[RFC PATCH v2 3/4] crypto: dh - allow user to provide NULL privkey

[Tudor Ambarus]

If the user provides a NULL private key, the kernel will
generate it and further use it for dh.

Signed-off-by: Tudor Ambarus <tudor.amba...@microchip.com>
---
 crypto/dh.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/crypto/dh.c b/crypto/dh.c
index 87e3542..7b4ac5b 100644
--- a/crypto/dh.c
+++ b/crypto/dh.c
@@ -83,7 +83,9 @@ static int dh_set_secret(struct crypto_kpp *tfm, const void 
*buf,
                         unsigned int len)
 {
        struct dh_ctx *ctx = dh_get_ctx(tfm);
+       u8 *rndbuf = NULL;
        struct dh params;
+       int maxsize;
 
        if (crypto_dh_decode_key(buf, len, &params) < 0)
                return -EINVAL;
@@ -91,7 +93,26 @@ static int dh_set_secret(struct crypto_kpp *tfm, const void 
*buf,
        if (dh_set_params(ctx, &params) < 0)
                return -EINVAL;
 
+       if (!params.key || !params.key_size) {
+               maxsize = crypto_kpp_maxsize(tfm);
+               if (maxsize < 0) {
+                       dh_clear_params(ctx);
+                       return maxsize;
+               }
+
+               rndbuf = kmalloc(maxsize, GFP_KERNEL);
+               if (!rndbuf) {
+                       dh_clear_params(ctx);
+                       return -ENOMEM;
+               }
+
+               get_random_bytes(rndbuf, maxsize);
+               params.key = rndbuf;
+               params.key_size = maxsize;
+       }
+
        ctx->xa = mpi_read_raw_data(params.key, params.key_size);
+       kzfree(rndbuf);
        if (!ctx->xa) {
                dh_clear_params(ctx);
                return -EINVAL;
-- 
2.7.4