Skip to content

Python: Add support for extraction filters #14918

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
tausbn merged 4 commits into from
Nov 30, 2023
Merged

Python: Add support for extraction filters #14918

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
95e9284
Python: Add support for extraction filters
tausbn Nov 27, 2023
ad1a868
Python: Add change note
tausbn Nov 27, 2023
91643ad
Python: Update `hasUnsafeFilter` to use API graph
tausbn Nov 28, 2023
6e27918
Python: Remove unused `unsafeFilter` predicates
tausbn Nov 28, 2023
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
5 changes: 5 additions & 0 deletions python/ql/lib/change-notes/2023-11-27-tarfile-extraction-filters.md
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
category: minorAnalysis
---

- Added support for tarfile extraction filters as defined in [PEP-706](https://peps.python.org/pep-0706). In particular, calls to `TarFile.extract`, and `TarFile.extractall` are no longer considered to be sinks for the `py/tarslip` query if a sufficiently safe filter is provided.
45 changes: 40 additions & 5 deletions python/ql/lib/semmle/python/security/dataflow/TarSlipCustomizations.qll
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -55,10 +55,38 @@ module TarSlip {
ExcludeTarFilePy() { this.getLocation().getFile().getBaseName() = "tarfile.py" }
}

/**
* Holds if `call` has an unsafe extraction filter, either by default (as the default is unsafe),
* or by being set to an explicitly unsafe value, such as `"fully_trusted"`, or `None`.
*/
private predicate hasUnsafeFilter(API::CallNode call) {
call =
API::moduleImport("tarfile")
.getMember("open")
.getReturn()
.getMember(["extract", "extractall"])
.getACall() and
(
exists(Expr filterValue |
filterValue = call.getParameter(4, "filter").getAValueReachingSink().asExpr() and
(
filterValue.(StrConst).getText() = "fully_trusted"
or
filterValue instanceof None
)
)
or
not exists(call.getParameter(4, "filter"))
)
}

