1 files changed, 476 insertions, 0 deletions
diff --git a/searx/favicons/cache.py b/searx/favicons/cache.py
new file mode 100644
index 000000000..4b8276154
--- /dev/null
+++ b/searx/favicons/cache.py
@@ -0,0 +1,476 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
+"""Implementations for caching favicons.
+
+:py:obj:`FaviconCacheConfig`:
+  Configuration of the favicon cache
+
+:py:obj:`FaviconCache`:
+  Abstract base class for the implementation of a favicon cache.
+
+:py:obj:`FaviconCacheSQLite`:
+  Favicon cache that manages the favicon BLOBs in a SQLite DB.
+
+:py:obj:`FaviconCacheNull`:
+  Fallback solution if the configured cache cannot be used for system reasons.
+
+----
+
+"""
+
+from __future__ import annotations
+from typing import Literal
+
+import abc
+import dataclasses
+import hashlib
+import logging
+import pathlib
+import sqlite3
+import tempfile
+import time
+import typer
+
+from pydantic import BaseModel
+
+from searx import sqlitedb
+from searx import logger
+from searx.utils import humanize_bytes, humanize_number
+
+CACHE: "FaviconCache"
+FALLBACK_ICON = b"FALLBACK_ICON"
+
+logger = logger.getChild('favicons.cache')
+app = typer.Typer()
+
+
+@app.command()
+def state():
+    """show state of the cache"""
+    print(CACHE.state().report())
+
+
+@app.command()
+def maintenance(force: bool = True, debug: bool = False):
+    """perform maintenance of the cache"""
+    root_log = logging.getLogger()
+    if debug:
+        root_log.setLevel(logging.DEBUG)
+    else:
+        root_log.handlers = []
+        handler = logging.StreamHandler()
+        handler.setFormatter(logging.Formatter("%(message)s"))
+        logger.addHandler(handler)
+        logger.setLevel(logging.DEBUG)
+
+    state_t0 = CACHE.state()
+    CACHE.maintenance(force=force)
+    state_t1 = CACHE.state()
+    state_delta = state_t0 - state_t1
+    print("The cache has been reduced by:")
+    print(state_delta.report("\n- {descr}: {val}").lstrip("\n"))
+
+
+def init(cfg: "FaviconCacheConfig"):
+    """Initialization of a global ``CACHE``"""
+
+    global CACHE  # pylint: disable=global-statement
+    if cfg.db_type == "sqlite":
+        if sqlite3.sqlite_version_info <= (3, 35):
+            logger.critical(
+                "Disable favicon caching completely: SQLite library (%s) is too old! (require >= 3.35)",
+                sqlite3.sqlite_version,
+            )
+            CACHE = FaviconCacheNull(cfg)
+        else:
+            CACHE = FaviconCacheSQLite(cfg)
+    elif cfg.db_type == "mem":
+        logger.error("Favicons are cached in memory, don't use this in production!")
+        CACHE = FaviconCacheMEM(cfg)
+    else:
+        raise NotImplementedError(f"favicons db_type '{cfg.db_type}' is unknown")
+
+
+class FaviconCacheConfig(BaseModel):
+    """Configuration of the favicon cache."""
+
+    db_type: Literal["sqlite", "mem"] = "sqlite"
+    """Type of the database:
+
+    ``sqlite``:
+      :py:obj:`.cache.FaviconCacheSQLite`
+
+    ``mem``:
+      :py:obj:`.cache.FaviconCacheMEM` (not recommended)
+    """
+
+    db_url: pathlib.Path = pathlib.Path(tempfile.gettempdir()) / "faviconcache.db"
+    """URL of the SQLite DB, the path to the database file."""
+
+    HOLD_TIME: int = 60 * 60 * 24 * 30  # 30 days
+    """Hold time (default in sec.), after which a BLOB is removed from the cache."""
+
+    LIMIT_TOTAL_BYTES: int = 1024 * 1024 * 50  # 50 MB
+    """Maximum of bytes (default) stored in the cache of all blobs.  Note: The
+    limit is only reached at each maintenance interval after which the oldest
+    BLOBs are deleted; the limit is exceeded during the maintenance period. If
+    the maintenance period is *too long* or maintenance is switched off
+    completely, the cache grows uncontrollably."""
+
+    BLOB_MAX_BYTES: int = 1024 * 20  # 20 KB
+    """The maximum BLOB size in bytes that a favicon may have so that it can be
+    saved in the cache.  If the favicon is larger, it is not saved in the cache
+    and must be requested by the client via the proxy."""
