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infrastructure.providers.encryption_service

src.infrastructure.providers.encryption_service

Encryption service for provider credentials.

Provides AES-256-GCM encryption for secure storage of OAuth tokens and other sensitive provider credentials.

Security Properties
  • Confidentiality: Only holder of key can decrypt
  • Integrity: Tampering is detected via GCM authentication tag
  • Uniqueness: Random IV per encryption prevents pattern analysis
Architecture
  • Infrastructure adapter (catches cryptography exceptions)
  • Returns Result types (railway-oriented programming)
  • Uses domain error codes (ErrorCode enum)
Reference
  • docs/architecture/provider-integration-architecture.md
  • docs/architecture/error-handling-architecture.md

Classes

DecryptionError dataclass

Bases: EncryptionError

Decryption failure.

Occurs when: - Wrong encryption key - Data has been tampered with - Invalid encrypted data format

Source code in src/domain/protocols/encryption_protocol.py 
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@dataclass(frozen=True, slots=True, kw_only=True)
class DecryptionError(EncryptionError):
    """Decryption failure.

    Occurs when:
    - Wrong encryption key
    - Data has been tampered with
    - Invalid encrypted data format
    """

    pass

EncryptionError dataclass

Bases: DomainError

Base encryption error.

Used when encryption or decryption fails. Does NOT inherit from Exception - used in Result types.

Source code in src/domain/protocols/encryption_protocol.py 
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@dataclass(frozen=True, slots=True, kw_only=True)
class EncryptionError(DomainError):
    """Base encryption error.

    Used when encryption or decryption fails.
    Does NOT inherit from Exception - used in Result types.
    """

    pass

EncryptionKeyError dataclass

Bases: EncryptionError

Invalid encryption key.

Occurs when key doesn't meet requirements (wrong length, etc.).

Source code in src/domain/protocols/encryption_protocol.py 
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@dataclass(frozen=True, slots=True, kw_only=True)
class EncryptionKeyError(EncryptionError):
    """Invalid encryption key.

    Occurs when key doesn't meet requirements (wrong length, etc.).
    """

    pass

SerializationError dataclass

Bases: EncryptionError

Serialization/deserialization failure.

Occurs when data cannot be serialized to JSON or decrypted data cannot be parsed as JSON.

Source code in src/domain/protocols/encryption_protocol.py 
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@dataclass(frozen=True, slots=True, kw_only=True)
class SerializationError(EncryptionError):
    """Serialization/deserialization failure.

    Occurs when data cannot be serialized to JSON
    or decrypted data cannot be parsed as JSON.
    """

    pass

EncryptionService

AES-256-GCM encryption service for provider credentials.

Encrypts and decrypts credential dictionaries (containing access tokens, refresh tokens, etc.) to/from bytes for secure database storage.

Format

Encrypted bytes = IV (12 bytes) || ciphertext || auth_tag (16 bytes)

Usage

from src.core.config import get_settings service = EncryptionService.create(get_settings().encryption_key) match service: ... case Success(svc): ... # Encrypt credentials ... result = svc.encrypt({"access_token": "abc123"}) ... case Failure(error): ... # Handle invalid key ... ...

Thread Safety

This service is thread-safe. The AESGCM instance can be used concurrently from multiple threads.

Reference
  • NIST SP 800-38D (GCM specification)
  • docs/architecture/provider-integration-architecture.md
Source code in src/infrastructure/providers/encryption_service.py 
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class EncryptionService:
    """AES-256-GCM encryption service for provider credentials.

    Encrypts and decrypts credential dictionaries (containing access tokens,
    refresh tokens, etc.) to/from bytes for secure database storage.

    Format:
        Encrypted bytes = IV (12 bytes) || ciphertext || auth_tag (16 bytes)

    Usage:
        >>> from src.core.config import get_settings
        >>> service = EncryptionService.create(get_settings().encryption_key)
        >>> match service:
        ...     case Success(svc):
        ...         # Encrypt credentials
        ...         result = svc.encrypt({"access_token": "abc123"})
        ...     case Failure(error):
        ...         # Handle invalid key
        ...         ...

    Thread Safety:
        This service is thread-safe. The AESGCM instance can be used
        concurrently from multiple threads.

    Reference:
        - NIST SP 800-38D (GCM specification)
        - docs/architecture/provider-integration-architecture.md
    """

    IV_SIZE = 12  # 96 bits - NIST recommended for GCM
    MIN_ENCRYPTED_SIZE = 12 + 16  # IV + auth tag

    def __init__(self, aesgcm: AESGCM) -> None:
        """Initialize with pre-validated AESGCM instance.

        Use EncryptionService.create() factory instead of direct construction.

