--- /dev/null
+/*
+ * gzlog.c
+ * Copyright (C) 2004, 2008, 2012, 2016 Mark Adler, all rights reserved
+ * For conditions of distribution and use, see copyright notice in gzlog.h
+ * version 2.2, 14 Aug 2012
+ */
+
+/*
+ gzlog provides a mechanism for frequently appending short strings to a gzip
+ file that is efficient both in execution time and compression ratio. The
+ strategy is to write the short strings in an uncompressed form to the end of
+ the gzip file, only compressing when the amount of uncompressed data has
+ reached a given threshold.
+
+ gzlog also provides protection against interruptions in the process due to
+ system crashes. The status of the operation is recorded in an extra field
+ in the gzip file, and is only updated once the gzip file is brought to a
+ valid state. The last data to be appended or compressed is saved in an
+ auxiliary file, so that if the operation is interrupted, it can be completed
+ the next time an append operation is attempted.
+
+ gzlog maintains another auxiliary file with the last 32K of data from the
+ compressed portion, which is preloaded for the compression of the subsequent
+ data. This minimizes the impact to the compression ratio of appending.
+ */
+
+/*
+ Operations Concept:
+
+ Files (log name "foo"):
+ foo.gz -- gzip file with the complete log
+ foo.add -- last message to append or last data to compress
+ foo.dict -- dictionary of the last 32K of data for next compression
+ foo.temp -- temporary dictionary file for compression after this one
+ foo.lock -- lock file for reading and writing the other files
+ foo.repairs -- log file for log file recovery operations (not compressed)
+
+ gzip file structure:
+ - fixed-length (no file name) header with extra field (see below)
+ - compressed data ending initially with empty stored block
+ - uncompressed data filling out originally empty stored block and
+ subsequent stored blocks as needed (16K max each)
+ - gzip trailer
+ - no junk at end (no other gzip streams)
+
+ When appending data, the information in the first three items above plus the
+ foo.add file are sufficient to recover an interrupted append operation. The
+ extra field has the necessary information to restore the start of the last
+ stored block and determine where to append the data in the foo.add file, as
+ well as the crc and length of the gzip data before the append operation.
+
+ The foo.add file is created before the gzip file is marked for append, and
+ deleted after the gzip file is marked as complete. So if the append
+ operation is interrupted, the data to add will still be there. If due to
+ some external force, the foo.add file gets deleted between when the append
+ operation was interrupted and when recovery is attempted, the gzip file will
+ still be restored, but without the appended data.
+
+ When compressing data, the information in the first two items above plus the
+ foo.add file are sufficient to recover an interrupted compress operation.
+ The extra field has the necessary information to find the end of the
+ compressed data, and contains both the crc and length of just the compressed
+ data and of the complete set of data including the contents of the foo.add
+ file.
+
+ Again, the foo.add file is maintained during the compress operation in case
+ of an interruption. If in the unlikely event the foo.add file with the data
+ to be compressed is missing due to some external force, a gzip file with
+ just the previous compressed data will be reconstructed. In this case, all
+ of the data that was to be compressed is lost (approximately one megabyte).
+ This will not occur if all that happened was an interruption of the compress
+ operation.
+
+ The third state that is marked is the replacement of the old dictionary with
+ the new dictionary after a compress operation. Once compression is
+ complete, the gzip file is marked as being in the replace state. This
+ completes the gzip file, so an interrupt after being so marked does not
+ result in recompression. Then the dictionary file is replaced, and the gzip
+ file is marked as completed. This state prevents the possibility of
+ restarting compression with the wrong dictionary file.
+
+ All three operations are wrapped by a lock/unlock procedure. In order to
+ gain exclusive access to the log files, first a foo.lock file must be
+ exclusively created. When all operations are complete, the lock is
+ released by deleting the foo.lock file. If when attempting to create the
+ lock file, it already exists and the modify time of the lock file is more
+ than five minutes old (set by the PATIENCE define below), then the old
+ lock file is considered stale and deleted, and the exclusive creation of
+ the lock file is retried. To assure that there are no false assessments
+ of the staleness of the lock file, the operations periodically touch the
+ lock file to update the modified date.
+
+ Following is the definition of the extra field with all of the information
+ required to enable the above append and compress operations and their
+ recovery if interrupted. Multi-byte values are stored little endian
+ (consistent with the gzip format). File pointers are eight bytes long.
+ The crc's and lengths for the gzip trailer are four bytes long. (Note that
+ the length at the end of a gzip file is used for error checking only, and
+ for large files is actually the length modulo 2^32.) The stored block
+ length is two bytes long. The gzip extra field two-byte identification is
+ "ap" for append. It is assumed that writing the extra field to the file is
+ an "atomic" operation. That is, either all of the extra field is written
+ to the file, or none of it is, if the operation is interrupted right at the
+ point of updating the extra field. This is a reasonable assumption, since
+ the extra field is within the first 52 bytes of the file, which is smaller
+ than any expected block size for a mass storage device (usually 512 bytes or
+ larger).
