[deft-security] Fix 4 vulnerabilities in src/cache.c

[539hex]

Security Fixes

File: src/cache.c
Highest Severity: MEDIUM
Fixes Applied: 4

CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition

• Severity: MEDIUM
• Confidence: 88%
• The function get_from_cache() returns a pointer to a DataItem while releasing the mutex. Another thread could modify or delete this item after the mutex is unlocked but before the caller uses it, leading to use-after-free or data corruption.

CWE-190: Integer Overflow or Wraparound

• Severity: MEDIUM
• Confidence: 90%
• Casting time(NULL) to unsigned int can cause integer overflow. The subtraction on line 63 (time(NULL) - item->last_accessed) will produce incorrect results when time_t is 64-bit and wraps around the unsigned int boundary.

CWE-190: Integer Overflow or Wraparound

• Severity: MEDIUM
• Confidence: 92%
• Casting time(NULL) to unsigned int can cause integer overflow on systems where time_t is 64-bit (most modern systems). After year 2106, this will wrap around to 0, breaking cache expiration logic.

CWE-476: NULL Pointer Dereference

• Severity: LOW
• Confidence: 75%
• If hash_table_insert() fails or hash_table_search() returns NULL after insertion (due to memory issues or hash collision handling), dereferencing item without checking could cause a crash. While unlikely, defensive programming should verify the pointer.

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