Datadog dd-trace-py: ReDoS in URL query string obfuscation

Summary

A regular expression used to obfuscate URL query strings can consume excessive CPU when processing certain attacker-controlled input. This can stall request processing and cause denial of service in applications using affected HTTP tracing integrations.

Details

The default query-string obfuscation pattern can exhibit excessive backtracking. The pattern is applied synchronously when recording HTTP URL metadata, allowing query-string processing to occupy application resources for an extended period.

As a workaround, set both DD_TRACE_OBFUSCATION_QUERY_STRING_REGEXP and DD_TRACE_OBFUSCATION_QUERY_STRING_PATTERN to the fixed Python-compatible regex below, then restart the application. Setting both variables covers all affected ddtrace versions, including releases before 1.19.0.

export DD_TRACE_OBFUSCATION_QUERY_STRING_REGEXP='(?i)(?:(?:"|%22)?)(?:(?:old[-_]?|new[-_]?)?p(?:ass)?w(?:or)?d(?:1|2)?|pass(?:[-_]?phrase)?|secret|(?:api[-_]?|private[-_]?|public[-_]?|access[-_]?|secret[-_]?|app(?:lication)?[-_]?)key(?:[-_]?id)?|token|consumer[-_]?(?:id|key|secret)|sign(?:ed|ature)?|auth(?:entication|orization)?)(?:(?:\s|%20)*(?:=|%3D)[^&]+|(?:"|%22)(?:\s|%20)*(?::|%3A)(?:\s|%20)*(?:"|%22)(?:%2[^2]|%[^2]|[^"%])+(?:"|%22))|(?:bearer(?:\s|%20)+[a-z0-9._\-]+|token(?::|%3A)[a-z0-9]{13}|gh[opsu]_[0-9a-zA-Z]{36}|(?:(?<![\w-])|(?<=%[0-9a-f]{2}))ey[I-L][\w-]+(?:=|%3D)*\.ey[I-L][\w-]+(?:=|%3D)*(?:\.(?:[\w.+/=-]|%3D|%2F|%2B)+)?|-{5}BEGIN(?:[a-z\s]|%20)+PRIVATE(?:\s|%20)KEY-{5}[^\-]+-{5}END(?:[a-z\s]|%20)+PRIVATE(?:\s|%20)KEY(?:-{5})?(?:\n|%0A)?|(?:ssh-(?:rsa|dss)|ecdsa-[a-z0-9]+-[a-z0-9]+)(?:\s|%20|%09)+(?:[a-z0-9/.+]|%2F|%5C|%2B){100,}(?:=|%3D)*(?:(?:\s|%20|%09)+[a-z0-9._-]+)?)'

export DD_TRACE_OBFUSCATION_QUERY_STRING_PATTERN="$DD_TRACE_OBFUSCATION_QUERY_STRING_REGEXP"

Proof of concept

Detailed triggering inputs and reproduction steps are omitted from this advisory. The patched version includes regression coverage for the affected behavior.

Impact

Regular expression denial of service (ReDoS) affecting applications that process attacker-controlled URL query strings through the vulnerable obfuscation pattern. Successful exploitation can cause excessive CPU consumption, prolonged request latency, and service unavailability.

The vulnerable processing is enabled by default for affected HTTP integrations that include query strings in URL span tags.