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authorSverker Eriksson <[email protected]>2014-02-12 15:05:52 +0100
committerSverker Eriksson <[email protected]>2014-02-12 15:05:52 +0100
commit651b949d85f847318ece301b64c099ad7959e9d0 (patch)
treeee454d37c1ddddfa72247f7530a37da52a14c0d3 /lib/crypto/doc/src
parent4082c3d1ad3d0e8bb85706c5f3b2bde97bb43fcb (diff)
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crypto: Fix bug when using old hmac context
Symptom: Using an old context (that had already been passed as argument to either hmac_upgrade or hmac_final) could cause VM crash or worse. Reason: Only a shallow copy (memcpy) of the context was made causing a new context to partly mutate its parent context into an inconsistent state. Problem: Only OpenSSL v1.0 supports deep copy of hmac context. It is thus not possible to implement a functional interface for older OpenSSL versions (0.9.8) which still have wide spread use. Solution: Change hmac contexts into a mutable state using NIF resources. Document reuse of old contexts as undefined. Future: If a need for reusing old context variables arise, a new hmac_copy function could be introduced that is only supported for OpenSSL v1.0.
Diffstat (limited to 'lib/crypto/doc/src')
-rw-r--r--lib/crypto/doc/src/crypto.xml8
1 files changed, 6 insertions, 2 deletions
diff --git a/lib/crypto/doc/src/crypto.xml b/lib/crypto/doc/src/crypto.xml
index 40f829e704..c95827c371 100644
--- a/lib/crypto/doc/src/crypto.xml
+++ b/lib/crypto/doc/src/crypto.xml
@@ -4,7 +4,7 @@
<erlref>
<header>
<copyright>
- <year>1999</year><year>2013</year>
+ <year>1999</year><year>2014</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
@@ -366,7 +366,11 @@
or to one of the functions <seealso marker="#hmac_final-1">hmac_final</seealso> and
<seealso marker="#hmac_final_n-2">hmac_final_n</seealso>
</p>
-
+ <warning><p>Do not use a <c>Context</c> as argument in more than one
+ call to hmac_update or hmac_final. The semantics of reusing old contexts
+ in any way is undefined and could even crash the VM in earlier releases.
+ The reason for this limitation is a lack of support in the underlying
+ OpenSSL API.</p></warning>
</desc>
</func>