        Args:
            aesgcm: Pre-initialized AESGCM cipher instance.
        """
        self._aesgcm = aesgcm

    @classmethod
    def create(cls, key: bytes) -> Result["EncryptionService", EncryptionKeyError]:
        """Create encryption service with validated key.

        Factory method that validates the encryption key and returns
        a Result type.

        Args:
            key: 32-byte (256-bit) encryption key.

        Returns:
            Success(EncryptionService) if key is valid.
            Failure(EncryptionKeyError) if key is invalid.

        Example:
            >>> key = os.urandom(32)
            >>> match EncryptionService.create(key):
            ...     case Success(service):
            ...         # Use service
            ...     case Failure(error):
            ...         logger.error(f"Invalid key: {error.message}")
        """
        if len(key) != 32:
            return Failure(
                error=EncryptionKeyError(
                    code=ErrorCode.ENCRYPTION_KEY_INVALID,
                    message=(
                        f"Encryption key must be exactly 32 bytes (256 bits), "
                        f"got {len(key)} bytes"
                    ),
                    details={"expected_length": "32", "actual_length": str(len(key))},
                )
            )

        try:
            aesgcm = AESGCM(key)
            return Success(value=cls(aesgcm))
        except Exception as e:
            return Failure(
                error=EncryptionKeyError(
                    code=ErrorCode.ENCRYPTION_KEY_INVALID,
                    message=f"Failed to initialize encryption: {e}",
                )
            )

    def encrypt(self, data: dict[str, Any]) -> Result[bytes, EncryptionError]:
        """Encrypt credentials dictionary to bytes.

        Serializes the dictionary to JSON, then encrypts using AES-256-GCM
        with a random IV. The IV is prepended to the ciphertext.

        Args:
            data: Credentials dictionary to encrypt. Must be JSON-serializable.
                Typically contains access_token, refresh_token, etc.

        Returns:
            Success(bytes) with encrypted data in format:
                IV (12 bytes) || ciphertext || auth_tag (16 bytes)
            Failure(SerializationError) if data cannot be serialized.
            Failure(EncryptionError) if encryption fails.

        Example:
            >>> credentials = {
            ...     "access_token": "abc123",
            ...     "refresh_token": "xyz789",
            ... }
            >>> match service.encrypt(credentials):
            ...     case Success(encrypted):
            ...         # Store encrypted bytes in database
            ...     case Failure(error):
            ...         # Handle error
        """
        # Serialize to JSON
        try:
            plaintext = json.dumps(data, separators=(",", ":")).encode("utf-8")
        except (TypeError, ValueError) as e:
            return Failure(
                error=SerializationError(
                    code=ErrorCode.INVALID_INPUT,
                    message=f"Failed to serialize credentials to JSON: {e}",
                )
            )

        # Generate random IV and encrypt
        try:
            iv = os.urandom(self.IV_SIZE)
            ciphertext = self._aesgcm.encrypt(iv, plaintext, associated_data=None)
            return Success(value=iv + ciphertext)
        except Exception as e:
            return Failure(
                error=EncryptionError(
                    code=ErrorCode.ENCRYPTION_FAILED,
                    message=f"Encryption failed: {e}",
                )
            )

    def decrypt(self, encrypted: bytes) -> Result[dict[str, Any], EncryptionError]:
        """Decrypt bytes back to credentials dictionary.

        Extracts the IV from the first 12 bytes, then decrypts the remaining
        ciphertext using AES-256-GCM.

        Args:
            encrypted: Encrypted bytes from encrypt().

        Returns:
            Success(dict) with original credentials dictionary.
            Failure(DecryptionError) if decryption fails (wrong key, tampered).
            Failure(SerializationError) if decrypted data is not valid JSON.

        Example:
            >>> match service.decrypt(encrypted_bytes):
            ...     case Success(credentials):
            ...         access_token = credentials["access_token"]
            ...     case Failure(error):
            ...         # Handle error - may need user to re-authenticate
        """
        # Validate minimum size
        if len(encrypted) < self.MIN_ENCRYPTED_SIZE:
            return Failure(
                error=DecryptionError(
                    code=ErrorCode.INVALID_INPUT,
                    message=(
                        f"Encrypted data too short: {len(encrypted)} bytes "
                        f"(minimum {self.MIN_ENCRYPTED_SIZE} bytes)"
                    ),
                    details={
                        "actual_length": str(len(encrypted)),
                        "minimum_length": str(self.MIN_ENCRYPTED_SIZE),
                    },
                )
            )

