Modified version of fritz_cal_extract.c to handle reversed calibration

data.

New options:
-t Number of bytes to truncate (before optional reversal of data).
-r Re-reverse calibration data. This is necessary for some AVM devices
   (e.g. Fritzbox 4040, 7430, ...).

package/utils/fritz-tools/src/fritz_cal_extract.c

@@ -8,6 +8,9 @@
  * that is Not copyrighted -- provided to the public domain
  * Version 1.4  11 December 2005  Mark Adler
  *
+ * Modifications to also handle calibration data in reversed byte order
+ * and truncation of data (c) 2024 by <dzsoftware@posteo.org>.
+ *
  * 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
@@ -28,32 +31,41 @@
 #include <assert.h>
 #include <unistd.h>
 #include <stdint.h>
+#include <stdbool.h>
 #include <stdlib.h>
 #include <endian.h>
 #include <errno.h>
 #include "zlib.h"
 
 #define CHUNK 1024
+#define DEFAULT_BUFFERSIZE (1024 * 64)
 
-static inline size_t special_min(size_t a, size_t b)
+/* Reverse only buffer elements inside range [bottom:top] */
+static void buffer_reverse(unsigned char *data, unsigned int bottom, unsigned int top)
 {
-	return a == 0 ? b : (a < b ? a : b);
+	register unsigned char swapbyte;
+	unsigned int center = bottom + (top - bottom) / 2;
+
+	for (; bottom < center; ++bottom, --top) {
+		swapbyte = data[bottom];
+		data[bottom] = data[top];
+		data[top] = swapbyte;
+	}
 }
 
-/* Decompress from file source to file dest until stream ends or EOF.
-   inf() returns Z_OK on success, Z_MEM_ERROR if memory could not be
-   allocated for processing, Z_DATA_ERROR if the deflate data is
-   invalid or incomplete, Z_VERSION_ERROR if the version of zlib.h and
-   the version of the library linked do not match, or Z_ERRNO if there
-   is an error reading or writing the files. */
-static int inf(FILE *source, FILE *dest, size_t limit, size_t skip)
+/* Decompress from file source to data buffer until stream ends or 
+   buffer is full.
+   inflate_to_buffer() returns Z_OK on success, Z_MEM_ERROR if memory 
+   could not be allocated for processing, Z_DATA_ERROR if the deflate 
+   data is invalid or incomplete, Z_VERSION_ERROR if the version of 
+   zlib.h and the version of the library linked do not match, or 
+   Z_ERRNO if there is an error reading or writing the files. */
+static int inflate_to_buffer(FILE *source, unsigned char *buf, size_t *limit)
 {
     int ret;
-    size_t have;
     z_stream strm;
     unsigned char in[CHUNK];
-    unsigned char out[CHUNK];
-
+
     /* allocate inflate state */
     strm.zalloc = Z_NULL;
     strm.zfree = Z_NULL;
@@ -64,6 +76,10 @@ static int inf(FILE *source, FILE *dest, size_t limit, size_t skip)
     if (ret != Z_OK)
         return ret;
 
+    /* set data buffer as stream output */
+    strm.avail_out = *limit;
+    strm.next_out = buf;
+
     /* decompress until deflate stream ends or end of file */
     do {
         strm.avail_in = fread(in, 1, CHUNK, source);
@@ -75,35 +91,35 @@ static int inf(FILE *source, FILE *dest, size_t limit, size_t skip)
             break;
         strm.next_in = in;
 
-        /* run inflate() on input until output buffer not full */
-        do {
-            strm.avail_out = CHUNK;
-            strm.next_out = out;
-            ret = inflate(&strm, Z_NO_FLUSH);
-            assert(ret != Z_STREAM_ERROR);  /* state not clobbered */
-            switch (ret) {
-            case Z_NEED_DICT:
-                ret = Z_DATA_ERROR;     /* and fall through */
-            case Z_DATA_ERROR:
-            case Z_MEM_ERROR:
-                (void)inflateEnd(&strm);
-                return ret;
-            }
-            have = special_min(limit, CHUNK - strm.avail_out) - skip;
-            if (fwrite(&out[skip], have, 1, dest) != 1 || ferror(dest)) {
-                (void)inflateEnd(&strm);
-                return Z_ERRNO;
-            }
-	    skip = 0;
-	    limit -= have;
-        } while (strm.avail_out == 0 && limit > 0);
+        /* run inflate(), fill data buffer with all available output */
+	ret = inflate(&strm, Z_FINISH);
+	assert(ret != Z_STREAM_ERROR);  /* state not clobbered */
+
+	switch (ret) {
+		case Z_NEED_DICT:
+			ret = Z_DATA_ERROR;     /* and fall through */
+		case Z_DATA_ERROR:
+		case Z_MEM_ERROR:
+			(void)inflateEnd(&strm);
+			return ret;
+	}
 
