full-disclosure - authentication bug in KAME's racoon

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From: thomas-fd at unproved.org (Thomas Walpuski)
Subject: authentication bug in KAME's racoon

Summary

  There is a severe bug in racoon's authentication via digital
  signatures with certificates.

Description

  racoon verifies the peer's certificate using eay_check_x509cert().
  For some strange reason eay_check_x509cert() sets a verify callback:

    X509_STORE_set_verify_cb_func(cert_ctx, cb_check_cert);

  Verify callbacks are usually used for debugging purpose. Take a look
  at what racoon uses the verify callback for: 

    static int
    cb_check_cert(ok, ctx)
            int ok;
            X509_STORE_CTX *ctx;
    {
            char buf[256];
            int log_tag;

            if (!ok) {
                    [..]
                    switch (ctx->error) {
                    case X509_V_ERR_CERT_HAS_EXPIRED:
                    case X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT:
    #if OPENSSL_VERSION_NUMBER >= 0x00905100L
                    case X509_V_ERR_INVALID_CA:
                    case X509_V_ERR_PATH_LENGTH_EXCEEDED:
                    case X509_V_ERR_INVALID_PURPOSE:
    #endif
                            ok = 1;
                            log_tag = LLV_WARNING;
                            break;
                    default:
                            log_tag = LLV_ERROR;
                    }
                    [..]
            }
            ERR_clear_error();

            return ok;
    }

  If OpenSSL fails on verifying the certificate, because it is expired,
  self-signed, signed by an inappropriate CA, not allowed for that
  purpose or the certificate chain is too long, racoon does not care
  about that and declares the verification successful. I dare to say
  that is brain dead.

Affected Systems

  All version of racoon known to me are vulnerable.

Impact

  IMO besides remote privilege escalation that is the worst case
  scenario for an IKE daemon.

Solution?

  There are no bug fixes, yet. I recommend not using racoon at all.

Thomas Walpuski