Opening and closing braces for if
, for
, or while
statements should always be used, even if the statement's body contains only a single statement.
Braces improve the uniformity and readability of code.
More importantly, when inserting an additional statement into a body containing only a single statement, it is easy to forget to add braces because the indentation gives strong (but misleading) guidance to the structure.
This noncompliant code example uses an if
statement without braces to authenticate a user.
int login; if (invalid_login()) login = 0; else login = 1; |
A developer might add a debugging statement to determine when the login is valid, but forget to add opening and closing braces.
int login; if (invalid_login()) login = 0; else System.out.println("Login is valid\n"); // debugging line added here login = 1; // this line always gets executed, regardless of a valid login! |
Due to the indentation of the code, it is difficult to tell that the code will not function as intended by the programmer, potentially leading to a security breach.
In this compliant solution, opening and closing braces are used even when the body is a single statement.
int login; if (invalid_login()) { login = 0; } else { login = 1; } |
This noncompliant code example has an if
statement nested in another if
statement without braces around if
and else
bodies.
int privileges; if (invalid_login()) if (allow_guests()) privileges = GUEST; else privileges = ADMINISTRATOR; |
The indentation could lead the programmer to believe that a user is given administrator privileges only when the user's login is valid. However, the else
statement actually attaches to the inner if
statement:
int privileges; if (invalid_login()) if (allow_guests()) privileges = GUEST; else privileges = ADMINISTRATOR; |
This is a security loophole, as users with invalid logins can still obtain administrator privileges.
In this compliant solution, adding braces removes the ambiguity and ensures that privileges are correctly assigned.
int privileges; if (invalid_login()) { if (allow_guests()) { privileges = GUEST; } } else { privileges = ADMINISTRATOR; } |
Recommendation |
Severity |
Likelihood |
Remediation Cost |
Priority |
Level |
---|---|---|---|---|---|
EXP05-J |
medium |
probable |
medium |
P8 |
L2 |
EXP19-C
CERT C Secure Coding Standard: EXP19-C. Use braces for the body of an if, for, or while statement
\[[GNU 2010|AA. Bibliography#GNU 10]\] [Coding Standards, Section 5.3, "Clean Use of C Constructs"|http://www.gnu.org/prep/standards/standards.html#Syntactic-Conventions] |
EXP18-C. Do not perform assignments in selection statements 03. Expressions (EXP) EXP20-C. Perform explicit tests to determine success, true and false, and equality