firmware_handler.cpp - openbmc/phosphor-ipmi-flash - Gitiles

 /*
  * Copyright 2018 Google Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #include "firmware_handler.hpp"

 #include "image_handler.hpp"

 #include <algorithm>
 #include <cstdint>
 #include <cstring>
 #include <memory>
 #include <string>
 #include <vector>

 namespace blobs
 {
 // systemd service to kick start a target.
 static constexpr auto systemdService = "org.freedesktop.systemd1";
 static constexpr auto systemdRoot = "/org/freedesktop/systemd1";
 static constexpr auto systemdInterface = "org.freedesktop.systemd1.Manager";
 static constexpr auto verifyTarget = "verify_image.service";

 const std::string FirmwareBlobHandler::verifyBlobID = "/flash/verify";
 const std::string FirmwareBlobHandler::hashBlobID = "/flash/hash";
 const std::string FirmwareBlobHandler::activeImageBlobID =
     "/flash/active/image";
 const std::string FirmwareBlobHandler::activeHashBlobID = "/flash/active/hash";

 std::unique_ptr<GenericBlobInterface>
     FirmwareBlobHandler::CreateFirmwareBlobHandler(
         sdbusplus::bus::bus&& bus, const std::vector<HandlerPack>& firmwares,
         const std::vector<DataHandlerPack>& transports)
 {
     /* There must be at least one. */
     if (!firmwares.size())
     {
         return nullptr;
     }
     if (!transports.size())
     {
         return nullptr;
     }

     std::vector<std::string> blobs;
     for (const auto& item : firmwares)
     {
         blobs.push_back(item.blobName);
     }
     blobs.push_back(verifyBlobID); /* Add blob_id to always exist. */

     if (0 == std::count(blobs.begin(), blobs.end(), hashBlobID))
     {
         return nullptr;
     }

     std::uint16_t bitmask = 0;
     for (const auto& item : transports)
     {
         /* TODO: can use std::accumulate() unless I'm mistaken. :D */
         bitmask |= item.bitmask;
     }

     return std::make_unique<FirmwareBlobHandler>(std::move(bus), firmwares,
                                                  blobs, transports, bitmask);
 }

 /* Check if the path is in our supported list (or active list). */
 bool FirmwareBlobHandler::canHandleBlob(const std::string& path)
 {
     if (std::count(blobIDs.begin(), blobIDs.end(), path))
     {
         return true;
     }

     return false;
 }

 /*
  * Grab the list of supported firmware.
  *
  * If there's an open firmware session, it'll already be present in the
  * list as "/flash/active/image", and if the hash has started,
  * "/flash/active/hash" regardless of mechanism.  This is done in the open
  * comamnd, no extra work is required here.
  */
 std::vector<std::string> FirmwareBlobHandler::getBlobIds()
 {
     return blobIDs;
 }

 /*
  * Per the design, this mean abort, and this will trigger whatever
  * appropriate actions are required to abort the process.
  *
  * You cannot delete a blob that has an open handle in the system, therefore
  * this is never called if there's an open session.  Guaranteed by the blob
  * manager.
  */
 bool FirmwareBlobHandler::deleteBlob(const std::string& path)
 {
     const std::string* toDelete;

     /* You cannot delete the verify blob -- trying to delete it, currently has
      * no impact.
      * TODO: Should trying to delete this cause an abort?
      */
     if (path == verifyBlobID)
     {
         return false;
     }

     if (path == hashBlobID || path == activeHashBlobID)
     {
         /* They're deleting the hash. */
         toDelete = &activeHashBlobID;
     }
     else
     {
         /* They're deleting the image. */
         toDelete = &activeImageBlobID;
     }

     auto it = std::find_if(
         blobIDs.begin(), blobIDs.end(),
         [toDelete](const auto& iter) { return (iter == *toDelete); });
     if (it == blobIDs.end())
     {
         /* Somehow they've asked to delete something we didn't say we could
          * handle.
          */
         return false;
     }

     blobIDs.erase(it);

