Build scripts changed to support FreeBSD. File size check

implemented for input files. Fixed error that caused data corruption in the last few bytes of bannerless images of certain sizes. Added and expanded code comments all around.
dbohdan · Jul 25, 2013 · dbd988a · dbd988a
1 parent 5fcdebc
commit dbd988a
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diff --git a/.gitignore b/.gitignore
@@ -3,7 +3,8 @@ doc-pak
 s2png
 *.deb
 *.png
-python github flavored markdown.py
+pymd.py
+README.html
 s2png.o
 rc4.o
 core

diff --git a/Makefile b/Makefile
@@ -1,11 +1,12 @@
-CFLAGS=-g -O2 -Wall
+CFLAGS=-g -O2 -Wall -I/usr/local/include/
+LDFLAGS=-L/usr/local/lib/
 INCS = `libpng-config --cflags`
-LIBS = `libpng-config --libs` -lgd -lm
+LIBS = `libpng-config --libs` -lgd
 
 all: test readme
 
-s2png: rc4.o s2png.o
-	$(CC) $^ -o $@ $(CFLAGS) $(INCS) $(LIBS)
+s2png:
+	$(CC) -o s2png rc4.c s2png.c $(CFLAGS) $(LDFLAGS) $(INCS) $(LIBS)
 
 install:
 	cp s2png /usr/local/bin

diff --git a/README.in b/README.in
@@ -9,11 +9,11 @@ Building and installing
 -----------------------
 
 1. Install the dependencies. On Debian, Ubuntu and Linux Mint you can do so with
-`sudo apt-get install libgd2-xpm-dev libgd2-xpm`.
+`sudo apt-get install libgd2-xpm-dev libgd2-xpm libpng-dev`. On FreeBSD you will need to install `graphics/gd` and `graphics/png`.
 
-2. Type `make` in your terminal and hit the enter key. Building has been tested on Linux Mint 13 and Ubuntu 12.10.
+2. Type `make` in your terminal and hit the enter key. Building has been tested on Linux Mint 13, Ubuntu 12.10 and FreeBSD 9.1-RELEASE.
 
-3. Install with `sudo make install`. On Debian-derived distributions use `sudo checkinstall` instead.
+3. Install with `sudo make install`. On Debian-derived Linux distributions use `sudo checkinstall` instead.
 
 Usage
 -----

diff --git a/README.md b/README.md
@@ -9,11 +9,11 @@ Building and installing
 -----------------------
 
 1. Install the dependencies. On Debian, Ubuntu and Linux Mint you can do so with
-`sudo apt-get install libgd2-xpm-dev libgd2-xpm`.
+`sudo apt-get install libgd2-xpm-dev libgd2-xpm libpng-dev`. On FreeBSD you will need to install `graphics/gd` and `graphics/png`.
 
-2. Type `make` in your terminal and hit the enter key. Building has been tested on Linux Mint 13 and Ubuntu 12.10.
+2. Type `make` in your terminal and hit the enter key. Building has been tested on Linux Mint 13, Ubuntu 12.10 and FreeBSD 9.1-RELEASE.
 
-3. Install with `sudo make install`. On Debian-derived distributions use `sudo checkinstall` instead.
+3. Install with `sudo make install`. On Debian-derived Linux distributions use `sudo checkinstall` instead.
 
 Usage
 -----
@@ -22,17 +22,20 @@ Usage
     usage: s2png [-h] [-o filename] [-w width (600) | -s] [-b text]
                  [-p password] [-e | -d] file
 
+    Store any data in a PNG image.
+    This version can encode files of up to 16777215 bytes.
+
       -h            display this message and quit
       -o filename   output the converted data (image or binary) to filename
       -w width      set the width of PNG image output (600 by default)
       -s            make the output image roughly square
       -b text       custom banner text ("" for no banner)
       -p password   encrypt/decrypt the output with password using RC4
                     (Warning: do not use this if you need actual security!)
-      -e            force encoding mode avoiding file type detection 
+    Normally s2png detects which operation to perform by file type. You can
+    circumvent this with the following switches:
+      -e            force encoding mode
       -d            force decoding mode
-
-    See README.md for details.
 