+
+    MAINTENANCE_PERIOD: int = 60 * 60
+    """Maintenance period in seconds / when :py:obj:`MAINTENANCE_MODE` is set to
+    ``auto``."""
+
+    MAINTENANCE_MODE: Literal["auto", "off"] = "auto"
+    """Type of maintenance mode
+
+    ``auto``:
+      Maintenance is carried out automatically as part of the maintenance
+      intervals (:py:obj:`MAINTENANCE_PERIOD`); no external process is required.
+
+    ``off``:
+      Maintenance is switched off and must be carried out by an external process
+      if required.
+    """
+
+
+@dataclasses.dataclass
+class FaviconCacheStats:
+    """Dataclass wich provides information on the status of the cache."""
+
+    favicons: int | None = None
+    bytes: int | None = None
+    domains: int | None = None
+    resolvers: int | None = None
+
+    field_descr = (
+        ("favicons", "number of favicons in cache", humanize_number),
+        ("bytes", "total size (approx. bytes) of cache", humanize_bytes),
+        ("domains", "total number of domains in cache", humanize_number),
+        ("resolvers", "number of resolvers", str),
+    )
+
+    def __sub__(self, other) -> FaviconCacheStats:
+        if not isinstance(other, self.__class__):
+            raise TypeError(f"unsupported operand type(s) for +: '{self.__class__}' and '{type(other)}'")
+        kwargs = {}
+        for field, _, _ in self.field_descr:
+            self_val, other_val = getattr(self, field), getattr(other, field)
+            if None in (self_val, other_val):
+                continue
+            if isinstance(self_val, int):
+                kwargs[field] = self_val - other_val
+            else:
+                kwargs[field] = self_val
+        return self.__class__(**kwargs)
+
+    def report(self, fmt: str = "{descr}: {val}\n"):
+        s = []
+        for field, descr, cast in self.field_descr:
+            val = getattr(self, field)
+            if val is None:
+                val = "--"
+            else:
+                val = cast(val)
+            s.append(fmt.format(descr=descr, val=val))
+        return "".join(s)
+
+
+class FaviconCache(abc.ABC):
+    """Abstract base class for the implementation of a favicon cache."""
+
+    @abc.abstractmethod
+    def __init__(self, cfg: FaviconCacheConfig):
+        """An instance of the favicon cache is build up from the configuration."""
+
+    @abc.abstractmethod
+    def __call__(self, resolver: str, authority: str) -> None | tuple[None | bytes, None | str]:
+        """Returns ``None`` or the tuple of ``(data, mime)`` that has been
+        registered in the cache.  The ``None`` indicates that there was no entry
+        in the cache."""
+
+    @abc.abstractmethod
+    def set(self, resolver: str, authority: str, mime: str | None, data: bytes | None) -> bool:
+        """Set data and mime-type in the cache.  If data is None, the
+        :py:obj:`FALLBACK_ICON` is registered. in the cache."""
+
+    @abc.abstractmethod
+    def state(self) -> FaviconCacheStats:
+        """Returns a :py:obj:`FaviconCacheStats` (key/values) with information
+        on the state of the cache."""
+
+    @abc.abstractmethod
+    def maintenance(self, force=False):
+        """Performs maintenance on the cache"""
+
+
+class FaviconCacheNull(FaviconCache):
+    """A dummy favicon cache that caches nothing / a fallback solution. The
+    NullCache is used when more efficient caches such as the
+    :py:obj:`FaviconCacheSQLite` cannot be used because, for example, the SQLite
+    library is only available in an old version and does not meet the
+    requirements."""
+
+    def __init__(self, cfg: FaviconCacheConfig):
+        return None
+
+    def __call__(self, resolver: str, authority: str) -> None | tuple[None | bytes, None | str]:
+        return None
+
+    def set(self, resolver: str, authority: str, mime: str | None, data: bytes | None) -> bool:
+        return False
+
+    def state(self):
+        return FaviconCacheStats(favicons=0)
+
+    def maintenance(self, force=False):
+        pass
+
+
+class FaviconCacheSQLite(sqlitedb.SQLiteAppl, FaviconCache):
+    """Favicon cache that manages the favicon BLOBs in a SQLite DB.  The DB
+    model in the SQLite DB is implemented using the abstract class
+    :py:obj:`sqlitedb.SQLiteAppl`.
