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Gnark out-of-memory during deserialization with crafted inputs

Moderate severity GitHub Reviewed Published Oct 31, 2024 in Consensys/gnark

Package

gomod github.com/consensys/gnark (Go)

Affected versions

<= 0.11.0

Patched versions

0.11.1

Description

Thanks @pventuzelo for reporting.

From the correspondence:

Hi,

We (Fuzzinglabs & Lambdaclass) found that during deserialization of certain files representing a VerifyingKey, an excessive memory allocation is happening consuming a lot of resources and even triggering a crash with the error fatal error: runtime: out of memory.

Please find the details below:

Vulnerability Details

  • Severity: Critical -> DoS
  • Affected Component: Deserialization

Environment

  • Compiler Version: go version go1.22.2 linux/amd64

  • Distro Version: Ubuntu 24.04.1 LTS

  • Additional Environment Details:

    • [github.com/consensys/gnark](http://github.com/consensys/gnark) v0.11.0
    • [github.com/consensys/gnark-crypto](http://github.com/consensys/gnark-crypto) v0.14.1-0.20240909142611-e6b99e74cec1

Steps to Reproduce

You can download the needed files here: https://drive.google.com/drive/folders/1KQ5I3vv4bUllvqbatGappwbAkIcR2NI_?usp=sharing

You have to run

go run gnark_poc.go

in a terminal.

Running the provided code will result in a memory crash or an extremely large memory allocation, which can be observed using the following command:

go tool pprof -web mem.pprof

Root Cause Analysis

The provided code loads a VerifyingKey from old.vk by calling the ReadFrom function. This function is implemented in backend/groth16/bn254/marshal.go within the gnark library.

The provided example uses the elliptic curve BN-254, so the code resides in the backend/groth16/bn254/ repertory. However, the same error exists in other repertories, such as backend/groth16/bls12-377/.

At line 207, a slice is allocated with a length of nbCommitments. This variable is directly extracted from the deserialized file, which, in our case, has a value of 2,327,186,600. This large value may be too big for some configurations, leading to memory allocations of approximately ±1 TB, as observed with pprof.

Detailed Behavior

go run gnark_poc.go
fatal error: runtime: out of memory

runtime stack:
runtime.throw({0x5fe946?, 0x2052ae?})
/usr/lib/go-1.22/src/runtime/panic.go:1023 +0x5c fp=0x7ffd65b321a0 sp=0x7ffd65b32170 pc=0x438a9c
runtime.sysMapOS(0xc000400000, 0x8ab6400000)
/usr/lib/go-1.22/src/runtime/mem_linux.go:167 +0x11b fp=0x7ffd65b321e0 sp=0x7ffd65b321a0 pc=0x418bbb
runtime.sysMap(0xc000400000, 0x8ab6400000, 0x7b19c8?)
/usr/lib/go-1.22/src/runtime/mem.go:155 +0x34 fp=0x7ffd65b32200 sp=0x7ffd65b321e0 pc=0x418634
runtime.(*mheap).grow(0x7a17c0, 0x455b066?)
/usr/lib/go-1.22/src/runtime/mheap.go:1534 +0x236 fp=0x7ffd65b32270 sp=0x7ffd65b32200 pc=0x42b176
runtime.(*mheap).allocSpan(0x7a17c0, 0x455b066, 0x0, 0x1)
/usr/lib/go-1.22/src/runtime/mheap.go:1246 +0x1b0 fp=0x7ffd65b32310 sp=0x7ffd65b32270 pc=0x42a850
runtime.(*mheap).alloc.func1()
/usr/lib/go-1.22/src/runtime/mheap.go:964 +0x5c fp=0x7ffd65b32358 sp=0x7ffd65b32310 pc=0x42a2fc
runtime.systemstack(0x46d79f)
/usr/lib/go-1.22/src/runtime/asm_amd64.s:509 +0x4a fp=0x7ffd65b32368 sp=0x7ffd65b32358 pc=0x46912a

