Skip to content

Improper calculations in ECC implementation can trigger a Denial-of-Service (DoS)

High severity GitHub Reviewed Published Feb 16, 2023 in cisco/node-jose • Updated Feb 16, 2023

Package

npm node-jose (npm)

Affected versions

< 2.2.0

Patched versions

2.2.0

Description

Description

When using the non-default "fallback" crypto back-end, ECC operations in node-jose can trigger a Denial-of-Service (DoS) condition, due to a possible infinite loop in an internal calculation. For some ECC operations, this condition is triggered randomly; for others, it can be triggered by malicious input.

Technical summary

The JOSE logic implemented by node-jose usually relies on an external cryptographic library for the underlying cryptographic primitives that JOSE operations require. When WebCrypto or the Node crypto module are available, they are used. When neither of these libraries is available, node-jose includes its own "fallback" implementations of some algorithms based on node-forge, in particular implementations of ECDH and ECDSA.

A various points, these algorithm implementations need to compute to the X coordinate of an elliptic curve point. This is done by calling the getX() method of the object representing the point, which is an alias of the function pointFpGetX() in lib/deps/ecc/math.js.

Computing the X coordinate from the form in which the point is stored requires computing the modular inverse of the Z coordinate, using the modInverse function from the jsbn library (e.g., this.z.modInverse(this.curve.p)). The output of this function call is multiplied by another value before being reduced with the barrettReduce() function.

The root cause of this issue is that the jsbn modInverse function sometimes returns negative results. These results are correct in that they are equivalent mod the relevant modulus, but can be problematic for functions that expect modular operations to always return positive results (in the range [0, p), where p is the modulus).

In particular, while the Barrett reduction algorithm in general can handle negative inputs, the implementation in node-jose explicitly does not. Therefore, while the negative value that is returned by modInverse() is mathematically correct, it leads to an error in barrettReduce() causing an infinite loop which may result in a Denial of Service condition.

For a given prime modulus, we estimate that roughly one in every 2^20 inputs produce a negative modInverse(). This estimate was validated with exhaustive testing on small primes (<30 bits) and randomized testing with regard to the P-256 prime.

Impact

This issue is only present in situations where the "fallback" cryptographic implementation is being used, i.e., situations where neither WebCrypto nor the Node crypto module is available.

The following elliptic curve algorithms are impacted by this issue (all in lib/deps/ecc/index.js):

  • Elliptic curve key generation (exports.generateKeyPair)
  • Converting an elliptic curve private key to a public key (ECPrivateKey.prototype.toPublicKey)
  • ECDSA signing (ECPrivateKey.prototype.sign)
  • ECDSA verification (ECPublicKey.prototype.verify)
  • ECDH key agreement (ECPrivateKey.prototype.computeSecret)

In the first three cases, the points being evaluated are generated randomly, so an attack could only arise due to a bad value being randomly selected (as noted above, with probability roughly 2^{-20}). In the latter two cases, the points being evaluated are provided from outside the library, and thus potentially by attackers.

Patches

Has the problem been patched? What versions should users upgrade to?

Workarounds

Since this issue is only present in the "fallback" crypto implementation, it can be avoided by ensuring that either WebCrypto or the Node crypto module is available in the JS environment where node-jose is being run.

References

For more information

If you have any questions or comments about this advisory:

Credits

References

@justaugustus justaugustus published to cisco/node-jose Feb 16, 2023
Published to the GitHub Advisory Database Feb 16, 2023
Reviewed Feb 16, 2023
Published by the National Vulnerability Database Feb 16, 2023
Last updated Feb 16, 2023

Severity

High

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
None
User interaction
None
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:N/UI:N/S:U/C:N/I:N/A:H

EPSS score

0.099%
(42nd percentile)

Weaknesses

CVE ID

CVE-2023-25653

GHSA ID

GHSA-5h4j-qrvg-9xhw

Source code

Credits

Loading Checking history
See something to contribute? Suggest improvements for this vulnerability.