Secure C Coding

Avoid dangerous functions, use safe alternatives, enable compiler hardening.

Banned Functions → Safe Alternatives

| Banned | Why | Use Instead | |--------|-----|-------------| | strcpy | No bounds | strncpy, strlcpy, snprintf | | strcat | No bounds | strncat, strlcat | | sprintf | No bounds | snprintf | | gets | Always unsafe | fgets | | scanf("%s") | No bounds | scanf("%Ns") with width | | mktemp | Race condition | mkstemp | | atoi | No error detection | strtol with validation |

Compiler Hardening

CFLAGS += -fstack-protector-strong  # Stack canaries
CFLAGS += -D_FORTIFY_SOURCE=2       # Runtime buffer checks
CFLAGS += -fPIE -pie                # ASLR for executables
LDFLAGS += -Wl,-z,relro,-z,now      # GOT protection

Static Analysis

• make lint - clang-tidy checks
• cppcheck --enable=all
• Compiler warnings: -Wall -Wextra -Werror

Review red flags: Any banned function, missing bounds on string ops, char buf[N] with unchecked input.