gecko/media/gmp-clearkey/0.1/ClearKeyUtils.cpp

557 lines
13 KiB
C++

/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include <assert.h>
#include <ctype.h>
#include <stdarg.h>
#include <stdint.h>
#include <vector>
#include "ClearKeyUtils.h"
#include "mozilla/Endian.h"
#include "mozilla/NullPtr.h"
#include "openaes/oaes_lib.h"
using namespace std;
#define FOURCC(a,b,c,d) ((a << 24) + (b << 16) + (c << 8) + d)
// System ID identifying the cenc v2 pssh box format; specified at:
// https://dvcs.w3.org/hg/html-media/raw-file/tip/encrypted-media/cenc-format.html
const uint8_t kSystemID[] = {
0x10, 0x77, 0xef, 0xec, 0xc0, 0xb2, 0x4d, 0x02,
0xac, 0xe3, 0x3c, 0x1e, 0x52, 0xe2, 0xfb, 0x4b
};
void
CK_Log(const char* aFmt, ...)
{
va_list ap;
va_start(ap, aFmt);
vprintf(aFmt, ap);
va_end(ap);
printf("\n");
}
static void
IncrementIV(vector<uint8_t>& aIV) {
using mozilla::BigEndian;
assert(aIV.size() == 16);
BigEndian::writeUint64(&aIV[8], BigEndian::readUint64(&aIV[8]) + 1);
}
/* static */ void
ClearKeyUtils::DecryptAES(const vector<uint8_t>& aKey,
vector<uint8_t>& aData, vector<uint8_t>& aIV)
{
assert(aIV.size() == CLEARKEY_KEY_LEN);
assert(aKey.size() == CLEARKEY_KEY_LEN);
OAES_CTX* aes = oaes_alloc();
oaes_key_import_data(aes, &aKey[0], aKey.size());
oaes_set_option(aes, OAES_OPTION_ECB, nullptr);
for (size_t i = 0; i < aData.size(); i += CLEARKEY_KEY_LEN) {
size_t encLen;
oaes_encrypt(aes, &aIV[0], CLEARKEY_KEY_LEN, nullptr, &encLen);
vector<uint8_t> enc(encLen);
oaes_encrypt(aes, &aIV[0], CLEARKEY_KEY_LEN, &enc[0], &encLen);
for (size_t j = 0; j < CLEARKEY_KEY_LEN; j++) {
aData[i + j] ^= enc[2 * OAES_BLOCK_SIZE + j];
}
IncrementIV(aIV);
}
oaes_free(&aes);
}
/**
* ClearKey expects all Key IDs to be base64 encoded with non-standard alphabet
* and padding.
*/
static bool
EncodeBase64Web(vector<uint8_t> aBinary, string& aEncoded)
{
const char sAlphabet[] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
const uint8_t sMask = 0x3f;
aEncoded.resize((aBinary.size() * 8 + 5) / 6);
// Pad binary data in case there's rubbish past the last byte.
