SAGE OS Security Best Practices

Introduction

This document outlines security best practices for developing, deploying, and maintaining SAGE OS. These guidelines help ensure the security and integrity of the operating system and applications running on it.

Secure Development Practices

Code Security

String Handling

// ❌ Unsafe - Buffer overflow risk
strcpy(dest, src);
sprintf(buffer, format, data);

// ✅ Safe - Bounds checking
strncpy(dest, src, sizeof(dest) - 1);
dest[sizeof(dest) - 1] = '\0';
snprintf(buffer, sizeof(buffer), format, data);

// ✅ Best - Use safe alternatives
strcpy_safe(dest, src, sizeof(dest));

Memory Management

// ✅ Always check allocation success
void* ptr = malloc(size);
if (ptr == NULL) {
    // Handle allocation failure
    return ERROR_OUT_OF_MEMORY;
}

// ✅ Clear sensitive data before freeing
memset(sensitive_data, 0, sizeof(sensitive_data));
free(sensitive_data);
sensitive_data = NULL;

// ✅ Avoid double-free vulnerabilities
if (ptr != NULL) {
    free(ptr);
    ptr = NULL;
}

Input Validation

// ✅ Validate all inputs
int validate_input(const char* input, size_t max_len) {
    if (input == NULL) return -1;
    if (strlen(input) >= max_len) return -1;

    // Check for malicious characters
    for (size_t i = 0; input[i]; i++) {
        if (!isprint(input[i]) && !isspace(input[i])) {
            return -1;
        }
    }
    return 0;
}

Error Handling

Secure Error Messages

// ❌ Information disclosure
printf("Login failed for user %s with password %s", user, pass);

// ✅ Generic error messages
printf("Authentication failed");
log_security_event("Failed login attempt for user: %s", user);

Resource Cleanup

// ✅ Always cleanup resources
int secure_function(void) {
    FILE* file = NULL;
    char* buffer = NULL;
    int result = -1;

    file = fopen("sensitive.dat", "r");
    if (!file) goto cleanup;

    buffer = malloc(BUFFER_SIZE);
    if (!buffer) goto cleanup;

    // Process data...
    result = 0;

cleanup:
    if (buffer) {
        memset(buffer, 0, BUFFER_SIZE);
        free(buffer);
    }
    if (file) fclose(file);
    return result;
}

Cryptographic Security

Key Management

// ✅ Secure key generation
int generate_key(uint8_t* key, size_t key_len) {
    // Use hardware random number generator
    if (get_random_bytes(key, key_len) != 0) {
        return -1;
    }
    return 0;
}

// ✅ Secure key storage
typedef struct {
    uint8_t key[32];
    uint32_t usage_count;
    time_t created;
    time_t expires;
} secure_key_t;

Encryption Best Practices

// ✅ Use authenticated encryption
int encrypt_data(const uint8_t* plaintext, size_t len,
                 const uint8_t* key, uint8_t* ciphertext,
                 uint8_t* tag) {
    // Use AES-GCM or ChaCha20-Poly1305
    return aes_gcm_encrypt(plaintext, len, key, ciphertext, tag);
}

Access Control

Privilege Separation

// ✅ Drop privileges after initialization
int drop_privileges(void) {
    if (setuid(getuid()) != 0) {
        return -1;
    }
    if (setgid(getgid()) != 0) {
        return -1;
    }
    return 0;
}

Resource Limits

// ✅ Set resource limits
int set_security_limits(void) {
    struct rlimit limit;

    // Limit memory usage
    limit.rlim_cur = MAX_MEMORY;
    limit.rlim_max = MAX_MEMORY;
    if (setrlimit(RLIMIT_AS, &limit) != 0) {
        return -1;
    }

    // Limit file descriptors
    limit.rlim_cur = MAX_FDS;
    limit.rlim_max = MAX_FDS;
    if (setrlimit(RLIMIT_NOFILE, &limit) != 0) {
        return -1;
    }

    return 0;
}

Network Security

Secure Communication

// ✅ Use TLS for network communication
int secure_connect(const char* hostname, int port) {
    SSL_CTX* ctx = SSL_CTX_new(TLS_client_method());
    if (!ctx) return -1;

    // Set minimum TLS version
    SSL_CTX_set_min_proto_version(ctx, TLS1_2_VERSION);

    // Verify certificates
    SSL_CTX_set_verify(ctx, SSL_VERIFY_PEER, NULL);

    return establish_connection(ctx, hostname, port);
}

Input Sanitization

// ✅ Sanitize network input
int process_network_data(const uint8_t* data, size_t len) {
    if (len > MAX_PACKET_SIZE) {
        log_security_event("Oversized packet received");
        return -1;
    }

    // Validate packet structure
    if (!validate_packet_format(data, len)) {
        return -1;
    }

    return process_packet(data, len);
}

Logging and Monitoring

Security Logging

// ✅ Comprehensive security logging
void log_security_event(const char* event, ...) {
    va_list args;
    char buffer[1024];
    time_t now = time(NULL);

    va_start(args, event);
    vsnprintf(buffer, sizeof(buffer), event, args);
    va_end(args);

