Finished implementation of encode and decode

Makefile

@@ -87,7 +87,7 @@ $U/initcode: $U/initcode.S
 tags: $(OBJS) _init
 	etags *.S *.c
 
-ULIB = $U/ulib.o $U/usys.o $U/printf.o $U/umalloc.o
+ULIB = $U/ulib.o $U/usys.o $U/printf.o $U/umalloc.o $U/base64.o $U/sha256.o $U/arcfour.o
 
 _%: %.o $(ULIB)
 	$(LD) $(LDFLAGS) -T $U/user.ld -o $@ $^
@@ -117,7 +117,9 @@ mkfs/mkfs: mkfs/mkfs.c $K/fs.h $K/param.h
 
 UPROGS=\
 	$U/_cat\
+	$U/_decode\
 	$U/_echo\
+	$U/_encode\
 	$U/_forktest\
 	$U/_grep\
 	$U/_init\
@@ -133,8 +135,8 @@ UPROGS=\
 	$U/_wc\
 	$U/_zombie\
 
-fs.img: mkfs/mkfs README.md $(UPROGS)
-	mkfs/mkfs fs.img README.md $(UPROGS)
+fs.img: mkfs/mkfs README.md project1.txt encrypted.txt $(UPROGS)
+	mkfs/mkfs fs.img README.md project1.txt encrypted.txt $(UPROGS)
 
 -include kernel/*.d user/*.d
 

encrypted.txt

@@ -0,0 +1 @@
+hi

project1.txt

@@ -0,0 +1 @@
+hi this is a secret

user/arcfour.c

@@ -0,0 +1,49 @@
+/*********************************************************************
+* Filename:   arcfour.c
+* Author:     Brad Conte (brad AT bradconte.com)
+* Copyright:
+* Disclaimer: This code is presented "as is" without any guarantees.
+* Details:    Implementation of the ARCFOUR encryption algorithm.
+              Algorithm specification can be found here:
+               * http://en.wikipedia.org/wiki/RC4
+*********************************************************************/
+
+/*************************** HEADER FILES ***************************/
+#include "arcfour.h"
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+/*********************** FUNCTION DEFINITIONS ***********************/
+void arcfour_key_setup(BYTE state[], const BYTE key[], int len)
+{
+	int i, j;
+	BYTE t;
+
+	for (i = 0; i < 256; ++i)
+		state[i] = i;
+	for (i = 0, j = 0; i < 256; ++i) {
+		j = (j + state[i] + key[i % len]) % 256;
+		t = state[i];
+		state[i] = state[j];
+		state[j] = t;
+	}
+}
+
+// This does not hold state between calls. It always generates the
+// stream starting from the first  output byte.
+void arcfour_generate_stream(BYTE state[], BYTE out[], size_t len)
+{
+	int i, j;
+	size_t idx;
+	BYTE t;
+
+	for (idx = 0, i = 0, j = 0; idx < len; ++idx)  {
+		i = (i + 1) % 256;
+		j = (j + state[i]) % 256;
+		t = state[i];
+		state[i] = state[j];
+		state[j] = t;
+		out[idx] = state[(state[i] + state[j]) % 256];
+	}
+}

user/arcfour.h

@@ -0,0 +1,30 @@
+/*********************************************************************
+* Filename:   arcfour.h
+* Author:     Brad Conte (brad AT bradconte.com)
+* Copyright:
+* Disclaimer: This code is presented "as is" without any guarantees.
+* Details:    Defines the API for the corresponding ARCFOUR implementation.
+*********************************************************************/
+
+#ifndef ARCFOUR_H
+#define ARCFOUR_H
+
+/*************************** HEADER FILES ***************************/
+#include <stddef.h>
+
+/**************************** DATA TYPES ****************************/
+typedef unsigned char BYTE;             // 8-bit byte
+
+/*********************** FUNCTION DECLARATIONS **********************/
+// Input: state - the state used to generate the keystream
+//        key - Key to use to initialize the state
+//        len - length of key in bytes (valid lenth is 1 to 256)
+void arcfour_key_setup(BYTE state[], const BYTE key[], int len);
+
+// Pseudo-Random Generator Algorithm
+// Input: state - the state used to generate the keystream
+//        out - Must be allocated to be of at least "len" length
+//        len - number of bytes to generate
+void arcfour_generate_stream(BYTE state[], BYTE out[], size_t len);
+
+#endif   // ARCFOUR_H

