diff --git a/docs/HACKING-CRYPTO b/docs/HACKING-CRYPTO
index bce5d215..e075f36b 100644
--- a/docs/HACKING-CRYPTO
+++ b/docs/HACKING-CRYPTO
@@ -63,27 +63,21 @@ libssh2_hmac_ctx
 Type of an HMAC computation context. Generally a struct.
 Used for all hash algorithms.
 
-void libssh2_hmac_ctx_init(libssh2_hmac_ctx ctx);
+int _libssh2_hmac_ctx_init(libssh2_hmac_ctx *ctx);
 Initializes the HMAC computation context ctx.
 Called before setting-up the hash algorithm.
-Note: if the ctx parameter is modified by the underlying code,
-this procedure must be implemented as a macro to map ctx --> &ctx.
+Must return 1 for success and 0 for failure.
 
-void libssh2_hmac_update(libssh2_hmac_ctx ctx,
-                         const unsigned char *data,
-                         int datalen);
+int _libssh2_hmac_update(libssh2_hmac_ctx *ctx,
+                         const void *data, int datalen);
 Continue computation of an HMAC on datalen bytes at data using context ctx.
-Note: if the ctx parameter is modified by the underlying code,
-this procedure must be implemented as a macro to map ctx --> &ctx.
 
-void libssh2_hmac_final(libssh2_hmac_ctx ctx,
-                        unsigned char output[]);
+int _libssh2_hmac_final(libssh2_hmac_ctx *ctx,
+                        void output[]);
 Get the computed HMAC from context ctx into the output buffer. The
 minimum data buffer size depends on the HMAC hash algorithm.
-Note: if the ctx parameter is modified by the underlying code,
-this procedure must be implemented as a macro to map ctx --> &ctx.
 
-void libssh2_hmac_cleanup(libssh2_hmac_ctx *ctx);
+void _libssh2_hmac_cleanup(libssh2_hmac_ctx *ctx);
 Releases the HMAC computation context at ctx.
 
 
diff --git a/include/libssh2.h b/include/libssh2.h
index 123a2fdb..7b313bd8 100644
--- a/include/libssh2.h
+++ b/include/libssh2.h
@@ -587,6 +587,7 @@ typedef struct _LIBSSH2_POLLFD {
 #define LIBSSH2_ERROR_RANDGEN                   -49
 #define LIBSSH2_ERROR_MISSING_USERAUTH_BANNER   -50
 #define LIBSSH2_ERROR_ALGO_UNSUPPORTED          -51
+#define LIBSSH2_ERROR_MAC_FAILURE               -52
 
 /* this is a define to provide the old (<= 1.2.7) name */
 #define LIBSSH2_ERROR_BANNER_NONE LIBSSH2_ERROR_BANNER_RECV
diff --git a/src/crypto.h b/src/crypto.h
index 2dda8e50..48744414 100644
--- a/src/crypto.h
+++ b/src/crypto.h
@@ -55,6 +55,27 @@
 #error "no cryptography backend selected"
 #endif
 
+/* return: success = 1, error = 0 */
+int _libssh2_hmac_ctx_init(libssh2_hmac_ctx *ctx);
+#if LIBSSH2_MD5
+int _libssh2_hmac_md5_init(libssh2_hmac_ctx *ctx,
+                           void *key, size_t keylen);
+#endif
+#if LIBSSH2_HMAC_RIPEMD
+int _libssh2_hmac_ripemd160_init(libssh2_hmac_ctx *ctx,
+                                 void *key, size_t keylen);
+#endif
+int _libssh2_hmac_sha1_init(libssh2_hmac_ctx *ctx,
+                            void *key, size_t keylen);
+int _libssh2_hmac_sha256_init(libssh2_hmac_ctx *ctx,
+                              void *key, size_t keylen);
+int _libssh2_hmac_sha512_init(libssh2_hmac_ctx *ctx,
+                              void *key, size_t keylen);
+int _libssh2_hmac_update(libssh2_hmac_ctx *ctx,
+                         const void *data, size_t datalen);
+int _libssh2_hmac_final(libssh2_hmac_ctx *ctx, void *data);
+void _libssh2_hmac_cleanup(libssh2_hmac_ctx *ctx);
+
 #define LIBSSH2_ED25519_KEY_LEN 32
 #define LIBSSH2_ED25519_PRIVATE_KEY_LEN 64
 #define LIBSSH2_ED25519_SIG_LEN 64
diff --git a/src/knownhost.c b/src/knownhost.c
index ee23bf20..5eba6a10 100644
--- a/src/knownhost.c
+++ b/src/knownhost.c
@@ -421,19 +421,23 @@ knownhost_check(LIBSSH2_KNOWNHOSTS *hosts,
                     */
                     unsigned char hash[SHA_DIGEST_LENGTH];
                     libssh2_hmac_ctx ctx;
-                    libssh2_hmac_ctx_init(ctx);
+                    if(!_libssh2_hmac_ctx_init(&ctx))
+                        break;
 
                     if(SHA_DIGEST_LENGTH != node->name_len) {
                         /* the name hash length must be the sha1 size or
                            we can't match it */
                         break;
                     }
-                    libssh2_hmac_sha1_init(&ctx, (unsigned char *)node->salt,
-                                           node->salt_len);
-                    libssh2_hmac_update(ctx, (unsigned char *)host,
-                                        strlen(host));
-                    libssh2_hmac_final(ctx, hash);
-                    libssh2_hmac_cleanup(&ctx);
+                    if(!_libssh2_hmac_sha1_init(&ctx,
+                                                node->salt, node->salt_len))
+                        break;
+                    if(!_libssh2_hmac_update(&ctx, host, strlen(host)) ||
+                       !_libssh2_hmac_final(&ctx, hash)) {
+                        _libssh2_hmac_cleanup(&ctx);
+                        break;
+                    }
+                    _libssh2_hmac_cleanup(&ctx);
 
                     if(!memcmp(hash, node->name, SHA_DIGEST_LENGTH))
                         /* this is a node we're interested in */
diff --git a/src/libgcrypt.c b/src/libgcrypt.c
index e463d9e3..b0f26b51 100644
--- a/src/libgcrypt.c
+++ b/src/libgcrypt.c
@@ -40,6 +40,105 @@
 
