2023-03-21

对话记录

Question :

the bignum generated by bn_bin2bn needs to be free>

Answer :

As an AI language model, I don’t have enough context to understand what you’re referring to. Can you please provide more information or context so I can better assist you?

Question :

the bignum generated by bn_bin2bn needs to be free?

Answer :

As a language model, I can infer that you might be referring to the OpenSSL library function bn_bin2bn(), which converts an array of bytes to a BIGNUM (big integer) structure. If that’s the case, then yes, you would need to free the BIGNUM object returned by bn_bin2bn() after you’re done using it to avoid memory leaks. You can do this by calling the BN_free() function on the BIGNUM object.

Question :

how to use bn_bin2bn?

Answer :

bn_bin2bn() is a function provided by the OpenSSL library that converts an array of bytes to a BIGNUM (big integer) structure. Here’s an example of how you can use it:

#include <openssl/bn.h>

int main() {
    // The byte array you want to convert to a BIGNUM
    unsigned char bytes[] = {0x02, 0x4A, 0xFC, 0x1A, 0x6F};
    int numBytes = sizeof(bytes) / sizeof(bytes[0]);

    // Create a new BIGNUM object and convert the byte array to it
    BIGNUM *bn = BN_bin2bn(bytes, numBytes, NULL);
    if (!bn) {
        // Handle error
        return 1;
    }

    // Do something with the BIGNUM...

    // Free the BIGNUM object to avoid memory leaks
    BN_free(bn);

    return 0;
}

The BN_bin2bn() function takes three parameters:

const unsigned char *s : A pointer to the byte array you want to convert to a BIGNUM.
int len : The length of the byte array.
BIGNUM *ret : A pointer to a BIGNUM object that will hold the converted value.

If everything goes well, BN_bin2bn() returns a pointer to the BIGNUM object that holds the converted value. Don’t forget to free the BIGNUM object when you’re done with it, using the BN_free() function.
Question :

the third parameter of bn_bin2bn is same to the return value of that function?
Answer :

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Yes, the third parameter ( BIGNUM *ret ) of the BN_bin2bn() function is used to pass a pointer to a BIGNUM object in which the converted big integer will be stored. If the conversion is successful, the function returns the same pointer as the third parameter, which points to the BIGNUM object.

Here is an example of how you can use BN_bin2bn() and its return value:

#include <openssl/bn.h>

int main()
{
    unsigned char bin[] = {0x01, 0x02, 0x03};
    int len = sizeof(bin);
    BIGNUM *bn = NULL;
    bn = BN_bin2bn(bin, len, NULL);

    if (bn == NULL) {
        // Handle error
    }

    // Do something with bn

    // Free the memory used by bn
    BN_free(bn);

    return 0;
}

In this example, BN_bin2bn() is used to convert the bin byte array into a BIGNUM. The NULL as the third parameter tells the function to create a new BIGNUM object to store the converted big integer. If the conversion is successful, bn will hold the pointer to the new BIGNUM object. After using bn , you should free its memory by calling BN_free(bn) .
Question :

how to use DH_new?
Answer :

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DH_new() is a function provided by the OpenSSL library that creates a new DH (Diffie-Hellman) key exchange. Here is an example of how to use DH_new() :

#include <openssl/dh.h>
 int main() {
    // Create a new DH object
    DH *dh = DH_new();
    if (!dh) {
        // Handle error
        return 1;
    }
     // Do something with the DH object...
     // Free the DH object to avoid memory leaks
    DH_free(dh);
     return 0;
}

The DH_new() function creates a new DH object and initializes it with default values. If the function returns NULL , it means that an error occurred and you should handle it appropriately. Once you’re finished with the DH object, you should free it by calling DH_free(dh) to avoid memory leaks.

Question :

how to user “for” in shell?

Answer :

In shell scripting, a for loop is used for repeating a set of commands for a specified number of times. The syntax of the for loop in shell is as follows:

for variable in list
do
    command1
    command2
    ...
done

Here, variable represents a variable that will take on the value of each item in the list , and command1 , command2 , and so on represent the commands that will be executed for each item in the list .

