checksum.c: Use the EVP API to compute the MD5 checksum

As MD5 function has been marked as deprecated in OpenSSL 3.0, this change
uses EVP (Envelope) API to compute the MD5 checksum.
Reference:
https://www.openssl.org/docs/man1.0.2/man3/EVP_md5.html

Fixes: gluster#4243
Signed-off-by: root <root@li-9b8608cc-32eb-11b2-a85c-953d7297bf45.ibm.com>

libglusterfs/src/checksum.c

@@ -8,7 +8,7 @@
   cases as published by the Free Software Foundation.
 */
 
-#include <openssl/md5.h>
+#include <openssl/evp.h>
 #include <openssl/sha.h>
 #include <zlib.h>
 #include <stdint.h>
@@ -40,5 +40,13 @@ gf_rsync_strong_checksum(unsigned char *data, size_t len,
 void
 gf_rsync_md5_checksum(unsigned char *data, size_t len, unsigned char *md5)
 {
-    MD5(data, len, md5);
+    EVP_MD_CTX *mdctx;
+    // Use the MD5 digest algorithm
+    const EVP_MD *md = EVP_md5();
+
+    mdctx = EVP_MD_CTX_new();
+    EVP_DigestInit_ex(mdctx, md, NULL);
+    EVP_DigestUpdate(mdctx, data, len);
+    EVP_DigestFinal_ex(mdctx, md5, NULL);
+    EVP_MD_CTX_free(mdctx);
 }