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diff --git a/src/lookups/cdb.c b/src/lookups/cdb.c
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+/*************************************************
+* Exim - an Internet mail transport agent *
+*************************************************/
+
+/*
+ * Exim - CDB database lookup module
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ * Copyright (c) 1998 Nigel Metheringham, Planet Online Ltd
+ * Copyright (c) The Exim Maintainers 2020
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * --------------------------------------------------------------
+ * Modified by PH for Exim 4:
+ * Changed over to using unsigned chars
+ * Makes use of lf_check_file() for file checking
+ * --------------------------------------------------------------
+ * Modified by The Exim Maintainers 2015:
+ * const propagation
+ * --------------------------------------------------------------
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ *
+ *
+ * This code implements Dan Bernstein's Constant DataBase (cdb) spec.
+ * Information, the spec and sample code for cdb can be obtained from
+ * http://www.pobox.com/~djb/cdb.html
+ *
+ * This implementation borrows some code from Dan Bernstein's
+ * implementation (which has no license restrictions applied to it).
+ * This (read-only) implementation is completely contained within
+ * cdb.[ch] it does *not* link against an external cdb library.
+ *
+ *
+ * There are 2 variants included within this code. One uses MMAP and
+ * should give better performance especially for multiple lookups on a
+ * modern machine. The other is the default implementation which is
+ * used in the case where the MMAP fails or if MMAP was not compiled
+ * in. this implementation is the same as the original reference cdb
+ * implementation. The MMAP version is compiled in if the HAVE_MMAP
+ * preprocessor define is defined - this should be set in the system
+ * specific os.h file.
+ *
+ */
+
+
+#include "../exim.h"
+#include "lf_functions.h"
+
+#ifdef HAVE_MMAP
+# include <sys/mman.h>
+/* Not all implementations declare MAP_FAILED */
+# ifndef MAP_FAILED
+# define MAP_FAILED ((void *) -1)
+# endif /* MAP_FAILED */
+#endif /* HAVE_MMAP */
+
+
+#define CDB_HASH_SPLIT 256 /* num pieces the hash table is split into */
+#define CDB_HASH_MASK 255 /* mask to and off split value */
+#define CDB_HASH_ENTRY 8 /* how big each offset it */
+#define CDB_HASH_TABLE (CDB_HASH_SPLIT * CDB_HASH_ENTRY)
+
+/* State information for cdb databases that are open NB while the db
+ * is open its contents will not change (cdb dbs are normally updated
+ * atomically by renaming). However the lifetime of one of these
+ * state structures should be limited - ie a long running daemon
+ * that opens one may hit problems....
+ */
+
+struct cdb_state {
+ int fileno;
+ off_t filelen;
+ uschar *cdb_map;
+ uschar *cdb_offsets;
+};
+
+/* 32 bit unsigned type - this is an int on all modern machines */
+typedef unsigned int uint32;
+
+/*
+ * cdb_hash()
+ * Internal function to make hash value */
+
+static uint32