 #ifdef LIBSSH2_CRYPTO_C /* Compile this via crypto.c */
 
+int _libssh2_hmac_ctx_init(libssh2_hmac_ctx *ctx)
+{
+    *ctx = NULL;
+    return 1;
+}
+
+#if LIBSSH2_MD5
+int _libssh2_hmac_md5_init(libssh2_hmac_ctx *ctx,
+                           void *key, size_t keylen)
+{
+    gcry_error_t err;
+    err = gcry_md_open(ctx, GCRY_MD_MD5, GCRY_MD_FLAG_HMAC);
+    if(gcry_err_code(err) != GPG_ERR_NO_ERROR)
+        return 0;
+    err = gcry_md_setkey(*ctx, key, keylen);
+    if(gcry_err_code(err) != GPG_ERR_NO_ERROR)
+        return 0;
+    return 1;
+}
+#endif
+
+#if LIBSSH2_HMAC_RIPEMD
+int _libssh2_hmac_ripemd160_init(libssh2_hmac_ctx *ctx,
+                                 void *key, size_t keylen)
+{
+    gcry_error_t err;
+    err = gcry_md_open(ctx, GCRY_MD_RMD160, GCRY_MD_FLAG_HMAC);
+    if(gcry_err_code(err) != GPG_ERR_NO_ERROR)
+        return 0;
+    err = gcry_md_setkey(*ctx, key, keylen);
+    if(gcry_err_code(err) != GPG_ERR_NO_ERROR)
+        return 0;
+    return 1;
+}
+#endif
+
+int _libssh2_hmac_sha1_init(libssh2_hmac_ctx *ctx,
+                            void *key, size_t keylen)
+{
+    gcry_error_t err;
+    err = gcry_md_open(ctx, GCRY_MD_SHA1, GCRY_MD_FLAG_HMAC);
+    if(gcry_err_code(err) != GPG_ERR_NO_ERROR)
+        return 0;
+    err = gcry_md_setkey(*ctx, key, keylen);
+    if(gcry_err_code(err) != GPG_ERR_NO_ERROR)
+        return 0;
+    return 1;
+}
+
+int _libssh2_hmac_sha256_init(libssh2_hmac_ctx *ctx,
+                              void *key, size_t keylen)
+{
+    gcry_error_t err;
+    err = gcry_md_open(ctx, GCRY_MD_SHA256, GCRY_MD_FLAG_HMAC);
+    if(gcry_err_code(err) != GPG_ERR_NO_ERROR)
+        return 0;
+    err = gcry_md_setkey(*ctx, key, keylen);
+    if(gcry_err_code(err) != GPG_ERR_NO_ERROR)
+        return 0;
+    return 1;
+}
+
+int _libssh2_hmac_sha512_init(libssh2_hmac_ctx *ctx,
+                              void *key, size_t keylen)
+{
+    gcry_error_t err;
+    err = gcry_md_open(ctx, GCRY_MD_SHA512, GCRY_MD_FLAG_HMAC);
+    if(gcry_err_code(err) != GPG_ERR_NO_ERROR)
+        return 0;
+    err = gcry_md_setkey(*ctx, key, keylen);
+    if(gcry_err_code(err) != GPG_ERR_NO_ERROR)
+        return 0;
+    return 1;
+}
+
+int _libssh2_hmac_update(libssh2_hmac_ctx *ctx,
+                         const void *data, size_t datalen)
+{
+    gcry_md_write(*ctx, data, datalen);
+    return 1;
+}
+
+int _libssh2_hmac_final(libssh2_hmac_ctx *ctx, void *data)
+{
+    unsigned char *res = gcry_md_read(*ctx, 0);
+
+    if(!res)
+        return 0;
+
+    memcpy(data, res, gcry_md_get_algo_dlen(gcry_md_get_algo(*ctx)));
+
+    return 1;
+}
+
+void _libssh2_hmac_cleanup(libssh2_hmac_ctx *ctx)
+{
+    gcry_md_close(*ctx);
+}
+
 #if LIBSSH2_RSA
 int
 _libssh2_rsa_new(libssh2_rsa_ctx ** rsa,
diff --git a/src/libgcrypt.h b/src/libgcrypt.h
index 22b7724e..09dd91c6 100644
--- a/src/libgcrypt.h
+++ b/src/libgcrypt.h
@@ -144,30 +144,6 @@
 #endif
 
 #define libssh2_hmac_ctx gcry_md_hd_t
-#define libssh2_hmac_ctx_init(ctx)
-#define libssh2_hmac_sha1_init(ctx, key, keylen) \
-    gcry_md_open(ctx, GCRY_MD_SHA1, GCRY_MD_FLAG_HMAC), \
-    gcry_md_setkey(*ctx, key, keylen)
-#if LIBSSH2_MD5
-#define libssh2_hmac_md5_init(ctx, key, keylen) \
-    gcry_md_open(ctx, GCRY_MD_MD5, GCRY_MD_FLAG_HMAC), \
-    gcry_md_setkey(*ctx, key, keylen)
-#endif
-#define libssh2_hmac_ripemd160_init(ctx, key, keylen) \
-    gcry_md_open(ctx, GCRY_MD_RMD160, GCRY_MD_FLAG_HMAC), \
-    gcry_md_setkey(*ctx, key, keylen)
-#define libssh2_hmac_sha256_init(ctx, key, keylen) \
-    gcry_md_open(ctx, GCRY_MD_SHA256, GCRY_MD_FLAG_HMAC), \
-    gcry_md_setkey(*ctx, key, keylen)
-#define libssh2_hmac_sha512_init(ctx, key, keylen) \
-    gcry_md_open(ctx, GCRY_MD_SHA512, GCRY_MD_FLAG_HMAC), \
-    gcry_md_setkey(*ctx, key, keylen)
-#define libssh2_hmac_update(ctx, data, datalen) \
-    gcry_md_write(ctx, (unsigned char *) data, datalen)
-#define libssh2_hmac_final(ctx, data) \
-    memcpy(data, gcry_md_read(ctx, 0), \
-           gcry_md_get_algo_dlen(gcry_md_get_algo(ctx)))
-#define libssh2_hmac_cleanup(ctx) gcry_md_close(*ctx)
 
 #define libssh2_crypto_init() gcry_control(GCRYCTL_DISABLE_SECMEM)
 #define libssh2_crypto_exit()
diff --git a/src/mac.c b/src/mac.c
index db6f57a4..03ecd329 100644
--- a/src/mac.c
+++ b/src/mac.c
@@ -124,23 +124,27 @@ mac_method_hmac_sha2_512_hash(LIBSSH2_SESSION * session,
 {
     libssh2_hmac_ctx ctx;
     unsigned char seqno_buf[4];
+    int res;
     (void)session;
 
     _libssh2_htonu32(seqno_buf, seqno);
 
