SHA-1 hash calculate in Kernel.

SHA-1 hash calculate in Kernel.

[lx]

hi all:
      I built a module for calculate the SHA-1. The code is:
##################
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/crypto.h>
#include <linux/err.h>
#include <linux/scatterlist.h>
MODULE_LICENSE("Dual BSD/GPL");

#define SHA1_LENGTH     20

static int hello_init(void)
{
    /*
     * http://lxr.oss.org.cn/source/fs/ecryptfs/crypto.c?v=2.6.30
     */
    struct scatterlist sg;
    struct hash_desc desc;

    //way 1
    /*
    char *plaintext = "c";
    size_t len = strlen(plaintext);
    */

    //way 2
    /*
    char *plaintext = kmalloc(sizeof(char), GFP_KERNEL);
    plaintext = "c";
    size_t len = 1;
    */

    // way 3.
    /*
    char plaintext[1] = {'c'};
    size_t len = 1;
    */

    // way 4.
    /*
    char *plaintext = (char *)__get_free_page(GFP_KERNEL);
    memcpy(plaintext, "c", 1);
    size_t len = 1;
    */

    int rc = 0;
    int i;
    char hashtext[SHA1_LENGTH];

    memset(hashtext, 0x00, SHA1_LENGTH);
    printk(KERN_INFO "sha1: %s\n", __FUNCTION__);

    sg_init_one(&sg, plaintext, len);
    desc.tfm = crypto_alloc_hash("sha1", 0, CRYPTO_ALG_ASYNC);
    desc.flags = 0;

    rc = crypto_hash_init(&desc);
    if (rc) {
        printk(KERN_ERR "%s: Error initializing crypto hash; rc = [%d]\n",
__func__, rc);
        goto out;
    }
    rc = crypto_hash_update(&desc, &sg, len);
    if (rc) {
        printk(KERN_ERR "%s: Error updating crypto hash; rc = [%d]\n",
__func__, rc);
        goto out;
    }
    rc = crypto_hash_final(&desc, hashtext);
    if (rc) {
        printk(KERN_ERR "%s: Error finalizing crypto hash; rc = [%d]\n",
__func__, rc);
        goto out;
    }
    crypto_free_hash(desc.tfm);

    for (i = 0; i < 20; i++) {
        printk(KERN_INFO "%02x-%d\n", hashtext[i]&0xff, i);
    }

out:
    printk(KERN_INFO "end\n");
    return rc;
}

static void hello_exit(void)
{
    printk(KERN_ALERT "Goodbye, cruel world\n");
}

module_init(hello_init);
module_exit(hello_exit);
##################
I can just get the right result by way 3 and 4, In way 1 and 2 , I get the
wrong result,
I check the result by link: http://www.xorbin.com/tools/sha1-hash-calculator
.
Please tell me why? Thank you.
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SHA-1 hash calculate in Kernel.

[Bjørn Mork]

lx <lxlenovostar@gmail.com> writes:

> hi all:
>       I built a module for calculate the SHA-1. The code is:
> ##################
> #include <linux/init.h>
> #include <linux/module.h>
> #include <linux/kernel.h>
> #include <linux/crypto.h>
> #include <linux/err.h>
> #include <linux/scatterlist.h>
> MODULE_LICENSE("Dual BSD/GPL");
>
> #define SHA1_LENGTH     20
>
> static int hello_init(void)
> {
>     /*
>      * http://lxr.oss.org.cn/source/fs/ecryptfs/crypto.c?v=2.6.30
>      */
>     struct scatterlist sg;
>     struct hash_desc desc;
>
>     //way 1
>     /*
>     char *plaintext = "c";
>     size_t len = strlen(plaintext);
>     */
>
>     //way 2
>     /*
>     char *plaintext = kmalloc(sizeof(char), GFP_KERNEL);
>     plaintext = "c";
>     size_t len = 1;
>     */
>
>     // way 3.
>     /*
>     char plaintext[1] = {'c'};
>     size_t len = 1;
>     */
>
>     // way 4.
>     /*
>     char *plaintext = (char *)__get_free_page(GFP_KERNEL);
>     memcpy(plaintext, "c", 1);
>     size_t len = 1;
>     */
>
>     int rc = 0;
>     int i;
>     char hashtext[SHA1_LENGTH];
>
>     memset(hashtext, 0x00, SHA1_LENGTH);
>     printk(KERN_INFO "sha1: %s\n", __FUNCTION__);
>
>     sg_init_one(&sg, plaintext, len);
>     desc.tfm = crypto_alloc_hash("sha1", 0, CRYPTO_ALG_ASYNC);
>     desc.flags = 0;
>
>     rc = crypto_hash_init(&desc);
>     if (rc) {
>         printk(KERN_ERR "%s: Error initializing crypto hash; rc = [%d]\n",
> __func__, rc);
>         goto out;
>     }
>     rc = crypto_hash_update(&desc, &sg, len);
>     if (rc) {
>         printk(KERN_ERR "%s: Error updating crypto hash; rc = [%d]\n",
> __func__, rc);
>         goto out;
>     }
>     rc = crypto_hash_final(&desc, hashtext);
>     if (rc) {
>         printk(KERN_ERR "%s: Error finalizing crypto hash; rc = [%d]\n",
> __func__, rc);
>         goto out;
>     }
>     crypto_free_hash(desc.tfm);
>
>     for (i = 0; i < 20; i++) {
>         printk(KERN_INFO "%02x-%d\n", hashtext[i]&0xff, i);
>     }
>
> out:
>     printk(KERN_INFO "end\n");
>     return rc;
> }
>
> static void hello_exit(void)
> {
>     printk(KERN_ALERT "Goodbye, cruel world\n");
> }
>
> module_init(hello_init);
> module_exit(hello_exit);
> ##################
> I can just get the right result by way 3 and 4, In way 1 and 2 , I get the
> wrong result,