goroutine 1 gp=0xc0000061c0 m=0 mp=0x798ca0 [running]:
runtime.systemstack_switch()
/usr/lib/go-1.22/src/runtime/asm_amd64.s:474 +0x8 fp=0xc000031b68 sp=0xc000031b58 pc=0x4690c8
runtime.(*mheap).alloc(0x5bc040?, 0xc00012bb08?, 0xa0?)
/usr/lib/go-1.22/src/runtime/mheap.go:958 +0x5b fp=0xc000031bb0 sp=0xc000031b68 pc=0x42a25b
runtime.(*mcache).allocLarge(0xc000126510?, 0x8ab60ca800, 0x1)
/usr/lib/go-1.22/src/runtime/mcache.go:234 +0x87 fp=0xc000031c00 sp=0xc000031bb0 pc=0x4176e7
runtime.mallocgc(0x8ab60ca800, 0x5d92a0, 0x1)
/usr/lib/go-1.22/src/runtime/malloc.go:1165 +0x597 fp=0xc000031c88 sp=0xc000031c00 pc=0x40ef97
runtime.makeslice(0xc00011c180?, 0x0?, 0x2?)
/usr/lib/go-1.22/src/runtime/slice.go:107 +0x49 fp=0xc000031cb0 sp=0xc000031c88 pc=0x4500c9
[github.com/consensys/gnark/backend/groth16/bn254.(*VerifyingKey).readFrom(0xc0001b7088](http://github.com/consensys/gnark/backend/groth16/bn254.(*VerifyingKey).readFrom(0xc0001b7088), {0x6598a0, 0xc00011dc50}, 0x0)
/home/raunan/go/pkg/mod/[github.com/!ronan!thoraval/gnark@v0.0.0-20241007163125-4c0a7511c3d1/backend/groth16/bn254/marshal.go:214](http://github.com/!ronan!thoraval/gnark@v0.0.0-20241007163125-4c0a7511c3d1/backend/groth16/bn254/marshal.go:214) +0x765 fp=0xc000031ea8 sp=0xc000031cb0 pc=0x59b205
[github.com/consensys/gnark/backend/groth16/bn254.(*VerifyingKey).ReadFrom(0x100469020](http://github.com/consensys/gnark/backend/groth16/bn254.(*VerifyingKey).ReadFrom(0x100469020)?, {0x6598a0?, 0xc00011dc50?})
/home/raunan/go/pkg/mod/[github.com/!ronan!thoraval/gnark@v0.0.0-20241007163125-4c0a7511c3d1/backend/groth16/bn254/marshal.go:166](http://github.com/!ronan!thoraval/gnark@v0.0.0-20241007163125-4c0a7511c3d1/backend/groth16/bn254/marshal.go:166) +0x1f fp=0xc000031ed8 sp=0xc000031ea8 pc=0x59aa5f
main.main()
/home/raunan/gnark_poc/gnark_poc/gnark_poc.go:19 +0xba fp=0xc000031f50 sp=0xc000031ed8 pc=0x5addda
runtime.main()
/usr/lib/go-1.22/src/runtime/proc.go:271 +0x29d fp=0xc000031fe0 sp=0xc000031f50 pc=0x43b55d
runtime.goexit({})
/usr/lib/go-1.22/src/runtime/asm_amd64.s:1695 +0x1 fp=0xc000031fe8 sp=0xc000031fe0 pc=0x46b0e1

goroutine 2 gp=0xc000006c40 m=nil [force gc (idle)]:
runtime.gopark(0x0?, 0x0?, 0x0?, 0x0?, 0x0?)
/usr/lib/go-1.22/src/runtime/proc.go:402 +0xce fp=0xc000074fa8 sp=0xc000074f88 pc=0x43b98e
runtime.goparkunlock(...)
/usr/lib/go-1.22/src/runtime/proc.go:408
runtime.forcegchelper()
/usr/lib/go-1.22/src/runtime/proc.go:326 +0xb3 fp=0xc000074fe0 sp=0xc000074fa8 pc=0x43b813
runtime.goexit({})
/usr/lib/go-1.22/src/runtime/asm_amd64.s:1695 +0x1 fp=0xc000074fe8 sp=0xc000074fe0 pc=0x46b0e1
created by runtime.init.6 in goroutine 1
/usr/lib/go-1.22/src/runtime/proc.go:314 +0x1a

