[PATCH v2 09/27] storage_backend_iscsi(_direct): Properly clear secrets

[Daniel P. Berrangé]

On Tue, Feb 02, 2021 at 05:55:46PM +0100, Peter Krempa wrote:
> The code pretends that it cares about clearing the secret values, but
> passes the secret value to a realloc, which may copy the value somewhere
> else and doesn't sanitize the original location when it does so.
> 
> Since we want to construct a string from the value, let's copy it to a
> new piece of memory which has the space for the 'NUL' byte ourselves, to
> prevent a random realloc keeping the data around.
> 
> While at it, use virSecureErase instead of VIR_DISPOSE_N since it's
> being phased out.
> 
> Signed-off-by: Peter Krempa <pkrempa at redhat.com>
> ---
>  src/storage/storage_backend_iscsi.c        | 16 +++++++++-------
>  src/storage/storage_backend_iscsi_direct.c | 17 +++++++++--------
>  2 files changed, 18 insertions(+), 15 deletions(-)


> diff --git a/src/storage/storage_backend_iscsi_direct.c b/src/storage/storage_backend_iscsi_direct.c
> index 12b075db0b..78b12f057f 100644
> --- a/src/storage/storage_backend_iscsi_direct.c
> +++ b/src/storage/storage_backend_iscsi_direct.c
> @@ -87,8 +87,9 @@ static int
>  virStorageBackendISCSIDirectSetAuth(struct iscsi_context *iscsi,
>                                      virStoragePoolSourcePtr source)
>  {
> -    unsigned char *secret_value = NULL;
> +    g_autofree unsigned char *secret_value = NULL;
>      size_t secret_size;
> +    g_autofree char *secret_str = NULL;
>      virStorageAuthDefPtr authdef = source->auth;
>      int ret = -1;
>      virConnectPtr conn = NULL;
> @@ -113,14 +114,13 @@ virStorageBackendISCSIDirectSetAuth(struct iscsi_context *iscsi,
>                                   &secret_value, &secret_size) < 0)
>          goto cleanup;
> 
> -    if (VIR_REALLOC_N(secret_value, secret_size + 1) < 0)
> -        goto cleanup;
> -
> -    secret_value[secret_size] = '\0';
> +    secret_str = g_new0(char, secret_size + 1);
> +    memcpy(secret_str, secret_value, secret_size);
> +    memset(secret_value, 0, secret_size);
> +    secret_str[secret_size] = '\0';
> 
>      if (iscsi_set_initiator_username_pwd(iscsi,
> -                                         authdef->username,
> -                                         (const char *)secret_value) < 0) {
> +                                         authdef->username, secret_str) < 0) {
>          virReportError(VIR_ERR_INTERNAL_ERROR,
>                         _("Failed to set credential: %s"),
>                         iscsi_get_error(iscsi));
> @@ -129,7 +129,8 @@ virStorageBackendISCSIDirectSetAuth(struct iscsi_context *iscsi,
> 
>      ret = 0;
>   cleanup:
> -    VIR_DISPOSE_N(secret_value, secret_size);
> +    if (secret_str)
> +        memset(secret_str, 0, secret_size);

virSecureErase surely ?

Reviewed-by: Daniel P. Berrangé <berrange at redhat.com>


Regards,
Daniel
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