     /* TODO: Handle aborting the process and fixing up the state. */

     return true;
 }

 /*
  * Stat on the files will return information such as what supported
  * transport mechanisms are available.
  *
  * Stat on an active file or hash will return information such as the size
  * of the data cached, and any additional pertinent information.  The
  * blob_state on the active files will return the state of the update.
  */
 bool FirmwareBlobHandler::stat(const std::string& path, struct BlobMeta* meta)
 {
     /* We know we support this path because canHandle is called ahead */
     if (path == verifyBlobID)
     {
         /* We need to return information for the verify state -- did they call
          * commit() did things start?
          */
     }
     else if (path == activeImageBlobID)
     {
         /* We need to return information for the image that's staged. */
     }
     else if (path == activeHashBlobID)
     {
         /* We need to return information for the hash that's staged. */
     }
     else
     {
         /* They are requesting information about the generic blob_id. */
         meta->blobState = bitmask;
         meta->size = 0;

         /* The generic blob_ids state is only the bits related to the transport
          * mechanisms.
          */
         return true;
     }

     return false;
 }

 /*
  * Return stat information on an open session.  It therefore must be an active
  * handle to either the active image or active hash.
  *
  * The stat() and sessionstat() commands will return the same information in
  * many cases, therefore the logic will be combined.
  *
  * TODO: combine the logic for stat and sessionstat().
  */
 bool FirmwareBlobHandler::stat(uint16_t session, struct BlobMeta* meta)
 {
     auto item = lookup.find(session);
     if (item == lookup.end())
     {
         return false;
     }

     /* The blobState here relates to an active sesion, so we should return the
      * flags used to open this session.
      */
     meta->blobState = item->second->flags;
     /* The size here refers to the size of the file -- of something analagous.
      */
     meta->size = item->second->imageHandler->getSize();

     /* The metadata blob returned comes from the data handler... it's used for
      * instance, in P2A bridging to get required information about the mapping,
      * and is the "opposite" of the lpc writemeta requirement.
      */
     meta->metadata.clear();
     if (item->second->dataHandler)
     {
         auto bytes = item->second->dataHandler->read();
         meta->metadata.insert(meta->metadata.begin(), bytes.begin(),
                               bytes.end());
     }

     /* TODO: During things like verification, etc, we can report the state as
      * committed, etc, so we'll need to do that.
      */

     return true;
 }

 /*
  * If you open /flash/image or /flash/tarball, or /flash/hash it will
  * interpret the open flags and perform whatever actions are required for
  * that update process.  The session returned can be used immediately for
  * sending data down, without requiring one to open the new active file.
  *
  * If you open the active flash image or active hash it will let you
  * overwrite pieces, depending on the state.
  *
  * Once the verification process has started the active files cannot be
  * opened.
  *
  * You can only have one open session at a time.  Which means, you can only
  * have one file open at a time.  Trying to open the hash blob_id while you
  * still have the flash image blob_id open will fail.  Opening the flash
  * blob_id when it is already open will fail.
  */
 bool FirmwareBlobHandler::open(uint16_t session, uint16_t flags,
                                const std::string& path)
 {
     /* Check that they've opened for writing - read back not currently
      * supported.
      */
     if ((flags & OpenFlags::write) == 0)
     {
         return false;
     }

     /* Is the verification process underway? */
     if (state == UpdateState::verificationStarted)
     {
         return false;
     }

     /* Is there an open session already? We only allow one at a time.
      *
      * TODO: Temporarily using a simple boolean flag until there's a full
      * session object to check.
      *
      * Further on this, if there's an active session to the hash we don't allow
      * re-opening the image, and if we have the image open, we don't allow
      * opening the hash.  This design decision may be re-evaluated, and changed
      * to only allow one session per object type (of the two types).  But,
      * consider if the hash is open, do we want to allow writing to the image?
      * And why would we?  But, really, the point of no-return is once the
      * verification process has begun -- which is done via commit() on the hash
      * blob_id, we no longer want to allow updating the contents.
      */
     if (fileOpen)
     {
         return false;
     }