        # Extract IV and ciphertext
        iv = encrypted[: self.IV_SIZE]
        ciphertext = encrypted[self.IV_SIZE :]

        # Decrypt
        try:
            plaintext = self._aesgcm.decrypt(iv, ciphertext, associated_data=None)
        except Exception:
            # AESGCM raises InvalidTag if authentication fails
            return Failure(
                error=DecryptionError(
                    code=ErrorCode.DECRYPTION_FAILED,
                    message="Failed to decrypt credentials: invalid key or tampered data",
                )
            )

        # Deserialize JSON
        try:
            return Success(value=json.loads(plaintext.decode("utf-8")))
        except (json.JSONDecodeError, UnicodeDecodeError) as e:
            return Failure(
                error=SerializationError(
                    code=ErrorCode.INVALID_INPUT,
                    message=f"Failed to deserialize decrypted credentials: {e}",
                )
            )
Functions
__init__ 
__init__(aesgcm: AESGCM) -> None

Use EncryptionService.create() factory instead of direct construction.

Parameters:

Name Type Description Default
aesgcm AESGCM

Pre-initialized AESGCM cipher instance.

 required
Source code in src/infrastructure/providers/encryption_service.py 
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def __init__(self, aesgcm: AESGCM) -> None:
    """Initialize with pre-validated AESGCM instance.

    Use EncryptionService.create() factory instead of direct construction.

    Args:
        aesgcm: Pre-initialized AESGCM cipher instance.
    """
    self._aesgcm = aesgcm
create classmethod 
create(
    key: bytes,
) -> Result[EncryptionService, EncryptionKeyError]

Create encryption service with validated key.

Factory method that validates the encryption key and returns a Result type.

Parameters:

Name Type Description Default
key bytes

32-byte (256-bit) encryption key.

 required

Returns:

Type Description
Result[EncryptionService, EncryptionKeyError]

Success(EncryptionService) if key is valid.
Result[EncryptionService, EncryptionKeyError]

Failure(EncryptionKeyError) if key is invalid.
Example

key = os.urandom(32) match EncryptionService.create(key): ... case Success(service): ... # Use service ... case Failure(error): ... logger.error(f"Invalid key: {error.message}")

Source code in src/infrastructure/providers/encryption_service.py 
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@classmethod
def create(cls, key: bytes) -> Result["EncryptionService", EncryptionKeyError]:
    """Create encryption service with validated key.

    Factory method that validates the encryption key and returns
    a Result type.

    Args:
        key: 32-byte (256-bit) encryption key.

    Returns:
        Success(EncryptionService) if key is valid.
        Failure(EncryptionKeyError) if key is invalid.

    Example:
        >>> key = os.urandom(32)
        >>> match EncryptionService.create(key):
        ...     case Success(service):
        ...         # Use service
        ...     case Failure(error):
        ...         logger.error(f"Invalid key: {error.message}")
    """
    if len(key) != 32:
        return Failure(
            error=EncryptionKeyError(
                code=ErrorCode.ENCRYPTION_KEY_INVALID,
                message=(
                    f"Encryption key must be exactly 32 bytes (256 bits), "
                    f"got {len(key)} bytes"
                ),
                details={"expected_length": "32", "actual_length": str(len(key))},
            )
        )

    try:
        aesgcm = AESGCM(key)
        return Success(value=cls(aesgcm))
    except Exception as e:
        return Failure(
            error=EncryptionKeyError(
                code=ErrorCode.ENCRYPTION_KEY_INVALID,
                message=f"Failed to initialize encryption: {e}",
            )
        )
encrypt 
encrypt(
    data: dict[str, Any],
) -> Result[bytes, EncryptionError]

Encrypt credentials dictionary to bytes.

Serializes the dictionary to JSON, then encrypts using AES-256-GCM with a random IV. The IV is prepended to the ciphertext.

Parameters:

Name Type Description Default
data dict[str, Any]

Credentials dictionary to encrypt. Must be JSON-serializable. Typically contains access_token, refresh_token, etc.

 required

Returns:

Type Description
Result[bytes, EncryptionError]

Success(bytes) with encrypted data in format: IV (12 bytes) || ciphertext || auth_tag (16 bytes)
Result[bytes, EncryptionError]

Failure(SerializationError) if data cannot be serialized.
Result[bytes, EncryptionError]

Failure(EncryptionError) if encryption fails.
Example

credentials = { ... "access_token": "abc123", ... "refresh_token": "xyz789", ... } match service.encrypt(credentials): ... case Success(encrypted): ... # Store encrypted bytes in database ... case Failure(error): ... # Handle error

Source code in src/infrastructure/providers/encryption_service.py 
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def encrypt(self, data: dict[str, Any]) -> Result[bytes, EncryptionError]:
    """Encrypt credentials dictionary to bytes.