I suggest you add something like this:

    printk(KERN_INFO "plaintext='%c', len=%zu, valid=%s\n", *plaintext, len, virt_addr_valid(plaintext) ? "true" : "false");


and then go figure out the relationship between that and the correct
result :)




Bj?rn

SHA-1 hash calculate in Kernel.

[Jeff Haran]

From: kernelnewbies-bounces@kernelnewbies.org [mailto:kernelnewbies-bounces at kernelnewbies.org] On Behalf Of lx
Sent: Friday, August 28, 2015 12:36 AM
To: kernelnewbies
Subject: SHA-1 hash calculate in Kernel.

hi all:
      I built a module for calculate the SHA-1. The code is:
##################
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/crypto.h>
#include <linux/err.h>
#include <linux/scatterlist.h>
MODULE_LICENSE("Dual BSD/GPL");

#define SHA1_LENGTH     20

static int hello_init(void)
{
    /*
     * http://lxr.oss.org.cn/source/fs/ecryptfs/crypto.c?v=2.6.30
     */
    struct scatterlist sg;
    struct hash_desc desc;

    //way 1
    /*
    char *plaintext = "c";
    size_t len = strlen(plaintext);
    */

    //way 2
    /*
    char *plaintext = kmalloc(sizeof(char), GFP_KERNEL);
    plaintext = "c";
    size_t len = 1;
    */

    // way 3.
    /*
    char plaintext[1] = {'c'};
    size_t len = 1;
    */

    // way 4.
    /*
    char *plaintext = (char *)__get_free_page(GFP_KERNEL);
    memcpy(plaintext, "c", 1);
    size_t len = 1;
    */

    int rc = 0;
    int i;
    char hashtext[SHA1_LENGTH];

    memset(hashtext, 0x00, SHA1_LENGTH);
    printk(KERN_INFO "sha1: %s\n", __FUNCTION__);

    sg_init_one(&sg, plaintext, len);
    desc.tfm = crypto_alloc_hash("sha1", 0, CRYPTO_ALG_ASYNC);
    desc.flags = 0;

    rc = crypto_hash_init(&desc);
    if (rc) {
        printk(KERN_ERR "%s: Error initializing crypto hash; rc = [%d]\n", __func__, rc);
        goto out;
    }
    rc = crypto_hash_update(&desc, &sg, len);
    if (rc) {
        printk(KERN_ERR "%s: Error updating crypto hash; rc = [%d]\n", __func__, rc);
        goto out;
    }
    rc = crypto_hash_final(&desc, hashtext);
    if (rc) {
        printk(KERN_ERR "%s: Error finalizing crypto hash; rc = [%d]\n", __func__, rc);
        goto out;
    }
    crypto_free_hash(desc.tfm);

    for (i = 0; i < 20; i++) {
        printk(KERN_INFO "%02x-%d\n", hashtext[i]&0xff, i);
    }

out:
    printk(KERN_INFO "end\n");
    return rc;
}

static void hello_exit(void)
{
    printk(KERN_ALERT "Goodbye, cruel world\n");
}

module_init(hello_init);
module_exit(hello_exit);
##################
I can just get the right result by way 3 and 4, In way 1 and 2 , I get the wrong result,
I check the result by link: http://www.xorbin.com/tools/sha1-hash-calculator .
Please tell me why? Thank you.

I don?t know why the crypto function isn?t generating the right result in the first two cases. Just pointing out that way 1 and way 2 are identical except that way 2 leaks the memory that was kmalloc()?ed.  This in way 2 is a pointer assignment, not a buffer copy:

    plaintext = "c";

The big difference it seems between ways 1 and 2 and ways 3 and 4 is in the former, plaintext points to a string constant that I believe is going to be read only whereas in the latter, plaintext points to r/w memory. Maybe the crypto functions need r/w access?

Jeff Haran


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SHA-1 hash calculate in Kernel.

