Update.setMD5() should downcase the MD5 string

[jksemple]

Board

ESP32 ESP32S3 ESP8266 etc

Device Description

Seeedstudio ESP32S3 Sense but any Espressif device

Hardware Configuration

No

Version

latest master (checkout manually)

IDE Name

Arduino IDE

Operating System

Windows 10

Flash frequency

40Mhz

PSRAM enabled

yes

Upload speed

115200

Description

When requesting a firmware update from a remote OTA server using HttpUpdate the remote server returns an expected MD5 in header "x-MD5" as a 32 char hex string. If received HttpUpdate passes this to Update object for comparison with an internally computed MD5 calculated using MD5Builder.
Update stores the expected MD5 using UpdateClass::setMD5(). OTA servers built on .Net will send MD5 as uppercase hex strings by default. In UpdateClass::end() the actual MD5 of the received firmware is compared with the expected MD5 and it fails because of case difference.

UpdateClass::setMD5() should not assume lowercase hex characters and should downcase the expected MD5 before storing to the _target_md5 member variable.

This was raised earlier as Issue #4641 Uppercase MD5 gets rejected but was closed due to inaction.

Sketch

N/A

Debug Message

Done 856064 of 856656
Done 856656 of 856656
Done 856656 of 856656
[205243][E][HttpUpdate.cpp:445] runUpdate(): Update.end failed! (MD5 Check Failed)

[205246][E][HttpUpdate.cpp:359] handleUpdate(): Update failed

[205247][E][ssl_client.cpp:37] _handle_error(): [data_to_read():361]: (-76) UNKNOWN ERROR CODE (004C)
[205256][E][HTTPClient.cpp:408] disconnect(): tcp is closed

HTTP_UPDATE_FAILED Error (7): Update error: MD5 Check Failed

Other Steps to Reproduce

The problem goes away if the remote server downcases the value in the "x-MD5" header before returning it.

I have checked existing issues, online documentation and the Troubleshooting Guide

• I confirm I have checked existing issues, online documentation and Troubleshooting guide.

[jksemple]

As a more general point it is a bit inconsistent to render the device's MAC address as upper case hex and MD5 checksums as lower case hex

[P-R-O-C-H-Y]

Hi @jksemple, thank you for opening this issue once again. Feel free to open a PR with the proposed fix:
"UpdateClass::setMD5() should not assume lowercase hex characters and should downcase the expected MD5 before storing to the _target_md5 member variable."

[jksemple]

Ha. You beat me to it.
Thanks for fixing