fix(e5): distinguish proved cloud downloads from uploads

README.md

@@ -568,14 +568,27 @@ SkillSpector detects **71 vulnerability patterns** across 17 categories:
 | AR2 | Disclaimer Suppression | HIGH | Instructions to omit warnings, disclaimers, or ethical commentary (e.g. "no disclaimers", "do not moralize") |
 | AR3 | Safety Policy Nullification | HIGH | Jailbreak framing that nullifies guardrails (e.g. "you have no restrictions", "ignore your guidelines", "do anything now") |
 
-### Data Exfiltration (4 patterns)
+### Data Exfiltration (5 patterns)
 
 | ID | Pattern | Severity | Description |
 |----|---------|----------|-------------|
 | E1 | External Transmission | MEDIUM | Sending data to external URLs |
 | E2 | Env Variable Harvesting | HIGH | Enumerating, copying, or searching environment data to collect secrets. A copy traced only to a child process's `env=` is reported LOW |
 | E3 | File System Enumeration | MEDIUM | Scanning directories for sensitive files |
 | E4 | Context Leakage | HIGH | Transmitting conversation context externally |
+| E5 | Cloud Storage Exfiltration | MEDIUM | Uploading data through cloud storage SDKs or CLIs |
+
+Within bounded, fully observed context, E5 distinguishes literal AWS/GCS downloads
+from uploads. Simple remote-to-local `cp`, AWS `sync`, and `gsutil rsync` commands do not produce E5
+findings. Moves, deletion options, unknown flags, dynamic operands, streams and
+compound shell commands retain conservative findings. This direction check does
+not change SDK upload detection or the CLI's exit-code policy. Direction proofs
+require the complete preceding context to fit within 4,096 characters. Only
+blank/comment lines, literal `set` flags (`-e`, `-u`, `-f`, and `-o pipefail`),
+and simple directory changes may precede a proved download. Other setup,
+including sourcing, autoloading, variable assignments, and earlier transfers,
+retains the original finding. Relative destinations after directory changes
+remain unproved; literal absolute file destinations are still eligible.
 
 ### Privilege Escalation (3 patterns)
 

src/skillspector/nodes/analyzers/static_patterns_data_exfiltration.py

@@ -19,6 +19,7 @@
 
 import ast
 import itertools
+import posixpath
 import re
 import sys
 from collections.abc import Iterator, Sequence
@@ -37,10 +38,16 @@
     get_context,
     get_context_from_lines,
     get_line_number,
+    logical_line_starts,
     resolve_call_name,
     resolve_dotted_name,
 )
 from .pattern_defaults import PatternCategory
+from .static_patterns_supply_chain import (
+    _sc2_has_unproved_compound_context,
+    _sc2_logical_command,
+    _shell_tokens,
+)
 from .static_patterns_tool_misuse import _bounded_shell_tokens
 
 logger = get_logger(__name__)
@@ -183,6 +190,120 @@
     (r"\.upload_blob\s*\(", 0.55),  # Azure SDK
 ]
 