 Basic examples
 --------------

diff --git a/s2png.c b/s2png.c
@@ -29,6 +29,7 @@
 #define MODE_DECODE 2
 
 #define RC4_DROP_N 3072
+#define MAX_FILE_SIZE 0xFFFFFF
 
 #define DEFAULT_BANNER ("This image contains binary data. \
 To extract it get s2png on GitHub.")
@@ -52,11 +53,13 @@ int png_to_file(char *fin_fn, char *fout_fn, char *password)
     gdImagePtr im = gdImageCreateFromPng(fin);
     fclose(fin);
 
+    /* Has libgd been about to read and interpret fin? */
     if (im == NULL) {
         fprintf(stderr, "error: file `%s' not readable as PNG\n", fin_fn);
         return EX_DATAERR;
     }
 
+    /* Get data size from the bottom right pixel of the image. */
     int c = gdImageGetPixel(im, gdImageSX(im) - 1, gdImageSY(im) - 1);
     int data_size = (gdImageRed(im, c) << 8*2) +
                     (gdImageGreen(im, c) << 8*1) + (gdImageBlue(im, c));
@@ -76,7 +79,7 @@ int png_to_file(char *fin_fn, char *fout_fn, char *password)
     struct rc4_key key;
     init_rc4(password, &key);
 
-
+    /* For each pixel of the image... */
     for (y = 0; y < gdImageSY(im); y++) {
         for (x = 0; x < gdImageSX(im); x++) {
             c = gdImageGetPixel(im, x, y);
@@ -112,6 +115,14 @@ int file_to_png(char *fin_fn, char *fout_fn, int image_width,
     fin = fopen(fin_fn, "rb");
     fstat(fileno(fin), &fin_stat);
     int data_size = fin_stat.st_size; /* st_size is off_t, which is int. */
+    if (data_size > MAX_FILE_SIZE) {
+        fprintf(stderr,
+                "error: file `%s' too large to encode (over %u bytes)\n",
+                fin_fn, MAX_FILE_SIZE);
+        return EX_DATAERR;
+    }
+
+    /* If given no banner text hide the banner. */
     int banner_height = (strcmp(banner, "") == 0 ? 0 : BANNER_HEIGHT);
 
     if (make_square) {
@@ -124,7 +135,13 @@ int file_to_png(char *fin_fn, char *fout_fn, int image_width,
     int image_height = ceil(((float) data_size / (float) image_width / 3.0)
                             + (float) banner_height);
 
-    /* printf("%d %d\n", image_width, image_height); */
+    /* Prevent data corruption on images with no banner where the bottom
+       right pixel is used for data and could get overwritten by the file
+       size pixel. */
+    if (banner_height == 0 &&
+        image_width * image_height * 3 - data_size <= 2) {
+        image_width++;
+    }
 
     im = gdImageCreateTrueColor(image_width, image_height);
 
@@ -137,6 +154,7 @@ int file_to_png(char *fin_fn, char *fout_fn, int image_width,
     struct rc4_key key;
     init_rc4(password, &key);
 
+    /* Read the input file in sets of three bytes. */
     while ((bytes_read = fread(buf, 1, 3, fin)) > 0) {
         if (password != NULL) {
             rc4(buf, 3, &key);
@@ -145,6 +163,7 @@ int file_to_png(char *fin_fn, char *fout_fn, int image_width,
         gdImageSetPixel(im, x, y, gdImageColorAllocate(im, buf[0], buf[1],
                         buf[2]));
 
+        /* Arrange the input data on a 2D grid of the image. */
         if (x + 1 < image_width) {
             x++;
         } else {
@@ -155,18 +174,20 @@ int file_to_png(char *fin_fn, char *fout_fn, int image_width,
 
     fclose(fin);
 
