Soon after learning that recompiling with -DOPENSSL_NO_HEARTBEATS will disable TLSv1 Heartbeats in OpenSSL 1.0.1e, I wondered why it was not a run-time option instead, maybe called something like SSL_OP_NO_TLS_HEARTBEATS.
Therefore I looked into SSL.H and discovered that 'options' is an unsigned long bitmask, which would be 32 or 64 bits depending on the compiling platform/mode, but it seemed that the OpenSSL code assumes is 32 bits, and -more importantly- it means it only has 32 possible options, which seems to have been exhausted already, all except the bit 0x00000400L, I copied them from SSL.H:
/* Option bits for SSL_CTX_set_options() */
#define SSL_OP_MICROSOFT_SESS_ID_BUG 0x00000001L
#define SSL_OP_NETSCAPE_CHALLENGE_BUG 0x00000002L
#define SSL_OP_LEGACY_SERVER_CONNECT 0x00000004L
#define SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG 0x00000008L
#define SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG 0x00000010L
#define SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER 0x00000020L
#define SSL_OP_MSIE_SSLV2_RSA_PADDING 0x00000040L
#define SSL_OP_SSLEAY_080_CLIENT_DH_BUG 0x00000080L
#define SSL_OP_TLS_D5_BUG 0x00000100L
#define SSL_OP_TLS_BLOCK_PADDING_BUG 0x00000200L
/***** 0x00000400L SEEMS TO BE THE ONLY OPTION BIT FREE *****/
#define SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS 0x00000800L
#define SSL_OP_NO_QUERY_MTU 0x00001000L
#define SSL_OP_COOKIE_EXCHANGE 0x00002000L
#define SSL_OP_NO_TICKET 0x00004000L
#define SSL_OP_CISCO_ANYCONNECT 0x00008000L
#define SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION 0x00010000L
#define SSL_OP_NO_COMPRESSION 0x00020000L
#define SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION 0x00040000L
#define SSL_OP_SINGLE_ECDH_USE 0x00080000L
#define SSL_OP_SINGLE_DH_USE 0x00100000L
#define SSL_OP_EPHEMERAL_RSA 0x00200000L
#define SSL_OP_CIPHER_SERVER_PREFERENCE 0x00400000L
#define SSL_OP_TLS_ROLLBACK_BUG 0x00800000L
#define SSL_OP_NO_SSLv2 0x01000000L
#define SSL_OP_NO_SSLv3 0x02000000L
#define SSL_OP_NO_TLSv1 0x04000000L
#define SSL_OP_NO_TLSv1_2 0x08000000L
#define SSL_OP_NO_TLSv1_1 0x10000000L
#define SSL_OP_NETSCAPE_CA_DN_BUG 0x20000000L
#define SSL_OP_NETSCAPE_DEMO_CIPHER_CHANGE_BUG 0x40000000L
#define SSL_OP_CRYPTOPRO_TLSEXT_BUG 0x80000000L
Do you think is this the reason why they decided to do -DOPENSSL_NO_HEARTBEATS instead SSL_OP_NO_TLS_HEARTBEATS ? If so, why didn't they use 0x00000400L for SSL_OP_NO_TLS_HEARTBEATS ? I would like to know your opinion on this. Actually, whatever is the output on this survey, it seems that OpenSSL needs to fix their option system, as it seems already exhausted. Please let me know if I am worng there too.