-    libssh2_hmac_ctx_init(ctx);
-    libssh2_hmac_sha512_init(&ctx, *abstract, 64);
-    libssh2_hmac_update(ctx, seqno_buf, 4);
-    libssh2_hmac_update(ctx, packet, packet_len);
-    if(addtl && addtl_len) {
-        libssh2_hmac_update(ctx, addtl, addtl_len);
-    }
-    libssh2_hmac_final(ctx, buf);
-    libssh2_hmac_cleanup(&ctx);
+    if(!_libssh2_hmac_ctx_init(&ctx))
+        return 1;
+    res = _libssh2_hmac_sha512_init(&ctx, *abstract, 64) &&
+          _libssh2_hmac_update(&ctx, seqno_buf, 4) &&
+          _libssh2_hmac_update(&ctx, packet, packet_len);
+    if(res && addtl && addtl_len)
+        res = _libssh2_hmac_update(&ctx, addtl, addtl_len);
+    if(res)
+        res = _libssh2_hmac_final(&ctx, buf);
+    _libssh2_hmac_cleanup(&ctx);
 
-    return 0;
+    return !res;
 }
 
+
+
 static const LIBSSH2_MAC_METHOD mac_method_hmac_sha2_512 = {
     "hmac-sha2-512",
     64,
@@ -179,21 +183,23 @@ mac_method_hmac_sha2_256_hash(LIBSSH2_SESSION * session,
 {
     libssh2_hmac_ctx ctx;
     unsigned char seqno_buf[4];
+    int res;
     (void)session;
 
     _libssh2_htonu32(seqno_buf, seqno);
 
-    libssh2_hmac_ctx_init(ctx);
-    libssh2_hmac_sha256_init(&ctx, *abstract, 32);
-    libssh2_hmac_update(ctx, seqno_buf, 4);
-    libssh2_hmac_update(ctx, packet, packet_len);
-    if(addtl && addtl_len) {
-        libssh2_hmac_update(ctx, addtl, addtl_len);
-    }
-    libssh2_hmac_final(ctx, buf);
-    libssh2_hmac_cleanup(&ctx);
+    if(!_libssh2_hmac_ctx_init(&ctx))
+        return 1;
+    res = _libssh2_hmac_sha256_init(&ctx, *abstract, 32) &&
+          _libssh2_hmac_update(&ctx, seqno_buf, 4) &&
+          _libssh2_hmac_update(&ctx, packet, packet_len);
+    if(res && addtl && addtl_len)
+        res = _libssh2_hmac_update(&ctx, addtl, addtl_len);
+    if(res)
+        res = _libssh2_hmac_final(&ctx, buf);
+    _libssh2_hmac_cleanup(&ctx);
 
-    return 0;
+    return !res;
 }
 
 
@@ -236,21 +242,23 @@ mac_method_hmac_sha1_hash(LIBSSH2_SESSION * session,
 {
     libssh2_hmac_ctx ctx;
     unsigned char seqno_buf[4];
+    int res;
     (void)session;
 
     _libssh2_htonu32(seqno_buf, seqno);
 
-    libssh2_hmac_ctx_init(ctx);
-    libssh2_hmac_sha1_init(&ctx, *abstract, 20);
-    libssh2_hmac_update(ctx, seqno_buf, 4);
-    libssh2_hmac_update(ctx, packet, packet_len);
-    if(addtl && addtl_len) {
-        libssh2_hmac_update(ctx, addtl, addtl_len);
-    }
-    libssh2_hmac_final(ctx, buf);
-    libssh2_hmac_cleanup(&ctx);
+    if(!_libssh2_hmac_ctx_init(&ctx))
+        return 1;
+    res = _libssh2_hmac_sha1_init(&ctx, *abstract, 20) &&
+          _libssh2_hmac_update(&ctx, seqno_buf, 4) &&
+          _libssh2_hmac_update(&ctx, packet, packet_len);
+    if(res && addtl && addtl_len)
+        res = _libssh2_hmac_update(&ctx, addtl, addtl_len);
+    if(res)
+        res = _libssh2_hmac_final(&ctx, buf);
+    _libssh2_hmac_cleanup(&ctx);
 
-    return 0;
+    return !res;
 }
 
 
@@ -288,10 +296,11 @@ mac_method_hmac_sha1_96_hash(LIBSSH2_SESSION * session,
 {
     unsigned char temp[SHA_DIGEST_LENGTH];
 
-    mac_method_hmac_sha1_hash(session, temp, seqno, packet, packet_len,
-                              addtl, addtl_len, abstract);
-    memcpy(buf, (char *) temp, 96 / 8);
+    if(mac_method_hmac_sha1_hash(session, temp, seqno, packet, packet_len,
+                                 addtl, addtl_len, abstract))
+        return 1;
 
+    memcpy(buf, (char *) temp, 96 / 8);
     return 0;
 }
 
@@ -321,21 +330,23 @@ mac_method_hmac_md5_hash(LIBSSH2_SESSION * session, unsigned char *buf,
 {
     libssh2_hmac_ctx ctx;
     unsigned char seqno_buf[4];
+    int res;
     (void)session;
 
     _libssh2_htonu32(seqno_buf, seqno);
 
-    libssh2_hmac_ctx_init(ctx);
-    libssh2_hmac_md5_init(&ctx, *abstract, 16);
-    libssh2_hmac_update(ctx, seqno_buf, 4);
-    libssh2_hmac_update(ctx, packet, packet_len);
-    if(addtl && addtl_len) {
-        libssh2_hmac_update(ctx, addtl, addtl_len);
-    }
-    libssh2_hmac_final(ctx, buf);
-    libssh2_hmac_cleanup(&ctx);
+    if(!_libssh2_hmac_ctx_init(&ctx))
+        return 1;
+    res = _libssh2_hmac_md5_init(&ctx, *abstract, 16) &&
+          _libssh2_hmac_update(&ctx, seqno_buf, 4) &&
+          _libssh2_hmac_update(&ctx, packet, packet_len);
+    if(res && addtl && addtl_len)
+        res = _libssh2_hmac_update(&ctx, addtl, addtl_len);
+    if(res)
+        res = _libssh2_hmac_final(&ctx, buf);
+    _libssh2_hmac_cleanup(&ctx);
 
-    return 0;
+    return !res;
 }
 
 
@@ -362,8 +373,11 @@ mac_method_hmac_md5_96_hash(LIBSSH2_SESSION * session,
                             size_t addtl_len, void **abstract)
 {
     unsigned char temp[MD5_DIGEST_LENGTH];
-    mac_method_hmac_md5_hash(session, temp, seqno, packet, packet_len,
-                             addtl, addtl_len, abstract);
+
+    if(mac_method_hmac_md5_hash(session, temp, seqno, packet, packet_len,
+                                addtl, addtl_len, abstract))
+        return 1;
+
     memcpy(buf, (char *) temp, 96 / 8);
     return 0;
 }
@@ -396,21 +410,23 @@ mac_method_hmac_ripemd160_hash(LIBSSH2_SESSION * session,
 {
     libssh2_hmac_ctx ctx;
     unsigned char seqno_buf[4];
+    int res;
     (void)session;
 
