Include a local static buffer for the SHA helper functions

This functionality existed in 1.1.1 but was lost.

Fixes #15718

Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/15752)

crypto/sha/sha1_one.c

@@ -37,25 +37,45 @@ unsigned char *ossl_sha1(const unsigned char *d, size_t n, unsigned char *md)
 
 unsigned char *SHA1(const unsigned char *d, size_t n, unsigned char *md)
 {
+    static unsigned char m[SHA_DIGEST_LENGTH];
+
+    if (md == NULL)
+        md = m;
     return EVP_Q_digest(NULL, "SHA1", NULL, d, n, md, NULL) ? md : NULL;
 }
 
 unsigned char *SHA224(const unsigned char *d, size_t n, unsigned char *md)
 {
+    static unsigned char m[SHA224_DIGEST_LENGTH];
+
+    if (md == NULL)
+        md = m;
     return EVP_Q_digest(NULL, "SHA224", NULL, d, n, md, NULL) ? md : NULL;
 }
 
 unsigned char *SHA256(const unsigned char *d, size_t n, unsigned char *md)
 {
+    static unsigned char m[SHA256_DIGEST_LENGTH];
+
+    if (md == NULL)
+        md = m;
     return EVP_Q_digest(NULL, "SHA256", NULL, d, n, md, NULL) ? md : NULL;
 }
 
 unsigned char *SHA384(const unsigned char *d, size_t n, unsigned char *md)
 {
+    static unsigned char m[SHA384_DIGEST_LENGTH];
+
+    if (md == NULL)
+        md = m;
     return EVP_Q_digest(NULL, "SHA384", NULL, d, n, md, NULL) ? md : NULL;
 }
 
 unsigned char *SHA512(const unsigned char *d, size_t n, unsigned char *md)
 {
+    static unsigned char m[SHA512_DIGEST_LENGTH];
+
+    if (md == NULL)
+        md = m;
     return EVP_Q_digest(NULL, "SHA512", NULL, d, n, md, NULL) ? md : NULL;
 }