When PHP web applications are injected, how does one write user logon to prevent bypass login through injection?

When PHP web applications are injected, how to write user logon to prevent bypass login through injection is assumed that the conditions cannot be changed. do not reply to prevent injection in general 2: 1 $ SQL & quot; select * fromuserwhereuser_name $ usernameandpassword $ password & quot; $ res... how to write user logon when PHP web applications are injected to prevent bypass login through injection

If the conditions cannot be changed, do not reply to prevent injection.

2 in general
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1
$ SQL = "select * from user where user_name = $ username and password = $ password ";
$ Res = $ db_obj-> get_one ($ SQL );
If ($ res ){
// Login successful
}
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·
2
$ SQL = "select * from user where user_name = $ username ";
$ Res = $ db_obj-> get_one ($ SQL );
If ($ res [password] = md5 ($ password )){
// Login successful
}
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Any of the above two can be bypassed to seek security

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How to write user logon when PHP web applications are injected to prevent bypass login through injection

If the conditions cannot be changed, do not reply to prevent injection.

2 in general
·
1
$ SQL = "select * from user where user_name = $ username and password = $ password ";
$ Res = $ db_obj-> get_one ($ SQL );
If ($ res ){
// Login successful
}
·
·
2
$ SQL = "select * from user where user_name = $ username ";
$ Res = $ db_obj-> get_one ($ SQL );
If ($ res [password] = md5 ($ password )){
// Login successful
}
·
Any of the above two can be bypassed to seek security

Since the injection vulnerability already exists, not only logon can be bypassed, but your database is not secure. If you know the structure of your table, it is easy to insert an administrator account. So the key is to prevent injection, instead of what to do after injection.

Simplest
$ SQL = "select * from user where user_name = '". addslashes ($ username )."'";

Isn't the general writing method using orm to read and write databases?
Handwriting SQL is inherently insecure

Use PDO preprocessing statements