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Debian – How to get the same CRC32 like cksum?

I took the source code of cksum and copied the polynomial. This gives the same as the predefined IEEE variant defined in the Go standard library.

package main

import (
    "fmt"
    "hash/crc32"
)

// https://github.com/coreutils/coreutils/blob/a9b78541fa7c06567c5b82fb4e89d85a1dc0c611/src/cksum.c#L54
//
//          32   26   23   22   16   12   11   10   8   7   5   4   2   1
//    G(X)=X  + X  + X  + X  + X  + X  + X  + X  + X + X + X + X + X + X + 1

const p = 0b11101101101110001000001100100000

func main() {
    cksum := crc32.MakeTable(p)
    fmt.Println(crc32.Checksum([]byte("moin"), cksum))
    fmt.Println(crc32.ChecksumIEEE([]byte("moin")))
}

The result is: 3048661102

But when I use the cksum on Debian 12 (coreutils 9.1) the result is something else:

$ printf "moin" | cksum 
1401816862 4

What is wrong here?

Update

I think the problem is explained here.

But the question is still: How to do with "hash/crc32" the same as cksum does?

It does not work even with a hard coded table.

Tags:

2

Answers


  1. 0

    That one is the CRC-32/CKSUM:

    width=32 poly=0x04c11db7 init=0x00000000 refin=false refout=false xorout=0xffffffff check=0x765e7680 residue=0xc704dd7b name="CRC-32/CKSUM"

    This CRC shifts up (refin and refout false), whereas the Go hash/crc32 package appears to only support CRC’s that shift down (refin and refout true). You would have to write your own CRC code.

    Here is an example in C, which you could translate to Go:

