Adding upstream version 3.8.1.upstream/3.8.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 955 insertions, 0 deletions

diff --git a/src/libstat/tokenizers/tokenizers.c b/src/libstat/tokenizers/tokenizers.c
new file mode 100644
index 0000000..ee7234d
--- /dev/null
+++ b/src/libstat/tokenizers/tokenizers.c
@@ -0,0 +1,955 @@
+/*
+ * Copyright 2023 Vsevolod Stakhov
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+/*
+ * Common tokenization functions
+ */
+
+#include "rspamd.h"
+#include "tokenizers.h"
+#include "stat_internal.h"
+#include "contrib/mumhash/mum.h"
+#include "libmime/lang_detection.h"
+#include "libstemmer.h"
+
+#include <unicode/utf8.h>
+#include <unicode/uchar.h>
+#include <unicode/uiter.h>
+#include <unicode/ubrk.h>
+#include <unicode/ucnv.h>
+#if U_ICU_VERSION_MAJOR_NUM >= 44
+#include <unicode/unorm2.h>
+#endif
+
+#include <math.h>
+
+typedef gboolean (*token_get_function)(rspamd_stat_token_t *buf, gchar const **pos,
+									   rspamd_stat_token_t *token,
+									   GList **exceptions, gsize *rl, gboolean check_signature);
+
+const gchar t_delimiters[256] = {
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 1,
+	1, 0, 0, 1, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 1, 0, 1, 1, 1, 1, 1, 0,
+	1, 1, 1, 1, 1, 1, 1, 1, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0, 1, 1,
+	1, 1, 1, 1, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0, 1, 1, 1, 1, 1, 1, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 1, 1, 1, 1, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0};
+
+/* Get next word from specified f_str_t buf */
+static gboolean
+rspamd_tokenizer_get_word_raw(rspamd_stat_token_t *buf,
+							  gchar const **cur, rspamd_stat_token_t *token,
+							  GList **exceptions, gsize *rl, gboolean unused)
+{
+	gsize remain, pos;
+	const gchar *p;
+	struct rspamd_process_exception *ex = NULL;
+
+	if (buf == NULL) {
+		return FALSE;
+	}
+
+	g_assert(cur != NULL);
+
+	if (exceptions != NULL && *exceptions != NULL) {
+		ex = (*exceptions)->data;
+	}
+
+	if (token->original.begin == NULL || *cur == NULL) {
+		if (ex != NULL) {
+			if (ex->pos == 0) {
+				token->original.begin = buf->original.begin + ex->len;
+				token->original.len = ex->len;
+				token->flags = RSPAMD_STAT_TOKEN_FLAG_EXCEPTION;
+			}
+			else {
+				token->original.begin = buf->original.begin;
+				token->original.len = 0;
+			}
+		}
+		else {
+			token->original.begin = buf->original.begin;
+			token->original.len = 0;
+		}
+		*cur = token->original.begin;
+	}
+
+	token->original.len = 0;
+
+	pos = *cur - buf->original.begin;
+	if (pos >= buf->original.len) {
+		return FALSE;
+	}
+
+	remain = buf->original.len - pos;
+	p = *cur;
+
+	/* Skip non delimiters symbols */
+	do {
+		if (ex != NULL && ex->pos == pos) {
+			/* Go to the next exception */
+			*exceptions = g_list_next(*exceptions);
+			*cur = p + ex->len;
+			return TRUE;
+		}
+		pos++;
+		p++;
+		remain--;
+	} while (remain > 0 && t_delimiters[(guchar) *p]);
+
+	token->original.begin = p;