user/base64.c

@@ -0,0 +1,137 @@
+/*********************************************************************
+* Filename:   base64.c
+* Author:     Brad Conte (brad AT bradconte.com)
+* Copyright:
+* Disclaimer: This code is presented "as is" without any guarantees.
+* Details:    Implementation of the Base64 encoding algorithm.
+*********************************************************************/
+
+/*************************** HEADER FILES ***************************/
+//#include <stdlib.h>
+#include "base64.h"
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+/****************************** MACROS ******************************/
+#define NEWLINE_INVL 76
+
+/**************************** VARIABLES *****************************/
+// Note: To change the charset to a URL encoding, replace the '+' and '/' with '*' and '-'
+static const BYTE charset[]={"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"};
+
+/*********************** FUNCTION DEFINITIONS ***********************/
+BYTE revchar(char ch)
+{
+	if (ch >= 'A' && ch <= 'Z')
+		ch -= 'A';
+	else if (ch >= 'a' && ch <='z')
+		ch = ch - 'a' + 26;
+	else if (ch >= '0' && ch <='9')
+		ch = ch - '0' + 52;
+	else if (ch == '+')
+		ch = 62;
+	else if (ch == '/')
+		ch = 63;
+
+	return(ch);
+}
+
+size_t base64_encode(const BYTE in[], BYTE out[], size_t len, int newline_flag)
+{
+	size_t idx, idx2, blks, blk_ceiling, left_over, newline_count = 0;
+
+	blks = (len / 3);
+	left_over = len % 3;
+
+	if (out == NULL) {
+		idx2 = blks * 4 ;
+		if (left_over)
+			idx2 += 4;
+		if (newline_flag)
+			idx2 += len / 57;   // (NEWLINE_INVL / 4) * 3 = 57. One newline per 57 input bytes.
+	}
+	else {
+		// Since 3 input bytes = 4 output bytes, determine out how many even sets of
+		// 3 bytes the input has.
+		blk_ceiling = blks * 3;
+		for (idx = 0, idx2 = 0; idx < blk_ceiling; idx += 3, idx2 += 4) {
+			out[idx2]     = charset[in[idx] >> 2];
+			out[idx2 + 1] = charset[((in[idx] & 0x03) << 4) | (in[idx + 1] >> 4)];
+			out[idx2 + 2] = charset[((in[idx + 1] & 0x0f) << 2) | (in[idx + 2] >> 6)];
+			out[idx2 + 3] = charset[in[idx + 2] & 0x3F];
+			// The offical standard requires a newline every 76 characters.
+			// (Eg, first newline is character 77 of the output.)
+			if (((idx2 - newline_count + 4) % NEWLINE_INVL == 0) && newline_flag) {
+				out[idx2 + 4] = '\n';
+				idx2++;
+				newline_count++;
+			}
+		}
+
+		if (left_over == 1) {
+			out[idx2]     = charset[in[idx] >> 2];
+			out[idx2 + 1] = charset[(in[idx] & 0x03) << 4];
+			out[idx2 + 2] = '=';
+			out[idx2 + 3] = '=';
+			idx2 += 4;
+		}
+		else if (left_over == 2) {
+			out[idx2]     = charset[in[idx] >> 2];
+			out[idx2 + 1] = charset[((in[idx] & 0x03) << 4) | (in[idx + 1] >> 4)];
+			out[idx2 + 2] = charset[(in[idx + 1] & 0x0F) << 2];
+			out[idx2 + 3] = '=';
+			idx2 += 4;
+		}
+	}
+
+	return(idx2);
+}
+
+size_t base64_decode(const BYTE in[], BYTE out[], size_t len)
+{
+	//BYTE ch;
+	size_t idx, idx2, blks, blk_ceiling, left_over;
+
+	if (in[len - 1] == '=')
+		len--;
+	if (in[len - 1] == '=')
+		len--;
+
+	blks = len / 4;
+	left_over = len % 4;
+
+	if (out == NULL) {
+		if (len >= 77 && in[NEWLINE_INVL] == '\n')   // Verify that newlines where used.
+			len -= len / (NEWLINE_INVL + 1);
+		blks = len / 4;
+		left_over = len % 4;
+
+		idx = blks * 3;
+		if (left_over == 2)
+			idx ++;
+		else if (left_over == 3)
+			idx += 2;
+	}
+	else {
+		blk_ceiling = blks * 4;
+		for (idx = 0, idx2 = 0; idx2 < blk_ceiling; idx += 3, idx2 += 4) {
+			if (in[idx2] == '\n')
+				idx2++;
+			out[idx]     = (revchar(in[idx2]) << 2) | ((revchar(in[idx2 + 1]) & 0x30) >> 4);
+			out[idx + 1] = (revchar(in[idx2 + 1]) << 4) | (revchar(in[idx2 + 2]) >> 2);
+			out[idx + 2] = (revchar(in[idx2 + 2]) << 6) | revchar(in[idx2 + 3]);
+		}
+
+		if (left_over == 2) {
+			out[idx]     = (revchar(in[idx2]) << 2) | ((revchar(in[idx2 + 1]) & 0x30) >> 4);
+			idx++;
+		}
+		else if (left_over == 3) {
+			out[idx]     = (revchar(in[idx2]) << 2) | ((revchar(in[idx2 + 1]) & 0x30) >> 4);
+			out[idx + 1] = (revchar(in[idx2 + 1]) << 4) | (revchar(in[idx2 + 2]) >> 2);
+			idx += 2;
+		}
+	}
+
+	return(idx);
+}