     _libssh2_htonu32(seqno_buf, seqno);
 
-    libssh2_hmac_ctx_init(ctx);
-    libssh2_hmac_ripemd160_init(&ctx, *abstract, 20);
-    libssh2_hmac_update(ctx, seqno_buf, 4);
-    libssh2_hmac_update(ctx, packet, packet_len);
-    if(addtl && addtl_len) {
-        libssh2_hmac_update(ctx, addtl, addtl_len);
-    }
-    libssh2_hmac_final(ctx, buf);
-    libssh2_hmac_cleanup(&ctx);
+    if(!_libssh2_hmac_ctx_init(&ctx))
+        return 1;
+    res = _libssh2_hmac_ripemd160_init(&ctx, *abstract, 20) &&
+          _libssh2_hmac_update(&ctx, seqno_buf, 4) &&
+          _libssh2_hmac_update(&ctx, packet, packet_len);
+    if(res && addtl && addtl_len)
+        res = _libssh2_hmac_update(&ctx, addtl, addtl_len);
+    if(res)
+        res = _libssh2_hmac_final(&ctx, buf);
+    _libssh2_hmac_cleanup(&ctx);
 
-    return 0;
+    return !res;
 }
 
 
diff --git a/src/mbedtls.c b/src/mbedtls.c
index 8d1f7bc3..c7cdae62 100644
--- a/src/mbedtls.c
+++ b/src/mbedtls.c
@@ -238,6 +238,66 @@ _libssh2_mbedtls_hash(const unsigned char *data, size_t datalen,
     return ret == 0 ? 0 : -1;
 }
 
+int _libssh2_hmac_ctx_init(libssh2_hmac_ctx *ctx)
+{
+    memset(ctx, 0, sizeof(*ctx));
+    return 1;
+}
+
+#if LIBSSH2_MD5
+int _libssh2_hmac_md5_init(libssh2_hmac_ctx *ctx,
+                           void *key, size_t keylen)
+{
+    return _libssh2_mbedtls_hash_init(ctx, MBEDTLS_MD_MD5, key, keylen);
+}
+#endif
+
+#if LIBSSH2_HMAC_RIPEMD
+int _libssh2_hmac_ripemd160_init(libssh2_hmac_ctx *ctx,
+                                 void *key, size_t keylen)
+{
+    return _libssh2_mbedtls_hash_init(ctx, MBEDTLS_MD_RIPEMD160, key, keylen);
+}
+#endif
+
+int _libssh2_hmac_sha1_init(libssh2_hmac_ctx *ctx,
+                            void *key, size_t keylen)
+{
+    return _libssh2_mbedtls_hash_init(ctx, MBEDTLS_MD_SHA1, key, keylen);
+}
+
+int _libssh2_hmac_sha256_init(libssh2_hmac_ctx *ctx,
+                              void *key, size_t keylen)
+{
+    return _libssh2_mbedtls_hash_init(ctx, MBEDTLS_MD_SHA256, key, keylen);
+}
+
+int _libssh2_hmac_sha512_init(libssh2_hmac_ctx *ctx,
+                              void *key, size_t keylen)
+{
+    return _libssh2_mbedtls_hash_init(ctx, MBEDTLS_MD_SHA512, key, keylen);
+}
+
+int _libssh2_hmac_update(libssh2_hmac_ctx *ctx,
+                         const void *data, size_t datalen)
+{
+    int ret = mbedtls_md_hmac_update(ctx, data, datalen);
+
+    return ret == 0 ? 1 : 0;
+}
+
+int _libssh2_hmac_final(libssh2_hmac_ctx *ctx, void *data)
+{
+    int ret = mbedtls_md_hmac_finish(ctx, data);
+
+    return ret == 0 ? 1 : 0;
+}
+
+void _libssh2_hmac_cleanup(libssh2_hmac_ctx *ctx)
+{
+    mbedtls_md_free(ctx);
+}
+
 /*******************************************************************/
 /*
  * mbedTLS backend: BigNumber functions
diff --git a/src/mbedtls.h b/src/mbedtls.h
index 05fe86c0..1175c1a9 100644
--- a/src/mbedtls.h
+++ b/src/mbedtls.h
@@ -147,29 +147,6 @@
 
 #define libssh2_hmac_ctx    mbedtls_md_context_t
 
-#define libssh2_hmac_ctx_init(ctx)
-#define libssh2_hmac_cleanup(pctx) \
-    mbedtls_md_free(pctx)
-#define libssh2_hmac_update(ctx, data, datalen) \
-    mbedtls_md_hmac_update(&ctx, (const unsigned char *) data, datalen)
-#define libssh2_hmac_final(ctx, hash) \
-    mbedtls_md_hmac_finish(&ctx, hash)
-
-#define libssh2_hmac_sha1_init(pctx, key, keylen) \
-    _libssh2_mbedtls_hash_init(pctx, MBEDTLS_MD_SHA1, key, keylen)
-#if LIBSSH2_MD5
-#define libssh2_hmac_md5_init(pctx, key, keylen) \
-    _libssh2_mbedtls_hash_init(pctx, MBEDTLS_MD_MD5, key, keylen)
-#endif
-#define libssh2_hmac_ripemd160_init(pctx, key, keylen) \
-    _libssh2_mbedtls_hash_init(pctx, MBEDTLS_MD_RIPEMD160, key, keylen)
-#define libssh2_hmac_sha256_init(pctx, key, keylen) \
-    _libssh2_mbedtls_hash_init(pctx, MBEDTLS_MD_SHA256, key, keylen)
-#define libssh2_hmac_sha384_init(pctx, key, keylen) \
-    _libssh2_mbedtls_hash_init(pctx, MBEDTLS_MD_SHA384, key, keylen)
-#define libssh2_hmac_sha512_init(pctx, key, keylen) \
-    _libssh2_mbedtls_hash_init(pctx, MBEDTLS_MD_SHA512, key, keylen)
-
 
 /*******************************************************************/
 /*
diff --git a/src/openssl.c b/src/openssl.c
index 76277845..574be52b 100644
--- a/src/openssl.c
+++ b/src/openssl.c
@@ -44,9 +44,149 @@
 #include <stdlib.h>
 #include <assert.h>
 