+
+	while (remain > 0 && !t_delimiters[(guchar) *p]) {
+		if (ex != NULL && ex->pos == pos) {
+			*exceptions = g_list_next(*exceptions);
+			*cur = p + ex->len;
+			return TRUE;
+		}
+		token->original.len++;
+		pos++;
+		remain--;
+		p++;
+	}
+
+	if (remain == 0) {
+		return FALSE;
+	}
+
+	if (rl) {
+		*rl = token->original.len;
+	}
+
+	token->flags = RSPAMD_STAT_TOKEN_FLAG_TEXT;
+
+	*cur = p;
+
+	return TRUE;
+}
+
+static inline gboolean
+rspamd_tokenize_check_limit(gboolean decay,
+							guint word_decay,
+							guint nwords,
+							guint64 *hv,
+							guint64 *prob,
+							const rspamd_stat_token_t *token,
+							gssize remain,
+							gssize total)
+{
+	static const gdouble avg_word_len = 6.0;
+
+	if (!decay) {
+		if (token->original.len >= sizeof(guint64)) {
+			guint64 tmp;
+			memcpy(&tmp, token->original.begin, sizeof(tmp));
+			*hv = mum_hash_step(*hv, tmp);
+		}
+
+		/* Check for decay */
+		if (word_decay > 0 && nwords > word_decay && remain < (gssize) total) {
+			/* Start decay */
+			gdouble decay_prob;
+
+			*hv = mum_hash_finish(*hv);
+
+			/* We assume that word is 6 symbols length in average */
+			decay_prob = (gdouble) word_decay / ((total - (remain)) / avg_word_len) * 10;
+			decay_prob = floor(decay_prob) / 10.0;
+
+			if (decay_prob >= 1.0) {
+				*prob = G_MAXUINT64;
+			}
+			else {
+				*prob = (guint64) (decay_prob * (double) G_MAXUINT64);
+			}
+
+			return TRUE;
+		}
+	}
+	else {
+		/* Decaying probability */
+		/* LCG64 x[n] = a x[n - 1] + b mod 2^64 */
+		*hv = (*hv) * 2862933555777941757ULL + 3037000493ULL;
+
+		if (*hv > *prob) {
+			return TRUE;
+		}
+	}
+
+	return FALSE;
+}
+
+static inline gboolean
+rspamd_utf_word_valid(const guchar *text, const guchar *end,
+					  gint32 start, gint32 finish)
+{
+	const guchar *st = text + start, *fin = text + finish;
+	UChar32 c;
+
+	if (st >= end || fin > end || st >= fin) {
+		return FALSE;
+	}
+
+	U8_NEXT(text, start, finish, c);
+
+	if (u_isJavaIDPart(c)) {
+		return TRUE;
+	}
+
+	return FALSE;
+}
+#define SHIFT_EX                                                \
+	do {                                                        \
+		cur = g_list_next(cur);                                 \
+		if (cur) {                                              \
+			ex = (struct rspamd_process_exception *) cur->data; \
+		}                                                       \
+		else {                                                  \
+			ex = NULL;                                          \
+		}                                                       \
+	} while (0)
+
+static inline void
+rspamd_tokenize_exception(struct rspamd_process_exception *ex, GArray *res)
+{
+	rspamd_stat_token_t token;
+
+	memset(&token, 0, sizeof(token));
+
+	if (ex->type == RSPAMD_EXCEPTION_GENERIC) {
+		token.original.begin = "!!EX!!";
+		token.original.len = sizeof("!!EX!!") - 1;
+		token.flags = RSPAMD_STAT_TOKEN_FLAG_EXCEPTION;
+
+		g_array_append_val(res, token);
+		token.flags = 0;
+	}
