Fix systemd get_version() (#1156)

Fixes: #1155

cve_bin_tool/checkers/systemd.py

@@ -7,8 +7,11 @@
 
 https://www.cvedetails.com/product/38088/Freedesktop-Systemd.html?vendor_id=7971
 """
+
 from cve_bin_tool.checkers import Checker
 
+from ..util import regex_find
+
 
 class SystemdChecker(Checker):
     CONTAINS_PATTERNS = [
@@ -28,9 +31,36 @@ class SystemdChecker(Checker):
     ]
     VENDOR_PRODUCT = [("freedesktop", "systemd")]
 
+    """
+    Using filenames (containing patterns like '.so' etc.) in the binaries as VERSION_PATTERNS aren't ideal.
+    The reason behind this is that these might depend on who packages the file (like it 
+    might work on fedora but not on ubuntu)
+    """
 
-"""
-Using filenames (containing patterns like '.so' etc.) in the binaries as VERSION_PATTERNS aren't ideal.
-The reason behind this is that these might depend on who packages the file (like it 
-might work on fedora but not on ubuntu)
-"""
+    def get_version(self, lines, filename):
+        def guess_contains_systemd(lines):
+            """Tries to determine if a file includes systemd"""
+            for line in lines:
+                if "sd_bus_error_copy" in line:
+                    return 1
+                if "sd_bus_error_is_set" in line:
+                    return 1
+                if "sd_bus_error_add_map" in line:
+                    return 1
+            return 0
+
+        version_info = {}
+
+        if "libsystemd.so." in filename:
+            version_info["is_or_contains"] = "is"
+
+        elif guess_contains_systemd(lines):
+            version_info["is_or_contains"] = "contains"
+
+        if "is_or_contains" in version_info:
+            version_info["modulename"] = "systemd"
+            version_info["version"] = regex_find(
+                sorted(lines, reverse=True), self.VERSION_PATTERNS
+            )
+
+        return version_info