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-rw-r--r--crypto/drbg.c41
1 files changed, 22 insertions, 19 deletions
diff --git a/crypto/drbg.c b/crypto/drbg.c
index c9b4c4906d9b..dba5ed2f83b6 100644
--- a/crypto/drbg.c
+++ b/crypto/drbg.c
@@ -562,7 +562,21 @@ out:
return ret;
}
-/* update function of CTR DRBG as defined in 10.2.1.2 */
+/*
+ * update function of CTR DRBG as defined in 10.2.1.2
+ *
+ * The reseed variable has an enhanced meaning compared to the update
+ * functions of the other DRBGs as follows:
+ * 0 => initial seed from initialization
+ * 1 => reseed via drbg_seed
+ * 2 => first invocation from drbg_ctr_update when addtl is present. In
+ * this case, the df_data scratchpad is not deleted so that it is
+ * available for another calls to prevent calling the DF function
+ * again.
+ * 3 => second invocation from drbg_ctr_update. When the update function
+ * was called with addtl, the df_data memory already contains the
+ * DFed addtl information and we do not need to call DF again.
+ */
static int drbg_ctr_update(struct drbg_state *drbg, struct list_head *seed,
int reseed)
{
@@ -577,7 +591,8 @@ static int drbg_ctr_update(struct drbg_state *drbg, struct list_head *seed,
unsigned char prefix = DRBG_PREFIX1;
memset(temp, 0, drbg_statelen(drbg) + drbg_blocklen(drbg));
- memset(df_data, 0, drbg_statelen(drbg));
+ if (3 > reseed)
+ memset(df_data, 0, drbg_statelen(drbg));
/* 10.2.1.3.2 step 2 and 10.2.1.4.2 step 2 */
if (seed) {
@@ -619,7 +634,8 @@ static int drbg_ctr_update(struct drbg_state *drbg, struct list_head *seed,
out:
memset(temp, 0, drbg_statelen(drbg) + drbg_blocklen(drbg));
- memset(df_data, 0, drbg_statelen(drbg));
+ if (2 != reseed)
+ memset(df_data, 0, drbg_statelen(drbg));
return ret;
}
@@ -644,7 +660,7 @@ static int drbg_ctr_generate(struct drbg_state *drbg,
LIST_HEAD(addtllist);
list_add_tail(&addtl->list, &addtllist);
- ret = drbg_ctr_update(drbg, &addtllist, 1);
+ ret = drbg_ctr_update(drbg, &addtllist, 2);
if (ret)
return 0;
}
@@ -675,21 +691,8 @@ static int drbg_ctr_generate(struct drbg_state *drbg,
drbg_add_buf(drbg->V, drbg_blocklen(drbg), &prefix, 1);
}
- /*
- * 10.2.1.5.2 step 6
- * The following call invokes the DF function again which could be
- * optimized. In step 2, the "additional_input" after step 2 is the
- * output of the DF function. If this result would be saved, the DF
- * function would not need to be invoked again at this point.
- */
- if (addtl && 0 < addtl->len) {
- LIST_HEAD(addtllist);
-
- list_add_tail(&addtl->list, &addtllist);
- ret = drbg_ctr_update(drbg, &addtllist, 1);
- } else {
- ret = drbg_ctr_update(drbg, NULL, 1);
- }
+ /* 10.2.1.5.2 step 6 */
+ ret = drbg_ctr_update(drbg, NULL, 3);
if (ret)
len = ret;