From 361da15eed25e2c6800057aa29ac328af1d399a8 Mon Sep 17 00:00:00 2001
From: David Fort <contact@hardening-consulting.com>
Date: Wed, 16 Aug 2023 11:06:17 +0200
Subject: [PATCH] [crypto] extend base64 to output crLf when encoding

Some windows APIs do put \r\n every 64 characters of the output of a
base64 encoded blob. The extended version of crypto_base64_encode allows
to do the same.
---
 include/freerdp/crypto/crypto.h     |  2 ++
 libfreerdp/crypto/base64.c          | 35 +++++++++++++++++++++++++++--
 libfreerdp/crypto/test/TestBase64.c | 18 ++++++++++++++-
 3 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/include/freerdp/crypto/crypto.h b/include/freerdp/crypto/crypto.h
index b10ed79d0..6137769b9 100644
--- a/include/freerdp/crypto/crypto.h
+++ b/include/freerdp/crypto/crypto.h
@@ -39,6 +39,8 @@ extern "C"
 	typedef struct rdp_CertInfo rdpCertInfo;
 
 	FREERDP_API char* crypto_base64_encode(const BYTE* data, size_t length);
+	FREERDP_API char* crypto_base64_encode_ex(const BYTE* data, size_t length, BOOL withCrLf);
+
 	FREERDP_API void crypto_base64_decode(const char* enc_data, size_t length, BYTE** dec_data,
 	                                      size_t* res_length);
 
diff --git a/libfreerdp/crypto/base64.c b/libfreerdp/crypto/base64.c
index ef699133b..6bbd9bb24 100644
--- a/libfreerdp/crypto/base64.c
+++ b/libfreerdp/crypto/base64.c
@@ -26,7 +26,8 @@
 static const char base64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 static const char base64url[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
 
-static char* base64_encode(const char* alphabet, const BYTE* data, size_t length, BOOL pad)
+static char* base64_encode_ex(const char* alphabet, const BYTE* data, size_t length, BOOL pad,
+                              BOOL crLf, size_t lineSize)
 {
 	int c;
 	const BYTE* q;
@@ -34,9 +35,17 @@ static char* base64_encode(const char* alphabet, const BYTE* data, size_t length
 	char* ret;
 	int i = 0;
 	int blocks;
+	size_t outLen = (length + 3) * 4 / 3;
+	size_t extra = 0;
+	if (crLf)
+	{
+		size_t nCrLf = (outLen + lineSize - 1) / lineSize;
+		extra = nCrLf * 2;
+	}
+	size_t outCounter = 0;
 
 	q = data;
-	p = ret = (char*)malloc((length + 3) * 4 / 3 + 1);
+	p = ret = (char*)malloc(outLen + extra + 1);
 	if (!p)
 		return NULL;
 
@@ -62,6 +71,13 @@ static char* base64_encode(const char* alphabet, const BYTE* data, size_t length
 		*p++ = alphabet[(c & 0x0003F000) >> 12];
 		*p++ = alphabet[(c & 0x00000FC0) >> 6];
 		*p++ = alphabet[c & 0x0000003F];
+
+		outCounter += 4;
+		if (crLf && (outCounter % lineSize == 0))
+		{
+			*p++ = '\r';
+			*p++ = '\n';
+		}
 	}
 
 	/* then remainder */
@@ -89,11 +105,21 @@ static char* base64_encode(const char* alphabet, const BYTE* data, size_t length
 			break;
 	}
 
+	if (crLf && length % 3)
+	{
+		*p++ = '\r';
+		*p++ = '\n';
+	}
 	*p = 0;
 
 	return ret;
 }
 
+static char* base64_encode(const char* alphabet, const BYTE* data, size_t length, BOOL pad)
+{
+	return base64_encode_ex(alphabet, data, length, pad, FALSE, 64);
+}
+
 static int base64_decode_char(const char* alphabet, char c)
 {
 	char* p = NULL;
@@ -197,6 +223,11 @@ out_free:
 	return NULL;
 }
 
+char* crypto_base64_encode_ex(const BYTE* data, size_t length, BOOL withCrLf)
+{
+	return base64_encode_ex(base64, data, length, TRUE, withCrLf, 64);
+}
+
 char* crypto_base64_encode(const BYTE* data, size_t length)
 {
 	return base64_encode(base64, data, length, TRUE);
diff --git a/libfreerdp/crypto/test/TestBase64.c b/libfreerdp/crypto/test/TestBase64.c
index dde275e35..1c01df799 100644
--- a/libfreerdp/crypto/test/TestBase64.c
+++ b/libfreerdp/crypto/test/TestBase64.c
@@ -156,7 +156,23 @@ int TestBase64(int argc, char* argv[])
 		fprintf(stderr, "ko, = in a wrong place\n");
 		return -1;
 	}
-
 	fprintf(stderr, "ok\n");
+	testNb++;
+
+	/* test the encode_ex version that will add \r\n */
+	fprintf(stderr, "%d:encode base64 with crLf...", testNb);
+	const char* longStr = "01234567890123456789012345678901234567890123456789";
+	const char* longStrExpected =
+	    "MDEyMzQ1Njc4OTAxMjM0NTY3ODkwMTIzNDU2Nzg5MDEyMzQ1Njc4OTAxMjM0NTY3\r\nODk=\r\n";
+
+	char* encoded = crypto_base64_encode_ex((const BYTE*)longStr, strlen(longStr), TRUE);
+	if (!encoded || strcmp(encoded, longStrExpected) != 0)
+	{
+		fprintf(stderr, "problem with encode with CRLF\n");
+		return -1;
+	}
+	free(encoded);
+	fprintf(stderr, "ok\n");
+
 	return 0;
 }