[Bernd Petrovitsch]

On Fre, 2015-08-28 at 15:36 +0800, lx wrote:
[...]
>     //way 2
>     /*
>     char *plaintext = kmalloc(sizeof(char), GFP_KERNEL);
>     plaintext = "c";

I don't think that this line doesn't give any warning ...

Kind regards,
	Bernd
-- 
"I dislike type abstraction if it has no real reason. And saving
on typing is not a good reason - if your typing speed is the main
issue when you're coding, you're doing something seriously wrong."
    - Linus Torvalds

SHA-1 hash calculate in Kernel.

[lx]

hi all:
       I finally implement it by learning form the function of tcp md5
checksum. This is the relative kernel source
<http://lxr.oss.org.cn/source/net/ipv4/tcp.c?v=2.6.30#L2667>. The SHA-1
implement is here
<https://github.com/lxlenovostar/kernel_test/blob/master/model/kernel_hash/sha.c>.But
I still have a question about __virt_addr_valid.

##############################
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/crypto.h>
#include <linux/err.h>
#include <linux/scatterlist.h>
#include <linux/mm.h>

#define SHA1_LENGTH 20
static inline int phys_addr_valid(resource_size_t addr)
{
#ifdef CONFIG_PHYS_ADDR_T_64BIT
          return !(addr >> boot_cpu_data.x86_phys_bits);
  #else
          return 1;
  #endif
}

bool __virt_addr_valid(unsigned long x)
{
        unsigned long old_x;
        old_x = x;
        //The kernel text is mapped into the region starting
from__START_KERNEL_MAP
        if (x >= __START_KERNEL_map) {
                if (x >= MODULES_VADDR && x <= MODULES_END) {
                    printk(KERN_INFO "right here");
                }
                x -= __START_KERNEL_map;
                 if (x >= KERNEL_IMAGE_SIZE) {
                          printk(KERN_INFO "error1");
                          return false;
                    }
                  x += phys_base;
          } else {
                  if (x < PAGE_OFFSET) {
                          printk(KERN_INFO "error2");
                          return false;
                    }
                  x -= PAGE_OFFSET;
                  if (!phys_addr_valid(x)) {
                          printk(KERN_INFO "error3");
                          return false;
                    }
          }

          return pfn_valid(x >> PAGE_SHIFT);
}

static int minit(void)
{
    /*
     * http://lxr.oss.org.cn/source/fs/ecryptfs/crypto.c?v=2.6.30
     */
    struct scatterlist sg;
    struct hash_desc desc;

    int rc = 0;
    int i;
    char hashtext[SHA1_LENGTH];


    char *plaintext = NULL;
    printk(KERN_INFO "valid=%s\n", virt_addr_valid(plaintext) ? "true" :
"false");
    plaintext = "c";
    printk(KERN_INFO "valid=%s\n", virt_addr_valid(plaintext) ? "true" :
"false");
    size_t len = strlen(plaintext);

    sg_init_one(&sg, (u8 *)plaintext, len);
    desc.tfm = crypto_alloc_hash("sha1", 0, CRYPTO_ALG_ASYNC);
    desc.flags = 0;

    rc = crypto_hash_init(&desc);
    if (rc) {
        printk(KERN_ERR "%s: Error initializing crypto hash; rc = [%d]\n",
__func__, rc);
        goto out;
    }
    rc = crypto_hash_update(&desc, &sg, len);
    if (rc) {
        printk(KERN_ERR "%s: Error updating crypto hash; rc = [%d]\n",
__func__, rc);
        goto out;
    }
    rc = crypto_hash_final(&desc, hashtext);
    if (rc) {
        printk(KERN_ERR "%s: Error finalizing crypto hash; rc = [%d]\n",
__func__, rc);
        goto out;
    }
    crypto_free_hash(desc.tfm);

    for (i = 0; i < 20; i++) {
        //printk(KERN_INFO "%02x-%d\n", hashtext[i]&0xff, i);
    }

out:
    return rc;
}

static void mexit(void)
{
    printk("Exit %s.\n", THIS_MODULE->name);
}
##############################

I make and insmod it. the log is:

##############################
[root at localhost sha]# dmesg -c
error2
valid=false
right here
error1
valid=false
##############################


I think plaintext is between MODULES_VADDR and MODULES_END, So why the
address in
MODULES not a valid virtual address?

Thank you.


2015-08-29 19:49 GMT+08:00 Bernd Petrovitsch <bernd@petrovitsch.priv.at>:

> On Fre, 2015-08-28 at 15:36 +0800, lx wrote:
> [...]
> >     //way 2
> >     /*
> >     char *plaintext = kmalloc(sizeof(char), GFP_KERNEL);
> >     plaintext = "c";
>
> I don't think that this line doesn't give any warning ...
>
> Kind regards,
>         Bernd
> --
> "I dislike type abstraction if it has no real reason. And saving
> on typing is not a good reason - if your typing speed is the main
> issue when you're coding, you're doing something seriously wrong."
>     - Linus Torvalds
>
>
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