Headline
GHSA-x9w5-v3q2-3rhw: browserify-sign upper bound check issue in `dsaVerify` leads to a signature forgery attack
Summary
An upper bound check issue in dsaVerify function allows an attacker to construct signatures that can be successfully verified by any public key, thus leading to a signature forgery attack.
Details
In dsaVerify function, it checks whether the value of the signature is legal by calling function checkValue, namely, whether r and s are both in the interval [1, q - 1]. However, the second line of the checkValue function wrongly checks the upper bound of the passed parameters, since the value of b.cmp(q) can only be 0, 1 and -1, and it can never be greater than q.
In this way, although the values of s cannot be 0, an attacker can achieve the same effect as zero by setting its value to q, and then send (r, s) = (1, q) to pass the verification of any public key.
Impact
All places in this project that involve DSA verification of user-input signatures will be affected by this vulnerability.
Fix PR:
Since the temporary private fork was deleted, here’s a webarchive of the PR discussion and diff pages: PR webarchive.zip
Summary
An upper bound check issue in dsaVerify function allows an attacker to construct signatures that can be successfully verified by any public key, thus leading to a signature forgery attack.
Details
In dsaVerify function, it checks whether the value of the signature is legal by calling function checkValue, namely, whether r and s are both in the interval [1, q - 1]. However, the second line of the checkValue function wrongly checks the upper bound of the passed parameters, since the value of b.cmp(q) can only be 0, 1 and -1, and it can never be greater than q.
In this way, although the values of s cannot be 0, an attacker can achieve the same effect as zero by setting its value to q, and then send (r, s) = (1, q) to pass the verification of any public key.
Impact
All places in this project that involve DSA verification of user-input signatures will be affected by this vulnerability.
Fix PR:
Since the temporary private fork was deleted, here’s a webarchive of the PR discussion and diff pages: PR webarchive.zip
References
- GHSA-x9w5-v3q2-3rhw
- https://nvd.nist.gov/vuln/detail/CVE-2023-46234
- browserify/browserify-sign@85994cd
Related news
Ubuntu Security Notice 6800-1 - It was discovered that browserify-sign incorrectly handled an upper bound check in signature verification. If a user or an automated system were tricked into opening a specially crafted input file, a remote attacker could possibly use this issue to perform a signature forgery attack.
Debian Linux Security Advisory 5539-1 - It was reported that incorrect bound checks in the dsaVerify function in node-browserify-sign, a Node.js library which adds crypto signing for browsers, allows an attacker to perform signature forgery attacks by constructing signatures that can be successfully verified by any public key.
browserify-sign is a package to duplicate the functionality of node's crypto public key functions, much of this is based on Fedor Indutny's work on indutny/tls.js. An upper bound check issue in `dsaVerify` function allows an attacker to construct signatures that can be successfully verified by any public key, thus leading to a signature forgery attack. All places in this project that involve DSA verification of user-input signatures will be affected by this vulnerability. This issue has been patched in version 4.2.2.