open-standards/scripts/check-wasmtime-pin.py

#!/usr/bin/env python3
"""check-wasmtime-pin.py: every workflow that runs wasmtime runs the one pinned release,
with both of its determinism settings.

WAI's WebAssembly legs hold a module's output to pinned bits. A stock wasmtime leaves NaN
canonicalisation off and lets each relaxed SIMD instruction take the host's behaviour, and
two versions of it can lower one instruction two ways, so a leg's bits would be the
engine's choice. The install steps' comment says every workflow pins one version and
passes both settings; this makes that true of every workflow, not only of the ones that
comment sits in.

In every `.github/workflows/*.yml`, with continued lines (`\\` at the end) joined, this
requires that

  1. every download of a wasmtime release names version PIN (the `v=` the step sets, or
     the version in the URL), and the SHA-256 it checks is the digest of that archive in
     DIGESTS;
  2. wasmtime is installed no other way (`cargo install wasmtime-cli`, the install
     script, or an action);
  3. every `wasmtime run`, `wasmtime serve` or `wasmtime compile`, every `wasmtime` given
     a module path, and every `CARGO_TARGET_<triple>_RUNNER` that is wasmtime, passes
     `-W nan-canonicalization=y` and `-W relaxed-simd-deterministic=y`;
  4. at least one download and one run were found, so a check that looked in the wrong
     place fails rather than passing on nothing.

    check-wasmtime-pin.py [--root DIR]

Exit 0 when all four hold, 1 with one line a finding otherwise. Standard library only.
"""
import os
import re
import sys

PIN = "50.0.1"
# The release archives a workflow may download, by name, with the SHA-256 the release lists.
DIGESTS = {
    "wasmtime-v50.0.1-x86_64-linux.tar.xz": "685466455dd42a14774a86c36c8f2e45cbb9bd6d92a850139315df60a75498a5",
}
FLAGS = ("nan-canonicalization=y", "relaxed-simd-deterministic=y")

DOWNLOAD = re.compile(r"bytecodealliance/wasmtime/releases/download/")
URL_VERSION = re.compile(r"releases/download/v(\d[^/\"'\s]*)/")
SET_VERSION = re.compile(r"^\s*v=[\"']?([^\"'\s;]+)")
ARCHIVE = re.compile(r"wasmtime-v(\$v|\$\{v\}|\d[^-\"'\s]*)-([a-z0-9_]+-[a-z]+)\.tar\.xz")
DIGEST = re.compile(r"\b([0-9a-f]{64})\b.*sha256sum -c")
OTHER_INSTALL = re.compile(
    r"cargo\s+(?:\S+\s+)*install\s+(?:\S+\s+)*wasmtime-cli|wasmtime\.dev/install|uses:\s*\S*wasmtime"
)
# wasmtime as a command: run, serve or compile, or given a module path (`wasmtime x.wasm`).
INVOKE = re.compile(
    r"(?:^|[\s;&|(`/\"'=])wasmtime\s+(?:(?:run|serve|compile)\b|[^\s-]\S*\.(?:c?wasm|wat)\b)"
)
RUNNER = re.compile(r"CARGO_TARGET_\w+_RUNNER\s*[:=]\s*[\"']?wasmtime\b")


def logical_lines(text):
    """(first line number, text) with backslash-continued lines joined."""
    out, buf, start = [], "", 0
    for n, line in enumerate(text.splitlines(), 1):
        if not buf:
            start = n
        if line.rstrip().endswith("\\"):
            buf += line.rstrip()[:-1] + " "
            continue
        out.append((start, buf + line))
        buf = ""
    if buf:
        out.append((start, buf))
    return out


def check_file(path, rel, findings):
    lines = logical_lines(open(path, encoding="utf-8").read())
    downloads = runs = 0
    for i, (n, line) in enumerate(lines):
        code = line.lstrip()
        if code.startswith("#"):
            continue
        if OTHER_INSTALL.search(line):
            findings.append(f"{rel}:{n}: installs wasmtime some other way; download the pinned release ({PIN}) by version and SHA-256")
        if DOWNLOAD.search(line):
            downloads += 1
            m = URL_VERSION.search(line)
            ver = m.group(1) if m else None
            if ver is None:  # the URL takes the version from the step's `v=`
                for _, prev in reversed(lines[max(0, i - 12) : i]):
                    s = SET_VERSION.match(prev)
                    if s:
                        ver = s.group(1)
                        break
            if ver != PIN:
                findings.append(f"{rel}:{n}: downloads wasmtime {ver or '(version not found)'}; every workflow pins {PIN}")
            near = lines[max(0, i - 12) : i + 5]
            arch = None
            for _, other in near:
                a = ARCHIVE.search(other)
                if a:
                    arch = a.group(2)
                    break
            name = f"wasmtime-v{ver}-{arch}.tar.xz" if arch else None
            digests = [d.group(1) for _, other in lines[i : i + 5] for d in [DIGEST.search(other)] if d]
            if name not in DIGESTS:
                findings.append(f"{rel}:{n}: downloads {name or 'an archive whose name was not found'}, which has no pinned digest here")
            elif not digests:
                findings.append(f"{rel}:{n}: downloads {name} and checks no SHA-256 within four lines")
            elif digests[0] != DIGESTS[name]:
                findings.append(f"{rel}:{n}: checks {name} against {digests[0][:12]}..., not its pinned digest {DIGESTS[name][:12]}...")
        for rx in (INVOKE, RUNNER):
            m = rx.search(line)
            if m:
                runs += 1
                rest = line[m.start() :]
                missing = [f for f in FLAGS if f not in rest]
                if missing:
                    findings.append(f"{rel}:{n}: runs wasmtime without {' and '.join('-W ' + f for f in missing)}")
                break
    return downloads, runs


def main(argv):
    root = "."
    if len(argv) == 3 and argv[1] == "--root":
        root = argv[2]
    elif len(argv) != 1:
        sys.exit("usage: check-wasmtime-pin.py [--root DIR]")
    wf = os.path.join(root, ".github", "workflows")
    findings, downloads, runs = [], 0, 0
    for name in sorted(os.listdir(wf)) if os.path.isdir(wf) else []:
        if name.endswith((".yml", ".yaml")):
            d, r = check_file(os.path.join(wf, name), f".github/workflows/{name}", findings)
            downloads += d
            runs += r
    if downloads == 0 or runs == 0:
        findings.append(f"found {downloads} wasmtime download(s) and {runs} run(s) under {wf}: this check looked in the wrong place")
    for f in findings:
        print(f"::error::{f}")
    if findings:
        return 1
    print(f"check-wasmtime-pin: {downloads} downloads of wasmtime {PIN}, each checked against its digest; {runs} runs, each with both settings")
    return 0


if __name__ == "__main__":
    sys.exit(main(sys.argv))