+
+ Extra field (35 bytes):
+ - Pointer to first stored block length -- this points to the two-byte length
+ of the first stored block, which is followed by the two-byte, one's
+ complement of that length. The stored block length is preceded by the
+ three-bit header of the stored block, which is the actual start of the
+ stored block in the deflate format. See the bit offset field below.
+ - Pointer to the last stored block length. This is the same as above, but
+ for the last stored block of the uncompressed data in the gzip file.
+ Initially this is the same as the first stored block length pointer.
+ When the stored block gets to 16K (see the MAX_STORE define), then a new
+ stored block as added, at which point the last stored block length pointer
+ is different from the first stored block length pointer. When they are
+ different, the first bit of the last stored block header is eight bits, or
+ one byte back from the block length.
+ - Compressed data crc and length. This is the crc and length of the data
+ that is in the compressed portion of the deflate stream. These are used
+ only in the event that the foo.add file containing the data to compress is
+ lost after a compress operation is interrupted.
+ - Total data crc and length. This is the crc and length of all of the data
+ stored in the gzip file, compressed and uncompressed. It is used to
+ reconstruct the gzip trailer when compressing, as well as when recovering
+ interrupted operations.
+ - Final stored block length. This is used to quickly find where to append,
+ and allows the restoration of the original final stored block state when
+ an append operation is interrupted.
+ - First stored block start as the number of bits back from the final stored
+ block first length byte. This value is in the range of 3..10, and is
+ stored as the low three bits of the final byte of the extra field after
+ subtracting three (0..7). This allows the last-block bit of the stored
+ block header to be updated when a new stored block is added, for the case
+ when the first stored block and the last stored block are the same. (When
+ they are different, the numbers of bits back is known to be eight.) This
+ also allows for new compressed data to be appended to the old compressed
+ data in the compress operation, overwriting the previous first stored
+ block, or for the compressed data to be terminated and a valid gzip file
+ reconstructed on the off chance that a compression operation was
+ interrupted and the data to compress in the foo.add file was deleted.
+ - The operation in process. This is the next two bits in the last byte (the
+ bits under the mask 0x18). The are interpreted as 0: nothing in process,
+ 1: append in process, 2: compress in process, 3: replace in process.
+ - The top three bits of the last byte in the extra field are reserved and
+ are currently set to zero.
+
+ Main procedure:
+ - Exclusively create the foo.lock file using the O_CREAT and O_EXCL modes of
+ the system open() call. If the modify time of an existing lock file is
+ more than PATIENCE seconds old, then the lock file is deleted and the
+ exclusive create is retried.
+ - Load the extra field from the foo.gz file, and see if an operation was in
+ progress but not completed. If so, apply the recovery procedure below.
+ - Perform the append procedure with the provided data.
+ - If the uncompressed data in the foo.gz file is 1MB or more, apply the
+ compress procedure.
+ - Delete the foo.lock file.
+
+ Append procedure:
+ - Put what to append in the foo.add file so that the operation can be
+ restarted if this procedure is interrupted.
+ - Mark the foo.gz extra field with the append operation in progress.
+ + Restore the original last-block bit and stored block length of the last
+ stored block from the information in the extra field, in case a previous
+ append operation was interrupted.
+ - Append the provided data to the last stored block, creating new stored
+ blocks as needed and updating the stored blocks last-block bits and
+ lengths.
+ - Update the crc and length with the new data, and write the gzip trailer.
+ - Write over the extra field (with a single write operation) with the new
+ pointers, lengths, and crc's, and mark the gzip file as not in process.
+ Though there is still a foo.add file, it will be ignored since nothing
+ is in process. If a foo.add file is leftover from a previously
+ completed operation, it is truncated when writing new data to it.
+ - Delete the foo.add file.
+
+ Compress and replace procedures:
+ - Read all of the uncompressed data in the stored blocks in foo.gz and write
+ it to foo.add. Also write foo.temp with the last 32K of that data to
+ provide a dictionary for the next invocation of this procedure.
+ - Rewrite the extra field marking foo.gz with a compression in process.
+ * If there is no data provided to compress (due to a missing foo.add file
+ when recovering), reconstruct and truncate the foo.gz file to contain
+ only the previous compressed data and proceed to the step after the next
+ one. Otherwise ...
+ - Compress the data with the dictionary in foo.dict, and write to the
+ foo.gz file starting at the bit immediately following the last previously
+ compressed block. If there is no foo.dict, proceed anyway with the
+ compression at slightly reduced efficiency. (For the foo.dict file to be
+ missing requires some external failure beyond simply the interruption of
+ a compress operation.) During this process, the foo.lock file is
+ periodically touched to assure that that file is not considered stale by
+ another process before we're done. The deflation is terminated with a
+ non-last empty static block (10 bits long), that is then located and
+ written over by a last-bit-set empty stored block.
+ - Append the crc and length of the data in the gzip file (previously
+ calculated during the append operations).
+ - Write over the extra field with the updated stored block offsets, bits
+ back, crc's, and lengths, and mark foo.gz as in process for a replacement
+ of the dictionary.
+ @ Delete the foo.add file.
+ - Replace foo.dict with foo.temp.
+ - Write over the extra field, marking foo.gz as complete.