     /* Handle opening the verifyBlobId --> we know the image and hash aren't
      * open because of the fileOpen check.
      *
      * The file must be opened for writing, but no transport mechanism specified
      * since it's irrelevant.
      */
     if (path == verifyBlobID)
     {
         /* In this case, there's no image handler to use, or data handler,
          * simply set up a session.
          */
         verifyImage.flags = flags;
         verifyImage.state = Session::State::open;

         lookup[session] = &verifyImage;

         fileOpen = true;

         return true;
     }

     /* There are two abstractions at play, how you get the data and how you
      * handle that data. such that, whether the data comes from the PCI bridge
      * or LPC bridge is not connected to whether the data goes into a static
      * layout flash update or a UBI tarball.
      */

     /* Check the flags for the transport mechanism: if none match we don't
      * support what they request.
      */
     if ((flags & bitmask) == 0)
     {
         return false;
     }

     /* 2) there isn't, so what are they opening? */
     if (path == activeImageBlobID)
     {
         /* 2a) are they opening the active image? this can only happen if they
          * already started one (due to canHandleBlob's behavior).
          */
         return false;
     }
     else if (path == activeHashBlobID)
     {
         /* 2b) are they opening the active hash? this can only happen if they
          * already started one (due to canHandleBlob's behavior).
          */
         return false;
     }

     /* How are they expecting to copy this data? */
     auto d = std::find_if(
         transports.begin(), transports.end(),
         [&flags](const auto& iter) { return (iter.bitmask & flags); });
     if (d == transports.end())
     {
         return false;
     }

     /* We found the transport handler they requested, no surprise since
      * above we verify they selected at least one we wanted.
      */
     Session* curr;
     const std::string* active;

     if (path == hashBlobID)
     {
         /* 2c) are they opening the /flash/hash ? (to start the process) */
         curr = &activeHash;
         active = &activeHashBlobID;
     }
     else
     {
         curr = &activeImage;
         active = &activeImageBlobID;
     }

     /* Elsewhere I do this check by checking "if ::ipmi" because that's the
      * only non-external data pathway -- but this is just a more generic
      * approach to that.
      */
     if (d->handler)
     {
         /* If the data handler open call fails, open fails. */
         if (!d->handler->open())
         {
             return false;
         }
     }

     /* 2d) are they opening the /flash/tarball ? (to start the UBI process)
      * 2e) are they opening the /flash/image ? (to start the process)
      * 2...) are they opening the /flash/... ? (to start the process)
      */
     auto h = std::find_if(
         handlers.begin(), handlers.end(),
         [&path](const auto& iter) { return (iter.blobName == path); });
     if (h == handlers.end())
     {
         return false;
     }

     /* Ok, so we found a handler that matched, so call open() */
     if (!h->handler->open(path))
     {
         return false;
     }

     curr->flags = flags;
     curr->dataHandler = d->handler;
     curr->imageHandler = h->handler;
     curr->state = Session::State::open;

     lookup[session] = curr;

     blobIDs.push_back(*active);

     fileOpen = true;

     return true;
 }

 /**
  * The write command really just grabs the data from wherever it is and sends it
  * to the image handler.  It's the image handler's responsibility to deal with
  * the data provided.
  *
  * This receives a session from the blob manager, therefore it is always called
  * between open() and close().
  */
 bool FirmwareBlobHandler::write(uint16_t session, uint32_t offset,
                                 const std::vector<uint8_t>& data)
 {
     auto item = lookup.find(session);
     if (item == lookup.end())
     {
         return false;
     }

