/* Provenance: openssl/openssl tls_handle_alpn (fixed).
 * repo: openssl/openssl
 * commit: 39a140597d874e554b736885ac4dea16ac40a87a
 * parent: 02b1636fe3db274497304a3e95a4e32ced7e841b
 * commit_url: https://github.com/openssl/openssl/commit/39a140597d874e554b736885ac4dea16ac40a87a
 * cve: CVE-2021-3449
 * license: OpenSSL License
 * function: tls_handle_alpn
 * relpath: ssl/statem/statem_srvr.c
 */

int tls_handle_alpn(SSL *s)
{
    const unsigned char *selected = NULL;
    unsigned char selected_len = 0;

    if (s->ctx->ext.alpn_select_cb != NULL && s->s3.alpn_proposed != NULL) {
        int r = s->ctx->ext.alpn_select_cb(s, &selected, &selected_len,
                                           s->s3.alpn_proposed,
                                           (unsigned int)s->s3.alpn_proposed_len,
                                           s->ctx->ext.alpn_select_cb_arg);

        if (r == SSL_TLSEXT_ERR_OK) {
            OPENSSL_free(s->s3.alpn_selected);
            s->s3.alpn_selected = OPENSSL_memdup(selected, selected_len);
            if (s->s3.alpn_selected == NULL) {
                s->s3.alpn_selected_len = 0;
                SSLfatal(s, SSL_AD_INTERNAL_ERROR, ERR_R_INTERNAL_ERROR);
                return 0;
            }
            s->s3.alpn_selected_len = selected_len;
#ifndef OPENSSL_NO_NEXTPROTONEG
            /* ALPN takes precedence over NPN. */
            s->s3.npn_seen = 0;
#endif

            /* Check ALPN is consistent with session */
            if (s->session->ext.alpn_selected == NULL
                        || selected_len != s->session->ext.alpn_selected_len
                        || memcmp(selected, s->session->ext.alpn_selected,
                                  selected_len) != 0) {
                /* Not consistent so can't be used for early_data */
                s->ext.early_data_ok = 0;

                if (!s->hit) {
                    /*
                     * This is a new session and so alpn_selected should have
                     * been initialised to NULL. We should update it with the
                     * selected ALPN.
                     */
                    if (!ossl_assert(s->session->ext.alpn_selected == NULL)) {
                        SSLfatal(s, SSL_AD_INTERNAL_ERROR,
                                 ERR_R_INTERNAL_ERROR);
                        return 0;
                    }
                    s->session->ext.alpn_selected = OPENSSL_memdup(selected,
                                                                   selected_len);
                    if (s->session->ext.alpn_selected == NULL) {
                        SSLfatal(s, SSL_AD_INTERNAL_ERROR,
                                 ERR_R_INTERNAL_ERROR);
                        return 0;
                    }
                    s->session->ext.alpn_selected_len = selected_len;
                }
            }

            return 1;
        } else if (r != SSL_TLSEXT_ERR_NOACK) {
            SSLfatal(s, SSL_AD_NO_APPLICATION_PROTOCOL,
                     SSL_R_NO_APPLICATION_PROTOCOL);
            return 0;
        }
        /*
         * If r == SSL_TLSEXT_ERR_NOACK then behave as if no callback was
         * present.
         */
    }

    /* Check ALPN is consistent with session */
    if (s->session->ext.alpn_selected != NULL) {
        /* Not consistent so can't be used for early_data */
        s->ext.early_data_ok = 0;
    }

    return 1;
}