aBinary.push_back(0);
// Number of bytes not consumed in the previous character
uint32_t shift = 0;
auto out = aEncoded.begin();
auto data = aBinary.begin();
for (int i = 0; i < aEncoded.length(); i++) {
if (shift) {
out[i] = (*data << (6 - shift)) & sMask;
data++;
} else {
out[i] = 0;
}
out[i] += (*data >> (shift + 2)) & sMask;
shift = (shift + 2) % 8;
out[i] = sAlphabet[out[i]];
}
return true;
}
/* static */ void
ClearKeyUtils::ParseInitData(const uint8_t* aInitData, uint32_t aInitDataSize,
vector<KeyId>& aOutKeys)
{
using mozilla::BigEndian;
uint32_t size = 0;
for (uint32_t offset = 0; offset + sizeof(uint32_t) < aInitDataSize; offset += size) {
const uint8_t* data = aInitData + offset;
size = BigEndian::readUint32(data); data += sizeof(uint32_t);
CK_LOGD("Looking for pssh at offset %u", offset);
if (size + offset > aInitDataSize) {
CK_LOGE("Box size %u overflows init data buffer", size);
return;
}
if (size < 36) {
// Too small to be a cenc2 pssh box
continue;
}
uint32_t box = BigEndian::readUint32(data); data += sizeof(uint32_t);
if (box != FOURCC('p','s','s','h')) {
CK_LOGE("ClearKey CDM passed non-pssh initData");
return;
}
uint32_t head = BigEndian::readUint32(data); data += sizeof(uint32_t);
CK_LOGD("Got version %u pssh box, length %u", head & 0xff, size);
if ((head >> 24) != 1) {
// Ignore pssh boxes with wrong version
CK_LOGD("Ignoring pssh box with wrong version");
continue;
}
if (memcmp(kSystemID, data, sizeof(kSystemID))) {
// Ignore pssh boxes with wrong system ID
continue;
}
data += sizeof(kSystemID);
uint32_t kidCount = BigEndian::readUint32(data); data += sizeof(uint32_t);
if (data + kidCount * CLEARKEY_KEY_LEN > aInitData + aInitDataSize) {
CK_LOGE("pssh key IDs overflow init data buffer");
return;
}
for (uint32_t i = 0; i < kidCount; i++) {
aOutKeys.push_back(KeyId(data, data + CLEARKEY_KEY_LEN));
data += CLEARKEY_KEY_LEN;
}
}
}
/* static */ void
ClearKeyUtils::MakeKeyRequest(const vector<KeyId>& aKeyIDs,
string& aOutRequest)
{
MOZ_ASSERT(aKeyIDs.size() && aOutRequest.empty());
aOutRequest.append("{ \"kids\":[");
for (size_t i = 0; i < aKeyIDs.size(); i++) {
if (i) {
aOutRequest.append(",");
}
aOutRequest.append("\"");
string base64key;
EncodeBase64Web(aKeyIDs[i], base64key);
aOutRequest.append(base64key);
aOutRequest.append("\"");
}
aOutRequest.append("], \"type\":");
// TODO implement "persistent" session type
aOutRequest.append("\"temporary\"");
aOutRequest.append("}");
}
#define EXPECT_SYMBOL(CTX, X) do { \
if (GetNextSymbol(CTX) != (X)) { \
CK_LOGE("Unexpected symbol in JWK parser"); \
return false; \
} \
} while (false)
struct ParserContext {
const uint8_t* mIter;
const uint8_t* mEnd;
};
static uint8_t
PeekSymbol(ParserContext& aCtx)
{
for (; aCtx.mIter < aCtx.mEnd; (aCtx.mIter)++) {
if (!isspace(*aCtx.mIter)) {
return *aCtx.mIter;
}
}
return 0;
}
static uint8_t
GetNextSymbol(ParserContext& aCtx)
{
uint8_t sym = PeekSymbol(aCtx);
aCtx.mIter++;
return sym;
}
static bool SkipToken(ParserContext& aCtx);
static bool
SkipString(ParserContext& aCtx)
{
EXPECT_SYMBOL(aCtx, '"');
for (uint8_t sym = GetNextSymbol(aCtx); sym; sym = GetNextSymbol(aCtx)) {
if (sym == '\\') {
sym = GetNextSymbol(aCtx);
} else if (sym == '"') {
return true;
}
}
return false;
}
/**
* Skip whole object and values it contains.
*/
static bool
SkipObject(ParserContext& aCtx)
{
EXPECT_SYMBOL(aCtx, '{');
if (PeekSymbol(aCtx) == '}') {
GetNextSymbol(aCtx);
return true;
}
while (true) {
if (!SkipString(aCtx)) return false;
EXPECT_SYMBOL(aCtx, ':');
if (!SkipToken(aCtx)) return false;
if (PeekSymbol(aCtx) == '}') {
GetNextSymbol(aCtx);
return true;
}
EXPECT_SYMBOL(aCtx, ',');
}
return false;
}
/**
* Skip array value and the values it contains.
