Add API gpgme_op_random_value.
* src/genrandom.c (getrandom_size_t): New. (gpgme_op_random_value): New. * src/gpgme.def: Add new function. * src/libgpgme.vers: Ditto. * src/gpgme.h.in: Add prototype. * tests/run-genrandom.c: Add an option to use the new function. -- The implementation is not optimized but sufficient for our use case. Possible improvements for this and gpgme_op_random_bytes are a cache for random bytes in the context so that we do not need to get out to gpgme for just a few random bytes. GnuPG-bug-id: 6694
This commit is contained in:
Werner Koch
parent
7568566ef3
commit
926b1f1f1e
8
NEWS
8
NEWS
@ -1,8 +1,11 @@
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Noteworthy changes in version 2.0.0 (unreleased)
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------------------------------------------------
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* New function gpgme_op_random_bytes to get cryptographically strng
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random bytes from gpg.
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* New function gpgme_op_random_bytes to get cryptographically
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strong random bytes from gpg. [T6694]
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* New function gpgme_op_random_value to get a cryptographically
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strong unsigned integer random value. [T6694]
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* Removed the gpgme_attr_t enums and their functions which were
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deprecated since 2003. [rMd54d6eaa64]
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@ -16,6 +19,7 @@ Noteworthy changes in version 2.0.0 (unreleased)
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* Interface changes relative to the 1.24 branch:
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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gpgme_op_random_bytes NEW.
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gpgme_op_random_value NEW.
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GPGME_RANDOM_MODE_NORMAL NEW.
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GPGME_RANDOM_MODE_ZBASE32 NEW.
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gpgme_attr_t REMOVED.
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@ -7142,11 +7142,26 @@ The function @code{gpgme_op_random_bytes} returns random bytes.
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from gpg. However, if @var{mode} is @code{GPGME_RANDOM_MODE_ZBASE32}
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@var{bufsize} needs to be at least 31 and will be filled with a string
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of 30 ASCII characters followed by a Nul; the remainder of the buffer
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is not changed. This function has a limit of 1024 bytes to avoid
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accidental overuse of the random generator
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is not changed. The caller must provide a context @var{ctx}
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initialized for GPGME_PROTOCOL_OPENPGP. This function has a limit of
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1024 bytes to avoid accidental overuse of the random generator
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@end deftypefun
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@deftypefun {gpgme_error_t} gpgme_op_random_values ( @
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@w{gpgme_ctx_t @var{ctx}}, @
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@w{size_t @var{limit}}, @
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@w{size_t *@var{retval}})
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@since{2.0.0}
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The function @code{gpgme_op_random_value} returns an unbiased random
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value in the range 0 <= value < @var{limit}. The value is returned at
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@var{retval} if and only if the function returns with success. The
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caller must also provide a context @var{ctx} initialized for
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GPGME_PROTOCOL_OPENPGP.
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@end deftypefun
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@node Miscellaneous
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@ -58,6 +58,46 @@ do_genrandom (gpgme_ctx_t ctx, gpgme_data_t dataout, size_t length, int zbase)
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}
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/* Store a random value into RETVAL or return an error. */
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static gpgme_error_t
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getrandom_size_t (gpgme_ctx_t ctx, size_t *retval)
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{
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gpgme_error_t err = 0;
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gpgme_data_t data = NULL;
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char *datap = NULL;
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size_t datalen;
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err = gpgme_data_new (&data);
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if (err)
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goto leave;
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err = do_genrandom (ctx, data, sizeof (size_t), 0);
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if (!err)
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err = _gpgme_wait_one (ctx);
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if (err)
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goto leave;
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datap = gpgme_data_release_and_get_mem (data, &datalen);
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data = NULL;
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if (!datap)
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{
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err = gpg_error_from_syserror ();
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goto leave;
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}
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if (datalen != sizeof (size_t))
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{
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err = gpg_error (GPG_ERR_INTERNAL);
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goto leave;
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}
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memcpy (retval, datap, datalen);
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leave:
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free (datap);
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gpgme_data_release (data);
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return err;
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}
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/* Fill BUFFER of size BUFSIZE with random bytes retrieved from gpg.