user/base64.h

@@ -0,0 +1,27 @@
+/*********************************************************************
+* Filename:   base64.h
+* Author:     Brad Conte (brad AT bradconte.com)
+* Copyright:
+* Disclaimer: This code is presented "as is" without any guarantees.
+* Details:    Defines the API for the corresponding Base64 implementation.
+*********************************************************************/
+
+#ifndef BASE64_H
+#define BASE64_H
+
+/*************************** HEADER FILES ***************************/
+#include <stddef.h>
+
+/**************************** DATA TYPES ****************************/
+typedef unsigned char BYTE;             // 8-bit byte
+
+/*********************** FUNCTION DECLARATIONS **********************/
+// Returns the size of the output. If called with out = NULL, will just return
+// the size of what the output would have been (without a terminating NULL).
+size_t base64_encode(const BYTE in[], BYTE out[], size_t len, int newline_flag);
+
+// Returns the size of the output. If called with out = NULL, will just return
+// the size of what the output would have been (without a terminating NULL).
+size_t base64_decode(const BYTE in[], BYTE out[], size_t len);
+
+#endif   // BASE64_H

user/decode.c

@@ -0,0 +1,57 @@
+#include "base64.h"
+#include "arcfour.h"
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+#include "kernel/fcntl.h"
+
+/**
+ * This function reads Base64 encoded data from the specified file descriptor in chunks, decodes it back to its original form, and
+ * prints the decoded content to the console with its size.
+ *
+ * @param fd The file descriptor from which the encoded content is read
+ *
+ */
+void
+b64_decode(int fd)
+{
+  unsigned char buffer[1024];
+  unsigned char result[1024];
+  int n;
+
+  while ((n = read(fd, buffer, 1024)) > 0) {
+    int size = base64_decode(buffer, result, n);
+    printf("Your decoded secret is %s of size %d", result, size);
+  }
+  printf("\n");
+}
+
+/**
+ * This function reads command-line arguments to determine whether the arguments invoke the Base64 decoding function.
+ * It processes the specified input file accordingly.
+ *
+ * @param argc The number of command-line arguments
+ * @param argv The command-line arguments
+ * @return This function prints an error message and exits or closes and exits
+ *
+ */
+int
+main(int argc, char *argv[])
+{
+  char *crypto_option = argv[1];
+  char *file_name = argv[2];
+
+  int fd = open(file_name, O_RDONLY);
+  if (fd < 0) {
+    printf("ERROR, could not open the file %s\n", file_name);
+    exit(1);
+  }
+
+  if (strcmp(crypto_option, "-b") == 0) {
+    b64_decode(fd);
+  }
+
+  close(fd);
+  exit(1);
+
+}