_text.strip(),
        )
        self.keys.append(entry)
        self.save()
        return entry

    # ---------- import ----------
    def import_key(self, name: str, private_key_path: str, public_key_path: str | None = None) -> KeyEntry:
        priv_path = Path(private_key_path)
        key_type, pub_text = self._inspect_private_key(priv_path)

        pub_path_str = ""
        if public_key_path and Path(public_key_path).exists():
            pub_path_str = public_key_path
            pub_text = Path(public_key_path).read_text(encoding="utf-8").strip()
        else:
            guess = priv_path.with_suffix(priv_path.suffix + ".pub")
            if guess.exists():
                pub_path_str = str(guess)
                pub_text = guess.read_text(encoding="utf-8").strip()

        entry = KeyEntry(
            name=name,
            key_type=key_type,
            private_path=str(priv_path),
            public_path=pub_path_str,
            fingerprint=compute_fingerprint(pub_text) if pub_text else "",
            public_key_text=pub_text,
        )
        self.keys.append(entry)
        self.save()
        return entry

    def _inspect_private_key(self, priv_path: Path) -> tuple[str, str]:
        """Tente de determiner le type de cle sans mot de passe (best effort)."""
        for loader, ktype in (
            (paramiko.Ed25519Key, KEY_TYPE_ED25519),
            (paramiko.RSAKey, KEY_TYPE_RSA),
        ):
            try:
                pkey = loader.from_private_key_file(str(priv_path))
                pub_text = f"{pkey.get_name()} {pkey.get_base64()}"
                return ktype, pub_text
            except paramiko.PasswordRequiredException:
                return ktype, ""
            except (paramiko.SSHException, OSError):
                continue
        return "unknown", ""

    # ---------- export ----------
    def export_public_key(self, entry: KeyEntry, destination: str) -> None:
        Path(destination).write_text(entry.public_key_text + "\n", encoding="utf-8")

    def export_private_key(self, entry: KeyEntry, destination: str) -> None:
        shutil.copyfile(entry.private_path, destination)