+	if (strm.avail_out == 0 && ret != Z_STREAM_END) {
+		fprintf(stderr, "Failed to inflate input data: buffer too small!"
+				" Use option -l to increase caldata size limit.\n");
+		(void)inflateEnd(&strm);
+		return Z_ERRNO;
+	}
         /* done when inflate() says it's done */
-    } while (ret != Z_STREAM_END && limit > 0);
+    } while (ret != Z_STREAM_END);
+
+    /* set limit to end of retrieved data */
+    assert(strm.total_out <= *limit);
+    *limit = strm.total_out;
 
     /* clean up and return */
     (void)inflateEnd(&strm);
-    return (limit == 0 ? Z_OK : (ret == Z_STREAM_END ? Z_OK : Z_DATA_ERROR));
+    return (strm.avail_out == 0 ? Z_OK : (ret == Z_STREAM_END ? Z_OK : Z_DATA_ERROR));
 }
 
 /* report a zlib or i/o error */
@@ -140,7 +156,8 @@ static unsigned int get_num(char *str)
 
 static void usage(void)
 {
-	fprintf(stderr, "Usage: fritz_cal_extract [-s seek offset] [-i skip] [-o output file] [-l limit] [infile] -e entry_id\n"
+	fprintf(stderr, "Usage: fritz_cal_extract [-s seek offset] [-i skip] [-o output file] [-l limit]\n\t"
+			"[-t truncate n bytes] [-r reverse extracted data] [infile] -e entry_id\n"
 			"Finds and extracts zlib compressed calibration data in the EVA loader\n");
 	exit(EXIT_FAILURE);
 }
@@ -154,15 +171,17 @@ struct cal_entry {
 int main(int argc, char **argv)
 {
 	struct cal_entry cal = { .len = 0 };
+	unsigned char *buf = NULL;
 	FILE *in = stdin;
 	FILE *out = stdout;
-	size_t limit = 0, skip = 0;
+	size_t limit = 0, skip = 0, truncate = 0;
 	int initial_offset = 0;
 	int entry = -1;
+	bool reversed = false;
 	int ret;
 	int opt;
 
-	while ((opt = getopt(argc, argv, "s:e:o:l:i:")) != -1) {
+	while ((opt = getopt(argc, argv, "s:e:o:l:i:t:r")) != -1) {
 		switch (opt) {
 		case 's':
 			initial_offset = (int)get_num(optarg);
@@ -199,6 +218,16 @@ int main(int argc, char **argv)
 				goto out_bad;
 			}
 			break;
+		case 't':
+			truncate = (size_t)get_num(optarg);
+			if (errno) {
+				perror("Failed to parse truncate");
+				goto out_bad;
+			}
+			break;
+		case 'r':
+			reversed = true;
+			break;
 		default: /* '?' */
 			usage();
 		}
@@ -243,9 +272,33 @@ int main(int argc, char **argv)
 		goto out_bad;
 	}
 
-	ret = inf(in, out, limit, skip);
-	if (ret == Z_OK)
-		goto out;
+	/* Create data buffer.
+	 * 'limit' will be one-off the last valid buffer element. */
+	limit = (limit ? limit : DEFAULT_BUFFERSIZE) + skip;
+	buf = malloc(limit);
+	assert(buf != NULL);
+
+	ret = inflate_to_buffer(in, buf, &limit);
+	if (ret != Z_OK) {
+		zerr(ret);
+		goto out_bad;
+	}
+
+	limit -= truncate;
+	if (limit <= skip) {
+		fprintf(stderr, "Failed: Resulting data range [%ld:%ld] is invalid!\n", 
+				skip, limit - 1);
+		goto out_bad;
+	}
+
+	if (reversed)
+		buffer_reverse(buf, skip, limit - 1);
+
+	if (fwrite(&buf[skip], (limit - skip), 1, out) != 1 || ferror(out)) {
+		fprintf(stderr, "Failed to write data buffer to output file");
+		goto out_bad;
+	}
+	goto out;
 
 	zerr(ret);
 
@@ -257,5 +310,7 @@ int main(int argc, char **argv)
 		fclose(in);
 	if (out)
 		fclose(out);
+	free(buf);
+
 	return ret;
 }