Enhancing Fortran Security with Codee

Fortran remains a critical programming language in areas like scientific computing, aerospace, and defense, among others. However, security vulnerabilities in Fortran code can lead to computational inaccuracies, system crashes, or even mission-critical failures. Ensuring secure coding practices in large-scale Fortran projects is challenging, as manual reviews are time-consuming and error-prone.

This is where Codee comes in.

By automating a static analysis of the code, Codee systematically identifies security vulnerabilities aligned with ISO/IEC 24772-8 and SEI CERT C, ensuring compliance with best practices for secure Fortran development.

Codee’s Security Checks for Fortran

Codee identifies 40 key security vulnerabilities affecting Fortran applications, covering areas such as implicit variable declarations, unsafe memory access, concurrency issues, and legacy constructs.

Among the security checks provided by Codee are:
🔹 PWR007 – Disable implicit variable declarations.
🔹 PWR001 – Declare global variables as function parameters.
🔹 PWR008 – Declare intent for each procedure parameter.
🔹 PWR068 – Encapsulate procedures within modules.
🔹 PWD004 – Detect out-of-bounds array accesses.
🔹 PWD002 – Identify unprotected multithreading reduction operations
🔎 Explore the complete set of security checks in the Open Catalog.

Case Study: WRF Security Analysis with Codee

The Weather Research and Forecasting (WRF) Model is a widely used simulation tool in meteorology. Given its complexity and extensive Fortran codebase, ensuring security compliance is a major challenge.

Codee was applied to WRF’s source code to detect and fix security vulnerabilities. As an example, this section focuses on PWR007 (Disable implicit variable declarations), demonstrating how Codee helps enforce secure coding practices.

✅ Key Findings from WRF Security Analysis: 

Codee identifies a code improvement opportunity related to PWR007. In other words, Codee has detected a procedure affected by Fortran’s mechanisms for the implicit declaration of variables, along with the associated vulnerabilities. 

$ codee checks --verbose \
               --compile-commands src/NERSC_WRF/compile_commands.json \
               --check-id PWR007

<...>

/WRF/src/NERSC_WRF/phys/module_sf_ssib.f90:4421:7 [PWR007] (level: L1): Disable implicit declaration of variables
  Suggestion: Add IMPLICIT NONE in the specification part of the procedure 'STRES1'
  Documentation: https://github.com/codee-com/open-catalog/tree/main/Checks/PWR007
  AutoFix:
    codee rewrite --modernization implicit-none --in-place \
                  /WRF/src/NERSC_WRF/phys/module_sf_ssib.f90:STRES1 \
                  -p src/NERSC_WRF/compile_commands.json

<...>

Codee’s AutoFix Implementation in WRF

To automate security enforcement, Codee was used to automatically rewrite affected procedures, always under the supervision of the programmer.

The lines with a + at the beginning indicate code additions made by Codee.

Example Fix for PWR007 (Implicit Variables in WRF)

$ codee rewrite --modernization implicit-none --in-place \
                /WRF/src/NERSC_WRF/phys/module_sf_ssib.f90:STRES1 \
                -p src/NERSC_WRF/compile_commands.json

Results for file '/WRF/src/NERSC_WRF/phys/module_sf_ssib.f90':
  Successfully applied AutoFix to the procedure at
  '/WRF/src/NERSC_WRF/phys/module_sf_ssib.f90:4421:7' [using insert implicit none]

$ git diff /WRF/src/NERSC_WRF/phys/module_sf_ssib.f90

SUBROUTINE STRES1 (IFIRST,RSTM,ROOTP,                          &
           RSTFAC,RST,TC,ETC,RB,TGS,ETGS,RD,TU,TL,TOPT,EA,       &
           DEFAC,PH1,PH2,NROOT,ZDEPTH,PHSOIL,ROOTD,VCOVER,DROP)

+     ! Codee: Made all variable declarations explicit (2025-01-07 17:16:02)
+     implicit none
+     integer :: I
+     integer :: IFIRST
+     integer :: IVEG
+     integer :: NROOT
+     real :: D1
+     real :: D2
+     real :: DEFAC
+     real :: DEP
+     real :: DROP
+     real :: EA
+     real :: EPOT
+     real :: ETC
+     real :: ETGS
+     real :: ETV
+     real :: FTPD
+     <...>
+     real :: ZDEPTH

      DIMENSION TOPT(2), TL(2), TU(2), DEFAC(2), VCOVER(2)
      DIMENSION PH1(2), PH2(2), RST(2), RSTFAC(2,4),XDRR(3)
      DIMENSION ROOTD(2),ROOTP(3),ZDEPTH(3),PHSOIL(3),RSTM(2),DEP(3)

      DO 1000 IVEG = 1, 2

📌 Codee automatically inserted IMPLICIT NONE and declared variables explicitly to prevent unintended behavior​.

 Why Codee for Fortran Security?

🔹 Automated Security Checks: Detects critical vulnerabilities in large-scale Fortran projects.
🔹 Industry-Standard Compliance: Aligns with ISO/IEC 24772-8 and SEI CERT C recommendations.
🔹 AutoFix for Key Issues: Automatically corrects implicit declarations and unsafe variable usage.
🔹 CI/CD Integration: Ensures continuous security enforcement in Fortran development.

Get the Full Report

Discover how Codee enhances Fortran security by detecting vulnerabilities, enforcing best practices, and applying AutoFix solutions. See real examples, detailed checks, and the impact on WRF.

📄 Access the full report

Conclusion

Large-scale Fortran projects like WRF require rigorous security enforcement to prevent runtime issues and unpredictable behavior. Manual security reviews are slow and error-prone—Codee automates this process.

With 40 security checks and AutoFix capabilities, Codee ensures Fortran applications remain secure, modern, and reliable, without slowing down development.