Simplify context reuse protection in mbedtls_sha3_starts

gilles-peskine-arm · gilles-peskine-arm · commit 4c973cfdfdeb · 2026-01-19T13:12:46.000+01:00
Signed-off-by: Gilles Peskine &lt;Gilles.Peskine@arm.com&gt;
diff --git a/drivers/builtin/src/sha3.c b/drivers/builtin/src/sha3.c
@@ -270,6 +270,9 @@ void mbedtls_sha3_clone(mbedtls_sha3_context *dst,
  */
 int mbedtls_sha3_starts(mbedtls_sha3_context *ctx, mbedtls_sha3_id id)
 {
+    /* Clean up in case the context is being reused */
+    memset(ctx, 0, sizeof(*ctx));
+
     switch (id) {
 #if defined(MBEDTLS_PSA_BUILTIN_ALG_SHA3_224)
         case MBEDTLS_SHA3_224:
@@ -315,10 +318,6 @@ int mbedtls_sha3_starts(mbedtls_sha3_context *ctx, mbedtls_sha3_id id)
             return MBEDTLS_ERR_SHA3_BAD_INPUT_DATA;
     }
 
-    memset(ctx->state, 0, sizeof(ctx->state));
-    ctx->index = 0;
-    ctx->finished = 0;
-
     return 0;
 }
 

Original file line number	Diff line number	Diff line change
`@@ -270,6 +270,9 @@ void mbedtls_sha3_clone(mbedtls_sha3_context *dst,`
`270`	`270`	`*/`
`271`	`271`	`int mbedtls_sha3_starts(mbedtls_sha3_context *ctx, mbedtls_sha3_id id)`
`272`	`272`	`{`
	`273`	`+ /* Clean up in case the context is being reused */`
	`274`	`+ memset(ctx, 0, sizeof(*ctx));`
	`275`	`+`
`273`	`276`	`switch (id) {`
`274`	`277`	`#if defined(MBEDTLS_PSA_BUILTIN_ALG_SHA3_224)`
`275`	`278`	`case MBEDTLS_SHA3_224:`
`@@ -315,10 +318,6 @@ int mbedtls_sha3_starts(mbedtls_sha3_context *ctx, mbedtls_sha3_id id)`
`315`	`318`	`return MBEDTLS_ERR_SHA3_BAD_INPUT_DATA;`
`316`	`319`	`}`
`317`	`320`
`318`		`- memset(ctx->state, 0, sizeof(ctx->state));`
`319`		`- ctx->index = 0;`
`320`		`- ctx->finished = 0;`
`321`		`-`
`322`	`321`	`return 0;`
`323`	`322`	`}`
`324`	`323`