Add constant time check for shared secret #2319
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jcheng5
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wch
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Feb 5, 2019
R/server.R
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| @@ -161,7 +161,7 @@ createAppHandlers <- function(httpHandlers, serverFuncSource) { | |||
| # This value, if non-NULL, must be present on all HTTP and WebSocket | |||
| # requests as the Shiny-Shared-Secret header or else access will be | |||
| # denied (403 response for HTTP, and instant close for websocket). | |||
| sharedSecret <- getOption('shiny.sharedSecret') | |||
| sharedSecret <- loadSharedSecret() | |||
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A name like checkSharedSecret (as is used in the tests) would be a little clearer.
wch
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Feb 5, 2019
R/utils.R
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| constantTimeEquals <- function(raw1, raw2) { | ||
| stopifnot(is.raw(raw1)) | ||
| stopifnot(is.raw(raw2)) | ||
| stopifnot(length(raw1) == length(raw2)) |
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Does it matter that this could reveal the length using a timing attack?
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After discussion, we're not going to digest the input.
- Rename sharedSecret variables to checkSharedSecret - Don't perform the digest::digest(). This just means the timing could give away the length of the secret, but that's OK, there's enough entropy in the secret even if you know its length.
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@wch Can you review this last commit? Thanks! |
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Here's an exaggerated test to show that comparing two raw vectors using
identicalisn't constant-time, but usingconstantTimeEquals()is:Testing notes
Should verify that:
https://localhost:port; this should fail.