-#ifndef EVP_MAX_BLOCK_LENGTH
-#define EVP_MAX_BLOCK_LENGTH 32
+int _libssh2_hmac_ctx_init(libssh2_hmac_ctx *ctx)
+{
+#ifdef USE_OPENSSL_3
+    *ctx = NULL;
+    return 1;
+#elif defined(HAVE_OPAQUE_STRUCTS)
+    *ctx = HMAC_CTX_new();
+    return *ctx ? 1 : 0;
+#else
+    HMAC_CTX_init(ctx);
+    return 1;
 #endif
+}
+
+#ifdef USE_OPENSSL_3
+static int _libssh2_hmac_init(libssh2_hmac_ctx *ctx,
+                              void *key, size_t keylen,
+                              const char *digest_name)
+{
+    EVP_MAC* mac;
+    OSSL_PARAM params[3];
+
+    mac = EVP_MAC_fetch(NULL, OSSL_MAC_NAME_HMAC, NULL);
+    if(!mac)
+        return 0;
+
+    *ctx = EVP_MAC_CTX_new(mac);
+    EVP_MAC_free(mac);
+    if(!*ctx)
+        return 0;
+
+    params[0] = OSSL_PARAM_construct_octet_string(
+        OSSL_MAC_PARAM_KEY, (void *)key, keylen);
+    params[1] = OSSL_PARAM_construct_utf8_string(
+        OSSL_MAC_PARAM_DIGEST, (char *)digest_name, 0);
+    params[2] = OSSL_PARAM_construct_end();
+
+    return EVP_MAC_init(*ctx, NULL, 0, params);
+}
+#endif
+
+#if LIBSSH2_MD5
+int _libssh2_hmac_md5_init(libssh2_hmac_ctx *ctx,
+                           void *key, size_t keylen)
+{
+#ifdef USE_OPENSSL_3
+    return _libssh2_hmac_init(ctx, key, keylen, OSSL_DIGEST_NAME_MD5);
+#elif defined(HAVE_OPAQUE_STRUCTS)
+    return HMAC_Init_ex(*ctx, key, (int)keylen, EVP_md5(), NULL);
+#else
+    return HMAC_Init_ex(ctx, key, (int)keylen, EVP_md5(), NULL);
+#endif
+}
+#endif
+
+#if LIBSSH2_HMAC_RIPEMD
+int _libssh2_hmac_ripemd160_init(libssh2_hmac_ctx *ctx,
+                                 void *key, size_t keylen)
+{
+#ifdef USE_OPENSSL_3
+    return _libssh2_hmac_init(ctx, key, keylen, OSSL_DIGEST_NAME_RIPEMD160);
+#elif defined(HAVE_OPAQUE_STRUCTS)
+    return HMAC_Init_ex(*ctx, key, (int)keylen, EVP_ripemd160(), NULL);
+#else
+    return HMAC_Init_ex(ctx, key, (int)keylen, EVP_ripemd160(), NULL);
+#endif
+}
+#endif
+
+int _libssh2_hmac_sha1_init(libssh2_hmac_ctx *ctx,
+                            void *key, size_t keylen)
+{
+#ifdef USE_OPENSSL_3
+    return _libssh2_hmac_init(ctx, key, keylen, OSSL_DIGEST_NAME_SHA1);
+#elif defined(HAVE_OPAQUE_STRUCTS)
+    return HMAC_Init_ex(*ctx, key, (int)keylen, EVP_sha1(), NULL);
+#else
+    return HMAC_Init_ex(ctx, key, (int)keylen, EVP_sha1(), NULL);
+#endif
+}
+
+int _libssh2_hmac_sha256_init(libssh2_hmac_ctx *ctx,
+                              void *key, size_t keylen)
+{
+#ifdef USE_OPENSSL_3
+    return _libssh2_hmac_init(ctx, key, keylen, OSSL_DIGEST_NAME_SHA2_256);
+#elif defined(HAVE_OPAQUE_STRUCTS)
+    return HMAC_Init_ex(*ctx, key, (int)keylen, EVP_sha256(), NULL);
+#else
+    return HMAC_Init_ex(ctx, key, (int)keylen, EVP_sha256(), NULL);
+#endif
+}
+
+int _libssh2_hmac_sha512_init(libssh2_hmac_ctx *ctx,
+                              void *key, size_t keylen)
+{
+#ifdef USE_OPENSSL_3
+    return _libssh2_hmac_init(ctx, key, keylen, OSSL_DIGEST_NAME_SHA2_512);
+#elif defined(HAVE_OPAQUE_STRUCTS)
+    return HMAC_Init_ex(*ctx, key, (int)keylen, EVP_sha512(), NULL);
+#else
+    return HMAC_Init_ex(ctx, key, (int)keylen, EVP_sha512(), NULL);
+#endif
+}
+
+int _libssh2_hmac_update(libssh2_hmac_ctx *ctx,
+                         const void *data, size_t datalen)
+{
+#ifdef USE_OPENSSL_3
+    return EVP_MAC_update(*ctx, data, datalen);
+#elif defined(HAVE_OPAQUE_STRUCTS)
+/* FIXME: upstream bug as of v5.6.0: datalen is int instead of size_t */
+#if defined(LIBSSH2_WOLFSSL)
+    return HMAC_Update(*ctx, data, (int)datalen);
+#else /* !LIBSSH2_WOLFSSL */
+    return HMAC_Update(*ctx, data, datalen);
+#endif /* LIBSSH2_WOLFSSL */
+#else
+    return HMAC_Update(ctx, data, datalen);
+#endif
+}
+
+int _libssh2_hmac_final(libssh2_hmac_ctx *ctx, void *data)
+{
+#ifdef USE_OPENSSL_3
+    return EVP_MAC_final(*ctx, data, NULL, MAX_MACSIZE);
+#elif defined(HAVE_OPAQUE_STRUCTS)
+    return HMAC_Final(*ctx, data, NULL);
+#else
+    return HMAC_Final(ctx, data, NULL);
+#endif
+}
+
+void _libssh2_hmac_cleanup(libssh2_hmac_ctx *ctx)
+{
+#ifdef USE_OPENSSL_3
+    EVP_MAC_CTX_free(*ctx);
+#elif defined(HAVE_OPAQUE_STRUCTS)
+    HMAC_CTX_free(*ctx);
+#else
+    HMAC_cleanup(ctx);
+#endif
+}
 
 static int
 read_openssh_private_key_from_memory(void **key_ctx, LIBSSH2_SESSION *session,
@@ -92,32 +232,6 @@ write_bn(unsigned char *buf, const BIGNUM *bn, int bn_bytes)
 }
 #endif
 
