random: Add a RNG selection interface and system RNG wrapper.

* random/random-system.c: New.
* random/Makefile.am (librandom_la_SOURCES): Add new module.
* random/random.c (struct rng_types): New.
(_gcry_set_preferred_rng_type, _gcry_get_rng_type): New.
(_gcry_random_initialize, gcry_random_add_bytes, do_randomize)
(_gcry_set_random_seed_file, _gcry_update_random_seed_file)
(_gcry_fast_random_poll): Dispatch to the actual RNG.
* src/gcrypt.h.in (GCRYCTL_SET_PREFERRED_RNG_TYPE): New.
GCRYCTL_GET_CURRENT_RNG_TYPE): New.
(gcry_rng_types): New.
* src/global.c (print_config): Print the TNG type.
(global_init, _gcry_vcontrol): Implement the new control codes.
* doc/gcrypt.texi (Controlling the library): Document the new control
codes.

* tests/benchmark.c (main): Add options to test the RNG types.
* tests/random.c (main): Add new options.
(print_hex): Print to stderr.
(progress_cb, rng_type): New.
(check_rng_type_switching, check_early_rng_type_switching): New.
(run_all_rng_tests): New.
--

The purpose of this change is to allow applications with moderate
random requirements to use the system's RNG (e.g. /dev/urandom).  The
type switching logic makes sure that existing applications won't be
affected by this change.  A library is in almost all cases not able to
degrade the quality of the RNG.  The definition of "degrade" comes
from our own assertion of the quality/trustworthiness of the RNGs:

The most trustworthy RNG is the CSPRNG which dates back to the early
GnuPG days.  It is quite conservative and often requires more seeding
than might be justified.  GCRY_RNG_TYPE_STANDARD is the default unless
the process is in FIPS mode.

The second trustworthy RNG is the FIPS recommended X9.81 AES based
implementation.  It is seeded by the system's RNG.  GCRY_RNG_TYPE_FIPS
is the only available RNG if running in FIPS mode.

The third trustworthy RNG is a mere wrapper around the system's native
RNG.  Thus there is no extra step on top of what, for example,
/dev/random provides.  GCRY_RNG_TYPE_SYSTEM may be used by
applications which would use /dev/random or /dev/urandom instead.

1 files changed, 2 insertions, 0 deletions

diff --git a/random/random.h b/random/random.h
index 5f6a42c1..aae07ab0 100644
--- a/random/random.h
+++ b/random/random.h
@@ -26,7 +26,9 @@
 void _gcry_register_random_progress (void (*cb)(void *,const char*,int,int,int),
                                      void *cb_data );
 
+void _gcry_set_preferred_rng_type (int type);
 void _gcry_random_initialize (int full);
+int  _gcry_get_rng_type (int ignore_fips_mode);
 void _gcry_random_dump_stats(void);
 void _gcry_secure_random_alloc(void);
 void _gcry_enable_quick_random_gen (void);