+	else if (ex->type == RSPAMD_EXCEPTION_URL) {
+		struct rspamd_url *uri;
+
+		uri = ex->ptr;
+
+		if (uri && uri->tldlen > 0) {
+			token.original.begin = rspamd_url_tld_unsafe(uri);
+			token.original.len = uri->tldlen;
+		}
+		else {
+			token.original.begin = "!!EX!!";
+			token.original.len = sizeof("!!EX!!") - 1;
+		}
+
+		token.flags = RSPAMD_STAT_TOKEN_FLAG_EXCEPTION;
+		g_array_append_val(res, token);
+		token.flags = 0;
+	}
+}
+
+
+GArray *
+rspamd_tokenize_text(const gchar *text, gsize len,
+					 const UText *utxt,
+					 enum rspamd_tokenize_type how,
+					 struct rspamd_config *cfg,
+					 GList *exceptions,
+					 guint64 *hash,
+					 GArray *cur_words,
+					 rspamd_mempool_t *pool)
+{
+	rspamd_stat_token_t token, buf;
+	const gchar *pos = NULL;
+	gsize l = 0;
+	GArray *res;
+	GList *cur = exceptions;
+	guint min_len = 0, max_len = 0, word_decay = 0, initial_size = 128;
+	guint64 hv = 0;
+	gboolean decay = FALSE, long_text_mode = FALSE;
+	guint64 prob = 0;
+	static UBreakIterator *bi = NULL;
+	static const gsize long_text_limit = 1 * 1024 * 1024;
+	static const ev_tstamp max_exec_time = 0.2; /* 200 ms */
+	ev_tstamp start;
+
+	if (text == NULL) {
+		return cur_words;
+	}
+
+	if (len > long_text_limit) {
+		/*
+		 * In this mode we do additional checks to avoid performance issues
+		 */
+		long_text_mode = TRUE;
+		start = ev_time();
+	}
+
+	buf.original.begin = text;
+	buf.original.len = len;
+	buf.flags = 0;
+
+	memset(&token, 0, sizeof(token));
+
+	if (cfg != NULL) {
+		min_len = cfg->min_word_len;
+		max_len = cfg->max_word_len;
+		word_decay = cfg->words_decay;
+		initial_size = word_decay * 2;
+	}
+
+	if (!cur_words) {
+		res = g_array_sized_new(FALSE, FALSE, sizeof(rspamd_stat_token_t),
+								initial_size);
+	}
+	else {
+		res = cur_words;
+	}
+
+	if (G_UNLIKELY(how == RSPAMD_TOKENIZE_RAW || utxt == NULL)) {
+		while (rspamd_tokenizer_get_word_raw(&buf, &pos, &token, &cur, &l, FALSE)) {
+			if (l == 0 || (min_len > 0 && l < min_len) ||
+				(max_len > 0 && l > max_len)) {
+				token.original.begin = pos;
+				continue;
+			}
+
+			if (token.original.len > 0 &&
+				rspamd_tokenize_check_limit(decay, word_decay, res->len,
+											&hv, &prob, &token, pos - text, len)) {
+				if (!decay) {
+					decay = TRUE;
+				}
+				else {
+					token.original.begin = pos;
+					continue;
+				}
+			}
+
+			if (long_text_mode) {
+				if ((res->len + 1) % 16 == 0) {
+					ev_tstamp now = ev_time();
+
+					if (now - start > max_exec_time) {
+						msg_warn_pool_check(
+							"too long time has been spent on tokenization:"
+							" %.1f ms, limit is %.1f ms; %d words added so far",
+							(now - start) * 1e3, max_exec_time * 1e3,
+							res->len);
+
+						goto end;
+					}
+				}
+			}
+
+			g_array_append_val(res, token);
+
+			if (((gsize) res->len) * sizeof(token) > (0x1ull << 30u)) {
+				/* Due to bug in glib ! */
+				msg_err_pool_check(
+					"too many words found: %d, stop tokenization to avoid DoS",
+					res->len);
+
+				goto end;
+			}
+
