static AesCtrState *
setup_aes_decrypt()
{
/* NIST SP800-38a section F.5.2; CTR-AES128 Decrypt */
const guint8 Key[]={ 0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6, 0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf, 0x4f, 0x3c };
const guint8 IV[] = { 0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff };
AesCtrState *state;
GstBuffer *gkey;
GBytes *giv;
gkey = gst_buffer_new_allocate (NULL,sizeof(Key),NULL);
fail_if(gkey==NULL);
gst_buffer_fill(gkey,0,Key,sizeof(Key));
giv = g_bytes_new_static(IV,sizeof(IV));
fail_if(giv==NULL);
state = gst_aes_ctr_decrypt_new(gkey, giv);
fail_if(state==NULL);
g_bytes_unref(giv);
gst_buffer_unref(gkey);
return state;
}
static GstFlowReturn
gst_cenc_decrypt_transform_ip (GstBaseTransform * base, GstBuffer * buf)
{
GstCencDecrypt *self = GST_CENC_DECRYPT (base);
GstFlowReturn ret = GST_FLOW_OK;
GstMapInfo map, iv_map;
const GstCencKeyPair *keypair;
const GstProtectionMeta *prot_meta = NULL;
guint pos = 0;
gint sample_index = 0;
guint subsample_count;
AesCtrState *state = NULL;
guint iv_size;
gboolean encrypted;
const GValue *value;
GstBuffer *key_id = NULL;
GstBuffer *iv_buf = NULL;
GBytes *iv_bytes = NULL;
GstBuffer *subsamples_buf = NULL;
GstMapInfo subsamples_map;
GstByteReader *reader=NULL;
GST_TRACE_OBJECT (self, "decrypt in-place");
prot_meta = (GstProtectionMeta*) gst_buffer_get_protection_meta (buf);
if (!prot_meta || !buf) {
if (!prot_meta) {
GST_ERROR_OBJECT (self, "Failed to get GstProtection metadata from buffer");
}
if (!buf) {
GST_ERROR_OBJECT (self, "Failed to get writable buffer");
}
ret = GST_FLOW_NOT_SUPPORTED;
goto out;
}
if (!gst_buffer_map (buf, &map, GST_MAP_READWRITE)) {
GST_ERROR_OBJECT (self, "Failed to map buffer");
ret = GST_FLOW_NOT_SUPPORTED;
goto release;
}
GST_TRACE_OBJECT (self, "decrypt sample %d", (gint)map.size);
if(!gst_structure_get_uint(prot_meta->info,"iv_size",&iv_size)){
GST_ERROR_OBJECT (self, "failed to get iv_size");
ret = GST_FLOW_NOT_SUPPORTED;
goto release;
}
if(!gst_structure_get_boolean(prot_meta->info,"encrypted",&encrypted)){
GST_ERROR_OBJECT (self, "failed to get encrypted flag");
ret = GST_FLOW_NOT_SUPPORTED;
goto release;
}
if (iv_size == 0 || !encrypted) {
/* sample is not encrypted */
goto beach;
}
GST_DEBUG_OBJECT (base, "protection meta: %" GST_PTR_FORMAT, prot_meta->info);
if(!gst_structure_get_uint(prot_meta->info,"subsample_count",&subsample_count)){
GST_ERROR_OBJECT (self, "failed to get subsample_count");
ret = GST_FLOW_NOT_SUPPORTED;
goto release;
}
value = gst_structure_get_value (prot_meta->info, "kid");
if(!value){
GST_ERROR_OBJECT (self, "Failed to get KID for sample");
ret = GST_FLOW_NOT_SUPPORTED;
goto release;
}
key_id = gst_value_get_buffer (value);
value = gst_structure_get_value (prot_meta->info, "iv");
if(!value){
GST_ERROR_OBJECT (self, "Failed to get IV for sample");
ret = GST_FLOW_NOT_SUPPORTED;
goto release;
}
iv_buf = gst_value_get_buffer (value);
if(!gst_buffer_map (iv_buf, &iv_map, GST_MAP_READ)){
GST_ERROR_OBJECT (self, "Failed to map IV");
ret = GST_FLOW_NOT_SUPPORTED;
goto release;
}
iv_bytes = g_bytes_new (iv_map.data, iv_map.size);
gst_buffer_unmap (iv_buf, &iv_map);
if(subsample_count){
value = gst_structure_get_value (prot_meta->info, "subsamples");
if(!value){
GST_ERROR_OBJECT (self, "Failed to get subsamples");
ret = GST_FLOW_NOT_SUPPORTED;
goto release;
}
subsamples_buf = gst_value_get_buffer (value);
if(!gst_buffer_map (subsamples_buf, &subsamples_map, GST_MAP_READ)){
GST_ERROR_OBJECT (self, "Failed to map subsample buffer");
ret = GST_FLOW_NOT_SUPPORTED;
goto release;
}
}
keypair = gst_cenc_decrypt_lookup_key (self,key_id);
if (!keypair) {
gsize sz;
GST_ERROR_OBJECT (self, "Failed to lookup key");
GST_MEMDUMP_OBJECT (self, "Key ID:",
g_bytes_get_data (keypair->key_id, &sz),
sz);
ret = GST_FLOW_NOT_SUPPORTED;
goto release;
}
state = gst_aes_ctr_decrypt_new (keypair->key, iv_bytes);
if (!state) {
GST_ERROR_OBJECT (self, "Failed to init AES cipher");
ret = GST_FLOW_NOT_SUPPORTED;
goto release;
}
if (subsample_count) {
reader = gst_byte_reader_new (subsamples_map.data, subsamples_map.size);
if(!reader){
GST_ERROR_OBJECT (self, "Failed to allocate subsample reader");
ret = GST_FLOW_NOT_SUPPORTED;
goto release;
}
}
while (pos < map.size) {
guint16 n_bytes_clear = 0;
guint32 n_bytes_encrypted = 0;
if (sample_index < subsample_count) {
if (!gst_byte_reader_get_uint16_be (reader, &n_bytes_clear)
|| !gst_byte_reader_get_uint32_be (reader, &n_bytes_encrypted)) {
ret = GST_FLOW_NOT_SUPPORTED;
goto release;
}
sample_index++;
} else {
n_bytes_clear = 0;
n_bytes_encrypted = map.size - pos;
}
GST_TRACE_OBJECT (self, "%u bytes clear (todo=%d)", n_bytes_clear,
(gint)map.size - pos);
pos += n_bytes_clear;
if (n_bytes_encrypted) {
GST_TRACE_OBJECT (self, "%u bytes encrypted (todo=%d)",
n_bytes_encrypted, (gint)map.size - pos);
gst_aes_ctr_decrypt_ip (state, map.data + pos, n_bytes_encrypted);
pos += n_bytes_encrypted;
}
}
beach:
gst_buffer_unmap (buf, &map);
if (state) {
gst_aes_ctr_decrypt_unref (state);
}
release:
if (reader){
gst_byte_reader_free (reader);
}
if(subsamples_buf){
gst_buffer_unmap (subsamples_buf, &subsamples_map);
}
if (prot_meta) {
gst_buffer_remove_meta (buf, (GstMeta *) prot_meta);
}
if (iv_bytes) {
g_bytes_unref (iv_bytes);
}
out:
return ret;
}