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[critical] fix: [export_mod/yara_export] escape attribute values in generated YARA string/meta literals #896

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[critical] fix: [export_mod/yara_export] escape attribute values in generated YARA string/meta literals #896

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17 changes: 13 additions & 4 deletions misp_modules/modules/export_mod/yara_export.py
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Original file line number Diff line number Diff line change
Expand Up @@ -70,17 +70,20 @@ def __str__(self):
for key, values in self.meta.items():
i = 0
if len(values) == 1:
result.append(f' {key} = "{values[0]}"')
escaped_value = values[0].replace("\\", "\\\\").replace('"', '\\"')
result.append(f' {key} = "{escaped_value}"')
continue
for value in values:
result.append(f' {key}_{i} = "{value}"')
escaped_value = value.replace("\\", "\\\\").replace('"', '\\"')
result.append(f' {key}_{i} = "{escaped_value}"')
i += 1

result.append(" strings:")
for key, values in self.strings.items():
i = 0
for value in values:
result.append(f' ${key}_{i} = "{value}"')
escaped_value = value.replace("\\", "\\\\").replace('"', '\\"')
result.append(f' ${key}_{i} = "{escaped_value}"')
i += 1

result.append(" condition:")
Expand Down Expand Up @@ -267,9 +270,15 @@ def handler(q=False):
# ignore unsupported types
pass
yara_rules.append(str(yr))
ruleset = "\n".join(yara_rules)
try:
yara.compile(source=ruleset)
except Exception:
misperrors["error"] = "The generated YARA ruleset does not compile."
return misperrors
r = {
"response": [],
"data": str(base64.b64encode(bytes("\n".join(yara_rules), "utf-8")), "utf-8"),
"data": str(base64.b64encode(bytes(ruleset, "utf-8")), "utf-8"),
}

return r
Expand Down