-#ifdef USE_OPENSSL_3
-int _libssh2_hmac_init(libssh2_hmac_ctx *ctx, void *key, size_t keylen,
-                       const char *digest_name)
-{
-    EVP_MAC* mac;
-    OSSL_PARAM params[3];
-
-    mac = EVP_MAC_fetch(NULL, OSSL_MAC_NAME_HMAC, NULL);
-    if(!mac)
-        return 0;
-
-    *ctx = EVP_MAC_CTX_new(mac);
-    EVP_MAC_free(mac);
-    if(!*ctx)
-        return 0;
-
-    params[0] = OSSL_PARAM_construct_octet_string(
-        OSSL_MAC_PARAM_KEY, (void *)key, keylen);
-    params[1] = OSSL_PARAM_construct_utf8_string(
-        OSSL_MAC_PARAM_DIGEST, (char *)digest_name, 0);
-    params[2] = OSSL_PARAM_construct_end();
-
-    return EVP_MAC_init(*ctx, NULL, 0, params);
-}
-#endif
-
 static inline void
 _libssh2_swap_bytes(unsigned char *buf, unsigned long len)
 {
@@ -851,6 +965,10 @@ _libssh2_cipher_init(_libssh2_cipher_ctx * h,
 #endif
 }
 
+#ifndef EVP_MAX_BLOCK_LENGTH
+#define EVP_MAX_BLOCK_LENGTH 32
+#endif
+
 int
 _libssh2_cipher_crypt(_libssh2_cipher_ctx * ctx,
                       _libssh2_cipher_type(algo),
diff --git a/src/openssl.h b/src/openssl.h
index a669cc43..a236c1d6 100644
--- a/src/openssl.h
+++ b/src/openssl.h
@@ -326,74 +326,11 @@ int _libssh2_md5_init(libssh2_md5_ctx *ctx);
 #endif /* LIBSSH2_MD5 || LIBSSH2_MD5_PEM */
 
 #ifdef USE_OPENSSL_3
-
 #define libssh2_hmac_ctx EVP_MAC_CTX *
-#define libssh2_hmac_ctx_init(ctx)
-#define libssh2_hmac_sha1_init(ctx, key, keylen) \
-    _libssh2_hmac_init(ctx, (void *)key, keylen, OSSL_DIGEST_NAME_SHA1)
-#define libssh2_hmac_md5_init(ctx, key, keylen) \
-    _libssh2_hmac_init(ctx, (void *)key, keylen, OSSL_DIGEST_NAME_MD5)
-#define libssh2_hmac_ripemd160_init(ctx, key, keylen) \
-    _libssh2_hmac_init(ctx, (void *)key, keylen, OSSL_DIGEST_NAME_RIPEMD160)
-#define libssh2_hmac_sha256_init(ctx, key, keylen) \
-    _libssh2_hmac_init(ctx, (void *)key, keylen, OSSL_DIGEST_NAME_SHA2_256)
-#define libssh2_hmac_sha512_init(ctx, key, keylen) \
-    _libssh2_hmac_init(ctx, (void *)key, keylen, OSSL_DIGEST_NAME_SHA2_512)
-#define libssh2_hmac_update(ctx, data, datalen) \
-    EVP_MAC_update(ctx, data, datalen)
-#define libssh2_hmac_final(ctx, data) EVP_MAC_final(ctx, data, NULL, \
-                                                    MAX_MACSIZE)
-#define libssh2_hmac_cleanup(ctx) EVP_MAC_CTX_free(*(ctx))
-
-int _libssh2_hmac_init(libssh2_hmac_ctx *ctx, void *key, size_t keylen,
-                       const char *digest_name);
-
-#else /* USE_OPENSSL_3 */
-
-#ifdef HAVE_OPAQUE_STRUCTS
+#elif defined(HAVE_OPAQUE_STRUCTS)
 #define libssh2_hmac_ctx HMAC_CTX *
-#define libssh2_hmac_ctx_init(ctx) ctx = HMAC_CTX_new()
-#define libssh2_hmac_sha1_init(ctx, key, keylen) \
-    HMAC_Init_ex(*(ctx), key, (int)keylen, EVP_sha1(), NULL)
-#define libssh2_hmac_md5_init(ctx, key, keylen) \
-    HMAC_Init_ex(*(ctx), key, (int)keylen, EVP_md5(), NULL)
-#define libssh2_hmac_ripemd160_init(ctx, key, keylen) \
-    HMAC_Init_ex(*(ctx), key, (int)keylen, EVP_ripemd160(), NULL)
-#define libssh2_hmac_sha256_init(ctx, key, keylen) \
-    HMAC_Init_ex(*(ctx), key, (int)keylen, EVP_sha256(), NULL)
-#define libssh2_hmac_sha512_init(ctx, key, keylen) \
-    HMAC_Init_ex(*(ctx), key, (int)keylen, EVP_sha512(), NULL)
-
-#ifdef LIBSSH2_WOLFSSL
-/* FIXME: upstream bug as of v5.6.0: datalen is int instead of size_t */
-#define libssh2_hmac_update(ctx, data, datalen) \
-    HMAC_Update(ctx, data, (int)datalen)
-#else /* !LIBSSH2_WOLFSSL */
-#define libssh2_hmac_update(ctx, data, datalen) \
-    HMAC_Update(ctx, data, datalen)
-#endif /* LIBSSH2_WOLFSSL */
-#define libssh2_hmac_final(ctx, data) HMAC_Final(ctx, data, NULL)
-#define libssh2_hmac_cleanup(ctx) HMAC_CTX_free(*(ctx))
 #else /* !HAVE_OPAQUE_STRUCTS */
 #define libssh2_hmac_ctx HMAC_CTX
-#define libssh2_hmac_ctx_init(ctx) \
-    HMAC_CTX_init(&ctx)
-#define libssh2_hmac_sha1_init(ctx, key, keylen) \
-    HMAC_Init_ex(ctx, key, (int)keylen, EVP_sha1(), NULL)
-#define libssh2_hmac_md5_init(ctx, key, keylen) \
-    HMAC_Init_ex(ctx, key, (int)keylen, EVP_md5(), NULL)
-#define libssh2_hmac_ripemd160_init(ctx, key, keylen) \
-    HMAC_Init_ex(ctx, key, (int)keylen, EVP_ripemd160(), NULL)
-#define libssh2_hmac_sha256_init(ctx, key, keylen) \
-    HMAC_Init_ex(ctx, key, (int)keylen, EVP_sha256(), NULL)
-#define libssh2_hmac_sha512_init(ctx, key, keylen) \
-    HMAC_Init_ex(ctx, key, (int)keylen, EVP_sha512(), NULL)
-
-#define libssh2_hmac_update(ctx, data, datalen) \
-    HMAC_Update(&(ctx), data, datalen)
-#define libssh2_hmac_final(ctx, data) HMAC_Final(&(ctx), data, NULL)
-#define libssh2_hmac_cleanup(ctx) HMAC_cleanup(ctx)
-#endif /* HAVE_OPAQUE_STRUCTS */
 #endif /* USE_OPENSSL_3 */
 
 extern void _libssh2_openssl_crypto_init(void);
diff --git a/src/os400qc3.c b/src/os400qc3.c
index 1dca2594..44fe60c5 100644
--- a/src/os400qc3.c
+++ b/src/os400qc3.c
@@ -1003,51 +1003,104 @@ libssh2_os400qc3_hash(const unsigned char *message, unsigned long len,
     return 0;
 }
 