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* If GPGME_RANDOM_MODE_ZBASE32 is used BUFSIZE needs to be at least
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* 31 and will be filled with a string of 30 ascii characters followed
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@ -147,3 +187,46 @@ gpgme_op_random_bytes (gpgme_ctx_t ctx, gpgme_random_mode_t mode,
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gpgme_data_release (data);
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return TRACE_ERR (err);
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}
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/* On success the function stores an unbiased random value in the
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* range [0,limit) at RETVAL. On error the function returns an error
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* code and the value at RETVAL is undefined. A context must be
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* provided so that the function can get raw random bytes from the gpg
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* enine (i.e. from Libgcrypt). */
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gpgme_error_t
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gpgme_op_random_value (gpgme_ctx_t ctx, size_t limit, size_t *retval)
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{
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gpgme_error_t err;
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size_t t, x;
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TRACE_BEG (DEBUG_CTX, "gpgme_op_random_value", ctx, "limit=%zu", limit);
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if (!ctx || limit < 2 || !retval)
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{
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err = gpg_error (GPG_ERR_INV_VALUE);
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goto leave;
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}
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/* This is the OpenBSD algorithm as used by arc4random_uniform and
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* described in "Fast Random Integer Generation in an Interval" by
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* Daniel Lemire (arXiv:1805.10941v4, 2018). */
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t = (-limit) % limit;
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x = 0; /* Avoid (false) compiler warning. */
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do
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{
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err = getrandom_size_t (ctx, &x);
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if (err)
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goto leave;
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/* fprintf (stderr, "getrandom returned %zu (limit=%zu, t=%zu)\n", */
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/* x, limit, t); */
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}
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while (x < t);
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x %= limit;
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*retval = x;
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leave:
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return TRACE_ERR (err);
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}
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@ -276,4 +276,5 @@ EXPORTS
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gpgme_op_setownertrust_start @214
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gpgme_op_random_bytes @215
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gpgme_op_random_value @216
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; END
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@ -2481,10 +2481,15 @@ typedef enum
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}
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gpgme_random_mode_t;
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/* Fill BUFFER with BUFSIZE random bytes from gpg. */
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/* Fill BUFFER with BUFSIZE random bytes from gpg or return an error. */
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gpgme_error_t gpgme_op_random_bytes (gpgme_ctx_t ctx, gpgme_random_mode_t mode,
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char *buffer, size_t bufsize);
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/* Store an unbiased random value in the range [0,LIMIT) at RETVAL or
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* return an error. */
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gpgme_error_t gpgme_op_random_value (gpgme_ctx_t ctx, size_t limit,
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size_t *retval);
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/*
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@ -274,6 +274,7 @@ GPGME_1.0 {
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gpgme_op_setownertrust_start;
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gpgme_op_random_bytes;
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gpgme_op_random_value;
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local:
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*;
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@ -28,6 +28,8 @@
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#include <stdio.h>
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#include <string.h>
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#include <assert.h>
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#include <errno.h>
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#include <stdint.h>
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#include <gpgme.h>
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@ -42,10 +44,13 @@ static int verbose;
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static int
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show_usage (int ex)
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{
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fputs ("usage: " PGM " [options]\n\n"
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fputs ("usage: " PGM " [options] [LIMIT]\n\n"
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"Options:\n"
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" --verbose run in verbose mode\n"
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" --zbase32 generate 30 zbase32 characters\n"
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" --hex return a hex value in LIMIT mode\n"
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"\n"
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"With LIMIT return a decimal value in the range [0,LIMIT)\n"
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, stderr);
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exit (ex);
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}
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@ -60,6 +65,8 @@ main (int argc, char **argv)
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gpgme_protocol_t protocol = GPGME_PROTOCOL_OPENPGP;
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gpgme_random_mode_t mode = 0;
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char buffer[128];
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int hexmode = 0;
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int valuemode = 0;
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if (argc)
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@ -85,11 +92,21 @@ main (int argc, char **argv)
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mode = GPGME_RANDOM_MODE_ZBASE32;
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argc--; argv++;
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}
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else if (!strcmp (*argv, "--hex"))
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{
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hexmode = 1;
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argc--; argv++;
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}
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else if (!strncmp (*argv, "--", 2))
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show_usage (1);
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}
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if (argc)
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if (argc == 1)
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valuemode = 1;
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else if (argc)
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show_usage (1);
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if ((valuemode && mode) || (!valuemode && hexmode))
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show_usage (1);
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init_gpgme (protocol);
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@ -98,26 +115,62 @@ main (int argc, char **argv)
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fail_if_err (err);
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gpgme_set_protocol (ctx, protocol);
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err = gpgme_op_random_bytes (ctx, mode, buffer, sizeof buffer);
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if (err)
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if (valuemode)
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{
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fprintf (stderr, PGM ": error getting random: %s\n", gpg_strerror (err));
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exit (1);
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}
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size_t limit, value;
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if (mode == GPGME_RANDOM_MODE_ZBASE32)
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puts (buffer);
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errno = 0;
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limit = strtoul (*argv, NULL, 0);
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if (errno)
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{
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fprintf (stderr, PGM ": error parsing LIMIT arg: %s\n",
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strerror (errno));
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exit (1);
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}
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if (limit > SIZE_MAX)
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{
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fprintf (stderr, PGM ": error parsing LIMIT arg: %s\n",
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"too large for size_t");
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exit (1);
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}
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err = gpgme_op_random_value (ctx, limit, &value);
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if (err)
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{
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fprintf (stderr, PGM ": error getting random: %s\n",
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gpg_strerror (err));
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exit (1);
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}
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if (hexmode)
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printf ("%zx\n", value);
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else
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printf ("%zu\n", value);
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}
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else
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{
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int i;
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for (i=0; i < sizeof buffer; i++)
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err = gpgme_op_random_bytes (ctx, mode, buffer, sizeof buffer);
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if (err)
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{
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if (i && !(i%32))
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putchar ('\n');
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printf ("%02x", ((unsigned char *)buffer)[i]);
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fprintf (stderr, PGM ": error getting random: %s\n",
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gpg_strerror (err));
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exit (1);
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}
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if (mode == GPGME_RANDOM_MODE_ZBASE32)
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puts (buffer);
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else
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{
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int i;
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for (i=0; i < sizeof buffer; i++)
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{
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if (i && !(i%32))
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putchar ('\n');
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printf ("%02x", ((unsigned char *)buffer)[i]);
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}
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putchar ('\n');
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}
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putchar ('\n');
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}
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gpgme_release (ctx);
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