+			token.original.begin = pos;
+		}
+	}
+	else {
+		/* UTF8 boundaries */
+		UErrorCode uc_err = U_ZERO_ERROR;
+		int32_t last, p;
+		struct rspamd_process_exception *ex = NULL;
+
+		if (bi == NULL) {
+			bi = ubrk_open(UBRK_WORD, NULL, NULL, 0, &uc_err);
+
+			g_assert(U_SUCCESS(uc_err));
+		}
+
+		ubrk_setUText(bi, (UText *) utxt, &uc_err);
+		last = ubrk_first(bi);
+		p = last;
+
+		if (cur) {
+			ex = (struct rspamd_process_exception *) cur->data;
+		}
+
+		while (p != UBRK_DONE) {
+		start_over:
+			token.original.len = 0;
+
+			if (p > last) {
+				if (ex && cur) {
+					/* Check exception */
+					if (ex->pos >= last && ex->pos <= p) {
+						/* We have an exception within boundary */
+						/* First, start to drain exceptions from the start */
+						while (cur && ex->pos <= last) {
+							/* We have an exception at the beginning, skip those */
+							last += ex->len;
+							rspamd_tokenize_exception(ex, res);
+
+							if (last > p) {
+								/* Exception spread over the boundaries */
+								while (last > p && p != UBRK_DONE) {
+									gint32 old_p = p;
+									p = ubrk_next(bi);
+
+									if (p != UBRK_DONE && p <= old_p) {
+										msg_warn_pool_check(
+											"tokenization reversed back on position %d,"
+											"%d new position (%d backward), likely libicu bug!",
+											(gint) (p), (gint) (old_p), old_p - p);
+
+										goto end;
+									}
+								}
+
+								/* We need to reset our scan with new p and last */
+								SHIFT_EX;
+								goto start_over;
+							}
+
+							SHIFT_EX;
+						}
+
+						/* Now, we can have an exception within boundary again */
+						if (cur && ex->pos >= last && ex->pos <= p) {
+							/* Append the first part */
+							if (rspamd_utf_word_valid(text, text + len, last,
+													  ex->pos)) {
+								token.original.begin = text + last;
+								token.original.len = ex->pos - last;
+								token.flags = RSPAMD_STAT_TOKEN_FLAG_TEXT |
+											  RSPAMD_STAT_TOKEN_FLAG_UTF;
+							}
+
+							/* Process the current exception */
+							last += ex->len + (ex->pos - last);
+
+							rspamd_tokenize_exception(ex, res);
+
+							if (last > p) {
+								/* Exception spread over the boundaries */
+								while (last > p && p != UBRK_DONE) {
+									gint32 old_p = p;
+									p = ubrk_next(bi);
+									if (p != UBRK_DONE && p <= old_p) {
+										msg_warn_pool_check(
+											"tokenization reversed back on position %d,"
+											"%d new position (%d backward), likely libicu bug!",
+											(gint) (p), (gint) (old_p), old_p - p);
+
+										goto end;
+									}
+								}
+								/* We need to reset our scan with new p and last */
+								SHIFT_EX;
+								goto start_over;
+							}
+
+							SHIFT_EX;
+						}
+						else if (p > last) {
+							if (rspamd_utf_word_valid(text, text + len, last, p)) {
+								token.original.begin = text + last;
+								token.original.len = p - last;
+								token.flags = RSPAMD_STAT_TOKEN_FLAG_TEXT |
+											  RSPAMD_STAT_TOKEN_FLAG_UTF;
