CODEWITHSUNDEEP
openssl
YeonJu Lee
YeonJu Lee

Reputation: 33

What does "__fips_constseg" means in openssl

In openssl C code, (aes_core.c, set_key.c, spr.h and so on) there is "__fips_constseg".

I don't know "__fips_constseg" means.

What's the role of it? Is it assembly code?

the source code is below:

#include < openssl/crypto.h >

#include "des_locl.h"

OPENSSL_IMPLEMENT_GLOBAL(int,DES_check_key,0) /* defaults to false */

__fips_constseg

static const unsigned char odd_parity[256]={};

Upvotes: 1

Views: 257

Answers (1)

Abrixas2
Abrixas2

Reputation: 3295

From the OpenSSL source code:

crypto/crypto.h

#if defined(OPENSSL_FIPSCANISTER)
# include <openssl/fipssyms.h>
#else
# define __fips_constseg
#endif

fips/fipssyms.h

#if defined(_MSC_VER)
# pragma const_seg("fipsro$b")
# pragma const_seg()
# define __fips_constseg __declspec(allocate("fipsro$b"))
#else
# define __fips_constseg
#endif

The __fips_constseg constant thus is only defined to a value, if

  • OPENSSL_FIPSCANISTER is defined and
  • the code is compiled using the Microsoft C compiler (which can be detected by the defined _MSC_VER constant).

Then, the code marked with that constant is placed in the constant data segment named fipsro$b (see the MSDN documentation on the allocate specifier for details).

If any of the conditions above is not met, __fips_constseg is defined to nothing and thus the variables marked with that constant are put in the data segment they would normally be located in.

Upvotes: 2

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