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Makefile

@@ -0,0 +1,18 @@
+.POSIX:
+CFLAGS = -O3 -Wall -Wextra
+PREFIX = /usr/local
+main: main.c
+	$(CC) $(CFLAGS) main.c -o corrupt
+
+all: main
+
+clean: 
+	rm -f corrupt
+
+install:
+	cp corrupt $(DESTDIR)$(PREFIX)/bin/
+
+uninstall:
+	rm $(DESTDIR)$(PREFIX)/bin/corrupt
+
+PHONY = all clean install uninstall

README.md

@@ -1,2 +1,21 @@
 # Corrupt
-A CLI tool for simple and efficient file shredding
+A minimal tool that shreds files using the Gutmann method  
+
+## Installation
+You need just a C compiler with the default libraries, and `make`
+```shell
+# Compiles to `corrupt`
+make
+# Optional, copy the binary to /usr/local/bin
+sudo make install
+```
+
+## Example
+```shell
+# Corrupts a file
+corrupt file
+# Corrupts multiple files
+corrupt file2 file3
+# Files still exist, but its contents were overwritten multiple times 
+cat file file2 file3 
+```

main.c

@@ -0,0 +1,109 @@
+#include <time.h> /* time */
+#include <stdio.h> /* FILE, fopen, fwrite, fclose, fprintf */
+#include <stdint.h> /* uint*_t int*_t */
+#include <string.h> /* strlen */
+#include <stdlib.h> /* srand, rand */
+#include <sys/stat.h> /* stat */
+#include <sys/types.h> /* off_t */
+
+static uint8_t
+CorruptStep(const char *filename, const off_t filesize, const char *pattern)
+{
+    uint8_t ret = 0;
+
+    FILE* fp = fopen(filename,  "w");
+    if (fp != NULL)
+    {
+        off_t i;
+        uint8_t length = (uint8_t) strlen(pattern);
+        if (length > 0)
+        {
+            off_t times = (filesize / length) + (filesize % length);
+            for (i = 0; i < times; i++)
+            {
+                fwrite(pattern, sizeof(char), length, fp);
+            }
+        } 
+        else
+        {
+            srand((unsigned int) time(NULL));
+            for (i = 0; i < filesize; i++)
+            {
+                int n = rand();
+                fwrite(&n, sizeof(char), 1, fp);
+            }
+        }
+        fclose(fp);
+    }
+    else
+    {   
+        ret = 1;
+    }
+    return ret;
+}
+
+static uint8_t
+CorruptFile(const char *filename)
+{
+    uint8_t ret = 0;
+
+    struct stat st;
+    if(stat(filename, &st) == 0)
+    {
+        if (S_ISREG(st.st_mode) != 0)
+        {
+            off_t filesize = st.st_size;
+            const char* steps[35] = {"", "", "", "", "\x55", "\xAA",
+                                     "\x92\x49\x24", "\x49\x24\x92",
+                                     "\x24\x92\x49", "\x00", "\x11",
+                                     "\x22", "\x33", "\x44", "\x55",
+                                     "\x66", "\x77", "\x88", "\x99",
+                                     "\xAA", "\xBB", "\xCC", "\xDD",
+                                     "\xEE", "\xFF", "\x92\x49\x24",
+                                     "\x49\x24\x92", "\x24\x92\x49",
+                                     "\x6D\xB6\xDB", "\xB6\xDB\x6D",
+                                     "\xDB\x6D\xB6", "", "", "", ""};
+            uint8_t i;
+            for (i = 0; i < 35; i++)
+            {
+                if (CorruptStep(filename, filesize, steps[i]) != 0)
+                {
+                    fprintf(stderr, "corrupt: shredding of '%s' ", filename);
+                    fprintf(stderr, "failed on step %d\n", i);
+                    ret = 1;
+                    break;
+                }
+            }
+        }
+        else
+        {
+            fprintf(stderr, "corrupt: '%s' is not a regular file\n", filename);
+            ret = 1;
+        }
+    }  
+    else
+    {
+        fprintf(stderr, "corrupt: '%s' not found\n", filename);
+        ret = 1;
+    }
+    return ret;
+}
+
+int
+main(int argc, char* argv[])
+{
+    if (argc > 1)
+    {
+        int i;
+        for (i = 1; i < argc; i++)
+        {
+            CorruptFile(argv[i]);
+        }
+    }
+    else
+    {
+        fprintf(stderr, "Usage: corrupt FILES...\n");
+        fprintf(stderr, "Shreds files using the Gutmann method\n");
+    }
+    return 0; 
+}