+void
+derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
+ u_int8_t cookie[8], u_int8_t id[16])
+{
+ const EVP_MD *evp_md = EVP_md5();
+ EVP_MD_CTX md;
+ u_int8_t nbuf[2048], obuf[EVP_MAX_MD_SIZE];
+ int len;
+
+ EVP_DigestInit(&md, evp_md);
+
+ len = BN_num_bytes(host_modulus);
+ if (len < (512 / 8) || len > sizeof(nbuf))
+ fatal("%s: bad host modulus (len %d)", __func__, len);
+ BN_bn2bin(host_modulus, nbuf);
+ EVP_DigestUpdate(&md, nbuf, len);
+
+ len = BN_num_bytes(server_modulus);
+ if (len < (512 / 8) || len > sizeof(nbuf))
+ fatal("%s: bad server modulus (len %d)", __func__, len);
+ BN_bn2bin(server_modulus, nbuf);
+ EVP_DigestUpdate(&md, nbuf, len);
+
+ EVP_DigestUpdate(&md, cookie, 8);
+
+ EVP_DigestFinal(&md, obuf, NULL);
+ memcpy(id, obuf, 16);
+
+ memset(nbuf, 0, sizeof(nbuf));
+ memset(obuf, 0, sizeof(obuf));
+ memset(&md, 0, sizeof(md));
+}
+