PlaylistFetcher: Add support for block-by-block decryption. (2cd94583) · Commits · e / os / android_frameworks_av

media/libstagefright/httplive/PlaylistFetcher.cpp

+59 −36

Original line number	Diff line number	Diff line
		@@ -170,7 +170,8 @@ int64_t PlaylistFetcher::delayUsToRefreshPlaylist() const {
		}

		status_t PlaylistFetcher::decryptBuffer(
		size_t playlistIndex, const sp<ABuffer> &buffer) {
		size_t playlistIndex, const sp<ABuffer> &buffer,
		bool first) {
		sp<AMessage> itemMeta;
		bool found = false;
		AString method;
		@@ -188,6 +189,7 @@ status_t PlaylistFetcher::decryptBuffer(
		if (!found) {
		method = "NONE";
		}
		buffer->meta()->setString("cipher-method", method.c_str());

		if (method == "NONE") {
		return OK;
		@@ -227,7 +229,15 @@ status_t PlaylistFetcher::decryptBuffer(
		return UNKNOWN_ERROR;
		}

		unsigned char aes_ivec[16];
		size_t n = buffer->size();
		if (!n) {
		return OK;
		}
		CHECK(n % 16 == 0);

		if (first) {
		// If decrypting the first block in a file, read the iv from the manifest
		// or derive the iv from the file's sequence number.

		AString iv;
		if (itemMeta->findString("cipher-iv", &iv)) {
		@@ -237,7 +247,7 @@ status_t PlaylistFetcher::decryptBuffer(
		return ERROR_MALFORMED;
		}

		memset(aes_ivec, 0, sizeof(aes_ivec));
		memset(mAESInitVec, 0, sizeof(mAESInitVec));
		for (size_t i = 0; i < 16; ++i) {
		char c1 = tolower(iv.c_str()[2 + 2 * i]);
		char c2 = tolower(iv.c_str()[3 + 2 * i]);
		@@ -248,38 +258,48 @@ status_t PlaylistFetcher::decryptBuffer(
		uint8_t nibble1 = isdigit(c1) ? c1 - '0' : c1 - 'a' + 10;
		uint8_t nibble2 = isdigit(c2) ? c2 - '0' : c2 - 'a' + 10;

		aes_ivec[i] = nibble1 << 4 \| nibble2;
		mAESInitVec[i] = nibble1 << 4 \| nibble2;
		}
		} else {
		memset(aes_ivec, 0, sizeof(aes_ivec));
		aes_ivec[15] = mSeqNumber & 0xff;
		aes_ivec[14] = (mSeqNumber >> 8) & 0xff;
		aes_ivec[13] = (mSeqNumber >> 16) & 0xff;
		aes_ivec[12] = (mSeqNumber >> 24) & 0xff;
		memset(mAESInitVec, 0, sizeof(mAESInitVec));
		mAESInitVec[15] = mSeqNumber & 0xff;
		mAESInitVec[14] = (mSeqNumber >> 8) & 0xff;
		mAESInitVec[13] = (mSeqNumber >> 16) & 0xff;
		mAESInitVec[12] = (mSeqNumber >> 24) & 0xff;
		}
		}

		AES_cbc_encrypt(
		buffer->data(), buffer->data(), buffer->size(),
		&aes_key, aes_ivec, AES_DECRYPT);
		&aes_key, mAESInitVec, AES_DECRYPT);

		// hexdump(buffer->data(), buffer->size());

		size_t n = buffer->size();
		CHECK_GT(n, 0u);
		return OK;
		}

		size_t pad = buffer->data()[n - 1];
		status_t PlaylistFetcher::checkDecryptPadding(const sp<ABuffer> &buffer) {
		status_t err;
		AString method;
		CHECK(buffer->meta()->findString("cipher-method", &method));
		if (method == "NONE") {
		return OK;
		}

		CHECK_GT(pad, 0u);
		CHECK_LE(pad, 16u);
		CHECK_GE((size_t)n, pad);
		for (size_t i = 0; i < pad; ++i) {
		CHECK_EQ((unsigned)buffer->data()[n - 1 - i], pad);
		uint8_t padding = 0;
		if (buffer->size() > 0) {
		padding = buffer->data()[buffer->size() - 1];
		}

		n -= pad;
		if (padding > 16) {
		return ERROR_MALFORMED;
		}

		buffer->setRange(buffer->offset(), n);
		for (size_t i = buffer->size() - padding; i < padding; i++) {
		if (buffer->data()[i] != padding) {
		return ERROR_MALFORMED;
		}
		}

		buffer->setRange(buffer->offset(), buffer->size() - padding);
		return OK;
		}

		@@ -706,6 +726,9 @@ void PlaylistFetcher::onDownloadNext() {
		CHECK(buffer != NULL);

		err = decryptBuffer(mSeqNumber - firstSeqNumberInPlaylist, buffer);
		if (err == OK) {
		err = checkDecryptPadding(buffer);
		}

		if (err != OK) {
		ALOGE("decryptBuffer failed w/ error %d", err);

media/libstagefright/httplive/PlaylistFetcher.h

+16 −1

Original line number	Diff line number	Diff line
		@@ -119,8 +119,23 @@ private:
		uint64_t mFirstPTS;
		int64_t mAbsoluteTimeAnchorUs;

		// Stores the initialization vector to decrypt the next block of cipher text, which can
		// either be derived from the sequence number, read from the manifest, or copied from
		// the last block of cipher text (cipher-block chaining).
		unsigned char mAESInitVec[16];

		// Set first to true if decrypting the first segment of a playlist segment. When
		// first is true, reset the initialization vector based on the available
		// information in the manifest; otherwise, use the initialization vector as
		// updated by the last call to AES_cbc_encrypt.
		//
		// For the input to decrypt correctly, decryptBuffer must be called on
		// consecutive byte ranges on block boundaries, e.g. 0..15, 16..47, 48..63,
		// and so on.
		status_t decryptBuffer(
		size_t playlistIndex, const sp<ABuffer> &buffer);
		size_t playlistIndex, const sp<ABuffer> &buffer,
		bool first = true);
		status_t checkDecryptPadding(const sp<ABuffer> &buffer);

		void postMonitorQueue(int64_t delayUs = 0, int64_t minDelayUs = 0);
		void cancelMonitorQueue();