+    /* Add a banner at the bottom of the image. */
     char *s = banner;
     gdImageFilledRectangle(im, 0, gdImageSY(im) - banner_height,
                            image_width - 1, gdImageSY(im) + banner_height,
                            gdImageColorAllocate(im, 255, 255, 255));
     gdImageString(im, (gdFontPtr) gdFontGetTiny(), 5,
                   gdImageSY(im) - banner_height, (unsigned char *) s,
                   gdImageColorAllocate(im, 0, 0, 0));
-    /* store data_size in the last pixel */
+    /* Store data_size in the bottom right ("last") pixel. */
     gdImageSetPixel(im, gdImageSX(im) - 1, gdImageSY(im) - 1,
                     gdImageColorAllocate(im, (data_size & 0xff0000) >> 8*2,
                     (data_size & 0xff00) >> 8*1, data_size & 0xff));
 
+    /* Save the created image to a PNG file. */
     fout = fopen(fout_fn, "wb");
     if (fout == NULL) {
         fprintf(stderr, "error: cannot open file `%s' for output\n",
@@ -212,18 +233,24 @@ void usage()
 void help()
 {
     usage();
-    printf("\n\
+    printf("\
+\n\
+Store any data in a PNG image.\n\
+This version can encode files of up to %u bytes.\n\
+\n\
   -h            display this message and quit\n\
   -o filename   output the converted data (image or binary) to filename\n\
   -w width      set the width of PNG image output (600 by default)\n\
   -s            make the output image roughly square\n\
   -b text       custom banner text (\"\" for no banner)\n\
   -p password   encrypt/decrypt the output with password using RC4\n\
                 (Warning: do not use this if you need actual security!)\n\
-  -e            force encoding mode avoiding file type detection \n\
+Normally s2png detects which operation to perform by file type. You can\n\
+circumvent this with the following switches:\n\
+  -e            force encoding mode\n\
   -d            force decoding mode\n\
 \n\
-See README.md for details.\n");
+See README.md for further details.\n", MAX_FILE_SIZE);
 }
 
 int main(int argc, char **argv)
@@ -233,7 +260,6 @@ int main(int argc, char **argv)
         return EX_USAGE;
     }
 
-    /* opts */
     char *in_fn = NULL;
     char *out_fn = NULL;
     char *banner_text = DEFAULT_BANNER;
@@ -242,6 +268,7 @@ int main(int argc, char **argv)
     int make_square = 0;
     int mode = MODE_NONE;
 
+    /* Process command line options. */
     int ch;
     while ((ch = getopt(argc, argv, "w:o:hsb:p:ed")) != -1) {
         switch (ch) {
@@ -279,15 +306,20 @@ int main(int argc, char **argv)
     }
 
     in_fn = argv[argc - 1];
+
+    /* Does the input file exist? */
     if (access(in_fn, R_OK) != 0) {
         fprintf(stderr, "error: can't open file `%s'\n", in_fn);
         return EX_NOINPUT;
     }
 
+    /* If we weren't specified what operation to perform explicitly through
+     * command line options we decide based on file type. */
     if (mode == MODE_NONE) {
         mode = is_png_file(in_fn) ? MODE_DECODE : MODE_ENCODE;
     }
 
+    /* If no output file name was given we generate one. */
     if (out_fn == NULL) {
         out_fn = calloc(strlen(in_fn) + strlen(".orig"), sizeof(char));
         if (mode == MODE_DECODE) {
@@ -305,24 +337,19 @@ int main(int argc, char **argv)
         }
     }
 
