fix(security): generate OTP with SecureRandom, uniform draw, zero-padded (A2) - #136
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fix(security): generate OTP with SecureRandom, uniform draw, zero-padded (A2)#136pallakartheekreddy wants to merge 1 commit into
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…ded (A2) KeycloakSmsAuthenticatorUtil.getSmsCode used java.util.Random + nextFloat(): Random r = new Random(); long code = (long) (r.nextFloat() * maxValue); return Long.toString(code); Three defects made the OTP guessable/undersized: (1) java.util.Random is a time-seeded LCG, predictable from a few outputs; (2) nextFloat()'s ~24-bit mantissa cannot uniformly address a 10^8 space (gaps/clustering); (3) Long.toString drops leading zeros, shrinking effective length and leaking high-zero digits. Replace with a shared SecureRandom, a uniform nextInt(10^n) draw, and %0Nd zero-padding so every code is exactly nrOfDigits long. Guard nrOfDigits to 1..9 (10^9 fits in int) and throw IllegalArgumentException (still a RuntimeException, so existing catch sites are unaffected). Pure utility change, no Keycloak SPI contract impact. Verified: sms-provider module test-compiles under JDK 11. Implements A2 from implementation-designs/sunbird-auth.md. A1 (OTP expiry/first-use invalidation), A3 (attempt lockout) and A4 (msg91 cleartext HTTP) are separate, higher-touch changes deferred to their own PRs.
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Summary
Fixes the predictable-OTP finding A2 (HIGH) in
implementation-designs/sunbird-auth.md.The vulnerability
KeycloakSmsAuthenticatorUtil.getSmsCodegenerated the OTP with:Three compounding defects:
java.util.Randomis a time-seeded LCG — not cryptographic, predictable from a couple of outputs.nextFloat()'s ~24-bit mantissa can't uniformly address a10^8space → gaps/clustering, some codes unreachable.Long.toString(code)drops leading zeros, shrinking effective length and leaking that the high digits were zero.The fix
private static final SecureRandom.SECURE_RANDOM.nextInt(10^n)draw.String.format("%0Nd", code)zero-padding so every OTP is exactlynrOfDigitslong.nrOfDigitsto1..9(fits inint); throwIllegalArgumentException(still aRuntimeException, so existing catch sites are unaffected).Pure utility change — no Keycloak SPI contract impact.
SecureRandom.nextIntis non-blocking at OTP volumes.Verification
sms-providermodule test-compiles under JDK 11 (exit 0; class recompiled).Scope / deferred
A1 (OTP expiry never enforced / no first-use invalidation), A3 (attempt lockout/rate-limit), and A4 (msg91 over cleartext HTTP, authkey in URL) are separate, higher-touch changes and get their own PRs.