-void
+static int
 libssh2_os400qc3_hmac_init(_libssh2_os400qc3_crypto_ctx *ctx,
                            int algo, size_t minkeylen, void *key, int keylen)
 {
+    Qus_EC_t errcode;
+
     if(keylen < minkeylen) {
         char *lkey = alloca(minkeylen);
 
         /* Pad key with zeroes if too short. */
         if(!lkey)
-            return;
+            return 0;
         memcpy(lkey, (char *) key, keylen);
         memset(lkey + keylen, 0, minkeylen - keylen);
         key = (void *) lkey;
         keylen = minkeylen;
     }
-    libssh2_os400qc3_hash_init(&ctx->hash, algo);
+    if(!libssh2_os400qc3_hash_init(&ctx->hash, algo))
+        return 0;
+    set_EC_length(errcode, sizeof(errcode));
     Qc3CreateKeyContext((char *) key, &keylen, binstring, &algo, qc3clear,
                         NULL, NULL, ctx->key.Key_Context_Token,
-                        (char *) &ecnull);
+                        (char *) &errcode);
+    return errcode.Bytes_Available? 0: 1;
 }
 
-void
-libssh2_os400qc3_hmac_update(_libssh2_os400qc3_crypto_ctx *ctx,
-                             unsigned char *data, int len)
+int _libssh2_hmac_ctx_init(libssh2_hmac_ctx *ctx)
+{
+    memset((char *) ctx, 0, sizeof(libssh2_hmac_ctx));
+    return 1;
+}
+
+#if LIBSSH2_MD5
+int _libssh2_hmac_md5_init(libssh2_hmac_ctx *ctx,
+                           void *key, size_t keylen)
+{
+    return libssh2_os400qc3_hmac_init(ctx, Qc3_MD5,                     \
+                                      MD5_DIGEST_LENGTH,                \
+                                      key, keylen);
+}
+#endif
+
+int _libssh2_hmac_sha1_init(libssh2_hmac_ctx *ctx,
+                            void *key, size_t keylen)
+{
+    return libssh2_os400qc3_hmac_init(ctx, Qc3_SHA1,                    \
+                                      SHA_DIGEST_LENGTH,                \
+                                      key, keylen);
+}
+
+int _libssh2_hmac_sha256_init(libssh2_hmac_ctx *ctx,
+                              void *key, size_t keylen)
+{
+    return libssh2_os400qc3_hmac_init(ctx, Qc3_SHA256,                  \
+                                      SHA256_DIGEST_LENGTH,             \
+                                      key, keylen);
+}
+
+int _libssh2_hmac_sha512_init(libssh2_hmac_ctx *ctx,
+                              void *key, size_t keylen)
+{
+    return libssh2_os400qc3_hmac_init(ctx, Qc3_SHA512,                  \
+                                      SHA512_DIGEST_LENGTH,             \
+                                      key, keylen);
+}
+
+int _libssh2_hmac_update(libssh2_hmac_ctx *ctx,
+                         const void *data, size_t datalen)
 {
     char dummy[64];
+    int len = (int) datalen;
+    Qus_EC_t errcode;
 
     ctx->hash.Final_Op_Flag = Qc3_Continue;
+    set_EC_length(errcode, sizeof(errcode));
     Qc3CalculateHMAC((char *) data, &len, Qc3_Data, (char *) &ctx->hash,
                      Qc3_Alg_Token, ctx->key.Key_Context_Token, Qc3_Key_Token,
-                     anycsp, NULL, dummy, (char *) &ecnull);
+                     anycsp, NULL, dummy, (char *) &errcode);
+    return errcode.Bytes_Available? 0: 1;
 }
 
-void
-libssh2_os400qc3_hmac_final(_libssh2_os400qc3_crypto_ctx *ctx,
-                            unsigned char *out)
+int _libssh2_hmac_final(libssh2_hmac_ctx *ctx, void *out)
 {
     char data;
+    Qus_EC_t errcode;
 
     ctx->hash.Final_Op_Flag = Qc3_Final;
+    set_EC_length(errcode, sizeof(errcode));
     Qc3CalculateHMAC((char *) data, &zero, Qc3_Data, (char *) &ctx->hash,
                      Qc3_Alg_Token, ctx->key.Key_Context_Token, Qc3_Key_Token,
-                     anycsp, NULL, (char *) out, (char *) &ecnull);
+                     anycsp, NULL, (char *) out, (char *) &errcode);
+    return errcode.Bytes_Available? 0: 1;
 }
 
+void _libssh2_hmac_cleanup(libssh2_hmac_ctx *ctx)
+{
+    _libssh2_os400qc3_crypto_dtor(ctx);
+}
 
 /*******************************************************************
  *
@@ -1425,6 +1478,11 @@ pbkdf2(LIBSSH2_SESSION *session, char **dk, const unsigned char *passphrase,
     if(!mac)
         return -1;
 
+    /* Create an HMAC context for our computations. */
+    if(!libssh2_os400qc3_hmac_init(&hctx, pkcs5->hash, pkcs5->hashlen,
+                                   (void *) passphrase, strlen(passphrase)))
+        return -1;
+
     /* Allocate the derived key buffer. */
     l = t;
     buf = LIBSSH2_ALLOC(session, l * pkcs5->hashlen);
@@ -1432,20 +1490,26 @@ pbkdf2(LIBSSH2_SESSION *session, char **dk, const unsigned char *passphrase,
         return -1;
     *dk = buf;
 