+							}
+						}
+					}
+					else if (ex->pos < last) {
+						/* Forward exceptions list */
+						while (cur && ex->pos <= last) {
+							/* We have an exception at the beginning, skip those */
+							SHIFT_EX;
+						}
+
+						if (rspamd_utf_word_valid(text, text + len, last, p)) {
+							token.original.begin = text + last;
+							token.original.len = p - last;
+							token.flags = RSPAMD_STAT_TOKEN_FLAG_TEXT |
+										  RSPAMD_STAT_TOKEN_FLAG_UTF;
+						}
+					}
+					else {
+						/* No exceptions within boundary */
+						if (rspamd_utf_word_valid(text, text + len, last, p)) {
+							token.original.begin = text + last;
+							token.original.len = p - last;
+							token.flags = RSPAMD_STAT_TOKEN_FLAG_TEXT |
+										  RSPAMD_STAT_TOKEN_FLAG_UTF;
+						}
+					}
+				}
+				else {
+					if (rspamd_utf_word_valid(text, text + len, last, p)) {
+						token.original.begin = text + last;
+						token.original.len = p - last;
+						token.flags = RSPAMD_STAT_TOKEN_FLAG_TEXT |
+									  RSPAMD_STAT_TOKEN_FLAG_UTF;
+					}
+				}
+
+				if (token.original.len > 0 &&
+					rspamd_tokenize_check_limit(decay, word_decay, res->len,
+												&hv, &prob, &token, p, len)) {
+					if (!decay) {
+						decay = TRUE;
+					}
+					else {
+						token.flags |= RSPAMD_STAT_TOKEN_FLAG_SKIPPED;
+					}
+				}
+			}
+
+			if (token.original.len > 0) {
+				/* Additional check for number of words */
+				if (((gsize) res->len) * sizeof(token) > (0x1ull << 30u)) {
+					/* Due to bug in glib ! */
+					msg_err("too many words found: %d, stop tokenization to avoid DoS",
+							res->len);
+
+					goto end;
+				}
+
+				g_array_append_val(res, token);
+			}
+
+			/* Also check for long text mode */
+			if (long_text_mode) {
+				/* Check time each 128 words added */
+				const int words_check_mask = 0x7F;
+
+				if ((res->len & words_check_mask) == words_check_mask) {
+					ev_tstamp now = ev_time();
+
+					if (now - start > max_exec_time) {
+						msg_warn_pool_check(
+							"too long time has been spent on tokenization:"
+							" %.1f ms, limit is %.1f ms; %d words added so far",
+							(now - start) * 1e3, max_exec_time * 1e3,
+							res->len);
+
+						goto end;
+					}
+				}
+			}
+
+			last = p;
+			p = ubrk_next(bi);
+
+			if (p != UBRK_DONE && p <= last) {
+				msg_warn_pool_check("tokenization reversed back on position %d,"
+									"%d new position (%d backward), likely libicu bug!",
+									(gint) (p), (gint) (last), last - p);
+
+				goto end;
+			}
+		}
+	}
+
+end:
+	if (!decay) {
+		hv = mum_hash_finish(hv);
+	}
+
+	if (hash) {
+		*hash = hv;
+	}
+
+	return res;
+}
+
+#undef SHIFT_EX
+
+static void
+rspamd_add_metawords_from_str(const gchar *beg, gsize len,
+							  struct rspamd_task *task)
+{
+	UText utxt = UTEXT_INITIALIZER;
+	UErrorCode uc_err = U_ZERO_ERROR;
+	guint i = 0;
+	UChar32 uc;
+	gboolean valid_utf = TRUE;
+
+	while (i < len) {
+		U8_NEXT(beg, i, len, uc);
+
+		if (((gint32) uc) < 0) {
+			valid_utf = FALSE;
+			break;