*/
static bool
SkipArray(ParserContext& aCtx)
{
EXPECT_SYMBOL(aCtx, '[');
if (PeekSymbol(aCtx) == ']') {
GetNextSymbol(aCtx);
return true;
}
while (SkipToken(aCtx)) {
if (PeekSymbol(aCtx) == ']') {
GetNextSymbol(aCtx);
return true;
}
EXPECT_SYMBOL(aCtx, ',');
}
return false;
}
/**
* Skip unquoted literals like numbers, |true|, and |null|.
* (XXX and anything else that matches /([:alnum:]|[+-.])+/)
*/
static bool
SkipLiteral(ParserContext& aCtx)
{
for (; aCtx.mIter < aCtx.mEnd; aCtx.mIter++) {
if (!isalnum(*aCtx.mIter) &&
*aCtx.mIter != '.' && *aCtx.mIter != '-' && *aCtx.mIter != '+') {
return true;
}
}
return false;
}
static bool
SkipToken(ParserContext& aCtx)
{
uint8_t startSym = PeekSymbol(aCtx);
if (startSym == '"') {
CK_LOGD("JWK parser skipping string");
return SkipString(aCtx);
} else if (startSym == '{') {
CK_LOGD("JWK parser skipping object");
return SkipObject(aCtx);
} else if (startSym == '[') {
CK_LOGD("JWK parser skipping array");
return SkipArray(aCtx);
} else {
CK_LOGD("JWK parser skipping literal");
return SkipLiteral(aCtx);
}
return false;
}
static bool
GetNextLabel(ParserContext& aCtx, string& aOutLabel)
{
EXPECT_SYMBOL(aCtx, '"');
const uint8_t* start = aCtx.mIter;
for (uint8_t sym = GetNextSymbol(aCtx); sym; sym = GetNextSymbol(aCtx)) {
if (sym == '\\') {
GetNextSymbol(aCtx);
continue;
}
if (sym == '"') {
aOutLabel.assign(start, aCtx.mIter - 1);
return true;
}
}
return false;
}
/**
* Take a base64-encoded string, convert (in-place) each character to its
* corresponding value in the [0x00, 0x3f] range, and truncate any padding.
*/
static bool
Decode6Bit(string& aStr)
{
for (size_t i = 0; i < aStr.length(); i++) {
if (aStr[i] >= 'A' && aStr[i] <= 'Z') {
aStr[i] -= 'A';
} else if (aStr[i] >= 'a' && aStr[i] <= 'z') {
aStr[i] -= 'a' - 26;
} else if (aStr[i] >= '0' && aStr[i] <= '9') {
aStr[i] -= '0' - 52;
} else if (aStr[i] == '-' || aStr[i] == '+') {
aStr[i] = 62;
} else if (aStr[i] == '_' || aStr[i] == '/') {
aStr[i] = 63;
} else {
// Truncate '=' padding at the end of the aString.
if (aStr[i] != '=') {
return false;
}
aStr[i] = '\0';
aStr.resize(i);
break;
}
}
return true;
}
static bool
DecodeBase64(string& aEncoded, vector<uint8_t>& aOutDecoded)
{
if (!Decode6Bit(aEncoded)) {
return false;
}
// The number of bytes we haven't yet filled in the current byte, mod 8.
int shift = 0;
aOutDecoded.resize(aEncoded.length() * 6 / 8);
aOutDecoded.reserve(aEncoded.length() * 6 / 8 + 1);
auto out = aOutDecoded.begin();
for (size_t i = 0; i < aEncoded.length(); i++) {
if (!shift) {
*out = aEncoded[i] << 2;
} else {
*out |= aEncoded[i] >> (6 - shift);
*(++out) = aEncoded[i] << (shift + 2);
}
shift = (shift + 2) % 8;
}
return true;
}
static bool
DecodeKey(string& aEncoded, Key& aOutDecoded)
{
return DecodeBase64(aEncoded, aOutDecoded) &&
// Key should be 128 bits long.
