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SEC-1446: Malformed Base64 in Basic Authentication header causes BasicAuthenticationFilter to throw a RuntimeException #1679
Since Base64.decode throws a RuntimeException if it detects bad characters in the input string, org.springframework.security.web.authentication.www.BasicAuthenticationFilter.doFilter throws the RTE if the Authentication header contains malformed base 64. The effect is that http servers return 500 rather than 401.
My fix just adds an additional check by calling Base64.isBase64, and if that fails, continues processing as if the Authentication header were missing.
Luke Taylor said:
I've made changes to treat an invalid header (either bad Base64 or an invalid token) as an authentication failure, which will generally result in the authentication entry point being invoked. Using Base64.isBase64() just decodes the encoded string an additional time which will not be necessary in most cases, so I've elected to trap the exception raised when the characters are invalid instead, throwing BadCredentialsException.