-    /* printf("in_fn: %s\nout_fn = %s\n", in_fn, out_fn); */
-
-    /* check opts */
+    /* Check for invalid image width. This code has provisions for reporting
+       other misc. errors. */
     char *err = calloc(1, sizeof(char) * 255);
     if (!image_width && mode == MODE_ENCODE) {
         strcpy(err, "image width not set or invalid");
-    } else if (!in_fn) {
-        strcpy(err, "no input file");
-    } else if (!out_fn) {
-        strcpy(err, "no output file");
     }
 
     if (strlen(err) > 0) {
         fprintf(stderr, "%s, see -h option for help\n", err);
         return EX_USAGE;
     }
 
-
+    /* Perform the chosen operation. */
     if (mode == MODE_ENCODE) {
         file_to_png(in_fn, out_fn, image_width, make_square, banner_text,
                     password);

diff --git a/scripts/gen-readme.sh b/scripts/gen-readme.sh
@@ -1,7 +1,10 @@
 #!/bin/sh
+# Generate README.md based on README.in and the output of ./s2png -h
 
-export tempfile=$(tempfile)
-./s2png -h | sed -e "s/^/    /" > $tempfile
+export tempfile=$(mktemp -t s2pngXXXXX)
+# Below sed strips "See README.md for details." and the preceding
+# empty line from from s2png's help.
+./s2png -h | sed -e '$d' | sed -e 's/^/    /;$d' > $tempfile
 sed -e "/S2PNGHELP/{
     r $tempfile
     d

diff --git a/scripts/test.sh b/scripts/test.sh
@@ -1,26 +1,61 @@
 #!/bin/sh
+# Test s2png encoding and decoding operations, as well as encryption, for
+# causing data corruption.
 
-runtests() {
+opstest() {
     testfile=$1
 
-    ./s2png $testfile -s -o $testfile.png || echo File encoding failed.
-    ./s2png $testfile.png -o $testfile.out || echo File decoding failed.
+    ./s2png -s -o $testfile.png $testfile || echo File encoding failed.
+    ./s2png -o $testfile.out $testfile.png || echo File decoding failed.
 
-    ./s2png $testfile -s -o $testfile.png -b "Hello" -p password || echo File encryption failed.
-    ./s2png $testfile.png -o $testfile.out2 -p password || echo File decryption failed.
+    ./s2png -s -o $testfile.png -b "Hello" -p password $testfile || echo File encryption failed.
+    ./s2png -o $testfile.out2 -p password $testfile.png || echo File decryption failed.
 
     diff $testfile $testfile.out || echo Basic test failed.
     diff $testfile $testfile.out2 || echo Encryption test failed.
 
     rm $testfile.png $testfile.out $testfile.out2
 }
 
+sizetest() {
+    n=$1
+    testfile=$2
+    encoded=$3
+    decoded=$4
+
+    dd bs=$1 count=1 if=/dev/urandom of=$testfile 2> /dev/null
+    ./s2png -e -o $encoded -b "" -w 10 $testfile
+    ./s2png -d -o $decoded $encoded
+    diff $testfile $decoded
+    if [ $? != 0 ]; then
+        echo Corruption at file size $n.
+        identify a.png
+    fi
+}
+
+echo Running basic operations tests.
+
+# Test for data corruption with an 0xFFFF pattern.
 echo -n -e \\0377\\0377\\0377\\0377\\0377\\0377\\0377\\0377 > test.bin
-runtests test.bin
+opstest test.bin
 rm test.bin
 
+# Test for data corruption with random data.
 dd if=/dev/urandom of=test.bin count=2k
-runtests test.bin
+opstest test.bin
 rm test.bin
 
+echo Running integrity tests for bannerless images.
+
+# Test for data corruption by file size pixel.
+t1=$(mktemp -t s2pngXXXXX)
+t2=$(mktemp -t s2pngXXXXX)
+t3=$(mktemp -t s2pngXXXXX)
+i=10
+while [ $i -le 256 ]; do
+    sizetest $i $t1 $t2 $t3
+    i=`expr $i + 1`
+done
+rm $t1 $t2 $t3
+
 echo Tests done.