s_rng_ansic hangs if system clock does not advance on its own

[niansa]

Prerequisites

• Checked the developer manual
• Checked that your issue isn't already filed: https://github.com/issues?utf8=✓&q=repo%3Alibtom%2Flibtomcrypt
• Checked that your issue isn't due to the fact that you're using asymmetric cryptography and you forgot linking in and/or setting an MPI provider (usually this causes either random crashes or runtime errors like LTC_ARGCHK 'ltc_mp.name != NULL' failure ...). c.f. Ch. "Math Descriptors" of the developer manual.
• Checked that your issue isn't related to TomsFastMath's limitation that PK operations can by default only be done with max. 2048bit keys

Description

s_rng_ansic expects the clock to advance on its own, causing an infinite loop on cooperatively-scheduled systems where the clock only advances when yielding the thread.

#0  0x001e9fe8 in clock ()
#1  0x0015eb60 in s_rng_ansic (buf=0x8007b20 ".1:53431)", len=63, callback=0x0) at libtomcrypt/src/prngs/rng_get_bytes.c:69
#2  0x0015ec8c in rng_get_bytes (out=0x8007b20 ".1:53431)", outlen=64, callback=0x0) at libtomcrypt/src/prngs/rng_get_bytes.c:163

Steps to Reproduce

One public system that causes this issue I was able to find is the Nintendo 3DS, using dev kit pro.

1. Download devkitpro
2. Create a project with it targeting Nintendo 3DS
3. Call rng_get_bytes

Alternatively:

1. Override clock() to always return the same value
2. Call rng_get_bytes

Version

v1.18.2-1013-g9a13375d

[sjaeckel]

Hey hey,

thanks for the detailed issue description!

I doubt we can do anything about a clock that needs manual pushing (i.e. it is broken).

I'm closing this as invalid, since it's not a problem of the library, but of the system you're trying to use the library on.

If you believe this is not the case feel free to re-open, or open another issue if you find something (in the library) that is not working as expected.