fix(http): add SSRF redirect protection to OkHttp client#159
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fix(http): add SSRF redirect protection to OkHttp client#159spicy-potato-cat wants to merge 2 commits into
spicy-potato-cat wants to merge 2 commits into
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OkHttp follows redirects transparently before any scope check, allowing an attacker-controlled target to redirect the scanner to cloud metadata endpoints (169.254.169.254) and exfiltrate credentials from the host VM. Add SsrfRedirectInterceptor as an OkHttp network interceptor that validates redirect Location headers against loopback, link-local, site-local, IPv6 unique-local ranges, and the metadata.google.internal hostname. Wire it into HttpClientModule's OkHttpClient builder. Refs google#153
Cover all blocked address ranges (loopback, link-local, site-local, IPv6 unique-local), the metadata.google.internal hostname block, public IP passthrough, and non-redirect response passthrough. Refs google#153
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Summary
Add an OkHttp network interceptor that blocks HTTP redirects to
internal and cloud metadata endpoints, preventing SSRF attacks
where an attacker-controlled scan target redirects the scanner to
sensitive addresses.
Problem
The OkHttp client follows redirects by default
(
DEFAULT_FOLLOW_REDIRECTS = true) with no destination validation.A malicious scan target can return a 302 redirect to
http://169.254.169.254/latest/meta-data/and the scanner willsilently follow it, potentially exfiltrating cloud IAM credentials
from the host VM.
Changes
SsrfRedirectInterceptor.java(new): Network interceptorthat inspects redirect responses (301/302/303/307/308) and blocks
Locationtargets resolving to loopback, link-local, site-local,IPv6 unique-local addresses, and
metadata.google.internalHttpClientModule.java: Wire interceptor into theOkHttpClient.BuilderSsrfRedirectInterceptorTest.java(new): Unit tests coveringall blocked ranges, public IP passthrough, hostname blocking, and
non-redirect passthrough
Notes
InetAddressbuilt-in checks andGuava
ImmutableSetunaffected
Refs #153