+		}
+
+#if U_ICU_VERSION_MAJOR_NUM < 50
+		if (u_isalpha(uc)) {
+			gint32 sc = ublock_getCode(uc);
+
+			if (sc == UBLOCK_THAI) {
+				valid_utf = FALSE;
+				msg_info_task("enable workaround for Thai characters for old libicu");
+				break;
+			}
+		}
+#endif
+	}
+
+	if (valid_utf) {
+		utext_openUTF8(&utxt,
+					   beg,
+					   len,
+					   &uc_err);
+
+		task->meta_words = rspamd_tokenize_text(beg, len,
+												&utxt, RSPAMD_TOKENIZE_UTF,
+												task->cfg, NULL, NULL,
+												task->meta_words,
+												task->task_pool);
+
+		utext_close(&utxt);
+	}
+	else {
+		task->meta_words = rspamd_tokenize_text(beg, len,
+												NULL, RSPAMD_TOKENIZE_RAW,
+												task->cfg, NULL, NULL, task->meta_words,
+												task->task_pool);
+	}
+}
+
+void rspamd_tokenize_meta_words(struct rspamd_task *task)
+{
+	guint i = 0;
+	rspamd_stat_token_t *tok;
+
+	if (MESSAGE_FIELD(task, subject)) {
+		rspamd_add_metawords_from_str(MESSAGE_FIELD(task, subject),
+									  strlen(MESSAGE_FIELD(task, subject)), task);
+	}
+
+	if (MESSAGE_FIELD(task, from_mime) && MESSAGE_FIELD(task, from_mime)->len > 0) {
+		struct rspamd_email_address *addr;
+
+		addr = g_ptr_array_index(MESSAGE_FIELD(task, from_mime), 0);
+
+		if (addr->name) {
+			rspamd_add_metawords_from_str(addr->name, strlen(addr->name), task);
+		}
+	}
+
+	if (task->meta_words != NULL) {
+		const gchar *language = NULL;
+
+		if (MESSAGE_FIELD(task, text_parts) &&
+			MESSAGE_FIELD(task, text_parts)->len > 0) {
+			struct rspamd_mime_text_part *tp = g_ptr_array_index(
+				MESSAGE_FIELD(task, text_parts), 0);
+
+			if (tp->language) {
+				language = tp->language;
+			}
+		}
+
+		rspamd_normalize_words(task->meta_words, task->task_pool);
+		rspamd_stem_words(task->meta_words, task->task_pool, language,
+						  task->lang_det);
+
+		for (i = 0; i < task->meta_words->len; i++) {
+			tok = &g_array_index(task->meta_words, rspamd_stat_token_t, i);
+			tok->flags |= RSPAMD_STAT_TOKEN_FLAG_HEADER;
+		}
+	}
+}
+
+static inline void
+rspamd_uchars_to_ucs32(const UChar *src, gsize srclen,
+					   rspamd_stat_token_t *tok,
+					   rspamd_mempool_t *pool)
+{
+	UChar32 *dest, t, *d;
+	gint32 i = 0;
+
+	dest = rspamd_mempool_alloc(pool, srclen * sizeof(UChar32));
+	d = dest;
+
+	while (i < srclen) {
+		U16_NEXT_UNSAFE(src, i, t);
+
+		if (u_isgraph(t)) {
+			UCharCategory cat;
+
+			cat = u_charType(t);
+#if U_ICU_VERSION_MAJOR_NUM >= 57
+			if (u_hasBinaryProperty(t, UCHAR_EMOJI)) {
+				tok->flags |= RSPAMD_STAT_TOKEN_FLAG_EMOJI;
+			}
+#endif
+
+			if ((cat >= U_UPPERCASE_LETTER && cat <= U_OTHER_NUMBER) ||
+				cat == U_CONNECTOR_PUNCTUATION ||
+				cat == U_MATH_SYMBOL ||
+				cat == U_CURRENCY_SYMBOL) {
+				*d++ = u_tolower(t);
+			}
+		}
+		else {
+			/* Invisible spaces ! */
+			tok->flags |= RSPAMD_STAT_TOKEN_FLAG_INVISIBLE_SPACES;
+		}
+	}
+
+	tok->unicode.begin = dest;
+	tok->unicode.len = d - dest;
+}
+
+static inline void
+rspamd_ucs32_to_normalised(rspamd_stat_token_t *tok,