+
+ Recovery procedure:
+ - If not a replace recovery, read in the foo.add file, and provide that data
+ to the appropriate recovery below. If there is no foo.add file, provide
+ a zero data length to the recovery. In that case, the append recovery
+ restores the foo.gz to the previous compressed + uncompressed data state.
+ For the the compress recovery, a missing foo.add file results in foo.gz
+ being restored to the previous compressed-only data state.
+ - Append recovery:
+ - Pick up append at + step above
+ - Compress recovery:
+ - Pick up compress at * step above
+ - Replace recovery:
+ - Pick up compress at @ step above
+ - Log the repair with a date stamp in foo.repairs
+ */
+
+#include <sys/types.h>
+#include <stdio.h> /* rename, fopen, fprintf, fclose */
+#include <stdlib.h> /* malloc, free */
+#include <string.h> /* strlen, strrchr, strcpy, strncpy, strcmp */
+#include <fcntl.h> /* open */
+#include <unistd.h> /* lseek, read, write, close, unlink, sleep, */
+ /* ftruncate, fsync */
+#include <errno.h> /* errno */
+#include <time.h> /* time, ctime */
+#include <sys/stat.h> /* stat */
+#include <sys/time.h> /* utimes */
+#include "zlib.h" /* crc32 */
+
+#include "gzlog.h" /* header for external access */
+
+#define local static
+typedef unsigned int uint;
+typedef unsigned long ulong;
+
+/* Macro for debugging to deterministically force recovery operations */
+#ifdef GZLOG_DEBUG
+ #include <setjmp.h> /* longjmp */
+ jmp_buf gzlog_jump; /* where to go back to */
+ int gzlog_bail = 0; /* which point to bail at (1..8) */
+ int gzlog_count = -1; /* number of times through to wait */
+# define BAIL(n) do { if (n == gzlog_bail && gzlog_count-- == 0) \
+ longjmp(gzlog_jump, gzlog_bail); } while (0)
+#else
+# define BAIL(n)
+#endif
+
+/* how old the lock file can be in seconds before considering it stale */
+#define PATIENCE 300
+
+/* maximum stored block size in Kbytes -- must be in 1..63 */
+#define MAX_STORE 16
+
+/* number of stored Kbytes to trigger compression (must be >= 32 to allow
+ dictionary construction, and <= 204 * MAX_STORE, in order for >> 10 to
+ discard the stored block headers contribution of five bytes each) */
+#define TRIGGER 1024
+
+/* size of a deflate dictionary (this cannot be changed) */
+#define DICT 32768U
+
+/* values for the operation (2 bits) */
+#define NO_OP 0
+#define APPEND_OP 1
+#define COMPRESS_OP 2
+#define REPLACE_OP 3
+
+/* macros to extract little-endian integers from an unsigned byte buffer */
+#define PULL2(p) ((p)[0]+((uint)((p)[1])<<8))
+#define PULL4(p) (PULL2(p)+((ulong)PULL2(p+2)<<16))
+#define PULL8(p) (PULL4(p)+((off_t)PULL4(p+4)<<32))
+
+/* macros to store integers into a byte buffer in little-endian order */
+#define PUT2(p,a) do {(p)[0]=a;(p)[1]=(a)>>8;} while(0)
+#define PUT4(p,a) do {PUT2(p,a);PUT2(p+2,a>>16);} while(0)
+#define PUT8(p,a) do {PUT4(p,a);PUT4(p+4,a>>32);} while(0)
+
+/* internal structure for log information */
+#define LOGID "\106\035\172" /* should be three non-zero characters */
+struct log {
+ char id[4]; /* contains LOGID to detect inadvertent overwrites */
+ int fd; /* file descriptor for .gz file, opened read/write */
+ char *path; /* allocated path, e.g. "/var/log/foo" or "foo" */
+ char *end; /* end of path, for appending suffices such as ".gz" */
+ off_t first; /* offset of first stored block first length byte */
+ int back; /* location of first block id in bits back from first */
+ uint stored; /* bytes currently in last stored block */
+ off_t last; /* offset of last stored block first length byte */
+ ulong ccrc; /* crc of compressed data */
+ ulong clen; /* length (modulo 2^32) of compressed data */
+ ulong tcrc; /* crc of total data */
+ ulong tlen; /* length (modulo 2^32) of total data */
+ time_t lock; /* last modify time of our lock file */
+};
+
+/* gzip header for gzlog */
+local unsigned char log_gzhead[] = {
+ 0x1f, 0x8b, /* magic gzip id */
+ 8, /* compression method is deflate */
+ 4, /* there is an extra field (no file name) */
+ 0, 0, 0, 0, /* no modification time provided */
+ 0, 0xff, /* no extra flags, no OS specified */
+ 39, 0, 'a', 'p', 35, 0 /* extra field with "ap" subfield */
+ /* 35 is EXTRA, 39 is EXTRA + 4 */
+};
+
+#define HEAD sizeof(log_gzhead) /* should be 16 */
+
+/* initial gzip extra field content (52 == HEAD + EXTRA + 1) */
+local unsigned char log_gzext[] = {
+ 52, 0, 0, 0, 0, 0, 0, 0, /* offset of first stored block length */
