CRYPT_ArcFourSetup: don't use key[0] when length is 0
Bug: 686128
Change-Id: Ie8d71d7c0b76abb3f39ea2ea5ce43c82994a047a
Reviewed-on: https://pdfium-review.googlesource.com/4750
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>
diff --git a/core/fdrm/crypto/fx_crypt.cpp b/core/fdrm/crypto/fx_crypt.cpp
index aac4edb..f4ead91 100644
--- a/core/fdrm/crypto/fx_crypt.cpp
+++ b/core/fdrm/crypto/fx_crypt.cpp
@@ -6,6 +6,8 @@
#include "core/fdrm/crypto/fx_crypt.h"
+#include <utility>
+
#define GET_UINT32(n, b, i) \
{ \
(n) = (uint32_t)((uint8_t*)b)[(i)] | \
@@ -139,22 +141,15 @@
void CRYPT_ArcFourSetup(CRYPT_rc4_context* s,
const uint8_t* key,
uint32_t length) {
- int i, j, k, *m, a;
s->x = 0;
s->y = 0;
- m = s->m;
- for (i = 0; i < 256; i++) {
- m[i] = i;
- }
- j = k = 0;
- for (i = 0; i < 256; i++) {
- a = m[i];
- j = (j + a + key[k]) & 0xFF;
- m[i] = m[j];
- m[j] = a;
- if (++k >= (int)length) {
- k = 0;
- }
+ for (int i = 0; i < 256; ++i)
+ s->m[i] = i;
+
+ int j = 0;
+ for (int i = 0; i < 256; ++i) {
+ j = (j + s->m[i] + (length ? key[i % length] : 0)) & 0xFF;
+ std::swap(s->m[i], s->m[j]);
}
}
