WebUI firmware upload - improve error handling and add MD5 check

[proddy]

From #629 (comment)_

• Report the OTA upload errors to the EMS-ESP log
• Create an MD5 check to validate if the firmware upload was successful

[proddy]

For the MD5 check I was talking to Rick last year about this. See rjwats/esp8266-react#260 (comment). The steps would be:

1. generate a sha512 signature for the artefact and sent as an optional header on the file upload, and verified if supplied.
2. in the upload loop call md_update() for each segment of the payload, and at the end verifying before calling the final Update.end(true)

something you'd like to look at Michael?

[MichaelDvP]

When playing around with different chipsets i dont want to break it by flashing the wrong software, so i checked the espressif file format for chip ID and take a look to the arduino OTA if there are any checks.
To keep it simple i don't like to change the bin file and keep the option to downgrade to any older software. The Arduino OTA have a MD5 check integrated, why not use this. MD5 is not a safe hash, but for file validation it is good enough.
My approach so far:

• in rename_fw.py generate a <filename>.md5, plain text with 32 bytes MD5. With the extra md5-file people can also validate the downloaded bin before trying to upload.
• add hint in upload page:
  
• after upload the md5-file it shows:
  
• if uploading a json next, the md5 is ignore and cleared, if uploading a different md5-file the md5 is updated, if upload a bin, the OTA checks the md5.
• if no md5 is uploaded, the md5 is not checked. So people can use it like before.
• bin header is checked for espressif-magic and chip-ID, also filename should have C3 or S2 or none of them.
• snackbar error shows (507) Insufficient Storage if partion is to small, (503) Service Unavailable for wrong chip and (500) internal server error for MD5 or transfer issues.

@proddy @bbqkees Other suggestions?

[MichaelDvP]

I've made a md5-branch to test, also firmwares and md5-files for all boards. Please check.

[proddy]

I'll check today

[MichaelDvP]

I'll change the way of md5 sending to web, in first appoach i added a hppt_get, but it's better to use direct respond of the post.

[proddy]

ok. it would good to validate the md5 on the server side too (at least the # chars). Another thing I noticed is the dropzone drag&drop box shows read when dragging in an md5 file, so the .md5 needs to be added to the list of accepted extensions.

Can I help anywhere?

[MichaelDvP]

Yes it's already done, md5-file is accepted, post to ems-esp, checked for 32 char (only length), stored as 32 char, send back to web and shown on web. On bin-upload the stored md5 is checked.
I've updated the md5 branch and merged the latest dev. Now building the bin/md5 files.

[proddy]

do we also need to change the WebUI 'version check' to pick up the right platform and board?

[MichaelDvP]

Yes, simple way to direct to the html_url, so the right bin and md5 can be downloaded, or enhance to right chip version and add an extra link to the md5?

[proddy]

yes!