+ 52, 0, 0, 0, 0, 0, 0, 0, /* offset of last stored block length */
+ 0, 0, 0, 0, 0, 0, 0, 0, /* compressed data crc and length */
+ 0, 0, 0, 0, 0, 0, 0, 0, /* total data crc and length */
+ 0, 0, /* final stored block data length */
+ 5 /* op is NO_OP, last bit 8 bits back */
+};
+
+#define EXTRA sizeof(log_gzext) /* should be 35 */
+
+/* initial gzip data and trailer */
+local unsigned char log_gzbody[] = {
+ 1, 0, 0, 0xff, 0xff, /* empty stored block (last) */
+ 0, 0, 0, 0, /* crc */
+ 0, 0, 0, 0 /* uncompressed length */
+};
+
+#define BODY sizeof(log_gzbody)
+
+/* Exclusively create foo.lock in order to negotiate exclusive access to the
+ foo.* files. If the modify time of an existing lock file is greater than
+ PATIENCE seconds in the past, then consider the lock file to have been
+ abandoned, delete it, and try the exclusive create again. Save the lock
+ file modify time for verification of ownership. Return 0 on success, or -1
+ on failure, usually due to an access restriction or invalid path. Note that
+ if stat() or unlink() fails, it may be due to another process noticing the
+ abandoned lock file a smidge sooner and deleting it, so those are not
+ flagged as an error. */
+local int log_lock(struct log *log)
+{
+ int fd;
+ struct stat st;
+
+ strcpy(log->end, ".lock");
+ while ((fd = open(log->path, O_CREAT | O_EXCL, 0644)) < 0) {
+ if (errno != EEXIST)
+ return -1;
+ if (stat(log->path, &st) == 0 && time(NULL) - st.st_mtime > PATIENCE) {
+ unlink(log->path);
+ continue;
+ }
+ sleep(2); /* relinquish the CPU for two seconds while waiting */
+ }
+ close(fd);
+ if (stat(log->path, &st) == 0)
+ log->lock = st.st_mtime;
+ return 0;
+}
+
+/* Update the modify time of the lock file to now, in order to prevent another
+ task from thinking that the lock is stale. Save the lock file modify time
+ for verification of ownership. */
+local void log_touch(struct log *log)
+{
+ struct stat st;
+
+ strcpy(log->end, ".lock");
+ utimes(log->path, NULL);
+ if (stat(log->path, &st) == 0)
+ log->lock = st.st_mtime;
+}
+
+/* Check the log file modify time against what is expected. Return true if
+ this is not our lock. If it is our lock, touch it to keep it. */
+local int log_check(struct log *log)
+{
+ struct stat st;
+
+ strcpy(log->end, ".lock");
+ if (stat(log->path, &st) || st.st_mtime != log->lock)
+ return 1;
+ log_touch(log);
+ return 0;
+}
+
+/* Unlock a previously acquired lock, but only if it's ours. */
+local void log_unlock(struct log *log)
+{
+ if (log_check(log))
+ return;
+ strcpy(log->end, ".lock");
+ unlink(log->path);
+ log->lock = 0;
+}
+
+/* Check the gzip header and read in the extra field, filling in the values in
+ the log structure. Return op on success or -1 if the gzip header was not as
+ expected. op is the current operation in progress last written to the extra
+ field. This assumes that the gzip file has already been opened, with the
+ file descriptor log->fd. */
+local int log_head(struct log *log)
+{
+ int op;
+ unsigned char buf[HEAD + EXTRA];
+
+ if (lseek(log->fd, 0, SEEK_SET) < 0 ||
+ read(log->fd, buf, HEAD + EXTRA) != HEAD + EXTRA ||
+ memcmp(buf, log_gzhead, HEAD)) {
+ return -1;
+ }
+ log->first = PULL8(buf + HEAD);
+ log->last = PULL8(buf + HEAD + 8);
+ log->ccrc = PULL4(buf + HEAD + 16);
+ log->clen = PULL4(buf + HEAD + 20);
+ log->tcrc = PULL4(buf + HEAD + 24);
+ log->tlen = PULL4(buf + HEAD + 28);
+ log->stored = PULL2(buf + HEAD + 32);
+ log->back = 3 + (buf[HEAD + 34] & 7);
+ op = (buf[HEAD + 34] >> 3) & 3;
+ return op;
+}
+
+/* Write over the extra field contents, marking the operation as op. Use fsync
+ to assure that the device is written to, and in the requested order. This
+ operation, and only this operation, is assumed to be atomic in order to
+ assure that the log is recoverable in the event of an interruption at any
+ point in the process. Return -1 if the write to foo.gz failed. */
+local int log_mark(struct log *log, int op)
+{
+ int ret;
+ unsigned char ext[EXTRA];
+
+ PUT8(ext, log->first);
+ PUT8(ext + 8, log->last);
+ PUT4(ext + 16, log->ccrc);
+ PUT4(ext + 20, log->clen);
+ PUT4(ext + 24, log->tcrc);
+ PUT4(ext + 28, log->tlen);
+ PUT2(ext + 32, log->stored);
+ ext[34] = log->back - 3 + (op << 3);
+ fsync(log->fd);
+ ret = lseek(log->fd, HEAD, SEEK_SET) < 0 ||
+ write(log->fd, ext, EXTRA) != EXTRA ? -1 : 0;
+ fsync(log->fd);
+ return ret;
+}
+
