path: root/coreutils/uudecode.c

/* vi: set sw=4 ts=4: */
/*
 * Copyright 2003, Glenn McGrath
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 *
 * Based on specification from
 * http://www.opengroup.org/onlinepubs/007904975/utilities/uuencode.html
 *
 * Bugs: the spec doesn't mention anything about "`\n`\n" prior to the
 * "end" line
 */
#include "libbb.h"

#if ENABLE_UUDECODE
static void read_stduu(FILE *src_stream, FILE *dst_stream)
{
	char *line;

	while ((line = xmalloc_fgetline(src_stream)) != NULL) {
		int encoded_len, str_len;
		char *line_ptr, *dst;

		if (strcmp(line, "end") == 0) {
			return; /* the only non-error exit */
		}

		line_ptr = line;
		while (*line_ptr) {
			*line_ptr = (*line_ptr - 0x20) & 0x3f;
			line_ptr++;
		}
		str_len = line_ptr - line;

		encoded_len = line[0] * 4 / 3;
		/* Check that line is not too short. (we tolerate
		 * overly _long_ line to accomodate possible extra '`').
		 * Empty line case is also caught here. */
		if (str_len <= encoded_len) {
			break; /* go to bb_error_msg_and_die("short file"); */
		}
		if (encoded_len <= 0) {
			/* Ignore the "`\n" line, why is it even in the encode file ? */
			free(line);
			continue;
		}
		if (encoded_len > 60) {
			bb_error_msg_and_die("line too long");
		}

		dst = line;
		line_ptr = line + 1;
		do {
			/* Merge four 6 bit chars to three 8 bit chars */
			*dst++ = line_ptr[0] << 2 | line_ptr[1] >> 4;
			encoded_len--;
			if (encoded_len == 0) {
				break;
			}

			*dst++ = line_ptr[1] << 4 | line_ptr[2] >> 2;
			encoded_len--;
			if (encoded_len == 0) {
				break;
			}

			*dst++ = line_ptr[2] << 6 | line_ptr[3];
			line_ptr += 4;
			encoded_len -= 2;
		} while (encoded_len > 0);
		fwrite(line, 1, dst - line, dst_stream);
		free(line);
	}
	bb_error_msg_and_die("short file");
}
#endif

static void read_base64(FILE *src_stream, FILE *dst_stream)
{
	int term_count = 0;

	while (1) {
		unsigned char translated[4];
		int count = 0;

		/* Process one group of 4 chars */
		while (count < 4) {
			char *table_ptr;
			int ch;

			/* Get next _valid_ character.
			 * bb_uuenc_tbl_base64[] contains this string:
			 *  0         1         2         3         4         5         6
			 *  012345678901234567890123456789012345678901234567890123456789012345
			 * "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=\n"
			 */
			do {
				ch = fgetc(src_stream);
				if (ch == EOF) {
					if (ENABLE_BASE64
					 && (!ENABLE_UUDECODE || applet_name[0] == 'b')
					 && count == 0
					) {
						return;
					}
					bb_error_msg_and_die("short file");
				}
				table_ptr = strchr(bb_uuenc_tbl_base64, ch);
			} while (!table_ptr);

			/* Convert encoded character to decimal */
			ch = table_ptr - bb_uuenc_tbl_base64;

			if (ch == 65 /* '\n' */) {
				/* Terminating "====" line? */
				if (term_count == 4)
					return; /* yes */
				term_count = 0;
				continue;
			}
			/* ch is 64 is char was '=', otherwise 0..63 */
			translated[count] = ch & 63; /* 64 -> 0 */
			if (ch == 64) {
				term_count++;
				break;
			}
			count++;
		}

		/* Merge 6 bit chars to 8 bit.
		 * count can be < 4 when we decode the tail:
		 * "eQ==" -> "y", not "y NUL NUL"
		 */
		if (count > 1)
			fputc(translated[0] << 2 | translated[1] >> 4, dst_stream);
		if (count > 2)
			fputc(translated[1] << 4 | translated[2] >> 2, dst_stream);
		if (count > 3)
			fputc(translated[2] << 6 | translated[3], dst_stream);
	} /* while (1) */
}

#if ENABLE_UUDECODE
int uudecode_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int uudecode_main(int argc UNUSED_PARAM, char **argv)
{
	FILE *src_stream;
	char *outname = NULL;
	char *line;

	opt_complementary = "?1"; /* 1 argument max */
	getopt32(argv, "o:", &outname);
	argv += optind;

	if (!argv[0])
		*--argv = (char*)"-";
	src_stream = xfopen_stdin(argv[0]);

	/* Search for the start of the encoding */
	while ((line = xmalloc_fgetline(src_stream)) != NULL) {
		void (*decode_fn_ptr)(FILE *src, FILE *dst);
		char *line_ptr;
		FILE *dst_stream;
		int mode;

		if (strncmp(line, "begin-base64 ", 13) == 0) {
			line_ptr = line + 13;
			decode_fn_ptr = read_base64;
		} else if (strncmp(line, "begin ", 6) == 0) {
			line_ptr = line + 6;
			decode_fn_ptr = read_stduu;
		} else {
			free(line);
			continue;
		}

		/* begin line found. decode and exit */
		mode = bb_strtou(line_ptr, NULL, 8);
		if (outname == NULL) {
			outname = strchr(line_ptr, ' ');
			if ((outname == NULL) || (*outname == '\0')) {
				break;
			}
			outname++;
		}
		dst_stream = stdout;
		if (NOT_LONE_DASH(outname)) {
			dst_stream = xfopen_for_write(outname);
			fchmod(fileno(dst_stream), mode & (S_IRWXU | S_IRWXG | S_IRWXO));
		}
		free(line);
		decode_fn_ptr(src_stream, dst_stream);
		/* fclose_if_not_stdin(src_stream); - redundant */
		return EXIT_SUCCESS;
	}
	bb_error_msg_and_die("no 'begin' line");
}
#endif

//applet:IF_BASE64(APPLET(base64, _BB_DIR_BIN, _BB_SUID_DROP))

//kbuild:lib-$(CONFIG_BASE64) += uudecode.o

//config:config BASE64
//config:	bool "base64"
//config:	default y
//config:	help
//config:	  Base64 encode and decode

//usage:#define base64_trivial_usage
//usage:	"[-d] [FILE]"
//usage:#define base64_full_usage "\n\n"
//usage:       "Base64 encode or decode FILE to standard output"
//usage:     "\nOptions:"
//usage:     "\n	-d	Decode data"
////usage:     "\n	-w COL	Wrap lines at COL (default 76, 0 disables)"
////usage:     "\n	-i	When decoding, ignore non-alphabet characters"

#if ENABLE_BASE64
int base64_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int base64_main(int argc UNUSED_PARAM, char **argv)
{
	FILE *src_stream;
	unsigned opts;

	opt_complementary = "?1"; /* 1 argument max */
	opts = getopt32(argv, "d");
	argv += optind;

	if (!argv[0])
		*--argv = (char*)"-";
	src_stream = xfopen_stdin(argv[0]);
	if (opts) {
		read_base64(src_stream, stdout);
	} else {
		enum {
			SRC_BUF_SIZE = 76/4*3,  /* This *MUST* be a multiple of 3 */
			DST_BUF_SIZE = 4 * ((SRC_BUF_SIZE + 2) / 3),
		};
		char src_buf[SRC_BUF_SIZE];
		char dst_buf[DST_BUF_SIZE + 1];
		int src_fd = fileno(src_stream);
		while (1) {
			size_t size = full_read(src_fd, src_buf, SRC_BUF_SIZE);
			if (!size)
				break;
			if ((ssize_t)size < 0)
				bb_perror_msg_and_die(bb_msg_read_error);
			/* Encode the buffer we just read in */
			bb_uuencode(dst_buf, src_buf, size, bb_uuenc_tbl_base64);
			xwrite(STDOUT_FILENO, dst_buf, 4 * ((size + 2) / 3));
			bb_putchar('\n');
			fflush(stdout);
		}
	}

	fflush_stdout_and_exit(EXIT_SUCCESS);
}
#endif

/* Test script.
Put this into an empty dir with busybox binary, an run.

#!/bin/sh
test -x busybox || { echo "No ./busybox?"; exit; }
ln -sf busybox uudecode
ln -sf busybox uuencode
>A_null
echo -n A >A
echo -n AB >AB
echo -n ABC >ABC
echo -n ABCD >ABCD
echo -n ABCDE >ABCDE
echo -n ABCDEF >ABCDEF
cat busybox >A_bbox
for f in A*; do
    echo uuencode $f
    ./uuencode    $f <$f >u_$f
    ./uuencode -m $f <$f >m_$f
done
mkdir unpk_u unpk_m 2>/dev/null
for f in u_*; do
    ./uudecode <$f -o unpk_u/${f:2}
    diff -a ${f:2} unpk_u/${f:2} >/dev/null 2>&1
    echo uudecode $f: $?
done
for f in m_*; do
    ./uudecode <$f -o unpk_m/${f:2}
    diff -a ${f:2} unpk_m/${f:2} >/dev/null 2>&1
    echo uudecode $f: $?
done
*/