/**
* A sink capturing method calls to `extractall`.
*
* For a call to `file.extractall` without arguments, `file` is considered a sink.
* For a call to `file.extractall`, `file` is considered a sink if
*
* - there are no other arguments, or
* - there are other arguments (except `members`), and the extraction filter is unsafe.
*/
class ExtractAllSink extends Sink {
ExtractAllSink() {
Expand All @@ -69,8 +97,13 @@ module TarSlip {
.getReturn()
.getMember("extractall")
.getACall() and
not exists(call.getArg(_)) and
not exists(call.getArgByName(_)) and
(
not exists(call.getArg(_)) and
not exists(call.getArgByName(_))
or
hasUnsafeFilter(call)
) and
not exists(call.getArgByName("members")) and
this = call.(DataFlow::MethodCallNode).getObject()
)
}
Expand All @@ -84,7 +117,8 @@ module TarSlip {
exists(DataFlow::CallCfgNode call |
call =
API::moduleImport("tarfile").getMember("open").getReturn().getMember("extract").getACall() and
this = call.getArg(0)
this = call.getArg(0) and
hasUnsafeFilter(call)
)
}
}
Expand All @@ -99,7 +133,8 @@ module TarSlip {
.getReturn()
.getMember("extractall")
.getACall() and
this in [call.getArg(0), call.getArgByName("members")]
this in [call.getArg(0), call.getArgByName("members")] and
hasUnsafeFilter(call)
)
}
}
Expand Down
26 changes: 26 additions & 0 deletions python/ql/test/query-tests/Security/CWE-022-TarSlip/TarSlip.expected
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,15 @@ edges
| tarslip.py:58:1:58:3 | GSSA Variable tar | tarslip.py:59:5:59:9 | GSSA Variable entry |
| tarslip.py:58:7:58:39 | ControlFlowNode for Attribute() | tarslip.py:58:1:58:3 | GSSA Variable tar |
| tarslip.py:59:5:59:9 | GSSA Variable entry | tarslip.py:61:21:61:25 | ControlFlowNode for entry |
| tarslip.py:90:1:90:3 | GSSA Variable tar | tarslip.py:91:1:91:3 | ControlFlowNode for tar |
| tarslip.py:90:7:90:39 | ControlFlowNode for Attribute() | tarslip.py:90:1:90:3 | GSSA Variable tar |
| tarslip.py:94:1:94:3 | GSSA Variable tar | tarslip.py:95:5:95:9 | GSSA Variable entry |
| tarslip.py:94:7:94:39 | ControlFlowNode for Attribute() | tarslip.py:94:1:94:3 | GSSA Variable tar |
| tarslip.py:95:5:95:9 | GSSA Variable entry | tarslip.py:96:17:96:21 | ControlFlowNode for entry |
| tarslip.py:109:1:109:3 | GSSA Variable tar | tarslip.py:110:1:110:3 | ControlFlowNode for tar |
| tarslip.py:109:7:109:39 | ControlFlowNode for Attribute() | tarslip.py:109:1:109:3 | GSSA Variable tar |
| tarslip.py:112:1:112:3 | GSSA Variable tar | tarslip.py:113:24:113:26 | ControlFlowNode for tar |
| tarslip.py:112:7:112:39 | ControlFlowNode for Attribute() | tarslip.py:112:1:112:3 | GSSA Variable tar |
nodes
| tarslip.py:14:1:14:3 | GSSA Variable tar | semmle.label | GSSA Variable tar |
| tarslip.py:14:7:14:39 | ControlFlowNode for Attribute() | semmle.label | ControlFlowNode for Attribute() |
Expand All @@ -31,10 +40,27 @@ nodes
| tarslip.py:58:7:58:39 | ControlFlowNode for Attribute() | semmle.label | ControlFlowNode for Attribute() |
| tarslip.py:59:5:59:9 | GSSA Variable entry | semmle.label | GSSA Variable entry |
| tarslip.py:61:21:61:25 | ControlFlowNode for entry | semmle.label | ControlFlowNode for entry |
| tarslip.py:90:1:90:3 | GSSA Variable tar | semmle.label | GSSA Variable tar |
| tarslip.py:90:7:90:39 | ControlFlowNode for Attribute() | semmle.label | ControlFlowNode for Attribute() |
| tarslip.py:91:1:91:3 | ControlFlowNode for tar | semmle.label | ControlFlowNode for tar |
| tarslip.py:94:1:94:3 | GSSA Variable tar | semmle.label | GSSA Variable tar |
| tarslip.py:94:7:94:39 | ControlFlowNode for Attribute() | semmle.label | ControlFlowNode for Attribute() |
| tarslip.py:95:5:95:9 | GSSA Variable entry | semmle.label | GSSA Variable entry |
| tarslip.py:96:17:96:21 | ControlFlowNode for entry | semmle.label | ControlFlowNode for entry |
| tarslip.py:109:1:109:3 | GSSA Variable tar | semmle.label | GSSA Variable tar |
| tarslip.py:109:7:109:39 | ControlFlowNode for Attribute() | semmle.label | ControlFlowNode for Attribute() |
| tarslip.py:110:1:110:3 | ControlFlowNode for tar | semmle.label | ControlFlowNode for tar |