+/* Rewrite the last block header bits and subsequent zero bits to get to a byte
+ boundary, setting the last block bit if last is true, and then write the
+ remainder of the stored block header (length and one's complement). Leave
+ the file pointer after the end of the last stored block data. Return -1 if
+ there is a read or write failure on the foo.gz file */
+local int log_last(struct log *log, int last)
+{
+ int back, len, mask;
+ unsigned char buf[6];
+
+ /* determine the locations of the bytes and bits to modify */
+ back = log->last == log->first ? log->back : 8;
+ len = back > 8 ? 2 : 1; /* bytes back from log->last */
+ mask = 0x80 >> ((back - 1) & 7); /* mask for block last-bit */
+
+ /* get the byte to modify (one or two back) into buf[0] -- don't need to
+ read the byte if the last-bit is eight bits back, since in that case
+ the entire byte will be modified */
+ buf[0] = 0;
+ if (back != 8 && (lseek(log->fd, log->last - len, SEEK_SET) < 0 ||
+ read(log->fd, buf, 1) != 1))
+ return -1;
+
+ /* change the last-bit of the last stored block as requested -- note
+ that all bits above the last-bit are set to zero, per the type bits
+ of a stored block being 00 and per the convention that the bits to
+ bring the stream to a byte boundary are also zeros */
+ buf[1] = 0;
+ buf[2 - len] = (*buf & (mask - 1)) + (last ? mask : 0);
+
+ /* write the modified stored block header and lengths, move the file
+ pointer to after the last stored block data */
+ PUT2(buf + 2, log->stored);
+ PUT2(buf + 4, log->stored ^ 0xffff);
+ return lseek(log->fd, log->last - len, SEEK_SET) < 0 ||
+ write(log->fd, buf + 2 - len, len + 4) != len + 4 ||
+ lseek(log->fd, log->stored, SEEK_CUR) < 0 ? -1 : 0;
+}
+
+/* Append len bytes from data to the locked and open log file. len may be zero
+ if recovering and no .add file was found. In that case, the previous state
+ of the foo.gz file is restored. The data is appended uncompressed in
+ deflate stored blocks. Return -1 if there was an error reading or writing
+ the foo.gz file. */
+local int log_append(struct log *log, unsigned char *data, size_t len)
+{
+ uint put;
+ off_t end;
+ unsigned char buf[8];
+
+ /* set the last block last-bit and length, in case recovering an
+ interrupted append, then position the file pointer to append to the
+ block */
+ if (log_last(log, 1))
+ return -1;
+
+ /* append, adding stored blocks and updating the offset of the last stored
+ block as needed, and update the total crc and length */
+ while (len) {
+ /* append as much as we can to the last block */
+ put = (MAX_STORE << 10) - log->stored;
+ if (put > len)
+ put = (uint)len;
+ if (put) {
+ if (write(log->fd, data, put) != put)
+ return -1;
+ BAIL(1);
+ log->tcrc = crc32(log->tcrc, data, put);
+ log->tlen += put;
+ log->stored += put;
+ data += put;
+ len -= put;
+ }
+
+ /* if we need to, add a new empty stored block */
+ if (len) {
+ /* mark current block as not last */
+ if (log_last(log, 0))
+ return -1;
+
+ /* point to new, empty stored block */
+ log->last += 4 + log->stored + 1;
+ log->stored = 0;
+ }
+
+ /* mark last block as last, update its length */
+ if (log_last(log, 1))
+ return -1;
+ BAIL(2);
+ }
+
+ /* write the new crc and length trailer, and truncate just in case (could
+ be recovering from partial append with a missing foo.add file) */
+ PUT4(buf, log->tcrc);
+ PUT4(buf + 4, log->tlen);
+ if (write(log->fd, buf, 8) != 8 ||
+ (end = lseek(log->fd, 0, SEEK_CUR)) < 0 || ftruncate(log->fd, end))
+ return -1;
+
+ /* write the extra field, marking the log file as done, delete .add file */
+ if (log_mark(log, NO_OP))
+ return -1;
+ strcpy(log->end, ".add");
+ unlink(log->path); /* ignore error, since may not exist */
+ return 0;
+}
+
+/* Replace the foo.dict file with the foo.temp file. Also delete the foo.add
+ file, since the compress operation may have been interrupted before that was
+ done. Returns 1 if memory could not be allocated, or -1 if reading or
+ writing foo.gz fails, or if the rename fails for some reason other than
+ foo.temp not existing. foo.temp not existing is a permitted error, since
+ the replace operation may have been interrupted after the rename is done,
+ but before foo.gz is marked as complete. */
+local int log_replace(struct log *log)
+{
+ int ret;
+ char *dest;
+
+ /* delete foo.add file */
+ strcpy(log->end, ".add");
+ unlink(log->path); /* ignore error, since may not exist */
