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Geth Node Vulnerable to DoS via maliciously crafted p2p message

Moderate severity GitHub Reviewed Published Oct 25, 2021 in ethereum/go-ethereum • Updated Aug 29, 2023

Package

gomod github.com/ethereum/go-ethereum (Go)

Affected versions

< 1.10.9

Patched versions

1.10.9

Description

Impact

A vulnerable node is susceptible to crash when processing a maliciously crafted message from a peer, via the snap/1 protocol. The crash can be triggered by sending a malicious snap/1 GetTrieNodes package.

Details

On September 21, 2021, geth-team member Gary Rong (@rjl493456442) found a way to crash the snap request handler .
By using this vulnerability, a peer connected on the snap/1 protocol could cause a vulnerable node to crash with a panic.

In the trie.TryGetNode implementation, if the requested path is reached, the associated node will be returned. However the nilness is
not checked there.

func (t *Trie) tryGetNode(origNode node, path []byte, pos int) (item []byte, newnode node, resolved int, err error) {
	// If we reached the requested path, return the current node
	if pos >= len(path) {
		// Although we most probably have the original node expanded, encoding
		// that into consensus form can be nasty (needs to cascade down) and
		// time consuming. Instead, just pull the hash up from disk directly.
		var hash hashNode
		if node, ok := origNode.(hashNode); ok {
			hash = node
		} else {
			hash, _ = origNode.cache()
		}

More specifically the origNode can be nil(e.g. the child of fullnode) and system can panic at line hash, _ = origNode.cache().

When investigating this, @holiman tried to find it via fuzzing, which uncovered a second crasher, also related to the snap GetTrieNodes package. If the caller requests a storage trie:

				// Storage slots requested, open the storage trie and retrieve from there
				account, err := snap.Account(common.BytesToHash(pathset[0]))
				loads++ // always account database reads, even for failures
				if account == nil {
					break
				}
				stTrie, err := trie.NewSecure(common.BytesToHash(account.Root), triedb)

The code assumes that snap.Account returns either a non-nil response unless error is also provided. This is however not the case, since snap.Account can return nil, nil.

Patches

--- a/eth/protocols/snap/handler.go
+++ b/eth/protocols/snap/handler.go
@@ -469,7 +469,7 @@ func handleMessage(backend Backend, peer *Peer) error {
 				// Storage slots requested, open the storage trie and retrieve from there
 				account, err := snap.Account(common.BytesToHash(pathset[0]))
 				loads++ // always account database reads, even for failures
-				if err != nil {
+				if err != nil || account == nil {
 					break
 				}
 				stTrie, err := trie.NewSecure(common.BytesToHash(account.Root), triedb)
diff --git a/trie/trie.go b/trie/trie.go
index 7ea7efa835..d0f0d4e2bc 100644
--- a/trie/trie.go
+++ b/trie/trie.go
@@ -174,6 +174,10 @@ func (t *Trie) TryGetNode(path []byte) ([]byte, int, error) {
 }
 
 func (t *Trie) tryGetNode(origNode node, path []byte, pos int) (item []byte, newnode node, resolved int, err error) {
+	// If non-existent path requested, abort
+	if origNode == nil {
+		return nil, nil, 0, nil
+	}
 	// If we reached the requested path, return the current node
 	if pos >= len(path) {
 		// Although we most probably have the original node expanded, encoding
@@ -193,10 +197,6 @@ func (t *Trie) tryGetNode(origNode node, path []byte, pos int) (item []byte, new
 	}
 	// Path still needs to be traversed, descend into children
 	switch n := (origNode).(type) {
-	case nil:
-		// Non-existent path requested, abort
-		return nil, nil, 0, nil
-
 	case valueNode:
 		// Path prematurely ended, abort
 		return nil, nil, 0, nil

The fixes were merged into #23657, with commit f1fd963, and released as part of Geth v1.10.9 on Sept 29, 2021.

Workarounds

Apply the patch above or upgrade to a version which is not vulnerable.

For more information

If you have any questions or comments about this advisory:

References

@holiman holiman published to ethereum/go-ethereum Oct 25, 2021
Reviewed Oct 25, 2021
Published to the GitHub Advisory Database Oct 25, 2021
Published by the National Vulnerability Database Oct 26, 2021
Last updated Aug 29, 2023

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H

EPSS score

0.203%
(59th percentile)

Weaknesses

CVE ID

CVE-2021-41173

GHSA ID

GHSA-59hh-656j-3p7v

Source code

Credits

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