     /* Prevent writing during verification. */
     if (state == UpdateState::verificationStarted)
     {
         return false;
     }

     std::vector<std::uint8_t> bytes;

     if (item->second->flags & UpdateFlags::ipmi)
     {
         bytes = data;
     }
     else
     {
         /* little endian required per design, and so on, but TODO: do endianness
          * with boost.
          */
         struct ExtChunkHdr header;

         if (data.size() != sizeof(header))
         {
             return false;
         }

         std::memcpy(&header, data.data(), data.size());
         bytes = item->second->dataHandler->copyFrom(header.length);
     }

     return item->second->imageHandler->write(offset, bytes);
 }

 /*
  * If the active session (image or hash) is over LPC, this allows
  * configuring it.  This option is only available before you start
  * writing data for the given item (image or hash).  This will return
  * false at any other part. -- the lpc handler portion will know to return
  * false.
  */
 bool FirmwareBlobHandler::writeMeta(uint16_t session, uint32_t offset,
                                     const std::vector<uint8_t>& data)
 {
     auto item = lookup.find(session);
     if (item == lookup.end())
     {
         return false;
     }

     if (item->second->flags & UpdateFlags::ipmi)
     {
         return false;
     }

     return item->second->dataHandler->write(data);
 }

 /*
  * If this command is called on the session for the verifyBlobID, it'll
  * trigger a systemd service `verify_image.service` to attempt to verify
  * the image.
  *
  * For this file to have opened, the other two must be closed, which means any
  * out-of-band transport mechanism involved is closed.
  */
 bool FirmwareBlobHandler::commit(uint16_t session,
                                  const std::vector<uint8_t>& data)
 {
     auto item = lookup.find(session);
     if (item == lookup.end())
     {
         return false;
     }

     /* You can only commit on the verifyBlodId */
     if (item->second->activePath != verifyBlobID)
     {
         return false;
     }

     /* Can only be called once per verification. */
     if (state == UpdateState::verificationStarted)
     {
         return false;
     }

     /* Set state to committing. */
     item->second->flags |= StateFlags::committing;

     return triggerVerification();
 }

 /*
  * Close must be called on the firmware image before triggering
  * verification via commit. Once the verification is complete, you can
  * then close the hash file.
  *
  * If the `verify_image.service` returned success, closing the hash file
  * will have a specific behavior depending on the update. If it's UBI,
  * it'll perform the install. If it's static layout, it'll do nothing. The
  * verify_image service in the static layout case is responsible for placing
  * the file in the correct staging position.
  */
 bool FirmwareBlobHandler::close(uint16_t session)
 {
     auto item = lookup.find(session);
     if (item == lookup.end())
     {
         return false;
     }

     /* Are you closing the verify blob? */
     if (item->second->activePath == verifyBlobID)
     {
         /* If they close this blob before verification finishes, that's an
          * abort.
          * TODO: implement this, for now just let them close the file.
          */
         if (state == UpdateState::verificationStarted)
         {
             return false;
         }
     }

     if (item->second->dataHandler)
     {
         item->second->dataHandler->close();
     }
     if (item->second->imageHandler)
     {
         item->second->imageHandler->close();
     }

     item->second->state = Session::State::closed;
     /* Do not delete the active blob_id from the list of blob_ids, because that
      * blob_id indicates there is data stored.  Delete will destroy it.
      */

     lookup.erase(item);

     fileOpen = false;

     /* TODO: implement other aspects of closing out a session, such as changing
      * global firmware state.
      */
     return true;
 }

 bool FirmwareBlobHandler::expire(uint16_t session)
 {
     return false;
 }

 /*
  * Currently, the design does not provide this with a function, however,
  * it will likely change to support reading data back.
  */
 std::vector<uint8_t> FirmwareBlobHandler::read(uint16_t session,
                                                uint32_t offset,
                                                uint32_t requestedSize)
 {
     return {};
 }

 bool FirmwareBlobHandler::triggerVerification()
 {
     auto method = bus.new_method_call(systemdService, systemdRoot,
                                       systemdInterface, "StartUnit");
     method.append(verifyTarget);
     method.append("replace");

     try
     {
         bus.call_noreply(method);
     }
     catch (const sdbusplus::exception::SdBusError& ex)
     {
         /* TODO: Once logging supports unit-tests, add a log message to test
          * this failure.
          */
         return false;
     }

     state = UpdateState::verificationStarted;