| tarslip.py:112:1:112:3 | GSSA Variable tar | semmle.label | GSSA Variable tar |
| tarslip.py:112:7:112:39 | ControlFlowNode for Attribute() | semmle.label | ControlFlowNode for Attribute() |
| tarslip.py:113:24:113:26 | ControlFlowNode for tar | semmle.label | ControlFlowNode for tar |
subpaths
#select
| tarslip.py:15:1:15:3 | ControlFlowNode for tar | tarslip.py:14:7:14:39 | ControlFlowNode for Attribute() | tarslip.py:15:1:15:3 | ControlFlowNode for tar | This file extraction depends on a $@. | tarslip.py:14:7:14:39 | ControlFlowNode for Attribute() | potentially untrusted source |
| tarslip.py:20:17:20:21 | ControlFlowNode for entry | tarslip.py:18:7:18:39 | ControlFlowNode for Attribute() | tarslip.py:20:17:20:21 | ControlFlowNode for entry | This file extraction depends on a $@. | tarslip.py:18:7:18:39 | ControlFlowNode for Attribute() | potentially untrusted source |
| tarslip.py:39:17:39:21 | ControlFlowNode for entry | tarslip.py:35:7:35:39 | ControlFlowNode for Attribute() | tarslip.py:39:17:39:21 | ControlFlowNode for entry | This file extraction depends on a $@. | tarslip.py:35:7:35:39 | ControlFlowNode for Attribute() | potentially untrusted source |
| tarslip.py:43:24:43:26 | ControlFlowNode for tar | tarslip.py:42:7:42:39 | ControlFlowNode for Attribute() | tarslip.py:43:24:43:26 | ControlFlowNode for tar | This file extraction depends on a $@. | tarslip.py:42:7:42:39 | ControlFlowNode for Attribute() | potentially untrusted source |
| tarslip.py:61:21:61:25 | ControlFlowNode for entry | tarslip.py:58:7:58:39 | ControlFlowNode for Attribute() | tarslip.py:61:21:61:25 | ControlFlowNode for entry | This file extraction depends on a $@. | tarslip.py:58:7:58:39 | ControlFlowNode for Attribute() | potentially untrusted source |
| tarslip.py:91:1:91:3 | ControlFlowNode for tar | tarslip.py:90:7:90:39 | ControlFlowNode for Attribute() | tarslip.py:91:1:91:3 | ControlFlowNode for tar | This file extraction depends on a $@. | tarslip.py:90:7:90:39 | ControlFlowNode for Attribute() | potentially untrusted source |
| tarslip.py:96:17:96:21 | ControlFlowNode for entry | tarslip.py:94:7:94:39 | ControlFlowNode for Attribute() | tarslip.py:96:17:96:21 | ControlFlowNode for entry | This file extraction depends on a $@. | tarslip.py:94:7:94:39 | ControlFlowNode for Attribute() | potentially untrusted source |
| tarslip.py:110:1:110:3 | ControlFlowNode for tar | tarslip.py:109:7:109:39 | ControlFlowNode for Attribute() | tarslip.py:110:1:110:3 | ControlFlowNode for tar | This file extraction depends on a $@. | tarslip.py:109:7:109:39 | ControlFlowNode for Attribute() | potentially untrusted source |
| tarslip.py:113:24:113:26 | ControlFlowNode for tar | tarslip.py:112:7:112:39 | ControlFlowNode for Attribute() | tarslip.py:113:24:113:26 | ControlFlowNode for tar | This file extraction depends on a $@. | tarslip.py:112:7:112:39 | ControlFlowNode for Attribute() | potentially untrusted source |
32 changes: 32 additions & 0 deletions python/ql/test/query-tests/Security/CWE-022-TarSlip/tarslip.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -82,3 +82,35 @@ def safemembers(members):
for entry in tar:
if not os.path.isabs(entry.name):
tar.extract(entry, "/tmp/unpack/")

# Extraction filters

extraction_filter = "fully_trusted"

tar = tarfile.open(unsafe_filename_tar)
tar.extractall(filter=extraction_filter) # unsafe
tar.close()

tar = tarfile.open(unsafe_filename_tar)
for entry in tar:
tar.extract(entry, filter=extraction_filter) # unsafe

extraction_filter = "data"

tar = tarfile.open(unsafe_filename_tar)
tar.extractall(filter=extraction_filter) # safe
tar.close()

tar = tarfile.open(unsafe_filename_tar)
for entry in tar:
tar.extract(entry, filter=extraction_filter) # safe

extraction_filter = None
tar = tarfile.open(unsafe_filename_tar)
tar.extractall(filter=extraction_filter) # unsafe

tar = tarfile.open(unsafe_filename_tar)
tar.extractall(members=tar, filter=extraction_filter) # unsafe

tar = tarfile.open(unsafe_filename_tar)
tar.extractall(members=safemembers(tar), filter=extraction_filter) # safe -- we assume `safemembers` makes up for the unsafe filter