[pbs-devel] [PATCH proxmox v2 04/12] auth-api: use constant time comparison for csrf tokens
Stefan Sterz
s.sterz at proxmox.com
Wed Mar 6 13:36:01 CET 2024
by using openssl's `memcmp::eq()` we can avoid potential side-channel
attack on the csrf token comparison. this comparison's runtime only
depends on the length of the two byte vectors, not their contents.
Signed-off-by: Stefan Sterz <s.sterz at proxmox.com>
---
proxmox-auth-api/src/api/access.rs | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/proxmox-auth-api/src/api/access.rs b/proxmox-auth-api/src/api/access.rs
index 428d22a..e22eea2 100644
--- a/proxmox-auth-api/src/api/access.rs
+++ b/proxmox-auth-api/src/api/access.rs
@@ -286,14 +286,15 @@ fn verify_csrf_prevention_token_do(
}
let timestamp = parts.pop_front().unwrap();
- let sig = parts.pop_front().unwrap();
+ let sig = parts.pop_front().unwrap().as_bytes();
let ttime = i64::from_str_radix(timestamp, 16)
.map_err(|err| format_err!("timestamp format error - {}", err))?;
let digest = compute_csrf_secret_digest(ttime, secret, userid);
+ let digest = digest.as_bytes();
- if digest != sig {
+ if digest.len() != sig.len() || !openssl::memcmp::eq(digest, sig) {
bail!("invalid signature.");
}
--
2.39.2
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