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/* Copyright 2017 The ChromiumOS Authors
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
/* Base-32 encoding/decoding */
#include "base32.h"
#include "common.h"
#include "util.h"
static const unsigned char crc5_table1[] = { 0x00, 0x0E, 0x1C, 0x12, 0x11, 0x1F,
0x0D, 0x03, 0x0B, 0x05, 0x17, 0x19,
0x1A, 0x14, 0x06, 0x08 };
static const unsigned char crc5_table0[] = { 0x00, 0x16, 0x05, 0x13, 0x0A, 0x1C,
0x0F, 0x19, 0x14, 0x02, 0x11, 0x07,
0x1E, 0x08, 0x1B, 0x0D };
uint8_t crc5_sym(uint8_t sym, uint8_t previous_crc)
{
uint8_t tmp = sym ^ previous_crc;
return crc5_table1[tmp & 0x0F] ^ crc5_table0[(tmp >> 4) & 0x0F];
}
/* A-Z0-9 with I,O,0,1 removed */
const char base32_map[33] = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789";
/**
* Decode a base32 symbol.
*
* @param sym Input symbol
* @return The symbol value or -1 if error.
*/
static int decode_sym(int sym)
{
int i = 0;
for (i = 0; i < 32; i++) {
if (sym == base32_map[i])
return i;
}
return -1;
}
int base32_encode(char *dest, int destlen_chars, const void *srcbits,
int srclen_bits, int add_crc_every)
{
const uint8_t *src = srcbits;
int destlen_needed;
int crc = 0, crc_count = 0;
int didx = 0;
int i;
*dest = 0;
/* Make sure destination is big enough */
destlen_needed = (srclen_bits + 4) / 5; /* Symbols before adding CRC */
if (add_crc_every) {
/* Must be an exact number of groups to add CRC */
if (destlen_needed % add_crc_every)
return EC_ERROR_INVAL;
destlen_needed += destlen_needed / add_crc_every;
}
destlen_needed++; /* For terminating null */
if (destlen_chars < destlen_needed)
return EC_ERROR_INVAL;
for (i = 0; i < srclen_bits; i += 5) {
int sym;
int sidx = i / 8;
int bit_offs = i % 8;
if (bit_offs <= 3) {
/* Entire symbol fits in that byte */
sym = src[sidx] >> (3 - bit_offs);
} else {
/* Use the bits we have left */
sym = src[sidx] << (bit_offs - 3);
/* Use the bits from the next byte, if any */
if (i + 1 < srclen_bits)
sym |= src[sidx + 1] >> (11 - bit_offs);
}
sym &= 0x1f;
/* Pad incomplete symbol with 0 bits */
if (srclen_bits - i < 5)
sym &= 0x1f << (5 + i - srclen_bits);
dest[didx++] = base32_map[sym];
/* Add CRC if needed */
if (add_crc_every) {
crc = crc5_sym(sym, crc);
if (++crc_count == add_crc_every) {
dest[didx++] = base32_map[crc];
crc_count = crc = 0;
}
}
}
/* Terminate string and return */
dest[didx] = 0;
return EC_SUCCESS;
}
int base32_decode(uint8_t *dest, int destlen_bits, const char *src,
int crc_after_every)
{
int crc = 0, crc_count = 0;
int out_bits = 0;
for (; *src; src++) {
int sym, sbits, dbits, b;
if (isspace((unsigned char)*src) || *src == '-')
continue;
sym = decode_sym(*src);
if (sym < 0)
return -1; /* Bad input symbol */
/* Check CRC if needed */
if (crc_after_every) {
if (crc_count == crc_after_every) {
if (crc != sym)
return -1;
crc_count = crc = 0;
continue;
} else {
crc = crc5_sym(sym, crc);
crc_count++;
}
}
/*
* Stop if we're out of space. Have to do this after checking
* the CRC, or we might not check the last CRC.
*/
if (out_bits >= destlen_bits)
break;
/* See how many bits we get to use from this symbol */
sbits = MIN(5, destlen_bits - out_bits);
if (sbits < 5)
sym >>= (5 - sbits);
/* Fill up the rest of the current byte */
dbits = 8 - (out_bits & 7);
b = MIN(dbits, sbits);
if (dbits == 8)
dest[out_bits / 8] = 0; /* Starting a new byte */
dest[out_bits / 8] |= (sym << (dbits - b)) >> (sbits - b);
out_bits += b;
sbits -= b;
/* Start the next byte if there's space */
if (sbits > 0) {
dest[out_bits / 8] = sym << (8 - sbits);
out_bits += sbits;
}
}
/* If we have CRCs, should have a full group */
if (crc_after_every && crc_count)
return -1;
return out_bits;
}
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