Add: Offline installation fallbacks for Maldet when network is unavailable

Improvements:
- When all network sources are unreachable, checks for offline options
- Checks system package repositories (yum/apt) for Maldet availability
- Scans common locations (/root, /tmp, /opt) for pre-downloaded archives
- Provides clear multi-method installation instructions for offline scenarios
- Gracefully handles network-isolated servers
- Supports pre-downloaded archive transfer via SCP
- Falls back to system repositories if network-free alternative available

This allows installation on restricted networks where external downloads aren't possible.

modules/security/malware-scanner.sh

@@ -355,27 +355,114 @@ install_maldet_only() {
         best_url="https://github.com/rfxn/maldet/archive/refs/heads/main.tar.gz"
         echo "  → Downloading from GitHub main branch (fallback)"
     else
-        echo -e "${RED}✗ All sources unreachable${NC}"
+        # No internet access - check for offline options
+        echo -e "${YELLOW}Network access unavailable. Checking offline options...${NC}"
         echo ""
-        echo "Known working download URLs:"
+
-        echo "  Official: https://www.rfxn.com/downloads/maldetect-latest.tar.gz"
+        # Option 1: Check if Maldet is available in system package repos
-        echo "  GitHub:   https://github.com/rfxn/maldet/archive/refs/heads/main.tar.gz"
+        local repo_available=false
+        if command -v yum &>/dev/null; then
+            echo "  [1] Checking yum repositories..."
+            if yum search maldet 2>/dev/null | grep -q "maldet"; then
+                echo -e "      ${GREEN}✓ Maldet found in yum repos${NC}"
+                repo_available=true
+            else
+                echo "      ✗ Not in yum repos"
+            fi
+        elif command -v apt-get &>/dev/null; then
+            echo "  [1] Checking apt repositories..."
+            apt-get update > /dev/null 2>&1
+            if apt-cache search maldet 2>/dev/null | grep -q "maldet"; then
+                echo -e "      ${GREEN}✓ Maldet found in apt repos${NC}"
+                repo_available=true
+            else
+                echo "      ✗ Not in apt repos"
+            fi
+        fi
+
+        # Option 2: Check for pre-cached/pre-downloaded file
+        echo "  [2] Checking for pre-downloaded archive..."
+        local local_archive=""
+        for path in /root/maldetect*.tar.gz /tmp/maldetect*.tar.gz /opt/maldetect*.tar.gz; do
+            if [ -f "$path" ]; then
+                local_archive="$path"
+                echo -e "      ${GREEN}✓ Found: $path${NC}"
+                repo_available=true
+                break
+            fi
+        done
+
         echo ""
-        return 1
+
+        if [ "$repo_available" = true ]; then
+            if [ -n "$local_archive" ]; then
+                echo "Using pre-downloaded archive: $local_archive"
+                cp "$local_archive" /tmp/maldetect-offline.tar.gz
+                best_source="offline"
+                best_version="offline-archive"
+                best_url="none"
+            else
+                echo "Attempting to install from system repositories..."
+                if command -v yum &>/dev/null; then
+                    yum install -y maldet 2>&1 | tail -5
+                elif command -v apt-get &>/dev/null; then
+                    apt-get install -y maldet 2>&1 | tail -5
+                fi
+
+                if is_maldet_installed; then
+                    echo -e "${GREEN}✓ Maldet installed from repositories${NC}"
+                    echo ""
+                    echo "Updating malware signatures..."
+                    if command -v maldet &>/dev/null; then
+                        maldet -u > /dev/null 2>&1 &
+                        echo "  (signatures updating in background)"
+                    fi
+                    echo ""
+                    read -p "Press Enter to continue..." < /dev/tty 2>/dev/null || true
+                    return 0
+                fi
+            fi
+        else
+            echo -e "${RED}✗ No installation method available${NC}"
+            echo ""
+            echo "Network is unreachable. To install Maldet, use one of these methods:"
+            echo ""
+            echo "  METHOD 1 - From another networked machine:"
+            echo "    wget https://www.rfxn.com/downloads/maldetect-latest.tar.gz"
+            echo "    scp maldetect-latest.tar.gz root@YOUR-SERVER:/root/"
+            echo ""
+            echo "  METHOD 2 - Via GitHub (alternative):"
+            echo "    wget https://github.com/rfxn/maldet/archive/refs/heads/main.tar.gz"
+            echo "    scp main.tar.gz root@YOUR-SERVER:/root/"
+            echo ""
+            echo "  METHOD 3 - From system repositories:"
+            echo "    yum install -y maldet        # CentOS/RHEL"
+            echo "    apt-get install -y maldet    # Ubuntu/Debian"
+            echo ""
+            echo "After downloading, place the archive in /root/ and run this installer again."
+            echo ""
+            read -p "Press Enter to continue..." < /dev/tty 2>/dev/null || true
+            return 1
+        fi
     fi
 
     echo ""
 
-    # Download from the best source
+    # Download from the best source (or use offline if already copied)
     local temp_file="maldetect-${best_version}.tar.gz"
-    echo "Downloading $best_version..."
 
-    if wget -q --timeout=15 -O "$temp_file" "$best_url" 2>/dev/null; then
+    if [ "$best_source" = "offline" ]; then
-        echo -e "${GREEN}✓ Download successful${NC}"
+        echo "Using offline archive: /tmp/maldetect-offline.tar.gz"
+        temp_file="/tmp/maldetect-offline.tar.gz"
     else
-        echo -e "${RED}✗ Download failed from $best_source${NC}"
+        echo "Downloading $best_version..."
-        rm -f "$temp_file"
+        if wget -q --timeout=15 -O "$temp_file" "$best_url" 2>/dev/null; then
-        return 1
+            echo -e "${GREEN}✓ Download successful${NC}"
+        else
+            echo -e "${RED}✗ Download failed from $best_source${NC}"
+            rm -f "$temp_file"
+            return 1
+        fi
     fi
 
     echo ""