+						   rspamd_mempool_t *pool)
+{
+	guint i, doff = 0;
+	gsize utflen = 0;
+	gchar *dest;
+	UChar32 t;
+
+	for (i = 0; i < tok->unicode.len; i++) {
+		utflen += U8_LENGTH(tok->unicode.begin[i]);
+	}
+
+	dest = rspamd_mempool_alloc(pool, utflen + 1);
+
+	for (i = 0; i < tok->unicode.len; i++) {
+		t = tok->unicode.begin[i];
+		U8_APPEND_UNSAFE(dest, doff, t);
+	}
+
+	g_assert(doff <= utflen);
+	dest[doff] = '\0';
+
+	tok->normalized.len = doff;
+	tok->normalized.begin = dest;
+}
+
+void rspamd_normalize_single_word(rspamd_stat_token_t *tok, rspamd_mempool_t *pool)
+{
+	UErrorCode uc_err = U_ZERO_ERROR;
+	UConverter *utf8_converter;
+	UChar tmpbuf[1024]; /* Assume that we have no longer words... */
+	gsize ulen;
+
+	utf8_converter = rspamd_get_utf8_converter();
+
+	if (tok->flags & RSPAMD_STAT_TOKEN_FLAG_UTF) {
+		ulen = ucnv_toUChars(utf8_converter,
+							 tmpbuf,
+							 G_N_ELEMENTS(tmpbuf),
+							 tok->original.begin,
+							 tok->original.len,
+							 &uc_err);
+
+		/* Now, we need to understand if we need to normalise the word */
+		if (!U_SUCCESS(uc_err)) {
+			tok->flags |= RSPAMD_STAT_TOKEN_FLAG_BROKEN_UNICODE;
+			tok->unicode.begin = NULL;
+			tok->unicode.len = 0;
+			tok->normalized.begin = NULL;
+			tok->normalized.len = 0;
+		}
+		else {
+#if U_ICU_VERSION_MAJOR_NUM >= 44
+			const UNormalizer2 *norm = rspamd_get_unicode_normalizer();
+			gint32 end;
+
+			/* We can now check if we need to decompose */
+			end = unorm2_spanQuickCheckYes(norm, tmpbuf, ulen, &uc_err);
+
+			if (!U_SUCCESS(uc_err)) {
+				rspamd_uchars_to_ucs32(tmpbuf, ulen, tok, pool);
+				tok->normalized.begin = NULL;
+				tok->normalized.len = 0;
+				tok->flags |= RSPAMD_STAT_TOKEN_FLAG_BROKEN_UNICODE;
+			}
+			else {
+				if (end == ulen) {
+					/* Already normalised, just lowercase */
+					rspamd_uchars_to_ucs32(tmpbuf, ulen, tok, pool);
+					rspamd_ucs32_to_normalised(tok, pool);
+				}
+				else {
+					/* Perform normalization */
+					UChar normbuf[1024];
+
+					g_assert(end < G_N_ELEMENTS(normbuf));
+					/* First part */
+					memcpy(normbuf, tmpbuf, end * sizeof(UChar));
+					/* Second part */
+					ulen = unorm2_normalizeSecondAndAppend(norm,
+														   normbuf, end,
+														   G_N_ELEMENTS(normbuf),
+														   tmpbuf + end,
+														   ulen - end,
+														   &uc_err);
+
+					if (!U_SUCCESS(uc_err)) {
+						if (uc_err != U_BUFFER_OVERFLOW_ERROR) {
+							msg_warn_pool_check("cannot normalise text '%*s': %s",
+												(gint) tok->original.len, tok->original.begin,
+												u_errorName(uc_err));
+							rspamd_uchars_to_ucs32(tmpbuf, ulen, tok, pool);
+							rspamd_ucs32_to_normalised(tok, pool);
+							tok->flags |= RSPAMD_STAT_TOKEN_FLAG_BROKEN_UNICODE;
+						}
+					}
+					else {
+						/* Copy normalised back */
+						rspamd_uchars_to_ucs32(normbuf, ulen, tok, pool);
+						tok->flags |= RSPAMD_STAT_TOKEN_FLAG_NORMALISED;
+						rspamd_ucs32_to_normalised(tok, pool);
+					}
+				}
+			}
+#else
+			/* Legacy version with no unorm2 interface */