+cdb_hash(const uschar *buf, unsigned int len)
+{
+ uint32 h;
+
+ h = 5381;
+ while (len) {
+ --len;
+ h += (h << 5);
+ h ^= (uint32) *buf++;
+ }
+ return h;
+}
+
+/*
+ * cdb_bread()
+ * Internal function to read len bytes from disk, coping with oddities */
+
+static int
+cdb_bread(int fd,
+ uschar *buf,
+ int len)
+{
+ int r;
+ while (len > 0) {
+ do
+ r = Uread(fd,buf,len);
+ while ((r == -1) && (errno == EINTR));
+ if (r == -1) return -1;
+ if (r == 0) { errno = EIO; return -1; }
+ buf += r;
+ len -= r;
+ }
+ return 0;
+}
+
+/*
+ * cdb_bread()
+ * Internal function to parse 4 byte number (endian independent) */
+
+static uint32
+cdb_unpack(uschar *buf)
+{
+uint32 num;
+num = buf[3]; num <<= 8;
+num += buf[2]; num <<= 8;
+num += buf[1]; num <<= 8;
+num += buf[0];
+return num;
+}
+
+static void cdb_close(void *handle);
+
+static void *
+cdb_open(const uschar * filename, uschar ** errmsg)
+{
+int fileno;
+struct cdb_state *cdbp;
+struct stat statbuf;
+void * mapbuf;
+
+if ((fileno = Uopen(filename, O_RDONLY, 0)) < 0)
+ {
+ int save_errno = errno;
+ *errmsg = string_open_failed(errno, "%s for cdb lookup", filename);
+ errno = save_errno;
+ return NULL;
+ }
+
+if (fstat(fileno, &statbuf) != 0)
+ {
+ int save_errno = errno;
+ *errmsg = string_open_failed(errno,
+ "fstat(%s) failed - cannot do cdb lookup",
+ filename);
+ errno = save_errno;
+ return NULL;
+ }
+
+/* If this is a valid file, then it *must* be at least
+CDB_HASH_TABLE bytes long */
+
+if (statbuf.st_size < CDB_HASH_TABLE)
+ {
+ int save_errno = errno;
+ *errmsg = string_open_failed(errno,
+ "%s too short for cdb lookup",
+ filename);
+ errno = save_errno;
+ return NULL;
+ }
+
+/* Having got a file open we need the structure to put things in */
+cdbp = store_get(sizeof(struct cdb_state), FALSE);
+/* store_get() does not return if memory was not available... */
+/* preload the structure.... */
+cdbp->fileno = fileno;
+cdbp->filelen = statbuf.st_size;
+cdbp->cdb_map = NULL;
+cdbp->cdb_offsets = NULL;
+
+/* if we are allowed to we use mmap here.... */
+#ifdef HAVE_MMAP
+if ((mapbuf = mmap(NULL, statbuf.st_size, PROT_READ, MAP_SHARED, fileno, 0))
+ != MAP_FAILED)
+ {
+ /* We have an mmap-ed section. Now we can just use it */
+ cdbp->cdb_map = mapbuf;
+ /* The offsets can be set to the same value since they should
+ * effectively be cached as well
+ */
+ cdbp->cdb_offsets = mapbuf;
+
+ /* Now return the state struct */
+ return(cdbp);
+ }
+
+/* If we got here the map failed. Basically we can ignore this since we fall
+back to slower methods.... However lets debug log it... */
+
+DEBUG(D_lookup) debug_printf_indent("cdb mmap failed - %d\n", errno);
+#endif /* HAVE_MMAP */
+
+/* In this case we have either not got MMAP allowed, or it failed */
+
+/* get a buffer to stash the basic offsets in - this should speed
+things up a lot - especially on multiple lookups */
+
+cdbp->cdb_offsets = store_get(CDB_HASH_TABLE, FALSE);
+
+/* now fill the buffer up... */
+
+if (cdb_bread(fileno, cdbp->cdb_offsets, CDB_HASH_TABLE) == -1)
+ {
+ /* read of hash table failed, oh dear, oh..... time to give up I think....
