問題

When presented with a CAPTCHA during login symbols that can't be typed are presented instead of common characters that can be typed.

原因

This looks like an issue with font mapping on the OS. CAPTCHA library uses three fonts: nyala, Bell MT and Credit valley. If Java cannot find given font, it falls to the dialog font - an abstract one, which is mapped to some default system font.

診断

• check if given fonts (nyala, Bell MT, Credit valley) are present on the Crucible instance - upload them if not present. Fonts are typically stored as .ttf files and finding which fonts are installed differs depending on the OS:
  

  - Mac OS - https://support.apple.com/en-us/HT201722
  - Linux - command fc-list should work ( As it depends on the distro, please consult the relevant documentation for your distro)
  Windows - Have a look under Control Panel -> Fonts -> View installed fonts

  
  
  

• check what font Java uses as default - configuration should be present under $JAVA_HOME/jre/lib/fontconfig.properties.src; lines responsible for mapping should look like:

  dialog.plain.alphabetic=Arial
  dialog.plain.chinese-ms950=MingLiU
  dialog.plain.hebrew=David
  dialog.plain.japanese=MS Gothic
  dialog.plain.korean=Gulim
  
  dialog.bold.alphabetic=Arial Bold
  dialog.bold.chinese-ms950=PMingLiU
  dialog.bold.hebrew=David Bold
  dialog.bold.japanese=MS Gothic
  dialog.bold.korean=Gulim
  
  dialog.italic.alphabetic=Arial Italic
  dialog.italic.chinese-ms950=PMingLiU
  dialog.italic.hebrew=David
  dialog.italic.japanese=MS Gothic
  dialog.italic.korean=Gulim

ソリューション

Ensure that the instance's host machine has those fonts available and they can be accessed by Java.