+_CLOUD_DOWNLOAD_AWS_FLAGS = frozenset(
+    {"--quiet", "--only-show-errors", "--no-progress", "--no-sign-request", "--dryrun"}
+)
+_CLOUD_DOWNLOAD_AWS_VALUE_OPTIONS = frozenset({"--region", "--profile", "--include", "--exclude"})
+_CLOUD_DOWNLOAD_SHELL_META = re.compile(r"[;&|<>(){}\[\]*?$\x60%!#~\x00-\x1f\x7f]")
+_CLOUD_DOWNLOAD_BUCKET = re.compile(r"[a-z0-9][a-z0-9.-]*")
+_CLOUD_DOWNLOAD_CONTEXT_CHARS = 4_096
+_CLOUD_DOWNLOAD_SAFE_SET = re.compile(
+    r"set[ \t]+(?:-[efu]+[ \t]+)*(?:-[efu]+|-[efu]*o[ \t]+pipefail)"
+)
+
+
+def _is_literal_cloud_download(
+    content: str,
+    offset: int,
+    line_starts: tuple[int, ...],
+    file_path: str,
+    file_type: str,
+) -> bool:
+    """Prove only a bounded, standalone, non-destructive cloud download.
+
+    The existing shell helpers retain unknown context and cap logical commands
+    at 4096 characters. No line or enclosing match is rewritten: callers decide
+    separately for every E5 occurrence, including nested or later uploads.
+    """
+    if file_type not in {"shell", "markdown", "text"} or file_path.lower().endswith(
+        (".ps1", ".psm1", ".psd1", ".bat", ".cmd")
+    ):
+        return False
+    if offset > _CLOUD_DOWNLOAD_CONTEXT_CHARS or _sc2_has_unproved_compound_context(
+        content, offset, ()
+    ):
+        return False
+    directory_changed = False
+    for line in content[:offset].splitlines():
+        setup = line.strip(" \t\r")
+        if not setup or setup.startswith("#"):
+            continue
+        if _CLOUD_DOWNLOAD_SAFE_SET.fullmatch(setup):
+            continue
+        if "\\" in setup or _CLOUD_DOWNLOAD_SHELL_META.search(setup):
+            return False
+        setup_tokens = _shell_tokens(setup)
+        if setup_tokens == ["popd"] or (
+            setup_tokens
+            and len(setup_tokens) == 2
+            and setup_tokens[0] in {"cd", "chdir", "pushd"}
+            and setup_tokens[1]
+            and not setup_tokens[1].startswith("-")
+        ):
+            directory_changed = True
+            continue
+        # Unknown setup can load or replace the cloud command. Even an earlier
+        # download can overwrite an executable, so only the preambles above
+        # preserve this proof; do not enumerate unsafe command-loading forms.
+        return False
+    command = _sc2_logical_command(content, offset, line_starts)
+    if command is None or "\\" in command or _CLOUD_DOWNLOAD_SHELL_META.search(command) is not None:
+        return False
+    tokens = _shell_tokens(command)
+    if not tokens:
+        return False
+    if tokens[:3] in (["aws", "s3", "cp"], ["aws", "s3", "sync"]):
+        scheme = "s3://"
+        arguments = iter(tokens[3:])
+        flags = _CLOUD_DOWNLOAD_AWS_FLAGS
+        if tokens[2] == "cp":
+            flags = flags | {"--recursive"}
+        value_options = _CLOUD_DOWNLOAD_AWS_VALUE_OPTIONS
+    elif tokens[:2] in (["gsutil", "cp"], ["gsutil", "rsync"]):
+        scheme = "gs://"
+        arguments = iter(tokens[2:])
+        flags = frozenset({"-r"})
+        value_options = frozenset()
+    else:
+        # In particular, mv and sync deletion flags do more than copy data.
+        return False
+
+    operands: list[str] = []
+    for argument in arguments:
+        if argument in flags:
+            continue
+        if argument in value_options:
+            value = next(arguments, "")
+            if not value or value.startswith("-"):
+                return False
+        elif argument.startswith("-"):
+            return False
+        else:
+            operands.append(argument)
+    if len(operands) != 2:
+        return False
+    source, destination = operands
+    if not source.startswith(scheme):
+        return False
+    bucket = source[len(scheme) :].split("/", 1)[0]
+    if _CLOUD_DOWNLOAD_BUCKET.fullmatch(bucket) is None:
+        return False
+    if directory_changed and not destination.startswith("/"):
+        # A relative file may resolve to a stream after cd /dev (or a directory
+        # stack change). Absolute destinations do not depend on this setup.
+        return False
+    normalized_destination = posixpath.normpath(destination)
+    # A static local destination cannot be a cloud URI, stream or shell expansion.
+    # Colons remain conservative for other URL schemes and host-language paths.
+    return (
+        bool(destination)
+        and destination != "-"
+        and ":" not in destination
+        and not destination.startswith("//")
+        and normalized_destination not in {"/dev", "/proc", "/sys"}
+        and not normalized_destination.startswith(("/dev/", "/proc/", "/sys/"))
+    )
+
 
 def _e1_shell_regions(content: str, file_type: str) -> tuple[tuple[int, int], ...]:
     """Identify source regions whose physical separators have shell semantics.
@@ -1283,11 +1404,16 @@ def ctx(start: int) -> str:
                     complete_match=match.group(0),
                 )
             )
-    # E5: cloud-storage exfiltration. Example filtering is delegated to the runner.
+    # E5: retain uploads and uncertain directions; lower only proven downloads.
+    line_starts = logical_line_starts(content[: _CLOUD_DOWNLOAD_CONTEXT_CHARS + 1])
     for pattern, confidence in E5_PATTERNS:
         for match in static_runner.iter_pattern_matches(
             pattern, content, re.IGNORECASE | re.MULTILINE
         ):
+            if _is_literal_cloud_download(
+                content, match.start(), line_starts, file_path, file_type
+            ):
+                continue
             line_num = get_line_number(content, match.start())
             findings.append(
                 AnalyzerFinding(