+ call the close routine (deallocs the memory), and return NULL */
+
+ *errmsg = string_open_failed(errno,
+ "cannot read header from %s for cdb lookup",
+ filename);
+ cdb_close(cdbp);
+ return NULL;
+ }
+
+/* Everything else done - return the cache structure */
+return cdbp;
+}
+
+
+
+/*************************************************
+* Check entry point *
+*************************************************/
+
+static BOOL
+cdb_check(void * handle, const uschar * filename, int modemask,
+ uid_t * owners, gid_t * owngroups, uschar ** errmsg)
+{
+struct cdb_state * cdbp = handle;
+return lf_check_file(cdbp->fileno, filename, S_IFREG, modemask,
+ owners, owngroups, "cdb", errmsg) == 0;
+}
+
+
+
+/*************************************************
+* Find entry point *
+*************************************************/
+
+static int
+cdb_find(void * handle, const uschar * filename, const uschar * keystring,
+ int key_len, uschar ** result, uschar ** errmsg, uint * do_cache,
+ const uschar * opts)
+{
+struct cdb_state * cdbp = handle;
+uint32 item_key_len,
+item_dat_len,
+key_hash,
+item_hash,
+item_posn,
+cur_offset,
+end_offset,
+hash_offset_entry,
+hash_offset,
+hash_offlen,
+hash_slotnm;
+
+/* Keep picky compilers happy */
+do_cache = do_cache;
+
+key_hash = cdb_hash(keystring, key_len);
+
+hash_offset_entry = CDB_HASH_ENTRY * (key_hash & CDB_HASH_MASK);
+hash_offset = cdb_unpack(cdbp->cdb_offsets + hash_offset_entry);
+hash_offlen = cdb_unpack(cdbp->cdb_offsets + hash_offset_entry + 4);
+
+/* If the offset length is zero this key cannot be in the file */
+
+if (hash_offlen == 0)
+ return FAIL;
+
+hash_slotnm = (key_hash >> 8) % hash_offlen;
+
+/* check to ensure that the file is not corrupt
+ * if the hash_offset + (hash_offlen * CDB_HASH_ENTRY) is longer
+ * than the file, then we have problems.... */
+
+if ((hash_offset + (hash_offlen * CDB_HASH_ENTRY)) > cdbp->filelen)
+ {
+ *errmsg = string_sprintf("cdb: corrupt cdb file %s (too short)",
+ filename);
+ DEBUG(D_lookup) debug_printf_indent("%s\n", *errmsg);
+ return DEFER;
+ }
+
+cur_offset = hash_offset + (hash_slotnm * CDB_HASH_ENTRY);
+end_offset = hash_offset + (hash_offlen * CDB_HASH_ENTRY);
+
+/* if we are allowed to we use mmap here.... */
+
+#ifdef HAVE_MMAP
+/* make sure the mmap was OK */
+if (cdbp->cdb_map != NULL)
+ {
+ uschar * cur_pos = cur_offset + cdbp->cdb_map;
+ uschar * end_pos = end_offset + cdbp->cdb_map;
+
+ for (int loop = 0; (loop < hash_offlen); ++loop)
+ {
+ item_hash = cdb_unpack(cur_pos);
+ cur_pos += 4;
+ item_posn = cdb_unpack(cur_pos);
+ cur_pos += 4;
+
+ /* if the position is zero then we have a definite miss */
+
+ if (item_posn == 0)
+ return FAIL;
+
+ if (item_hash == key_hash)
+ { /* matching hash value */
+ uschar * item_ptr = cdbp->cdb_map + item_posn;
+
+ item_key_len = cdb_unpack(item_ptr);
+ item_ptr += 4;
+ item_dat_len = cdb_unpack(item_ptr);
+ item_ptr += 4;
+
+ /* check key length matches */
+
+ if (item_key_len == key_len)
+ {
+ /* finally check if key matches */
+ if (Ustrncmp(keystring, item_ptr, key_len) == 0)
+ {
+ /* we have a match.... * make item_ptr point to data */
+
+ item_ptr += item_key_len;
+
+ /* ... and the returned result. Assume it is not
+ tainted, lacking any way of telling. */
+
+ *result = store_get(item_dat_len + 1, FALSE);
+ memcpy(*result, item_ptr, item_dat_len);
+ (*result)[item_dat_len] = 0;
+ return OK;
+ }
+ }
+ }
+ /* handle warp round of table */
