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avformat/redspark: deobfuscate header decrypt code

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Signed-off-by: James Almer <jamrial@gmail.com>
This commit is contained in:
James Almer
2016-06-12 17:26:11 -03:00
parent 8fdad638f9
commit 15f9189b9c
1 changed files with 11 additions and 6 deletions
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17
libavformat/redspark.c
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@@ -26,6 +26,7 @@
#include "internal.h"
#define HEADER_SIZE 4096
#define rol(value, bits) (((value) << (bits)) | ((value) >> (32 - (bits))))
typedef struct RedSparkContext {
int samples_count;
@@ -38,11 +39,13 @@ static int redspark_probe(AVProbeData *p)
/* Decrypt first 8 bytes of the header */
data = AV_RB32(p->buf);
data = data ^ (key = data ^ 0x52656453);
key = data ^ 0x52656453;
data ^= key;
AV_WB32(header, data);
key = (key << 11) | (key >> 21);
key = rol(key, 11);
data = AV_RB32(p->buf + 4) ^ (((key << 3) | (key >> 29)) + key);
key += rol(key, 3);
data = AV_RB32(p->buf + 4) ^ key;
AV_WB32(header + 4, data);
if (AV_RB64(header) == AV_RB64("RedSpark"))
@@ -69,12 +72,14 @@ static int redspark_read_header(AVFormatContext *s)
/* Decrypt header */
data = avio_rb32(pb);
data = data ^ (key = data ^ 0x52656453);
key = data ^ 0x52656453;
data ^= key;
AV_WB32(header, data);
key = (key << 11) | (key >> 21);
key = rol(key, 11);
for (i = 4; i < HEADER_SIZE; i += 4) {
data = avio_rb32(pb) ^ (key = ((key << 3) | (key >> 29)) + key);
key += rol(key, 3);
data = avio_rb32(pb) ^ key;
AV_WB32(header + i, data);
}