     /* TODO: implement this. */
     return true;
 }

 } // namespace blobs
	/*
	* Copyright 2018 Google Inc.
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include "firmware_handler.hpp"

	#include "image_handler.hpp"

	#include <algorithm>
	#include <cstdint>
	#include <cstring>
	#include <memory>
	#include <string>
	#include <vector>

	namespace blobs
	{
	// systemd service to kick start a target.
	static constexpr auto systemdService = "org.freedesktop.systemd1";
	static constexpr auto systemdRoot = "/org/freedesktop/systemd1";
	static constexpr auto systemdInterface = "org.freedesktop.systemd1.Manager";
	static constexpr auto verifyTarget = "verify_image.service";

	const std::string FirmwareBlobHandler::verifyBlobID = "/flash/verify";
	const std::string FirmwareBlobHandler::hashBlobID = "/flash/hash";
	const std::string FirmwareBlobHandler::activeImageBlobID =
	"/flash/active/image";
	const std::string FirmwareBlobHandler::activeHashBlobID = "/flash/active/hash";

	std::unique_ptr<GenericBlobInterface>
	FirmwareBlobHandler::CreateFirmwareBlobHandler(
	sdbusplus::bus::bus&& bus, const std::vector<HandlerPack>& firmwares,
	const std::vector<DataHandlerPack>& transports)
	{
	/* There must be at least one. */
	if (!firmwares.size())
	{
	return nullptr;
	}
	if (!transports.size())
	{
	return nullptr;
	}

	std::vector<std::string> blobs;
	for (const auto& item : firmwares)
	{
	blobs.push_back(item.blobName);
	}
	blobs.push_back(verifyBlobID); /* Add blob_id to always exist. */

	if (0 == std::count(blobs.begin(), blobs.end(), hashBlobID))
	{
	return nullptr;
	}

	std::uint16_t bitmask = 0;
	for (const auto& item : transports)
	{
	/* TODO: can use std::accumulate() unless I'm mistaken. :D */
	bitmask \|= item.bitmask;
	}

	return std::make_unique<FirmwareBlobHandler>(std::move(bus), firmwares,
	blobs, transports, bitmask);
	}

	/* Check if the path is in our supported list (or active list). */
	bool FirmwareBlobHandler::canHandleBlob(const std::string& path)
	{
	if (std::count(blobIDs.begin(), blobIDs.end(), path))
	{
	return true;
	}

	return false;
	}

	/*
	* Grab the list of supported firmware.
	*
	* If there's an open firmware session, it'll already be present in the
	* list as "/flash/active/image", and if the hash has started,
	* "/flash/active/hash" regardless of mechanism. This is done in the open
	* comamnd, no extra work is required here.
	*/
	std::vector<std::string> FirmwareBlobHandler::getBlobIds()
	{
	return blobIDs;
	}

	/*
	* Per the design, this mean abort, and this will trigger whatever
	* appropriate actions are required to abort the process.
	*
	* You cannot delete a blob that has an open handle in the system, therefore
	* this is never called if there's an open session. Guaranteed by the blob
	* manager.
	*/
	bool FirmwareBlobHandler::deleteBlob(const std::string& path)
	{
	const std::string* toDelete;

	/* You cannot delete the verify blob -- trying to delete it, currently has
	* no impact.
	* TODO: Should trying to delete this cause an abort?
	*/
	if (path == verifyBlobID)
	{
	return false;
	}

	if (path == hashBlobID \|\| path == activeHashBlobID)
	{
	/* They're deleting the hash. */
	toDelete = &activeHashBlobID;
	}
	else
	{
	/* They're deleting the image. */
	toDelete = &activeImageBlobID;
	}

	auto it = std::find_if(
	blobIDs.begin(), blobIDs.end(),
	[toDelete](const auto& iter) { return (iter == *toDelete); });
	if (it == blobIDs.end())
	{
	/* Somehow they've asked to delete something we didn't say we could
	* handle.
	*/
	return false;
	}

	blobIDs.erase(it);