+ if (cur_pos == end_pos)
+ cur_pos = cdbp->cdb_map + hash_offset;
+ }
+ /* looks like we failed... */
+ return FAIL;
+ }
+
+#endif /* HAVE_MMAP */
+
+for (int loop = 0; (loop < hash_offlen); ++loop)
+ {
+ uschar packbuf[8];
+
+ if (lseek(cdbp->fileno, (off_t) cur_offset, SEEK_SET) == -1) return DEFER;
+ if (cdb_bread(cdbp->fileno, packbuf, 8) == -1) return DEFER;
+
+ item_hash = cdb_unpack(packbuf);
+ item_posn = cdb_unpack(packbuf + 4);
+
+ /* if the position is zero then we have a definite miss */
+
+ if (item_posn == 0)
+ return FAIL;
+
+ if (item_hash == key_hash)
+ { /* matching hash value */
+ if (lseek(cdbp->fileno, (off_t) item_posn, SEEK_SET) == -1) return DEFER;
+ if (cdb_bread(cdbp->fileno, packbuf, 8) == -1) return DEFER;
+
+ item_key_len = cdb_unpack(packbuf);
+
+ /* check key length matches */
+
+ if (item_key_len == key_len)
+ { /* finally check if key matches */
+ rmark reset_point = store_mark();
+ uschar * item_key = store_get(key_len, TRUE); /* keys liable to be tainted */
+
+ if (cdb_bread(cdbp->fileno, item_key, key_len) == -1) return DEFER;
+ if (Ustrncmp(keystring, item_key, key_len) == 0)
+ {
+ /* Reclaim some store */
+ store_reset(reset_point);
+
+ /* matches - get data length */
+ item_dat_len = cdb_unpack(packbuf + 4);
+
+ /* then we build a new result string. We know we have enough
+ memory so disable Coverity errors about the tainted item_dat_ken */
+
+ *result = store_get(item_dat_len + 1, FALSE);
+ /* coverity[tainted_data] */
+ if (cdb_bread(cdbp->fileno, *result, item_dat_len) == -1)
+ return DEFER;
+
+ /* coverity[tainted_data] */
+ (*result)[item_dat_len] = 0;
+ return OK;
+ }
+ /* Reclaim some store */
+ store_reset(reset_point);
+ }
+ }
+ cur_offset += 8;
+
+ /* handle warp round of table */
+ if (cur_offset == end_offset)
+ cur_offset = hash_offset;
+ }
+return FAIL;
+}
+
+
+
+/*************************************************
+* Close entry point *
+*************************************************/
+
+/* See local README for interface description */
+
+static void
+cdb_close(void *handle)
+{
+struct cdb_state * cdbp = handle;
+
+#ifdef HAVE_MMAP
+if (cdbp->cdb_map)
+ {
+ munmap(CS cdbp->cdb_map, cdbp->filelen);
+ if (cdbp->cdb_map == cdbp->cdb_offsets)
+ cdbp->cdb_offsets = NULL;
+ }
+#endif /* HAVE_MMAP */
+
+(void)close(cdbp->fileno);
+}
+
+
+
+/*************************************************
+* Version reporting entry point *
+*************************************************/
+
+/* See local README for interface description. */
+
+#include "../version.h"
+
+void
+cdb_version_report(FILE *f)
+{
+#ifdef DYNLOOKUP
+fprintf(f, "Library version: CDB: Exim version %s\n", EXIM_VERSION_STR);
+#endif
+}
+
+
+lookup_info cdb_lookup_info = {
+ .name = US"cdb", /* lookup name */
+ .type = lookup_absfile, /* absolute file name */
+ .open = cdb_open, /* open function */
+ .check = cdb_check, /* check function */
+ .find = cdb_find, /* find function */
+ .close = cdb_close, /* close function */
+ .tidy = NULL, /* no tidy function */
+ .quote = NULL, /* no quoting function */
+ .version_report = cdb_version_report /* version reporting */
+};
+
+#ifdef DYNLOOKUP
+#define cdb_lookup_module_info _lookup_module_info
+#endif
+
+static lookup_info *_lookup_list[] = { &cdb_lookup_info };
+lookup_module_info cdb_lookup_module_info = { LOOKUP_MODULE_INFO_MAGIC, _lookup_list, 1 };
+
+/* End of lookups/cdb.c */
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