diff options
authorStephan Mueller <smueller@chronox.de>2015-03-30 21:55:52 +0200
committerHerbert Xu <herbert@gondor.apana.org.au>2015-03-31 21:21:03 +0800
commit06ca7f68d4c861d549a8deb161e1527065a80bb1 (patch)
parentfa50d7ee45bfd6db66b38fc4930ce3cc3661b845 (diff)
crypto: api - prevent helper ciphers from being used
Several hardware related cipher implementations are implemented as follows: a "helper" cipher implementation is registered with the kernel crypto API. Such helper ciphers are never intended to be called by normal users. In some cases, calling them via the normal crypto API may even cause failures including kernel crashes. In a normal case, the "wrapping" ciphers that use the helpers ensure that these helpers are invoked such that they cannot cause any calamity. Considering the AF_ALG user space interface, unprivileged users can call all ciphers registered with the crypto API, including these helper ciphers that are not intended to be called directly. That means, with AF_ALG user space may invoke these helper ciphers and may cause undefined states or side effects. To avoid any potential side effects with such helpers, the patch prevents the helpers to be called directly. A new cipher type flag is added: CRYPTO_ALG_INTERNAL. This flag shall be used to mark helper ciphers. These ciphers can only be used if the caller invoke the cipher with CRYPTO_ALG_INTERNAL in the type and mask field. Signed-off-by: Stephan Mueller <smueller@chronox.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2 files changed, 16 insertions, 0 deletions
diff --git a/crypto/api.c b/crypto/api.c
index 2a81e98a0021..afe4610afc4b 100644
--- a/crypto/api.c
+++ b/crypto/api.c
@@ -257,6 +257,16 @@ struct crypto_alg *crypto_alg_mod_lookup(const char *name, u32 type, u32 mask)
+ /*
+ * If the internal flag is set for a cipher, require a caller to
+ * to invoke the cipher with the internal flag to use that cipher.
+ * Also, if a caller wants to allocate a cipher that may or may
+ * not be an internal cipher, use type | CRYPTO_ALG_INTERNAL and
+ * !(mask & CRYPTO_ALG_INTERNAL).
+ */
+ if (!((type | mask) & CRYPTO_ALG_INTERNAL))
larval = crypto_larval_lookup(name, type, mask);
if (IS_ERR(larval) || !crypto_is_larval(larval))
return larval;
diff --git a/include/linux/crypto.h b/include/linux/crypto.h
index fb5ef16d6a12..10df5d2d093a 100644
--- a/include/linux/crypto.h
+++ b/include/linux/crypto.h
@@ -95,6 +95,12 @@
#define CRYPTO_ALG_KERN_DRIVER_ONLY 0x00001000
+ * Mark a cipher as a service implementation only usable by another
+ * cipher and never by a normal user of the kernel crypto API
+ */
+#define CRYPTO_ALG_INTERNAL 0x00002000
* Transform masks and values (for crt_flags).
#define CRYPTO_TFM_REQ_MASK 0x000fff00

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