anti
19ceff4417
Seven instrumenters that mutate operator-supplied artifacts to
embed the callback URL:
- passthrough — bytes unchanged; only DNS-callback tokens trip
detection, with the slug embedded in the placement path
- plain — substitutes {{CANARY_URL}}/{{CANARY_HOST}} placeholders;
falls back to appending a comment line whose prefix adapts to the
apparent file syntax (#, //, ;)
- html — injects a 1x1 tracking pixel before </body>, appends
if the close tag is missing
- docx — direct zipfile manipulation (no python-docx dep):
inserts an external-image Relationship into word/_rels/document.xml.rels
and a matching <w:drawing> element before </w:body>
- xlsx — sibling of docx; injects an external-image relationship
into xl/_rels/workbook.xml.rels (orphan rels are still fetched on
open by most viewers)
- pdf — uses pikepdf to install /OpenAction /URI on the catalog;
rejects with a clear message when pikepdf isn't installed
- image — uses Pillow to embed slug + URL in PNG tEXt / JPEG
comment; rejects with a clear message when Pillow isn't installed
DOCX and XLSX share the rId allocator + relationship injector via
the docx module; both work on stdlib zipfile only.
Tests synthesise minimal real DOCX/XLSX fixtures inline, round-trip
each instrumenter, and assert the callback URL ends up in the
mutated bytes while the file still parses.
83 lines
2.9 KiB
Python
83 lines
2.9 KiB
Python
"""Plain-text / config-file instrumenter.
|
|
|
|
Two embedding strategies, picked in order:
|
|
|
|
1. **Token substitution.** If the blob contains the literal
|
|
placeholder ``{{CANARY_URL}}`` or ``{{CANARY_HOST}}``, replace it.
|
|
This gives operators full control over where the slug lands —
|
|
they can pre-edit the file with placeholders before uploading.
|
|
2. **Append.** Otherwise, append a comment line that mentions the
|
|
callback URL. The comment style adapts to the file's apparent
|
|
syntax (``#`` for shell/yaml/python/dockerfile, ``//`` for json5/
|
|
javascript-ish, ``;`` for ini).
|
|
|
|
Operators who want neither behavior should upload the file as
|
|
``passthrough``.
|
|
"""
|
|
from __future__ import annotations
|
|
|
|
from decnet.canary.base import CanaryArtifact, CanaryContext, CanaryInstrumenter
|
|
|
|
|
|
_HASH_HINTS = (b"\n#", b"#!/", b"---\n", b"version:", b"FROM ")
|
|
_SLASH_HINTS = (b"//", b"function ", b"const ", b"let ", b"var ")
|
|
_SEMI_HINTS = (b"[default]", b"[section]", b"\n[")
|
|
|
|
|
|
def _comment_prefix(blob: bytes) -> bytes:
|
|
head = blob[:512]
|
|
if any(h in head for h in _SEMI_HINTS):
|
|
return b"; "
|
|
if any(h in head for h in _SLASH_HINTS):
|
|
return b"// "
|
|
# Default to # — the most common comment glyph across config files
|
|
# we'd plausibly canary.
|
|
if any(h in head for h in _HASH_HINTS) or True:
|
|
return b"# "
|
|
return b"# "
|
|
|
|
|
|
class PlainInstrumenter(CanaryInstrumenter):
|
|
name = "plain"
|
|
mime_prefixes = ("text/", "application/json", "application/yaml", "application/toml")
|
|
|
|
def instrument(
|
|
self, blob: bytes, ctx: CanaryContext, *, target_path: str,
|
|
) -> CanaryArtifact:
|
|
base = ctx.http_base.rstrip("/")
|
|
callback_url = f"{base}/c/{ctx.callback_token}".encode()
|
|
callback_host = (
|
|
f"{ctx.callback_token}.{ctx.dns_zone}".encode()
|
|
if ctx.dns_zone else b""
|
|
)
|
|
notes: list[str] = []
|
|
out = blob
|
|
|
|
if b"{{CANARY_URL}}" in blob:
|
|
out = out.replace(b"{{CANARY_URL}}", callback_url)
|
|
notes.append(f"substituted {{{{CANARY_URL}}}} -> {callback_url.decode()}")
|
|
if b"{{CANARY_HOST}}" in blob and callback_host:
|
|
out = out.replace(b"{{CANARY_HOST}}", callback_host)
|
|
notes.append(f"substituted {{{{CANARY_HOST}}}} -> {callback_host.decode()}")
|
|
|
|
if not notes:
|
|
# No placeholders — append a comment line at the end.
|
|
prefix = _comment_prefix(blob)
|
|
tail = (
|
|
b"\n" + prefix + b"see " + callback_url
|
|
+ b" for the latest version\n"
|
|
)
|
|
out = (out if out.endswith(b"\n") else out + b"\n") + tail
|
|
notes.append(
|
|
f"appended comment line carrying {callback_url.decode()}"
|
|
)
|
|
|
|
return CanaryArtifact(
|
|
path=target_path,
|
|
content=out,
|
|
mode=0o644,
|
|
mtime_offset=-86400 * 7,
|
|
instrumenter=self.name,
|
|
notes=notes,
|
|
)
|