+
+    The following configurations are required / supported:
+
+    - :py:obj:`FaviconCacheConfig.db_url`
+    - :py:obj:`FaviconCacheConfig.HOLD_TIME`
+    - :py:obj:`FaviconCacheConfig.LIMIT_TOTAL_BYTES`
+    - :py:obj:`FaviconCacheConfig.BLOB_MAX_BYTES`
+    - :py:obj:`MAINTENANCE_PERIOD`
+    - :py:obj:`MAINTENANCE_MODE`
+    """
+
+    DB_SCHEMA = 1
+
+    DDL_BLOBS = """\
+CREATE TABLE IF NOT EXISTS blobs (
+  sha256     TEXT,
+  bytes_c    INTEGER,
+  mime       TEXT NOT NULL,
+  data       BLOB NOT NULL,
+  PRIMARY KEY (sha256))"""
+
+    """Table to store BLOB objects by their sha256 hash values."""
+
+    DDL_BLOB_MAP = """\
+CREATE TABLE IF NOT EXISTS blob_map (
+    m_time     INTEGER DEFAULT (strftime('%s', 'now')),  -- last modified (unix epoch) time in sec.
+    sha256     TEXT,
+    resolver   TEXT,
+    authority  TEXT,
+    PRIMARY KEY (resolver, authority))"""
+
+    """Table to map from (resolver, authority) to sha256 hash values."""
+
+    DDL_CREATE_TABLES = {
+        "blobs": DDL_BLOBS,
+        "blob_map": DDL_BLOB_MAP,
+    }
+
+    SQL_DROP_LEFTOVER_BLOBS = (
+        "DELETE FROM blobs WHERE sha256 IN ("
+        " SELECT b.sha256"
+        "   FROM blobs b"
+        "   LEFT JOIN blob_map bm"
+        "     ON b.sha256 = bm.sha256"
+        "  WHERE bm.sha256 IS NULL)"
+    )
+    """Delete blobs.sha256 (BLOBs) no longer in blob_map.sha256."""
+
+    SQL_ITER_BLOBS_SHA256_BYTES_C = (
+        "SELECT b.sha256, b.bytes_c FROM blobs b"
+        "  JOIN blob_map bm "
+        "    ON b.sha256 = bm.sha256"
+        " ORDER BY bm.m_time ASC"
+    )
+
+    SQL_INSERT_BLOBS = (
+        "INSERT INTO blobs (sha256, bytes_c, mime, data) VALUES (?, ?, ?, ?)"
+        "    ON CONFLICT (sha256) DO NOTHING"
+    )  # fmt: skip
+
+    SQL_INSERT_BLOB_MAP = (
+        "INSERT INTO blob_map (sha256, resolver, authority) VALUES (?, ?, ?)"
+        "    ON CONFLICT DO UPDATE "
+        "   SET sha256=excluded.sha256, m_time=strftime('%s', 'now')"
+    )
+
+    def __init__(self, cfg: FaviconCacheConfig):
+        """An instance of the favicon cache is build up from the configuration."""  #
+
+        if cfg.db_url == ":memory:":
+            logger.critical("don't use SQLite DB in :memory: in production!!")
+        super().__init__(cfg.db_url)
+        self.cfg = cfg
+
+    def __call__(self, resolver: str, authority: str) -> None | tuple[None | bytes, None | str]:
+
+        sql = "SELECT sha256 FROM blob_map WHERE resolver = ? AND authority = ?"
+        res = self.DB.execute(sql, (resolver, authority)).fetchone()
+        if res is None:
+            return None
+
+        data, mime = (None, None)
+        sha256 = res[0]
+        if sha256 == FALLBACK_ICON:
+            return data, mime
+
+        sql = "SELECT data, mime FROM blobs WHERE sha256 = ?"
+        res = self.DB.execute(sql, (sha256,)).fetchone()
+        if res is not None:
+            data, mime = res
+        return data, mime
+
+    def set(self, resolver: str, authority: str, mime: str | None, data: bytes | None) -> bool:
+
+        if self.cfg.MAINTENANCE_MODE == "auto" and int(time.time()) > self.next_maintenance_time:
+            # Should automatic maintenance be moved to a new thread?
+            self.maintenance()
+
+        if data is not None and mime is None:
+            logger.error(
+                "favicon resolver %s tries to cache mime-type None for authority %s",
+                resolver,
+                authority,
+            )
+            return False
+
+        bytes_c = len(data or b"")
+        if bytes_c > self.cfg.BLOB_MAX_BYTES:
+            logger.info(
+                "favicon of resolver: %s / authority: %s to big to cache (bytes: %s) " % (resolver, authority, bytes_c)
+            )
+            return False
+
+        if data is None:
+            sha256 = FALLBACK_ICON
+        else:
+            sha256 = hashlib.sha256(data).hexdigest()
+
+        with self.connect() as conn:
+            if sha256 != FALLBACK_ICON:
+                conn.execute(self.SQL_INSERT_BLOBS, (sha256, bytes_c, mime, data))
+            conn.execute(self.SQL_INSERT_BLOB_MAP, (sha256, resolver, authority))
+
+        return True
+
+    @property
+    def next_maintenance_time(self) -> int:
+        """Returns (unix epoch) time of the next maintenance."""