+			rspamd_uchars_to_ucs32(tmpbuf, ulen, tok, pool);
+			rspamd_ucs32_to_normalised(tok, pool);
+#endif
+		}
+	}
+	else {
+		if (tok->flags & RSPAMD_STAT_TOKEN_FLAG_TEXT) {
+			/* Simple lowercase */
+			gchar *dest;
+
+			dest = rspamd_mempool_alloc(pool, tok->original.len + 1);
+			rspamd_strlcpy(dest, tok->original.begin, tok->original.len + 1);
+			rspamd_str_lc(dest, tok->original.len);
+			tok->normalized.len = tok->original.len;
+			tok->normalized.begin = dest;
+		}
+	}
+}
+
+void rspamd_normalize_words(GArray *words, rspamd_mempool_t *pool)
+{
+	rspamd_stat_token_t *tok;
+	guint i;
+
+	for (i = 0; i < words->len; i++) {
+		tok = &g_array_index(words, rspamd_stat_token_t, i);
+		rspamd_normalize_single_word(tok, pool);
+	}
+}
+
+void rspamd_stem_words(GArray *words, rspamd_mempool_t *pool,
+					   const gchar *language,
+					   struct rspamd_lang_detector *lang_detector)
+{
+	static GHashTable *stemmers = NULL;
+	struct sb_stemmer *stem = NULL;
+	guint i;
+	rspamd_stat_token_t *tok;
+	gchar *dest;
+	gsize dlen;
+
+	if (!stemmers) {
+		stemmers = g_hash_table_new(rspamd_strcase_hash,
+									rspamd_strcase_equal);
+	}
+
+	if (language && language[0] != '\0') {
+		stem = g_hash_table_lookup(stemmers, language);
+
+		if (stem == NULL) {
+
+			stem = sb_stemmer_new(language, "UTF_8");
+
+			if (stem == NULL) {
+				msg_debug_pool(
+					"cannot create lemmatizer for %s language",
+					language);
+				g_hash_table_insert(stemmers, g_strdup(language),
+									GINT_TO_POINTER(-1));
+			}
+			else {
+				g_hash_table_insert(stemmers, g_strdup(language),
+									stem);
+			}
+		}
+		else if (stem == GINT_TO_POINTER(-1)) {
+			/* Negative cache */
+			stem = NULL;
+		}
+	}
+	for (i = 0; i < words->len; i++) {
+		tok = &g_array_index(words, rspamd_stat_token_t, i);
+
+		if (tok->flags & RSPAMD_STAT_TOKEN_FLAG_UTF) {
+			if (stem) {
+				const gchar *stemmed = NULL;
+
+				stemmed = sb_stemmer_stem(stem,
+										  tok->normalized.begin, tok->normalized.len);
+
+				dlen = sb_stemmer_length(stem);
+
+				if (stemmed != NULL && dlen > 0) {
+					dest = rspamd_mempool_alloc(pool, dlen);
+					memcpy(dest, stemmed, dlen);
+					tok->stemmed.len = dlen;
+					tok->stemmed.begin = dest;
+					tok->flags |= RSPAMD_STAT_TOKEN_FLAG_STEMMED;
+				}
+				else {
+					/* Fallback */
+					tok->stemmed.len = tok->normalized.len;
+					tok->stemmed.begin = tok->normalized.begin;
+				}
+			}
+			else {
+				tok->stemmed.len = tok->normalized.len;
+				tok->stemmed.begin = tok->normalized.begin;
+			}
+
+			if (tok->stemmed.len > 0 && lang_detector != NULL &&
+				rspamd_language_detector_is_stop_word(lang_detector, tok->stemmed.begin, tok->stemmed.len)) {
+				tok->flags |= RSPAMD_STAT_TOKEN_FLAG_STOP_WORD;
+			}
+		}
+		else {
+			if (tok->flags & RSPAMD_STAT_TOKEN_FLAG_TEXT) {
+				/* Raw text, lowercase */
+				tok->stemmed.len = tok->normalized.len;
+				tok->stemmed.begin = tok->normalized.begin;
+			}
+		}
+	}
+}
\ No newline at end of file