    #include <stddef.h>
#include <stdint.h>

static uint32_t const table_byte[] = {
    0xb1f7404b, 0xb5365dfc, 0xb8757b25, 0xbcb46692, 0xa2f33697, 0xa6322b20,
    0xab710df9, 0xafb0104e, 0x97ffadf3, 0x933eb044, 0x9e7d969d, 0x9abc8b2a,
    0x84fbdb2f, 0x803ac698, 0x8d79e041, 0x89b8fdf6, 0xfde69b3b, 0xf927868c,
    0xf464a055, 0xf0a5bde2, 0xeee2ede7, 0xea23f050, 0xe760d689, 0xe3a1cb3e,
    0xdbee7683, 0xdf2f6b34, 0xd26c4ded, 0xd6ad505a, 0xc8ea005f, 0xcc2b1de8,
    0xc1683b31, 0xc5a92686, 0x29d4f6ab, 0x2d15eb1c, 0x2056cdc5, 0x2497d072,
    0x3ad08077, 0x3e119dc0, 0x3352bb19, 0x3793a6ae, 0x0fdc1b13, 0x0b1d06a4,
    0x065e207d, 0x029f3dca, 0x1cd86dcf, 0x18197078, 0x155a56a1, 0x119b4b16,
    0x65c52ddb, 0x6104306c, 0x6c4716b5, 0x68860b02, 0x76c15b07, 0x720046b0,
    0x7f436069, 0x7b827dde, 0x43cdc063, 0x470cddd4, 0x4a4ffb0d, 0x4e8ee6ba,
    0x50c9b6bf, 0x5408ab08, 0x594b8dd1, 0x5d8a9066, 0x8571303c, 0x81b02d8b,
    0x8cf30b52, 0x883216e5, 0x967546e0, 0x92b45b57, 0x9ff77d8e, 0x9b366039,
    0xa379dd84, 0xa7b8c033, 0xaafbe6ea, 0xae3afb5d, 0xb07dab58, 0xb4bcb6ef,
    0xb9ff9036, 0xbd3e8d81, 0xc960eb4c, 0xcda1f6fb, 0xc0e2d022, 0xc423cd95,
    0xda649d90, 0xdea58027, 0xd3e6a6fe, 0xd727bb49, 0xef6806f4, 0xeba91b43,
    0xe6ea3d9a, 0xe22b202d, 0xfc6c7028, 0xf8ad6d9f, 0xf5ee4b46, 0xf12f56f1,
    0x1d5286dc, 0x19939b6b, 0x14d0bdb2, 0x1011a005, 0x0e56f000, 0x0a97edb7,
    0x07d4cb6e, 0x0315d6d9, 0x3b5a6b64, 0x3f9b76d3, 0x32d8500a, 0x36194dbd,
    0x285e1db8, 0x2c9f000f, 0x21dc26d6, 0x251d3b61, 0x51435dac, 0x5582401b,
    0x58c166c2, 0x5c007b75, 0x42472b70, 0x468636c7, 0x4bc5101e, 0x4f040da9,
    0x774bb014, 0x738aada3, 0x7ec98b7a, 0x7a0896cd, 0x644fc6c8, 0x608edb7f,
    0x6dcdfda6, 0x690ce011, 0xd8fba0a5, 0xdc3abd12, 0xd1799bcb, 0xd5b8867c,
    0xcbffd679, 0xcf3ecbce, 0xc27ded17, 0xc6bcf0a0, 0xfef34d1d, 0xfa3250aa,
    0xf7717673, 0xf3b06bc4, 0xedf73bc1, 0xe9362676, 0xe47500af, 0xe0b41d18,
    0x94ea7bd5, 0x902b6662, 0x9d6840bb, 0x99a95d0c, 0x87ee0d09, 0x832f10be,
    0x8e6c3667, 0x8aad2bd0, 0xb2e2966d, 0xb6238bda, 0xbb60ad03, 0xbfa1b0b4,
    0xa1e6e0b1, 0xa527fd06, 0xa864dbdf, 0xaca5c668, 0x40d81645, 0x44190bf2,
    0x495a2d2b, 0x4d9b309c, 0x53dc6099, 0x571d7d2e, 0x5a5e5bf7, 0x5e9f4640,
    0x66d0fbfd, 0x6211e64a, 0x6f52c093, 0x6b93dd24, 0x75d48d21, 0x71159096,
    0x7c56b64f, 0x7897abf8, 0x0cc9cd35, 0x0808d082, 0x054bf65b, 0x018aebec,
    0x1fcdbbe9, 0x1b0ca65e, 0x164f8087, 0x128e9d30, 0x2ac1208d, 0x2e003d3a,
    0x23431be3, 0x27820654, 0x39c55651, 0x3d044be6, 0x30476d3f, 0x34867088,
    0xec7dd0d2, 0xe8bccd65, 0xe5ffebbc, 0xe13ef60b, 0xff79a60e, 0xfbb8bbb9,
    0xf6fb9d60, 0xf23a80d7, 0xca753d6a, 0xceb420dd, 0xc3f70604, 0xc7361bb3,
    0xd9714bb6, 0xddb05601, 0xd0f370d8, 0xd4326d6f, 0xa06c0ba2, 0xa4ad1615,
    0xa9ee30cc, 0xad2f2d7b, 0xb3687d7e, 0xb7a960c9, 0xbaea4610, 0xbe2b5ba7,
    0x8664e61a, 0x82a5fbad, 0x8fe6dd74, 0x8b27c0c3, 0x956090c6, 0x91a18d71,
    0x9ce2aba8, 0x9823b61f, 0x745e6632, 0x709f7b85, 0x7ddc5d5c, 0x791d40eb,
    0x675a10ee, 0x639b0d59, 0x6ed82b80, 0x6a193637, 0x52568b8a, 0x5697963d,
    0x5bd4b0e4, 0x5f15ad53, 0x4152fd56, 0x4593e0e1, 0x48d0c638, 0x4c11db8f,
    0x384fbd42, 0x3c8ea0f5, 0x31cd862c, 0x350c9b9b, 0x2b4bcb9e, 0x2f8ad629,
    0x22c9f0f0, 0x2608ed47, 0x1e4750fa, 0x1a864d4d, 0x17c56b94, 0x13047623,
    0x0d432626, 0x09823b91, 0x04c11d48, 0x000000ff
};

uint32_t crc32cksum_byte(uint32_t crc, void const *mem, size_t len) {
    uint8_t const *data = mem;
    if (data == NULL)
        return 0xffffffff;
    for (size_t i = 0; i < len; i++)
        crc = (crc << 8) ^ table_byte[((crc >> 24) ^ data[i]) & 0xff];
    return crc;
}

    The initial CRC value (returned for mem == NULL) is 0xffffffff.

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  2. 0

    Check the parameters for CRC-32/CKSUM on
    https://reveng.sourceforge.io/crc-catalogue/all.htm

    width=32 poly=0x04c11db7 init=0x00000000 refin=false refout=false xorout=0xffffffff check=0x765e7680 residue=0xc704dd7b name="CRC-32/CKSUM"

    And compare with the parameters for CRC-32/ISO-HDLC, which I believe corresponds to the algorithm in hash/crc32:

    width=32 poly=0x04c11db7 init=0xffffffff refin=true refout=true xorout=0xffffffff check=0xcbf43926 residue=0xdebb20e3 name="CRC-32/ISO-HDLC"

    It is only possible to adjust poly (the polynom) in hash/crc32, but not init (initial value), refin (reflected input) or refout (reflected output).

    In addition to these parameters, the cksum program also processes a representation of the input stream length following the input.

    Here is some naive code that produces the expected output. A fast/real implementation would create another table from the polynom.

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