	/* TODO: Handle aborting the process and fixing up the state. */

	return true;
	}

	/*
	* Stat on the files will return information such as what supported
	* transport mechanisms are available.
	*
	* Stat on an active file or hash will return information such as the size
	* of the data cached, and any additional pertinent information. The
	* blob_state on the active files will return the state of the update.
	*/
	bool FirmwareBlobHandler::stat(const std::string& path, struct BlobMeta* meta)
	{
	/* We know we support this path because canHandle is called ahead */
	if (path == verifyBlobID)
	{
	/* We need to return information for the verify state -- did they call
	* commit() did things start?
	*/
	}
	else if (path == activeImageBlobID)
	{
	/* We need to return information for the image that's staged. */
	}
	else if (path == activeHashBlobID)
	{
	/* We need to return information for the hash that's staged. */
	}
	else
	{
	/* They are requesting information about the generic blob_id. */
	meta->blobState = bitmask;
	meta->size = 0;

	/* The generic blob_ids state is only the bits related to the transport
	* mechanisms.
	*/
	return true;
	}

	return false;
	}

	/*
	* Return stat information on an open session. It therefore must be an active
	* handle to either the active image or active hash.
	*
	* The stat() and sessionstat() commands will return the same information in
	* many cases, therefore the logic will be combined.
	*
	* TODO: combine the logic for stat and sessionstat().
	*/
	bool FirmwareBlobHandler::stat(uint16_t session, struct BlobMeta* meta)
	{
	auto item = lookup.find(session);
	if (item == lookup.end())
	{
	return false;
	}

	/* The blobState here relates to an active sesion, so we should return the
	* flags used to open this session.
	*/
	meta->blobState = item->second->flags;
	/* The size here refers to the size of the file -- of something analagous.
	*/
	meta->size = item->second->imageHandler->getSize();

	/* The metadata blob returned comes from the data handler... it's used for
	* instance, in P2A bridging to get required information about the mapping,
	* and is the "opposite" of the lpc writemeta requirement.
	*/
	meta->metadata.clear();
	if (item->second->dataHandler)
	{
	auto bytes = item->second->dataHandler->read();
	meta->metadata.insert(meta->metadata.begin(), bytes.begin(),
	bytes.end());
	}

	/* TODO: During things like verification, etc, we can report the state as
	* committed, etc, so we'll need to do that.
	*/

	return true;
	}

	/*
	* If you open /flash/image or /flash/tarball, or /flash/hash it will
	* interpret the open flags and perform whatever actions are required for
	* that update process. The session returned can be used immediately for
	* sending data down, without requiring one to open the new active file.
	*
	* If you open the active flash image or active hash it will let you
	* overwrite pieces, depending on the state.
	*
	* Once the verification process has started the active files cannot be
	* opened.
	*
	* You can only have one open session at a time. Which means, you can only
	* have one file open at a time. Trying to open the hash blob_id while you
	* still have the flash image blob_id open will fail. Opening the flash
	* blob_id when it is already open will fail.
	*/
	bool FirmwareBlobHandler::open(uint16_t session, uint16_t flags,
	const std::string& path)
	{
	/* Check that they've opened for writing - read back not currently
	* supported.
	*/
	if ((flags & OpenFlags::write) == 0)
	{
	return false;
	}

	/* Is the verification process underway? */
	if (state == UpdateState::verificationStarted)
	{
	return false;
	}

	/* Is there an open session already? We only allow one at a time.
	*
	* TODO: Temporarily using a simple boolean flag until there's a full
	* session object to check.
	*
	* Further on this, if there's an active session to the hash we don't allow
	* re-opening the image, and if we have the image open, we don't allow
	* opening the hash. This design decision may be re-evaluated, and changed
	* to only allow one session per object type (of the two types). But,
	* consider if the hash is open, do we want to allow writing to the image?
	* And why would we? But, really, the point of no-return is once the
	* verification process has begun -- which is done via commit() on the hash
	* blob_id, we no longer want to allow updating the contents.
	*/
	if (fileOpen)
	{
	return false;
	}

