fuzz: Add logging to fuzz targets (#985)

In order to make debugging fuzz test failures easier, it's useful to be
able to get logs from the proxy and libraries during a fuzz run.
However, because running the fuzz targets with a fuzzer will generate a
massive number of imputs, we probably don't want verbose logs by default
--- this would produce a huge amount of mostly useless data.

This branch adds a simple tracing setup to the fuzz targets. When
running without the `RUST_LOG` environment variable set, each run won't
log anything. This means the current behavior on cluster-fuzz is
unchanged and we won't output giant amounts of logs. However, when
running a minimized reproducer locally for debugging, we can enable any
amount of logging by setting `RUST_LOG`, which should make it easier to
diagnose fuzz failures.

linkerd/addr/fuzz/Cargo.lock

@@ -0,0 +1,304 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
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+checksum = "698b65a961a9d730fb45b6b0327e20207810c9f61ee421b082b27ba003f49e2b"
+
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+name = "bumpalo"
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+checksum = "63396b8a4b9de3f4fdfb320ab6080762242f66a8ef174c49d8e19b674db4cdbe"
+
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+version = "1.0.1"
+source = "registry+/~https://github.com/rust-lang/crates.io-index"
+checksum = "b700ce4376041dcd0a327fd0097c41095743c4c8af8887265942faf1100bd040"
+
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+
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+
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+dependencies = [
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+ "fnv",
+ "itoa",
+]
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+ "wasm-bindgen",
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+[[package]]
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+dependencies = [
+ "arbitrary",
+ "cc",
+]
+
+[[package]]
+name = "linkerd-addr"
+version = "0.1.0"
+dependencies = [
+ "http",
+ "linkerd-dns-name",
+ "thiserror",
+]
+
+[[package]]
+name = "linkerd-addr-fuzz"
+version = "0.0.0"
+dependencies = [
+ "libfuzzer-sys",
+ "linkerd-addr",
+]
+
+[[package]]
+name = "linkerd-dns-name"
+version = "0.1.0"
+dependencies = [
+ "thiserror",
+ "untrusted",
+ "webpki",
+]
+
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+ "cfg-if",
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+dependencies = [
+ "cc",
+ "libc",
+ "once_cell",
+ "spin",
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+ "web-sys",
+ "winapi",
+]
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+ "bumpalo",
+ "lazy_static",
+ "log",
+ "proc-macro2",
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+ "syn",
+ "wasm-bindgen-shared",
+]
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+dependencies = [
+ "proc-macro2",
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+ "wasm-bindgen-shared",
+]
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+ "wasm-bindgen",
+]
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+ "ring",
+ "untrusted",
+]
+
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+dependencies = [
+ "winapi-i686-pc-windows-gnu",
+ "winapi-x86_64-pc-windows-gnu",
+]
+
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+version = "0.4.0"
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+
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linkerd/addr/fuzz/Cargo.toml

@@ -10,6 +10,8 @@ cargo-fuzz = true
 
 [dependencies]
 libfuzzer-sys = "0.4"
+tracing = "0.1.23"
+tracing-subscriber = "0.2.17"
 
 [dependencies.linkerd-addr]
 path = ".."

linkerd/addr/fuzz/fuzz_targets/fuzz_target_1.rs

@@ -1,9 +1,10 @@
 #![no_main]
 use libfuzzer_sys::fuzz_target;
 
-
 fuzz_target!(|data: &[u8]| {
+    let _ = tracing_subscriber::fmt::try_init();
     if let Ok(s) = std::str::from_utf8(data) {
+        tracing::info!(data = ?s, "running with input");
         linkerd_addr::fuzz_logic::fuzz_addr_1(s);
     }
 });

linkerd/app/inbound/fuzz/Cargo.toml

@@ -17,6 +17,8 @@ hyper = { version = "0.14.2", features = ["http1", "http2"] }
 http = "0.2"
 linkerd-app-core = { path = "../../core" }
 linkerd-app-test = { path = "../../test" }
+tracing = "0.1"
+tracing-subscriber = "0.2"
 
 [dependencies.linkerd-app-inbound]
 path = ".."

linkerd/app/inbound/fuzz/fuzz_targets/fuzz_target_1.rs

@@ -3,6 +3,8 @@ use libfuzzer_sys::fuzz_target;
 use linkerd_app_inbound::http::fuzz_logic::*;
 
 fuzz_target!(|requests: Vec<HttpRequestSpec>| {
+    let _ = tracing_subscriber::fmt::try_init();
+    tracing::info!(?requests, "running with input");
     if requests.len() == 0 {
         return;
     }

linkerd/app/inbound/src/http/mod.rs

@@ -270,8 +270,9 @@ pub mod fuzz_logic {
     };
     pub use linkerd_app_test as support;
     use linkerd_app_test::*;
+    use std::{fmt, str};
 
-    #[derive(Debug, Arbitrary)]
+    #[derive(Arbitrary)]
     pub struct HttpRequestSpec {
         pub uri: Vec<u8>,
         pub header_name: Vec<u8>,
@@ -378,4 +379,34 @@ pub mod fuzz_logic {
             .push_http_server()
             .into_inner()
     }
+
+    impl fmt::Debug for HttpRequestSpec {
+        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+            // Custom `Debug` impl that formats the URI, header name, and header
+            // value as strings if they are UTF-8, or falls back to raw bytes
+            // otherwise.
+            let mut dbg = f.debug_struct("HttpRequestSpec");
+            dbg.field("http_method", &self.http_method);
+
+            if let Ok(uri) = str::from_utf8(&self.uri[..]) {
+                dbg.field("uri", &uri);
+            } else {
+                dbg.field("uri", &self.uri);
+            }
+
+            if let Ok(name) = str::from_utf8(&self.header_name[..]) {
+                dbg.field("header_name", &name);
+            } else {
+                dbg.field("header_name", &self.header_name);
+            }
+
+            if let Ok(value) = str::from_utf8(&self.header_value[..]) {
+                dbg.field("header_value", &value);
+            } else {
+                dbg.field("header_value", &self.header_value);
+            }
+
+            dbg.finish()
+        }
+    }
 }

linkerd/dns/fuzz/Cargo.toml

@@ -12,6 +12,8 @@ cargo-fuzz = true
 [dependencies]
 libfuzzer-sys = "0.4"
 tokio = { version = "1", features = ["rt", "time", "io-util"] }
+tracing = "0.1.23"
+tracing-subscriber = "0.2.17"
 
 [dependencies.linkerd-dns]
 path = ".."