+ BAIL(3);
+
+ /* rename foo.name to foo.dict, replacing foo.dict if it exists */
+ strcpy(log->end, ".dict");
+ dest = malloc(strlen(log->path) + 1);
+ if (dest == NULL)
+ return -2;
+ strcpy(dest, log->path);
+ strcpy(log->end, ".temp");
+ ret = rename(log->path, dest);
+ free(dest);
+ if (ret && errno != ENOENT)
+ return -1;
+ BAIL(4);
+
+ /* mark the foo.gz file as done */
+ return log_mark(log, NO_OP);
+}
+
+/* Compress the len bytes at data and append the compressed data to the
+ foo.gz deflate data immediately after the previous compressed data. This
+ overwrites the previous uncompressed data, which was stored in foo.add
+ and is the data provided in data[0..len-1]. If this operation is
+ interrupted, it picks up at the start of this routine, with the foo.add
+ file read in again. If there is no data to compress (len == 0), then we
+ simply terminate the foo.gz file after the previously compressed data,
+ appending a final empty stored block and the gzip trailer. Return -1 if
+ reading or writing the log.gz file failed, or -2 if there was a memory
+ allocation failure. */
+local int log_compress(struct log *log, unsigned char *data, size_t len)
+{
+ int fd;
+ uint got, max;
+ ssize_t dict;
+ off_t end;
+ z_stream strm;
+ unsigned char buf[DICT];
+
+ /* compress and append compressed data */
+ if (len) {
+ /* set up for deflate, allocating memory */
+ strm.zalloc = Z_NULL;
+ strm.zfree = Z_NULL;
+ strm.opaque = Z_NULL;
+ if (deflateInit2(&strm, Z_DEFAULT_COMPRESSION, Z_DEFLATED, -15, 8,
+ Z_DEFAULT_STRATEGY) != Z_OK)
+ return -2;
+
+ /* read in dictionary (last 32K of data that was compressed) */
+ strcpy(log->end, ".dict");
+ fd = open(log->path, O_RDONLY, 0);
+ if (fd >= 0) {
+ dict = read(fd, buf, DICT);
+ close(fd);
+ if (dict < 0) {
+ deflateEnd(&strm);
+ return -1;
+ }
+ if (dict)
+ deflateSetDictionary(&strm, buf, (uint)dict);
+ }
+ log_touch(log);
+
+ /* prime deflate with last bits of previous block, position write
+ pointer to write those bits and overwrite what follows */
+ if (lseek(log->fd, log->first - (log->back > 8 ? 2 : 1),
+ SEEK_SET) < 0 ||
+ read(log->fd, buf, 1) != 1 || lseek(log->fd, -1, SEEK_CUR) < 0) {
+ deflateEnd(&strm);
+ return -1;
+ }
+ deflatePrime(&strm, (8 - log->back) & 7, *buf);
+
+ /* compress, finishing with a partial non-last empty static block */
+ strm.next_in = data;
+ max = (((uint)0 - 1) >> 1) + 1; /* in case int smaller than size_t */
+ do {
+ strm.avail_in = len > max ? max : (uint)len;
+ len -= strm.avail_in;
+ do {
+ strm.avail_out = DICT;
+ strm.next_out = buf;
+ deflate(&strm, len ? Z_NO_FLUSH : Z_PARTIAL_FLUSH);
+ got = DICT - strm.avail_out;
+ if (got && write(log->fd, buf, got) != got) {
+ deflateEnd(&strm);
+ return -1;
+ }
+ log_touch(log);
+ } while (strm.avail_out == 0);
+ } while (len);
+ deflateEnd(&strm);
+ BAIL(5);
+
+ /* find start of empty static block -- scanning backwards the first one
+ bit is the second bit of the block, if the last byte is zero, then
+ we know the byte before that has a one in the top bit, since an
+ empty static block is ten bits long */
+ if ((log->first = lseek(log->fd, -1, SEEK_CUR)) < 0 ||
+ read(log->fd, buf, 1) != 1)
+ return -1;
+ log->first++;
+ if (*buf) {
+ log->back = 1;
+ while ((*buf & ((uint)1 << (8 - log->back++))) == 0)
+ ; /* guaranteed to terminate, since *buf != 0 */
+ }
+ else
+ log->back = 10;
+
+ /* update compressed crc and length */
+ log->ccrc = log->tcrc;
+ log->clen = log->tlen;
+ }
+ else {
+ /* no data to compress -- fix up existing gzip stream */
+ log->tcrc = log->ccrc;
+ log->tlen = log->clen;
+ }
+
+ /* complete and truncate gzip stream */
+ log->last = log->first;
+ log->stored = 0;
+ PUT4(buf, log->tcrc);
+ PUT4(buf + 4, log->tlen);
+ if (log_last(log, 1) || write(log->fd, buf, 8) != 8 ||
+ (end = lseek(log->fd, 0, SEEK_CUR)) < 0 || ftruncate(log->fd, end))
+ return -1;
+ BAIL(6);
+
+ /* mark as being in the replace operation */
+ if (log_mark(log, REPLACE_OP))
+ return -1;
+
+ /* execute the replace operation and mark the file as done */
+ return log_replace(log);
+}
+
+/* log a repair record to the .repairs file */
+local void log_log(struct log *log, int op, char *record)
+{
+ time_t now;
+ FILE *rec;
+
+ now = time(NULL);
+ strcpy(log->end, ".repairs");
+ rec = fopen(log->path, "a");
+ if (rec == NULL)
+ return;
+ fprintf(rec, "%.24s %s recovery: %s\n", ctime(&now), op == APPEND_OP ?