aOutDecoded.size() == CLEARKEY_KEY_LEN;
}
static bool
ParseKeyObject(ParserContext& aCtx, KeyIdPair& aOutKey, bool& aOutValid)
{
aOutValid = false;
EXPECT_SYMBOL(aCtx, '{');
// Ignore empty objects
if (PeekSymbol(aCtx) == '}') {
GetNextSymbol(aCtx);
return true;
}
// By spec, type should be "oct".
bool isExpectedType = false;
// By spec, alg should be "A128KW".
bool isExpectedAlg = false;
string keyId;
string key;
while (true) {
string label;
string value;
if (!GetNextLabel(aCtx, label)) {
return false;
}
EXPECT_SYMBOL(aCtx, ':');
if (label == "kty") {
if (!GetNextLabel(aCtx, value)) return false;
isExpectedType = value == "oct";
} else if (label == "alg") {
if (!GetNextLabel(aCtx, value)) return false;
isExpectedAlg = value == "A128KW";
} else if (label == "k" && PeekSymbol(aCtx) == '"') {
// if this isn't a string we will fall through to the SkipToken() path.
if (!GetNextLabel(aCtx, key)) return false;
} else if (label == "kid" && PeekSymbol(aCtx) == '"') {
if (!GetNextLabel(aCtx, keyId)) return false;
} else {
if (!SkipToken(aCtx)) return false;
}
uint8_t sym = PeekSymbol(aCtx);
if (!sym || sym == '}') {
break;
}
EXPECT_SYMBOL(aCtx, ',');
}
if (isExpectedType && isExpectedAlg &&
!key.empty() && !keyId.empty() &&
DecodeBase64(keyId, aOutKey.mKeyId) &&
DecodeKey(key, aOutKey.mKey)) {
aOutValid = true;
}
return GetNextSymbol(aCtx) == '}';
}
static bool
ParseKeys(ParserContext& aCtx, vector<KeyIdPair>& aOutKeys)
{
// Consume start of array.
EXPECT_SYMBOL(aCtx, '[');
while (true) {
KeyIdPair key;
bool valid;
if (!ParseKeyObject(aCtx, key, valid)) {
CK_LOGE("Failed to parse key object");
return false;
}
if (valid) {
aOutKeys.push_back(key);
}
uint8_t sym = PeekSymbol(aCtx);
if (!sym || sym == ']') {
break;
}
EXPECT_SYMBOL(aCtx, ',');
}
return GetNextSymbol(aCtx) == ']';
}
/* static */ bool
ClearKeyUtils::ParseJWK(const uint8_t* aKeyData, uint32_t aKeyDataSize,
vector<KeyIdPair>& aOutKeys)
{
ParserContext ctx;
ctx.mIter = aKeyData;
ctx.mEnd = aKeyData + aKeyDataSize;
// Consume '{' from start of object.
EXPECT_SYMBOL(ctx, '{');
while (true) {
string label;
// Consume member key.
if (!GetNextLabel(ctx, label)) return false;
EXPECT_SYMBOL(ctx, ':');
if (label == "keys") {
// Parse "keys" array.
if (!ParseKeys(ctx, aOutKeys)) return false;
} else if (label == "type") {
// Consume type string.
string type;
if (!GetNextLabel(ctx, type)) return false;
// XXX todo support "persistent" session type
if (type != "temporary") {
return false;
}
} else {
SkipToken(ctx);
}
// Check for end of object.
if (PeekSymbol(ctx) == '}') {
break;
}
// Consume ',' between object members.
EXPECT_SYMBOL(ctx, ',');
}
// Consume '}' from end of object.
EXPECT_SYMBOL(ctx, '}');
return true;
}