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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2020-2021 Jason A. Donenfeld. All Rights Reserved.
*/
#include "constants.h"
#include "crypto.h"
#include "filelist.h"
#include <stdbool.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
static inline int decode_base64(const char src[static 4])
{
int val = 0;
for (unsigned int i = 0; i < 4; ++i)
val |= (-1
+ ((((('A' - 1) - src[i]) & (src[i] - ('Z' + 1))) >> 8) & (src[i] - 64))
+ ((((('a' - 1) - src[i]) & (src[i] - ('z' + 1))) >> 8) & (src[i] - 70))
+ ((((('0' - 1) - src[i]) & (src[i] - ('9' + 1))) >> 8) & (src[i] + 5))
+ ((((('+' - 1) - src[i]) & (src[i] - ('+' + 1))) >> 8) & 63)
+ ((((('/' - 1) - src[i]) & (src[i] - ('/' + 1))) >> 8) & 64)
) << (18 - 6 * i);
return val;
}
bool signify_pubkey_from_base64(uint8_t key[static 42], const char base64[static 56])
{
unsigned int i;
volatile uint8_t ret = 0;
int val;
for (i = 0; i < 42 / 3; ++i) {
val = decode_base64(&base64[i * 4]);
ret |= (uint32_t)val >> 31;
key[i * 3 + 0] = (val >> 16) & 0xff;
key[i * 3 + 1] = (val >> 8) & 0xff;
key[i * 3 + 2] = val & 0xff;
}
return 1 & ((ret - 1) >> 8);
}
bool signify_signature_from_base64(uint8_t sig[static 74], const char base64[static 100])
{
unsigned int i;
volatile uint8_t ret = 0;
int val;
if (base64[99] != '=')
return false;
for (i = 0; i < 74 / 3; ++i) {
val = decode_base64(&base64[i * 4]);
ret |= (uint32_t)val >> 31;
sig[i * 3 + 0] = (val >> 16) & 0xff;
sig[i * 3 + 1] = (val >> 8) & 0xff;
sig[i * 3 + 2] = val & 0xff;
}
val = decode_base64((const char[]){ base64[i * 4 + 0], base64[i * 4 + 1], base64[i * 4 + 2], 'A' });
ret |= ((uint32_t)val >> 31) | (val & 0xff);
sig[i * 3 + 0] = (val >> 16) & 0xff;
sig[i * 3 + 1] = (val >> 8) & 0xff;
return 1 & ((ret - 1) >> 8);
}
bool hash_from_hex(uint8_t hash[static 32], const char hex[static 64])
{
uint8_t c, c_acc, c_alpha0, c_alpha, c_num0, c_num, c_val;
volatile uint8_t ret = 0;
for (unsigned int i = 0; i < 64; i += 2) {
c = (uint8_t)hex[i];
c_num = c ^ 48U;
c_num0 = (c_num - 10U) >> 8;
c_alpha = (c & ~32U) - 55U;
c_alpha0 = ((c_alpha - 10U) ^ (c_alpha - 16U)) >> 8;
ret |= ((c_num0 | c_alpha0) - 1) >> 8;
c_val = (c_num0 & c_num) | (c_alpha0 & c_alpha);
c_acc = c_val * 16U;
c = (uint8_t)hex[i + 1];
c_num = c ^ 48U;
c_num0 = (c_num - 10U) >> 8;
c_alpha = (c & ~32U) - 55U;
c_alpha0 = ((c_alpha - 10U) ^ (c_alpha - 16U)) >> 8;
ret |= ((c_num0 | c_alpha0) - 1) >> 8;
c_val = (c_num0 & c_num) | (c_alpha0 & c_alpha);
hash[i / 2] = c_acc | c_val;
}
return 1 & ((ret - 1) >> 8);
}
static uint64_t parse_version(const char *str, size_t len)
{
uint64_t version = 0;
unsigned long nibble;
const char *limit = str + len;
char *end;
for (int shift = 64 - 16; shift >= 0; shift -= 16, str = end + 1) {
if (str[0] == '-' || str[0] == '+')
return 0;
nibble = strtoul(str, &end, 10);
if (nibble > UINT16_MAX)
return 0;
version |= (uint64_t)nibble << shift;
if (end >= limit)
break;
if (end[0] != '.')
return 0;
}
return version;
}
bool extract_newest_file(char filename[static MAX_FILENAME_LEN], uint8_t hash[static 32], const char *list, size_t len, const char *arch)
{
const char *first_nl, *second_nl, *line_start, *line_end;
char msi_prefix[sizeof(msi_arch_prefix) + 10];
int msi_prefix_len;
uint8_t pubkey[42], signature[74];
uint64_t biggest_version = 0, version;
if ((msi_prefix_len = _snprintf_s(msi_prefix, sizeof(msi_prefix), _TRUNCATE, msi_arch_prefix, arch)) < 0)
return false;
if (!signify_pubkey_from_base64(pubkey, release_public_key_base64))
return false;
first_nl = memchr(list, '\n', len);
if (!first_nl)
return false;
second_nl = memchr(first_nl + 1, '\n', len - (first_nl + 1 - list));
if (!second_nl)
return false;
if (len < 19 || memcmp(list, "untrusted comment: ", 19))
return false;
if (second_nl - first_nl != 101)
return false;
if (!signify_signature_from_base64(signature, first_nl + 1))
return false;
if (memcmp(pubkey, signature, 10))
return false;
if (!ed25519_verify(signature + 10, pubkey + 10, second_nl + 1, len - (second_nl + 1 - list)))
return false;
for (line_start = second_nl + 1; line_start < list + len; line_start = line_end + 1) {
line_end = memchr(line_start + 1, '\n', len - (line_start + 1 - list));
if (!line_end)
break;
if ((size_t)(line_end - line_start) < (64 + 2 + msi_prefix_len + strlen(msi_suffix) + 1) || line_start[64] != ' ' || line_start[65] != ' ')
continue;
if (memcmp(msi_prefix, line_start + 66, msi_prefix_len) || memcmp(msi_suffix, line_end - strlen(msi_suffix), strlen(msi_suffix)))
continue;
if (line_end - line_start - 66 > MAX_FILENAME_LEN - 1)
continue;
version = parse_version(line_start + 66 + msi_prefix_len, line_end - strlen(msi_suffix) - line_start - 66 - msi_prefix_len);
if (version < biggest_version)
continue;
if (!hash_from_hex(hash, line_start))
continue;
memcpy(filename, line_start + 66, line_end - line_start - 66);
filename[line_end - line_start - 66] = '\0';
biggest_version = version;
}
return biggest_version > 0;
}
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