+ "append" : (op == COMPRESS_OP ? "compress" : "replace"), record);
+ fclose(rec);
+ return;
+}
+
+/* Recover the interrupted operation op. First read foo.add for recovering an
+ append or compress operation. Return -1 if there was an error reading or
+ writing foo.gz or reading an existing foo.add, or -2 if there was a memory
+ allocation failure. */
+local int log_recover(struct log *log, int op)
+{
+ int fd, ret = 0;
+ unsigned char *data = NULL;
+ size_t len = 0;
+ struct stat st;
+
+ /* log recovery */
+ log_log(log, op, "start");
+
+ /* load foo.add file if expected and present */
+ if (op == APPEND_OP || op == COMPRESS_OP) {
+ strcpy(log->end, ".add");
+ if (stat(log->path, &st) == 0 && st.st_size) {
+ len = (size_t)(st.st_size);
+ if ((off_t)len != st.st_size ||
+ (data = malloc(st.st_size)) == NULL) {
+ log_log(log, op, "allocation failure");
+ return -2;
+ }
+ if ((fd = open(log->path, O_RDONLY, 0)) < 0) {
+ log_log(log, op, ".add file read failure");
+ return -1;
+ }
+ ret = (size_t)read(fd, data, len) != len;
+ close(fd);
+ if (ret) {
+ log_log(log, op, ".add file read failure");
+ return -1;
+ }
+ log_log(log, op, "loaded .add file");
+ }
+ else
+ log_log(log, op, "missing .add file!");
+ }
+
+ /* recover the interrupted operation */
+ switch (op) {
+ case APPEND_OP:
+ ret = log_append(log, data, len);
+ break;
+ case COMPRESS_OP:
+ ret = log_compress(log, data, len);
+ break;
+ case REPLACE_OP:
+ ret = log_replace(log);
+ }
+
+ /* log status */
+ log_log(log, op, ret ? "failure" : "complete");
+
+ /* clean up */
+ if (data != NULL)
+ free(data);
+ return ret;
+}
+
+/* Close the foo.gz file (if open) and release the lock. */
+local void log_close(struct log *log)
+{
+ if (log->fd >= 0)
+ close(log->fd);
+ log->fd = -1;
+ log_unlock(log);
+}
+
+/* Open foo.gz, verify the header, and load the extra field contents, after
+ first creating the foo.lock file to gain exclusive access to the foo.*
+ files. If foo.gz does not exist or is empty, then write the initial header,
+ extra, and body content of an empty foo.gz log file. If there is an error
+ creating the lock file due to access restrictions, or an error reading or
+ writing the foo.gz file, or if the foo.gz file is not a proper log file for
+ this object (e.g. not a gzip file or does not contain the expected extra
+ field), then return true. If there is an error, the lock is released.
+ Otherwise, the lock is left in place. */
+local int log_open(struct log *log)
+{
+ int op;
+
+ /* release open file resource if left over -- can occur if lock lost
+ between gzlog_open() and gzlog_write() */
+ if (log->fd >= 0)
+ close(log->fd);
+ log->fd = -1;
+
+ /* negotiate exclusive access */
+ if (log_lock(log) < 0)
+ return -1;
+
+ /* open the log file, foo.gz */
+ strcpy(log->end, ".gz");
+ log->fd = open(log->path, O_RDWR | O_CREAT, 0644);
+ if (log->fd < 0) {
+ log_close(log);
+ return -1;
+ }
+
+ /* if new, initialize foo.gz with an empty log, delete old dictionary */
+ if (lseek(log->fd, 0, SEEK_END) == 0) {
+ if (write(log->fd, log_gzhead, HEAD) != HEAD ||
+ write(log->fd, log_gzext, EXTRA) != EXTRA ||
+ write(log->fd, log_gzbody, BODY) != BODY) {
+ log_close(log);
+ return -1;
+ }
+ strcpy(log->end, ".dict");
+ unlink(log->path);
+ }
+
+ /* verify log file and load extra field information */
+ if ((op = log_head(log)) < 0) {
+ log_close(log);
+ return -1;
+ }
+
+ /* check for interrupted process and if so, recover */
+ if (op != NO_OP && log_recover(log, op)) {
+ log_close(log);
+ return -1;
+ }
+
+ /* touch the lock file to prevent another process from grabbing it */
+ log_touch(log);
+ return 0;
+}
+
+/* See gzlog.h for the description of the external methods below */
+gzlog *gzlog_open(char *path)
+{
+ size_t n;
+ struct log *log;
+
+ /* check arguments */
+ if (path == NULL || *path == 0)
+ return NULL;
+
+ /* allocate and initialize log structure */
+ log = malloc(sizeof(struct log));
+ if (log == NULL)
+ return NULL;
+ strcpy(log->id, LOGID);
+ log->fd = -1;
+
+ /* save path and end of path for name construction */
+ n = strlen(path);
+ log->path = malloc(n + 9); /* allow for ".repairs" */
+ if (log->path == NULL) {
+ free(log);
+ return NULL;
+ }
+ strcpy(log->path, path);
+ log->end = log->path + n;
