Milestone 5: deliver embedded RDP sessions and lifecycle hardening

third_party/FreeRDP/winpr/libwinpr/crypto/rc4.c

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+/**
+ * WinPR: Windows Portable Runtime
+ * RC4 implementation for RDP
+ *
+ * Copyright 2023 Armin Novak <anovak@thincast.com>
+ * Copyright 2023 Thincast Technologies GmbH
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include <winpr/assert.h>
+#include <winpr/cast.h>
+
+#include "rc4.h"
+
+#define CTX_SIZE 256
+
+struct winpr_int_rc4_ctx
+{
+	size_t i;
+	size_t j;
+	BYTE s[CTX_SIZE];
+	BYTE t[CTX_SIZE];
+};
+
+static void swap(BYTE* p1, BYTE* p2)
+{
+	BYTE t = *p1;
+	*p1 = *p2;
+	*p2 = t;
+}
+
+winpr_int_RC4_CTX* winpr_int_rc4_new(const BYTE* key, size_t keylength)
+{
+	winpr_int_RC4_CTX* ctx = calloc(1, sizeof(winpr_int_RC4_CTX));
+	if (!ctx)
+		return nullptr;
+
+	for (size_t i = 0; i < CTX_SIZE; i++)
+	{
+		ctx->s[i] = WINPR_ASSERTING_INT_CAST(BYTE, i);
+		ctx->t[i] = key[i % keylength];
+	}
+
+	size_t j = 0;
+	for (size_t i = 0; i < CTX_SIZE; i++)
+	{
+		j = (j + ctx->s[i] + ctx->t[i]) % CTX_SIZE;
+		swap(&ctx->s[i], &ctx->s[j]);
+	}
+	return ctx;
+}
+
+void winpr_int_rc4_free(winpr_int_RC4_CTX* ctx)
+{
+	free(ctx);
+}
+
+BOOL winpr_int_rc4_update(winpr_int_RC4_CTX* ctx, size_t length, const BYTE* input, BYTE* output)
+{
+	WINPR_ASSERT(ctx);
+
+	size_t t1 = ctx->i;
+	size_t t2 = ctx->j;
+	for (size_t i = 0; i < length; i++)
+	{
+		t1 = (t1 + 1) % CTX_SIZE;
+		t2 = (t2 + ctx->s[t1]) % CTX_SIZE;
+		swap(&ctx->s[t1], &ctx->s[t2]);
+
+		const size_t idx = ((size_t)ctx->s[t1] + ctx->s[t2]) % CTX_SIZE;
+		const BYTE val = ctx->s[idx];
+		const BYTE out = *input++ ^ val;
+		*output++ = out;
+	}
+
+	ctx->i = t1;
+	ctx->j = t2;
+	return TRUE;
+}