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loader: Avoid reading UNC paths by default #6933

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ashutosh-narkar
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@ashutosh-narkar ashutosh-narkar commented Aug 15, 2024

If a UNC path is provided to OPA it won't read it
and instead return an error. This applies to paths
to load bundles and individual data/policy files.

One reason behind blocking UNC paths is they could
trigger a NTLMv2 hash leak. For example, if a SMB share
is provided, OPA will attempt to open it triggering LLMNR
queries which contain the client's NTLMv2 hash which can be cracked
using some tools. This could be exploited by a malicious user.

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Thanks for working on this. What do you think, can't we just not handle UNC paths, without an escape hatch? 🤔


for _, tc := range cases {
t.Run(tc.input, func(t *testing.T) {
os.Unsetenv(readUNCPathEnv)
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[nit] let's use t.Setenv

loader/loader.go Outdated
@@ -29,6 +29,8 @@ import (
"github.com/open-policy-agent/opa/util"
)

const readUNCPathEnv = "READ_UNC_PATH"
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I'm not a huge fan of shadow config via env vars 😅 But if we have to do it, let's prefix this with OPA_

@ashutosh-narkar ashutosh-narkar marked this pull request as ready for review August 16, 2024 18:52
srenatus
srenatus previously approved these changes Aug 16, 2024
loader/loader.go Outdated

func checkForUNCPath(path string) error {
if isUNC(path) {
return fmt.Errorf("UNC path read is not allowed")
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[nit] errors.New("...") or fmt.Errorf("UNC path read is not allowed: %s", path)

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Updated.

If a UNC path is provided to OPA it won't read it
and instead return an error. This applies to paths
to load bundles and individual data/policy files.

One reason behind blocking UNC paths is they could
trigger a NTLMv2 hash leak. For example, if a SMB share
is provided, OPA will attempt to open it triggering LLMNR
queries which contain the client's NTLMv2 hash which can be cracked
using some tools. This could be exploited by a malicious user.

Signed-off-by: Ashutosh Narkar <[email protected]>
@ashutosh-narkar ashutosh-narkar merged commit 10f4d55 into open-policy-agent:main Aug 16, 2024
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2 participants