How to use MD5 to realize user Authentication in Linux
This article mainly introduces in Linux how to use MD5 to achieve user authentication related knowledge, the content is detailed and easy to understand, the operation is simple and fast, with a certain reference value, I believe you will have something to gain after reading this article on how to use MD5 in Linux to achieve user authentication, let's take a look.
Using the md5 function in openssl, which returns 16 bytes of data of type unsigned char, each byte in the range of 0,0255. set the
It is formatted in hexadecimal, which is 32-bit md5 encoding. Note: a byte is 8 bits, which is exactly 2-bit hexadecimal.
Use the user name of the login client to get the salt value and the encrypted password from the redis database, and then encrypt the password of the login client through salt.
Compare passwords in the redis database. If the same is the same, the verification passes, otherwise the verification fails.
The password in the redis database is stored in password:salt format
The user authentication algorithm is as follows:
Int user_authenticate (char * username, char * password)
{
Char * salt_pw, * salt, * pw
Char buf [40]
Char tmp [3] = {'\ 0'}, md5_str [33] = {'\ 0'}
Unsigned char md [16]
Int i
/ / get_salt_pw calls redis database to get password:salt
Salt_pw = get_salt_pw (db, username)
Pw = strtok (salt_pw, ":")
If (! pw) {
Return 0
}
Salt = strtok (null, ":")
If (! salt) {
Return 0
}
Strcpy (buf, password)
Strcat (buf, salt)
Md5 ((const unsigned char*) buf, strlen (buf), md)
/ / transform to md5 string
For (I = 0; I < 16; iTunes +) {
Sprintf (tmp, "x", md [I])
Strcat (md5_str, tmp)
}
/ / compare encode password using md5
If (strcmp ((char*) md5_str, pw)) {
Return 0
}
Return 1
}
Note the use of the strtok function and the process of converting a 16-byte unsigned char into a 32-bit hexadecimal number.
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