How to Implement user verification using MD5 in Linux

Use the MD5 function in OpenSSL. This function returns 16 bytes of unsigned char data, with each byte ranging from 0 ~ 255

It is formatted as a 32-bit MD5 code in hexadecimal format. Note: one byte is 8 bits, which can represent two hexadecimal digits.

Use the username used to log on to the client to obtain the salt value and the encrypted password from the redis database, and then encrypt the password used to log on to the client with

Compare the passwords in the redis database. If they are the same, the verification succeeds. Otherwise, the verification fails.

The password storage format in the redis database is password: salt

User verificationAlgorithmAs 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 call redis database to obtain 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; I ++ ){

Sprintf (TMP, "% 02x", 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 16-byte unsigned char to 32-bit hexadecimal number.