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Memory leak in DiffieHellman.set{Privat,Public}Key() and some suggestions #8377
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/cc @nodejs/crypto |
@nodejs/crypto Should this stay open? |
I added a commit to #14122 that fixes the memory leak (thanks for the bug report!) As to the other suggestions, I don't have strong opinions except for the usual backwards compatibility concerns. Any API change or deprecation is going to be a drawn out process. |
bnoordhuis
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Jul 17, 2017
Fix a memory leak in dh.setPublicKey() and dh.setPrivateKey() where the old keys weren't freed. Fixes: nodejs#8377
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In https://github.com/nodejs/node/blob/master/src/node_crypto.cc#L4757 (void DiffieHellman::SetPublicKey):
but
...->pub_key
might already point to allocated memory, which is never freed.man OpenSSL says:
So it should be enough to pass diffieHellman->dh->pub_key as third parameter, instead of 0.
DiffieHellman::SetPrivateKey, a few lines later, has the same issue.
Alternatively, we could forbid calling set{Public,Private}Key after a key exists, because the DH api does not seem to encourage reuse of DiffieHellman classes:
generateKeys()
always returns the same key after the first call. According to OpenSSL documentation, this is caused bydh->priv_key
being non-null.Changing
generateKeys()
to return a new key on every call would be breaking API change; OTOHsetPrivateKey()
can (currently) not be used to resetdh->priv_key
to null (while freeing possibly allocated memory).All in all this suggests that the user should create a new DiffieHellman class for each key exchange, but the nodejs binding again thwarts such efforts:
Therefore I'd also suggest to add another "overload" to
createDiffieHellman
which takes an existingDiffieHellman
class and creates a new one with the same Prime and Generator, with empty keys, but without calling (slow)DH_check
(the parameters have already been checked earlier!) by just copying the.verifyError
result.A side note: Given the trivial conversion (via
.getPrime
, as shown above) of aDiffieHellmanGroup
class to aDiffieHellman
class and the same C++ class under the hood, the non-existence of.set{Public,Private}Key
on theDiffieHellmanGroup
class obtained by.getDiffieHellman
is completely arbitrary and unnecessary.BTW, why not add some way to directly use PEM-encoded
----BEGIN DH PARAMETERS-----
...END
parameters viaPEM_read_bio_DHparams
and a memory BIO, e.g. by overloadinggetDiffieHellman()
? E.g. RSA already reads keys in PEM format (via OpenSSL), and the natural format of new DiffieHellman Paramaters generated by (time-consuming!)openssl dhparams [bits]
is PEM, which currently has be converted manually to a format readable by nodejs...The text was updated successfully, but these errors were encountered: