various kdfs: Always reset buflen after clearing the buffer

Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/17165)

providers/implementations/kdfs/krb5kdf.c

@@ -98,6 +98,7 @@ static int krb5kdf_set_membuf(unsigned char **dst, size_t *dst_len,
 {
     OPENSSL_clear_free(*dst, *dst_len);
     *dst = NULL;
+    *dst_len = 0;
     return OSSL_PARAM_get_octet_string(p, (void **)dst, 0, dst_len);
 }
 

providers/implementations/kdfs/pbkdf1.c

@@ -134,13 +134,15 @@ static int kdf_pbkdf1_set_membuf(unsigned char **buffer, size_t *buflen,
                              const OSSL_PARAM *p)
 {
     OPENSSL_clear_free(*buffer, *buflen);
+    *buffer = NULL;
+    *buflen = 0;
+
     if (p->data_size == 0) {
         if ((*buffer = OPENSSL_malloc(1)) == NULL) {
             ERR_raise(ERR_LIB_PROV, ERR_R_MALLOC_FAILURE);
             return 0;
         }
     } else if (p->data != NULL) {
-        *buffer = NULL;
         if (!OSSL_PARAM_get_octet_string(p, (void **)buffer, 0, buflen))
             return 0;
     }

providers/implementations/kdfs/pbkdf2.c

@@ -126,13 +126,15 @@ static int pbkdf2_set_membuf(unsigned char **buffer, size_t *buflen,
                              const OSSL_PARAM *p)
 {
     OPENSSL_clear_free(*buffer, *buflen);
+    *buffer = NULL;
+    *buflen = 0;
+
     if (p->data_size == 0) {
         if ((*buffer = OPENSSL_malloc(1)) == NULL) {
             ERR_raise(ERR_LIB_PROV, ERR_R_MALLOC_FAILURE);
             return 0;
         }
     } else if (p->data != NULL) {
-        *buffer = NULL;
         if (!OSSL_PARAM_get_octet_string(p, (void **)buffer, 0, buflen))
             return 0;
     }

providers/implementations/kdfs/pkcs12kdf.c

@@ -182,13 +182,15 @@ static int pkcs12kdf_set_membuf(unsigned char **buffer, size_t *buflen,
                              const OSSL_PARAM *p)
 {
     OPENSSL_clear_free(*buffer, *buflen);
+    *buffer = NULL;
+    *buflen = 0;
+
     if (p->data_size == 0) {
         if ((*buffer = OPENSSL_malloc(1)) == NULL) {
             ERR_raise(ERR_LIB_PROV, ERR_R_MALLOC_FAILURE);
             return 0;
         }
     } else if (p->data != NULL) {
-        *buffer = NULL;
         if (!OSSL_PARAM_get_octet_string(p, (void **)buffer, 0, buflen))
             return 0;
     }

providers/implementations/kdfs/scrypt.c

@@ -108,13 +108,15 @@ static int scrypt_set_membuf(unsigned char **buffer, size_t *buflen,
                              const OSSL_PARAM *p)
 {
     OPENSSL_clear_free(*buffer, *buflen);
+    *buffer = NULL;
+    *buflen = 0;
+
     if (p->data_size == 0) {
         if ((*buffer = OPENSSL_malloc(1)) == NULL) {
             ERR_raise(ERR_LIB_PROV, ERR_R_MALLOC_FAILURE);
             return 0;
         }
     } else if (p->data != NULL) {
-        *buffer = NULL;
         if (!OSSL_PARAM_get_octet_string(p, (void **)buffer, 0, buflen))
             return 0;
     }

providers/implementations/kdfs/sshkdf.c

@@ -91,6 +91,7 @@ static int sshkdf_set_membuf(unsigned char **dst, size_t *dst_len,
 {
     OPENSSL_clear_free(*dst, *dst_len);
     *dst = NULL;
+    *dst_len = 0;
     return OSSL_PARAM_get_octet_string(p, (void **)dst, 0, dst_len);
 }