+
+        return self.cfg.MAINTENANCE_PERIOD + self.properties.m_time("LAST_MAINTENANCE")
+
+    def maintenance(self, force=False):
+
+        # Prevent parallel DB maintenance cycles from other DB connections
+        # (e.g. in multi thread or process environments).
+
+        if not force and int(time.time()) < self.next_maintenance_time:
+            logger.debug("no maintenance required yet, next maintenance interval is in the future")
+            return
+        self.properties.set("LAST_MAINTENANCE", "")  # hint: this (also) sets the m_time of the property!
+
+        # do maintenance tasks
+
+        with self.connect() as conn:
+
+            # drop items not in HOLD time
+            res = conn.execute(
+                f"DELETE FROM blob_map"
+                f" WHERE cast(m_time as integer) < cast(strftime('%s', 'now') as integer) - {self.cfg.HOLD_TIME}"
+            )
+            logger.debug("dropped %s obsolete blob_map items from db", res.rowcount)
+            res = conn.execute(self.SQL_DROP_LEFTOVER_BLOBS)
+            logger.debug("dropped %s obsolete BLOBS from db", res.rowcount)
+
+            # drop old items to be in LIMIT_TOTAL_BYTES
+            total_bytes = conn.execute("SELECT SUM(bytes_c) FROM blobs").fetchone()[0] or 0
+            if total_bytes > self.cfg.LIMIT_TOTAL_BYTES:
+
+                x = total_bytes - self.cfg.LIMIT_TOTAL_BYTES
+                c = 0
+                sha_list = []
+                for row in conn.execute(self.SQL_ITER_BLOBS_SHA256_BYTES_C):
+                    sha256, bytes_c = row
+                    sha_list.append(sha256)
+                    c += bytes_c
+                    if c > x:
+                        break
+                if sha_list:
+                    conn.execute("DELETE FROM blobs WHERE sha256 IN ('%s')" % "','".join(sha_list))
+                    conn.execute("DELETE FROM blob_map WHERE sha256 IN ('%s')" % "','".join(sha_list))
+                    logger.debug("dropped %s blobs with total size of %s bytes", len(sha_list), c)
+
+    def _query_val(self, sql, default=None):
+        val = self.DB.execute(sql).fetchone()
+        if val is not None:
+            val = val[0]
+        if val is None:
+            val = default
+        return val
+
+    def state(self) -> FaviconCacheStats:
+        return FaviconCacheStats(
+            favicons=self._query_val("SELECT count(*) FROM blobs", 0),
+            bytes=self._query_val("SELECT SUM(bytes_c) FROM blobs", 0),
+            domains=self._query_val("SELECT count(*) FROM (SELECT authority FROM blob_map GROUP BY authority)", 0),
+            resolvers=self._query_val("SELECT count(*) FROM (SELECT resolver FROM blob_map GROUP BY resolver)", 0),
+        )
+
+
+class FaviconCacheMEM(FaviconCache):
+    """Favicon cache in process' memory.  Its just a POC that stores the
+    favicons in the memory of the process.
+
+    .. attention::
+
+       Don't use it in production, it will blow up your memory!!
+
+    """
+
+    def __init__(self, cfg):
+
+        self.cfg = cfg
+        self._data = {}
+        self._sha_mime = {}
+
+    def __call__(self, resolver: str, authority: str) -> None | tuple[bytes | None, str | None]:
+
+        sha, mime = self._sha_mime.get(f"{resolver}:{authority}", (None, None))
+        if sha is None:
+            return None
+        data = self._data.get(sha)
+        if data == FALLBACK_ICON:
+            data = None
+        return data, mime
+
+    def set(self, resolver: str, authority: str, mime: str | None, data: bytes | None) -> bool:
+
+        if data is None:
+            data = FALLBACK_ICON
+            mime = None
+
+        elif mime is None:
+            logger.error(
+                "favicon resolver %s tries to cache mime-type None for authority %s",
+                resolver,
+                authority,
+            )
+            return False
+
+        digest = hashlib.sha256(data).hexdigest()
+        self._data[digest] = data
+        self._sha_mime[f"{resolver}:{authority}"] = (digest, mime)
+        return True
+
+    def state(self):
+        return FaviconCacheStats(favicons=len(self._data.keys()))
+
+    def maintenance(self, force=False):
+        pass