	/* Handle opening the verifyBlobId --> we know the image and hash aren't
	* open because of the fileOpen check.
	*
	* The file must be opened for writing, but no transport mechanism specified
	* since it's irrelevant.
	*/
	if (path == verifyBlobID)
	{
	/* In this case, there's no image handler to use, or data handler,
	* simply set up a session.
	*/
	verifyImage.flags = flags;
	verifyImage.state = Session::State::open;

	lookup[session] = &verifyImage;

	fileOpen = true;

	return true;
	}

	/* There are two abstractions at play, how you get the data and how you
	* handle that data. such that, whether the data comes from the PCI bridge
	* or LPC bridge is not connected to whether the data goes into a static
	* layout flash update or a UBI tarball.
	*/

	/* Check the flags for the transport mechanism: if none match we don't
	* support what they request.
	*/
	if ((flags & bitmask) == 0)
	{
	return false;
	}

	/* 2) there isn't, so what are they opening? */
	if (path == activeImageBlobID)
	{
	/* 2a) are they opening the active image? this can only happen if they
	* already started one (due to canHandleBlob's behavior).
	*/
	return false;
	}
	else if (path == activeHashBlobID)
	{
	/* 2b) are they opening the active hash? this can only happen if they
	* already started one (due to canHandleBlob's behavior).
	*/
	return false;
	}

	/* How are they expecting to copy this data? */
	auto d = std::find_if(
	transports.begin(), transports.end(),
	[&flags](const auto& iter) { return (iter.bitmask & flags); });
	if (d == transports.end())
	{
	return false;
	}

	/* We found the transport handler they requested, no surprise since
	* above we verify they selected at least one we wanted.
	*/
	Session* curr;
	const std::string* active;

	if (path == hashBlobID)
	{
	/* 2c) are they opening the /flash/hash ? (to start the process) */
	curr = &activeHash;
	active = &activeHashBlobID;
	}
	else
	{
	curr = &activeImage;
	active = &activeImageBlobID;
	}

	/* Elsewhere I do this check by checking "if ::ipmi" because that's the
	* only non-external data pathway -- but this is just a more generic
	* approach to that.
	*/
	if (d->handler)
	{
	/* If the data handler open call fails, open fails. */
	if (!d->handler->open())
	{
	return false;
	}
	}

	/* 2d) are they opening the /flash/tarball ? (to start the UBI process)
	* 2e) are they opening the /flash/image ? (to start the process)
	* 2...) are they opening the /flash/... ? (to start the process)
	*/
	auto h = std::find_if(
	handlers.begin(), handlers.end(),
	[&path](const auto& iter) { return (iter.blobName == path); });
	if (h == handlers.end())
	{
	return false;
	}

	/* Ok, so we found a handler that matched, so call open() */
	if (!h->handler->open(path))
	{
	return false;
	}

	curr->flags = flags;
	curr->dataHandler = d->handler;
	curr->imageHandler = h->handler;
	curr->state = Session::State::open;

	lookup[session] = curr;

	blobIDs.push_back(*active);

	fileOpen = true;

	return true;
	}

	/**
	* The write command really just grabs the data from wherever it is and sends it
	* to the image handler. It's the image handler's responsibility to deal with
	* the data provided.
	*
	* This receives a session from the blob manager, therefore it is always called
	* between open() and close().
	*/
	bool FirmwareBlobHandler::write(uint16_t session, uint32_t offset,
	const std::vector<uint8_t>& data)
	{
	auto item = lookup.find(session);
	if (item == lookup.end())
	{
	return false;
	}