    // Log to secure audit trail
    audit_log(LOG_SECURITY, now, buffer);

    // Alert on critical events
    if (is_critical_event(event)) {
        send_security_alert(buffer);
    }
}

Anomaly Detection

// ✅ Monitor for suspicious activity
int monitor_system_calls(void) {
    static uint32_t call_counts[MAX_SYSCALLS];
    static time_t last_reset = 0;
    time_t now = time(NULL);

    // Reset counters periodically
    if (now - last_reset > MONITOR_INTERVAL) {
        memset(call_counts, 0, sizeof(call_counts));
        last_reset = now;
    }

    // Check for anomalies
    for (int i = 0; i < MAX_SYSCALLS; i++) {
        if (call_counts[i] > THRESHOLD[i]) {
            log_security_event("Syscall %d threshold exceeded", i);
            return -1;
        }
    }

    return 0;
}

Build Security

Compiler Security Flags

# Enable security features
SECURITY_FLAGS = -fstack-protector-strong \
                 -D_FORTIFY_SOURCE=2 \
                 -fPIE \
                 -Wformat-security \
                 -Werror=format-security

# Enable all warnings
WARNING_FLAGS = -Wall -Wextra -Werror \
                -Wno-unused-parameter \
                -Wno-unused-variable

CFLAGS += $(SECURITY_FLAGS) $(WARNING_FLAGS)

Static Analysis

#!/bin/bash
# Run static analysis tools

# Clang Static Analyzer
scan-build make

# Cppcheck
cppcheck --enable=all --error-exitcode=1 src/

# Custom security scanner
python3 security-scanner.py src/

Testing Security

Unit Tests

// ✅ Test security functions
void test_strcpy_safe(void) {
    char dest[10];
    const char* src = "Hello, World!";  // Longer than dest

    // Should truncate and null-terminate
    char* result = strcpy_safe(dest, src, sizeof(dest));
    assert(result != NULL);
    assert(strlen(dest) == sizeof(dest) - 1);
    assert(dest[sizeof(dest) - 1] == '\0');
}

Fuzzing

// ✅ Fuzz test critical functions
void fuzz_input_parser(void) {
    for (int i = 0; i < 10000; i++) {
        uint8_t* random_data = generate_random_data(1024);

        // Should not crash or leak memory
        int result = parse_input(random_data, 1024);

        free(random_data);
    }
}

Deployment Security

System Hardening

#!/bin/bash
# System hardening script

# Disable unnecessary services
systemctl disable telnet
systemctl disable ftp

# Set secure permissions
chmod 600 /etc/shadow
chmod 644 /etc/passwd

# Configure firewall
iptables -P INPUT DROP
iptables -P FORWARD DROP
iptables -P OUTPUT ACCEPT

Configuration Management

# Secure configuration template
security:
  authentication:
    min_password_length: 12
    require_special_chars: true
    max_login_attempts: 3
    lockout_duration: 300

  encryption:
    algorithm: "AES-256-GCM"
    key_rotation_interval: 86400

  logging:
    level: "INFO"
    audit_enabled: true
    retention_days: 90

Incident Response

Detection

// ✅ Automated threat detection
int detect_intrusion(void) {
    // Check for suspicious patterns
    if (check_failed_logins() > MAX_FAILED_LOGINS) {
        trigger_security_alert("Multiple failed logins detected");
        return 1;
    }

    if (check_unusual_network_activity()) {
        trigger_security_alert("Unusual network activity detected");
        return 1;
    }

    return 0;
}

Response

// ✅ Automated response actions
void respond_to_threat(threat_type_t threat) {
    switch (threat) {
        case THREAT_BRUTE_FORCE:
            block_source_ip();
            increase_monitoring();
            break;

        case THREAT_MALWARE:
            isolate_system();
            scan_for_malware();
            break;

        case THREAT_DATA_BREACH:
            revoke_access_tokens();
            notify_security_team();
            break;
    }
}

Security Checklist

Development Phase

• [ ] Input validation implemented
• [ ] Safe string functions used
• [ ] Memory management secure
• [ ] Error handling comprehensive
• [ ] Cryptography properly implemented
• [ ] Access controls enforced

Testing Phase

• [ ] Unit tests for security functions
• [ ] Integration tests completed
• [ ] Penetration testing performed
• [ ] Fuzzing tests executed
• [ ] Static analysis clean
• [ ] Dynamic analysis clean

Deployment Phase

• [ ] System hardened
• [ ] Monitoring configured
• [ ] Logging enabled
• [ ] Backup procedures tested
• [ ] Incident response plan ready
• [ ] Security training completed

References

• OWASP Secure Coding Practices
• NIST Cybersecurity Framework
• CWE/SANS Top 25
• CERT C Coding Standard

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Last Updated: 2025-05-27
Version: 1.0.0
Approved By: Security Team