goroutine 3 gp=0xc000007180 m=nil [GC sweep wait]:
runtime.gopark(0x0?, 0x0?, 0x0?, 0x0?, 0x0?)
/usr/lib/go-1.22/src/runtime/proc.go:402 +0xce fp=0xc000075780 sp=0xc000075760 pc=0x43b98e
runtime.goparkunlock(...)
/usr/lib/go-1.22/src/runtime/proc.go:408
runtime.bgsweep(0xc0000240e0)
/usr/lib/go-1.22/src/runtime/mgcsweep.go:278 +0x94 fp=0xc0000757c8 sp=0xc000075780 pc=0x426cf4
runtime.gcenable.gowrap1()
/usr/lib/go-1.22/src/runtime/mgc.go:203 +0x25 fp=0xc0000757e0 sp=0xc0000757c8 pc=0x41b845
runtime.goexit({})
/usr/lib/go-1.22/src/runtime/asm_amd64.s:1695 +0x1 fp=0xc0000757e8 sp=0xc0000757e0 pc=0x46b0e1
created by runtime.gcenable in goroutine 1
/usr/lib/go-1.22/src/runtime/mgc.go:203 +0x66

goroutine 4 gp=0xc000007340 m=nil [GC scavenge wait]:
runtime.gopark(0xc0000240e0?, 0x657100?, 0x1?, 0x0?, 0xc000007340?)
/usr/lib/go-1.22/src/runtime/proc.go:402 +0xce fp=0xc000075f78 sp=0xc000075f58 pc=0x43b98e
runtime.goparkunlock(...)
/usr/lib/go-1.22/src/runtime/proc.go:408
runtime.(*scavengerState).park(0x797520)
/usr/lib/go-1.22/src/runtime/mgcscavenge.go:425 +0x49 fp=0xc000075fa8 sp=0xc000075f78 pc=0x4246e9
runtime.bgscavenge(0xc0000240e0)
/usr/lib/go-1.22/src/runtime/mgcscavenge.go:653 +0x3c fp=0xc000075fc8 sp=0xc000075fa8 pc=0x424c7c
runtime.gcenable.gowrap2()
/usr/lib/go-1.22/src/runtime/mgc.go:204 +0x25 fp=0xc000075fe0 sp=0xc000075fc8 pc=0x41b7e5
runtime.goexit({})
/usr/lib/go-1.22/src/runtime/asm_amd64.s:1695 +0x1 fp=0xc000075fe8 sp=0xc000075fe0 pc=0x46b0e1
created by runtime.gcenable in goroutine 1
/usr/lib/go-1.22/src/runtime/mgc.go:204 +0xa5

goroutine 18 gp=0xc000102700 m=nil [finalizer wait]:
runtime.gopark(0xc000074648?, 0x40f445?, 0xa8?, 0x1?, 0xc0000061c0?)
/usr/lib/go-1.22/src/runtime/proc.go:402 +0xce fp=0xc000074620 sp=0xc000074600 pc=0x43b98e
runtime.runfinq()
/usr/lib/go-1.22/src/runtime/mfinal.go:194 +0x107 fp=0xc0000747e0 sp=0xc000074620 pc=0x41a887
runtime.goexit({})
/usr/lib/go-1.22/src/runtime/asm_amd64.s:1695 +0x1 fp=0xc0000747e8 sp=0xc0000747e0 pc=0x46b0e1
created by runtime.createfing in goroutine 1
/usr/lib/go-1.22/src/runtime/mfinal.go:164 +0x3d
exit status 2

Appendices

This problem can also happen with ProvingKey.

Impact

Prover and verifier denial of service in case of maliciously crafted inputs (public key, verification key).

Patches

The issue is patched in Consensys/gnark#1307. It was merged to gnark master at Consensys/gnark@47ae846. The fix will be incorporated in the next minor release of gnark (v0.11.1).

Workarounds

There are no convenient work-arounds currently. The best approach currently is to run key verification as a separate service which halts the verification pipeline in case of OOM when verification keys come from untrusted sources.

References

@ivokub ivokub published to Consensys/gnark Oct 31, 2024
Published by the National Vulnerability Database Oct 31, 2024
Published to the GitHub Advisory Database Oct 31, 2024
Reviewed Oct 31, 2024

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 v4 base metrics

Exploitability Metrics
Attack Vector Local
Attack Complexity Low
Attack Requirements None
Privileges Required Low
User interaction None
Vulnerable System Impact Metrics
Confidentiality None
Integrity None
Availability High
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Weaknesses

CVE ID

CVE-2024-50354

GHSA ID

GHSA-cph5-3pgr-c82g

Source code

Credits

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