	/* Prevent writing during verification. */
	if (state == UpdateState::verificationStarted)
	{
	return false;
	}

	std::vector<std::uint8_t> bytes;

	if (item->second->flags & UpdateFlags::ipmi)
	{
	bytes = data;
	}
	else
	{
	/* little endian required per design, and so on, but TODO: do endianness
	* with boost.
	*/
	struct ExtChunkHdr header;

	if (data.size() != sizeof(header))
	{
	return false;
	}

	std::memcpy(&header, data.data(), data.size());
	bytes = item->second->dataHandler->copyFrom(header.length);
	}

	return item->second->imageHandler->write(offset, bytes);
	}

	/*
	* If the active session (image or hash) is over LPC, this allows
	* configuring it. This option is only available before you start
	* writing data for the given item (image or hash). This will return
	* false at any other part. -- the lpc handler portion will know to return
	* false.
	*/
	bool FirmwareBlobHandler::writeMeta(uint16_t session, uint32_t offset,
	const std::vector<uint8_t>& data)
	{
	auto item = lookup.find(session);
	if (item == lookup.end())
	{
	return false;
	}

	if (item->second->flags & UpdateFlags::ipmi)
	{
	return false;
	}

	return item->second->dataHandler->write(data);
	}

	/*
	* If this command is called on the session for the verifyBlobID, it'll
	* trigger a systemd service `verify_image.service` to attempt to verify
	* the image.
	*
	* For this file to have opened, the other two must be closed, which means any
	* out-of-band transport mechanism involved is closed.
	*/
	bool FirmwareBlobHandler::commit(uint16_t session,
	const std::vector<uint8_t>& data)
	{
	auto item = lookup.find(session);
	if (item == lookup.end())
	{
	return false;
	}

	/* You can only commit on the verifyBlodId */
	if (item->second->activePath != verifyBlobID)
	{
	return false;
	}

	/* Can only be called once per verification. */
	if (state == UpdateState::verificationStarted)
	{
	return false;
	}

	/* Set state to committing. */
	item->second->flags \|= StateFlags::committing;

	return triggerVerification();
	}

	/*
	* Close must be called on the firmware image before triggering
	* verification via commit. Once the verification is complete, you can
	* then close the hash file.
	*
	* If the `verify_image.service` returned success, closing the hash file
	* will have a specific behavior depending on the update. If it's UBI,
	* it'll perform the install. If it's static layout, it'll do nothing. The
	* verify_image service in the static layout case is responsible for placing
	* the file in the correct staging position.
	*/
	bool FirmwareBlobHandler::close(uint16_t session)
	{
	auto item = lookup.find(session);
	if (item == lookup.end())
	{
	return false;
	}

	/* Are you closing the verify blob? */
	if (item->second->activePath == verifyBlobID)
	{
	/* If they close this blob before verification finishes, that's an
	* abort.
	* TODO: implement this, for now just let them close the file.
	*/
	if (state == UpdateState::verificationStarted)
	{
	return false;
	}
	}

	if (item->second->dataHandler)
	{
	item->second->dataHandler->close();
	}
	if (item->second->imageHandler)
	{
	item->second->imageHandler->close();
	}

	item->second->state = Session::State::closed;
	/* Do not delete the active blob_id from the list of blob_ids, because that
	* blob_id indicates there is data stored. Delete will destroy it.
	*/

	lookup.erase(item);

	fileOpen = false;

	/* TODO: implement other aspects of closing out a session, such as changing
	* global firmware state.
	*/
	return true;
	}

	bool FirmwareBlobHandler::expire(uint16_t session)
	{
	return false;
	}

	/*
	* Currently, the design does not provide this with a function, however,
	* it will likely change to support reading data back.
	*/
	std::vector<uint8_t> FirmwareBlobHandler::read(uint16_t session,
	uint32_t offset,
	uint32_t requestedSize)
	{
	return {};
	}

	bool FirmwareBlobHandler::triggerVerification()
	{
	auto method = bus.new_method_call(systemdService, systemdRoot,
	systemdInterface, "StartUnit");
	method.append(verifyTarget);
	method.append("replace");

	try
	{
	bus.call_noreply(method);
	}
	catch (const sdbusplus::exception::SdBusError& ex)
	{
	/* TODO: Once logging supports unit-tests, add a log message to test
	* this failure.
	*/
	return false;
	}

	state = UpdateState::verificationStarted;

	/* TODO: implement this. */
	return true;
	}

	} // namespace blobs