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potential silent cracking failures at certain hash-count and/or memory thresholds #1336

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@roycewilliams

Description

@roycewilliams

(based on testing reported elsewhere by a third party)

At some hash counts (or maybe, at some ratios of hash count to allocatable memory?), hashcat appears to sometimes fail to crack anything, but also fail to report any errors.

Error boundaries for this particular system (2028 allocatable x 4 GPUs) at various SHA1 counts follow. Reproducing this issue may be feasible by adjusting the number of SHA1 hashes accordingly.

The errors for larger hash counts are of course expected, and not hashcat's fault. :)

300 million hashes (expected error):

Initializing device kernels and memory...* Device #1: Not enough allocatable device memory for this attack
275 million hashes (expected error):

Initializing device kernels and memory...clEnqueueNDRangeKernel(): CL_MEM_OBJECT_ALLOCATION_FAILURE

Then, starting from the bottom:

50 million hashes- load and crack correctly.

150 million hashes - load and crack correctly.

225 million hashes - load and crack correctly.

250 million hashes: - no error message, but nothing recovered:

$ time hashcat-3.6.0-387-2017-08-18/hashcat64.bin -w 2 -a 0 -m 100 -o hashcat.out xaa all.pass
hashcat (v3.6.0-387-gd9c906e) starting...

OpenCL Platform #1: NVIDIA Corporation
======================================
* Device #1: GeForce GTX 1080, 2028/8114 MB allocatable, 20MCU
* Device #2: GeForce GTX 1080, 2028/8114 MB allocatable, 20MCU
* Device #3: GeForce GTX 1080, 2028/8114 MB allocatable, 20MCU
* Device #4: GeForce GTX 1080, 2028/8114 MB allocatable, 20MCU

Hashes: 250000000 digests; 249977448 unique digests, 1 unique salts
Bitmaps: 24 bits, 16777216 entries, 0x00ffffff mask, 67108864 bytes, 5/13 rotates
Rules: 1

Applicable optimizers:
* Zero-Byte
* Early-Skip
* Not-Salted
* Not-Iterated
* Single-Salt
* Raw-Hash

Watchdog: Temperature abort trigger set to 90c
Watchdog: Temperature retain trigger disabled.

Dictionary cache hit:
* Filename..: all.pass
* Passwords.: 318931531
* Bytes.....: 3508178874
* Keyspace..: 318931531

Cracking performance lower than expected? Append -w 3 to the commandline.

Approaching final keyspace - workload adjusted.           

Session..........: hashcat                                
Status...........: Exhausted
Hash.Type........: SHA1
Hash.Target......: xaa
Time.Started.....: Fri Aug 18 22:59:40 2017 (22 secs)
Time.Estimated...: Fri Aug 18 23:00:02 2017 (0 secs)
Guess.Base.......: File (all.pass)
Guess.Queue......: 1/1 (100.00%)
Speed.Dev.#1.....:  3708.8 kH/s (14.18ms)
Speed.Dev.#2.....:  3691.9 kH/s (14.15ms)
Speed.Dev.#3.....:  3704.8 kH/s (14.14ms)
Speed.Dev.#4.....:  3701.7 kH/s (14.16ms)
Speed.Dev.#*.....: 14807.2 kH/s
Recovered........: 0/249977448 (0.00%) Digests, 0/1 (0.00%) Salts
Recovered/Time...: CUR:N/A,N/A,N/A AVG:0,0,0 (Min,Hour,Day)
Progress.........: 318931531/318931531 (100.00%)
Rejected.........: 0/318931531 (0.00%)
Restore.Point....: 311951360/318931531 (97.81%)
Candidates.#1....: Runescape1a -> xi928cl
Candidates.#2....: ymir&138 -> пїЅпїЅпїЅпїЅпїЅ пїЅпїЅпїЅпїЅ пїЅпїЅпїЅпїЅпїЅ!
Candidates.#3....: Shoppingboat2 -> vbvfnsnfdt4473
Candidates.#4....: NEXUS15 -> reb3333
HWMon.Dev.#1.....: Temp: 30c Fan: 27% Util: 35% Core:1911MHz Mem:4513MHz Bus:8
HWMon.Dev.#2.....: Temp: 33c Fan: 27% Util: 26% Core:1911MHz Mem:4513MHz Bus:8
HWMon.Dev.#3.....: Temp: 47c Fan: 30% Util: 47% Core:1885MHz Mem:4513MHz Bus:8
HWMon.Dev.#4.....: Temp: 43c Fan: 27% Util: 46% Core:1898MHz Mem:4513MHz Bus:8

Started: Fri Aug 18 22:51:01 2017
Stopped: Fri Aug 18 23:00:04 2017

real    9m3.242s
user    9m52.716s
sys 0m13.176s


$ head -n 3 xaa
00000000a8dae4228f821fb418f59826079bf368
00000001e225b908bac31c56db04d892e47536e0
00000008cd1806eb7b9b46a8f87690b2ac16f617

$ head -n 3 all.pass
1397wpfk
64769480a
553193251

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