+
+ /* gain exclusive access and verify log file -- may perform a
+ recovery operation if needed */
+ if (log_open(log)) {
+ free(log->path);
+ free(log);
+ return NULL;
+ }
+
+ /* return pointer to log structure */
+ return log;
+}
+
+/* gzlog_compress() return values:
+ 0: all good
+ -1: file i/o error (usually access issue)
+ -2: memory allocation failure
+ -3: invalid log pointer argument */
+int gzlog_compress(gzlog *logd)
+{
+ int fd, ret;
+ uint block;
+ size_t len, next;
+ unsigned char *data, buf[5];
+ struct log *log = logd;
+
+ /* check arguments */
+ if (log == NULL || strcmp(log->id, LOGID))
+ return -3;
+
+ /* see if we lost the lock -- if so get it again and reload the extra
+ field information (it probably changed), recover last operation if
+ necessary */
+ if (log_check(log) && log_open(log))
+ return -1;
+
+ /* create space for uncompressed data */
+ len = ((size_t)(log->last - log->first) & ~(((size_t)1 << 10) - 1)) +
+ log->stored;
+ if ((data = malloc(len)) == NULL)
+ return -2;
+
+ /* do statement here is just a cheap trick for error handling */
+ do {
+ /* read in the uncompressed data */
+ if (lseek(log->fd, log->first - 1, SEEK_SET) < 0)
+ break;
+ next = 0;
+ while (next < len) {
+ if (read(log->fd, buf, 5) != 5)
+ break;
+ block = PULL2(buf + 1);
+ if (next + block > len ||
+ read(log->fd, (char *)data + next, block) != block)
+ break;
+ next += block;
+ }
+ if (lseek(log->fd, 0, SEEK_CUR) != log->last + 4 + log->stored)
+ break;
+ log_touch(log);
+
+ /* write the uncompressed data to the .add file */
+ strcpy(log->end, ".add");
+ fd = open(log->path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
+ if (fd < 0)
+ break;
+ ret = (size_t)write(fd, data, len) != len;
+ if (ret | close(fd))
+ break;
+ log_touch(log);
+
+ /* write the dictionary for the next compress to the .temp file */
+ strcpy(log->end, ".temp");
+ fd = open(log->path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
+ if (fd < 0)
+ break;
+ next = DICT > len ? len : DICT;
+ ret = (size_t)write(fd, (char *)data + len - next, next) != next;
+ if (ret | close(fd))
+ break;
+ log_touch(log);
+
+ /* roll back to compressed data, mark the compress in progress */
+ log->last = log->first;
+ log->stored = 0;
+ if (log_mark(log, COMPRESS_OP))
+ break;
+ BAIL(7);
+
+ /* compress and append the data (clears mark) */
+ ret = log_compress(log, data, len);
+ free(data);
+ return ret;
+ } while (0);
+
+ /* broke out of do above on i/o error */
+ free(data);
+ return -1;
+}
+
+/* gzlog_write() return values:
+ 0: all good
+ -1: file i/o error (usually access issue)
+ -2: memory allocation failure
+ -3: invalid log pointer argument */
+int gzlog_write(gzlog *logd, void *data, size_t len)
+{
+ int fd, ret;
+ struct log *log = logd;
+
+ /* check arguments */
+ if (log == NULL || strcmp(log->id, LOGID))
+ return -3;
+ if (data == NULL || len <= 0)
+ return 0;
+
+ /* see if we lost the lock -- if so get it again and reload the extra
+ field information (it probably changed), recover last operation if
+ necessary */
+ if (log_check(log) && log_open(log))
+ return -1;
+
+ /* create and write .add file */
+ strcpy(log->end, ".add");
+ fd = open(log->path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
+ if (fd < 0)
+ return -1;
+ ret = (size_t)write(fd, data, len) != len;
+ if (ret | close(fd))
+ return -1;
+ log_touch(log);
+
+ /* mark log file with append in progress */
+ if (log_mark(log, APPEND_OP))
+ return -1;
+ BAIL(8);
+
+ /* append data (clears mark) */
+ if (log_append(log, data, len))
+ return -1;
+
+ /* check to see if it's time to compress -- if not, then done */
+ if (((log->last - log->first) >> 10) + (log->stored >> 10) < TRIGGER)
+ return 0;
+
+ /* time to compress */
+ return gzlog_compress(log);
+}
+
+/* gzlog_close() return values:
+ 0: ok
+ -3: invalid log pointer argument */
+int gzlog_close(gzlog *logd)
+{
+ struct log *log = logd;
+
+ /* check arguments */
+ if (log == NULL || strcmp(log->id, LOGID))
+ return -3;
+
+ /* close the log file and release the lock */
+ log_close(log);
+
+ /* free structure and return */
+ if (log->path != NULL)
+ free(log->path);
+ strcpy(log->id, "bad");
+ free(log);
+ return 0;
+}
projects / ossec-hids.git / blobdiff