    Serializes the dictionary to JSON, then encrypts using AES-256-GCM
    with a random IV. The IV is prepended to the ciphertext.

    Args:
        data: Credentials dictionary to encrypt. Must be JSON-serializable.
            Typically contains access_token, refresh_token, etc.

    Returns:
        Success(bytes) with encrypted data in format:
            IV (12 bytes) || ciphertext || auth_tag (16 bytes)
        Failure(SerializationError) if data cannot be serialized.
        Failure(EncryptionError) if encryption fails.

    Example:
        >>> credentials = {
        ...     "access_token": "abc123",
        ...     "refresh_token": "xyz789",
        ... }
        >>> match service.encrypt(credentials):
        ...     case Success(encrypted):
        ...         # Store encrypted bytes in database
        ...     case Failure(error):
        ...         # Handle error
    """
    # Serialize to JSON
    try:
        plaintext = json.dumps(data, separators=(",", ":")).encode("utf-8")
    except (TypeError, ValueError) as e:
        return Failure(
            error=SerializationError(
                code=ErrorCode.INVALID_INPUT,
                message=f"Failed to serialize credentials to JSON: {e}",
            )
        )

    # Generate random IV and encrypt
    try:
        iv = os.urandom(self.IV_SIZE)
        ciphertext = self._aesgcm.encrypt(iv, plaintext, associated_data=None)
        return Success(value=iv + ciphertext)
    except Exception as e:
        return Failure(
            error=EncryptionError(
                code=ErrorCode.ENCRYPTION_FAILED,
                message=f"Encryption failed: {e}",
            )
        )
decrypt 
decrypt(
    encrypted: bytes,
) -> Result[dict[str, Any], EncryptionError]

Decrypt bytes back to credentials dictionary.

Extracts the IV from the first 12 bytes, then decrypts the remaining ciphertext using AES-256-GCM.

Parameters:

Name Type Description Default
encrypted bytes

Encrypted bytes from encrypt().

 required

Returns:

Type Description
Result[dict[str, Any], EncryptionError]

Success(dict) with original credentials dictionary.
Result[dict[str, Any], EncryptionError]

Failure(DecryptionError) if decryption fails (wrong key, tampered).
Result[dict[str, Any], EncryptionError]

Failure(SerializationError) if decrypted data is not valid JSON.
Example

match service.decrypt(encrypted_bytes): ... case Success(credentials): ... access_token = credentials["access_token"] ... case Failure(error): ... # Handle error - may need user to re-authenticate

Source code in src/infrastructure/providers/encryption_service.py 
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def decrypt(self, encrypted: bytes) -> Result[dict[str, Any], EncryptionError]:
    """Decrypt bytes back to credentials dictionary.

    Extracts the IV from the first 12 bytes, then decrypts the remaining
    ciphertext using AES-256-GCM.

    Args:
        encrypted: Encrypted bytes from encrypt().

    Returns:
        Success(dict) with original credentials dictionary.
        Failure(DecryptionError) if decryption fails (wrong key, tampered).
        Failure(SerializationError) if decrypted data is not valid JSON.

    Example:
        >>> match service.decrypt(encrypted_bytes):
        ...     case Success(credentials):
        ...         access_token = credentials["access_token"]
        ...     case Failure(error):
        ...         # Handle error - may need user to re-authenticate
    """
    # Validate minimum size
    if len(encrypted) < self.MIN_ENCRYPTED_SIZE:
        return Failure(
            error=DecryptionError(
                code=ErrorCode.INVALID_INPUT,
                message=(
                    f"Encrypted data too short: {len(encrypted)} bytes "
                    f"(minimum {self.MIN_ENCRYPTED_SIZE} bytes)"
                ),
                details={
                    "actual_length": str(len(encrypted)),
                    "minimum_length": str(self.MIN_ENCRYPTED_SIZE),
                },
            )
        )

    # Extract IV and ciphertext
    iv = encrypted[: self.IV_SIZE]
    ciphertext = encrypted[self.IV_SIZE :]

    # Decrypt
    try:
        plaintext = self._aesgcm.decrypt(iv, ciphertext, associated_data=None)
    except Exception:
        # AESGCM raises InvalidTag if authentication fails
        return Failure(
            error=DecryptionError(
                code=ErrorCode.DECRYPTION_FAILED,
                message="Failed to decrypt credentials: invalid key or tampered data",
            )
        )

    # Deserialize JSON
    try:
        return Success(value=json.loads(plaintext.decode("utf-8")))
    except (json.JSONDecodeError, UnicodeDecodeError) as e:
        return Failure(
            error=SerializationError(
                code=ErrorCode.INVALID_INPUT,
                message=f"Failed to deserialize decrypted credentials: {e}",
            )
        )