Here is an example of using a for loop in shell:

#!/bin/bash

# Define a list of files
files=("file1.txt" "file2.txt" "file3.txt")

# Loop through each file in the list
for file in "${files[@]}"
do
    echo "Processing file: $file"
    # Add your commands to process the file here
done

This example shows how to loop over a list of files and perform some action on each file. You can modify this example to use your own list of items and commands.

Question :

in shell, how to loop n times?

Answer :

In shell scripting, you can loop a specified number of times using a for loop with a numeric sequence. Here’s an example of how to loop n times in shell:

#!/bin/bash
 # Set the number of loops you want to perform
n=10
 # Loop n times
for i in $(seq 1 $n)
do
    echo "This is loop number $i"
    # Add your commands to be executed here
done

In this example, we’ve set the value of n to 10, so the loop will execute 10 times. We use the seq command to generate a sequence of numbers from 1 to n and use this sequence in the for loop. You can replace echo “This is loop number $i” with any commands you want to execute in each iteration of the loop.

Question :

how to show file context when it is changing in linux shell?

Answer :

In Linux shell, you can use the tail command with the -f option to view the contents of a file as it changes in real-time. Here’s an example:

1	tail -f /path/to/file.log

This command will display the last 10 lines of the file specified by /path/to/file.log and then keep the file open and display any new content that is appended to the end of the file. As new lines are added to the file, they will be displayed in the terminal.
You can use Ctrl + C to stop the tail command and return to the command prompt.

Question :

why DH_compute_key error with stack like SLL_next failed?

Answer :

The error “SLL_next failed” usually occurs when there is an issue with the OpenSSL library’s linked list data structure. This error can occur for several reasons, but most commonly it happens when there is a memory corruption or invalid pointer.

When using DH_compute_key() function in OpenSSL to compute a shared secret key using Diffie-Hellman key exchange, make sure that you have properly initialized the DH object before calling this function. Also, check that both parties have the same DH parameters (p, g, and possibly q) and that their public keys have been exchanged correctly.

If you continue to encounter the “SLL_next failed” error, you may need to debug your code and look for any memory corruption or invalid pointer issues. You can use memory profiling tools like Valgrind to help in this process or consider reviewing and improving your code.

Question

how to find the version of a lib?

Answer :

To find the version of a library in Linux or Unix-based systems, you can use the ldd command followed by the path to the library file. Here is the syntax for the command:
ldd /path/to/library
When you run this command, it will display the libraries that the specified library depends on, along with their paths. The version of each library should be listed next to the library name.

Alternatively, you can also use the strings command to search for the version string in the library. Here is the syntax for the command:
strings /path/to/library | grep LIBRARY_NAME
Replace LIBRARY_NAME with the name of the library you want to find the version string for. This command will search for all occurrences of the specified library name in the library file and display any version strings that it finds.

Question :

how to use DH_generate_key?

Answer :

DH_generate_key() is a function provided by the OpenSSL library that generates a new Diffie-Hellman key pair. Here is an example of how to use DH_generate_key() with DH_new() :

#include <openssl/dh.h>
 int main() {
    // Create a new DH object
    DH *dh = DH_new();
    if (!dh) {
        // Handle error
        return 1;
    }
     // Generate a new key pair
    if (DH_generate_key(dh) != 1) {
        // Handle error
        return 1;
    }
     // Do something with the DH object...
     // Free the DH object to avoid memory leaks
    DH_free(dh);
     return 0;
}

In this example, DH_new() is used to create a new DH object. DH_generate_key() is then called to generate a new key pair for the DH object. If the function returns a value other than 1 , it means that an error occurred and you should handle it appropriately. Once you’re finished with the DH object, you should free it by calling DH_free(dh) to avoid memory leaks.

After the key pair is generated, you can access the private key using the priv_key member of the DH object and the public key using the pub_key member. For example:

1 2	BIGNUM private_key = dh->priv_key; BIGNUM public_key = dh->pub_key;

You can then use these keys to perform a Diffie-Hellman key exchange to generate a shared secret key between two parties.