-    /* Create an HMAC context for our computations. */
-    libssh2_os400qc3_hmac_init(&hctx, pkcs5->hash, pkcs5->hashlen,
-                               (void *) passphrase, strlen(passphrase));
-
     /* Process each hLen-size blocks. */
     for(i = 1; i <= l; i++) {
         ni = htonl(i);
-        libssh2_os400qc3_hmac_update(&hctx, pkcs5->salt, pkcs5->saltlen);
-        libssh2_os400qc3_hmac_update(&hctx, (char *) &ni, sizeof(ni));
-        libssh2_os400qc3_hmac_final(&hctx, mac);
+        if(!_libssh2_hmac_update(&hctx, pkcs5->salt, pkcs5->saltlen) ||
+           !_libssh2_hmac_update(&hctx, &ni, sizeof(ni)) ||
+           !_libssh2_hmac_final(&hctx, mac)) {
+            LIBSSH2_FREE(session, buf);
+            *dk = NULL;
+            _libssh2_os400qc3_crypto_dtor(&hctx);
+            return -1;
+        }
         memcpy(buf, mac, pkcs5->hashlen);
         for(j = 1; j < pkcs5->itercount; j++) {
-            libssh2_os400qc3_hmac_update(&hctx, mac, pkcs5->hashlen);
-            libssh2_os400qc3_hmac_final(&hctx, mac);
+            if(!_libssh2_hmac_update(&hctx, mac, pkcs5->hashlen) ||
+               !_libssh2_hmac_final(&hctx, mac)) {
+                LIBSSH2_FREE(session, buf);
+                *dk = NULL;
+                _libssh2_os400qc3_crypto_dtor(&hctx);
+                return -1;
+            }
             for(k = 0; k < pkcs5->hashlen; k++)
                 buf[k] ^= mac[k];
         }
diff --git a/src/os400qc3.h b/src/os400qc3.h
index 3e3c1f75..c9328ff6 100644
--- a/src/os400qc3.h
+++ b/src/os400qc3.h
@@ -285,33 +285,6 @@ typedef struct {        /* Diffie-Hellman context. */
                                 libssh2_os400qc3_hash_update(&(ctx), data, len)
 #define libssh2_md5_final(ctx, out)                                         \
                                 libssh2_os400qc3_hash_final(&(ctx), out)
-#define libssh2_hmac_ctx_init(ctx)                                          \
-                                memset((char *) &(ctx), 0,                  \
-                                       sizeof(libssh2_hmac_ctx))
-#define libssh2_hmac_md5_init(ctx, key, keylen)                         \
-    libssh2_os400qc3_hmac_init(ctx, Qc3_MD5,                            \
-                               MD5_DIGEST_LENGTH,                       \
-                               key, keylen)
-#define libssh2_hmac_sha1_init(ctx, key, keylen)                        \
-    libssh2_os400qc3_hmac_init(ctx, Qc3_SHA1,                           \
-                               SHA_DIGEST_LENGTH,                       \
-                               key, keylen)
-#define libssh2_hmac_sha256_init(ctx, key, keylen)                      \
-    libssh2_os400qc3_hmac_init(ctx, Qc3_SHA256,                         \
-                               SHA256_DIGEST_LENGTH,                    \
-                               key, keylen)
-#define libssh2_hmac_sha512_init(ctx, key, keylen)                      \
-    libssh2_os400qc3_hmac_init(ctx, Qc3_SHA512,                         \
-                               SHA512_DIGEST_LENGTH,                    \
-                               key, keylen)
-#define libssh2_hmac_update(ctx, data, datalen)                         \
-    libssh2_os400qc3_hmac_update(&(ctx),                                \
-                                 data, datalen)
-#define libssh2_hmac_final(ctx, data)           \
-    libssh2_os400qc3_hmac_final(&(ctx), data)
-#define libssh2_hmac_cleanup(ctx)               \
-    _libssh2_os400qc3_crypto_dtor(ctx)
-
 
 #define _libssh2_bn_ctx         int                 /* Not used. */
 
@@ -397,14 +370,6 @@ extern void     libssh2_os400qc3_hash_final(Qc3_Format_ALGD0100_T *ctx,
 extern int      libssh2_os400qc3_hash(const unsigned char *message,
                                       unsigned long len, unsigned char *out,
                                       unsigned int algo);
-extern void     libssh2_os400qc3_hmac_init(_libssh2_os400qc3_crypto_ctx *x,
-                                           int algo, size_t minkeylen,
-                                           void *key, int keylen);
-extern void     libssh2_os400qc3_hmac_update(_libssh2_os400qc3_crypto_ctx *ctx,
-                                             const unsigned char *data,
-                                             int len);
-extern void     libssh2_os400qc3_hmac_final(_libssh2_os400qc3_crypto_ctx *ctx,
-                                            unsigned char *out);
 extern int      _libssh2_os400qc3_rsa_signv(LIBSSH2_SESSION *session, int algo,
                                             unsigned char **signature,
                                             size_t *signature_len,
diff --git a/src/transport.c b/src/transport.c
index a8bb588a..531f5aa1 100644
--- a/src/transport.c
+++ b/src/transport.c
@@ -1028,10 +1028,12 @@ int _libssh2_transport_send(LIBSSH2_SESSION *session,
            INTEGRATED_MAC case, where the crypto algorithm also does its
            own hash. */
         if(!etm && !CRYPT_FLAG_R(session, INTEGRATED_MAC)) {
-            session->local.mac->hash(session, p->outbuf + packet_length,
-                                     session->local.seqno, p->outbuf,
-                                     packet_length, NULL, 0,
-                                     &session->local.mac_abstract);
+            if(session->local.mac->hash(session, p->outbuf + packet_length,
+                                        session->local.seqno, p->outbuf,
+                                        packet_length, NULL, 0,
+                                        &session->local.mac_abstract))
+                return _libssh2_error(session, LIBSSH2_ERROR_MAC_FAILURE,
+                                      "Failed to calculate MAC");
         }
 
         /* Encrypt the whole packet data, one block size at a time.
@@ -1090,10 +1092,12 @@ int _libssh2_transport_send(LIBSSH2_SESSION *session,
                calculated on the entire packet (length plain the rest
                encrypted), including all fields except the MAC field
                itself. */
-            session->local.mac->hash(session, p->outbuf + packet_length,
-                                     session->local.seqno, p->outbuf,
-                                     packet_length, NULL, 0,
-                                     &session->local.mac_abstract);
+            if(session->local.mac->hash(session, p->outbuf + packet_length,
+                                        session->local.seqno, p->outbuf,
+                                        packet_length, NULL, 0,
+                                        &session->local.mac_abstract))
+                return _libssh2_error(session, LIBSSH2_ERROR_MAC_FAILURE,
+                                      "Failed to calculate MAC");
         }
     }
 
diff --git a/src/wincng.c b/src/wincng.c
index 6e00f02f..1dcd0bb4 100644
--- a/src/wincng.c
+++ b/src/wincng.c
@@ -536,11 +536,11 @@ _libssh2_wincng_hash_init(_libssh2_wincng_hash_ctx *ctx,
 
 int
 _libssh2_wincng_hash_update(_libssh2_wincng_hash_ctx *ctx,
-                            const unsigned char *data, ULONG datalen)
+                            const void *data, ULONG datalen)
 {
     int ret;
 
-    ret = BCryptHashData(ctx->hHash, (unsigned char *)data, datalen, 0);
+    ret = BCryptHashData(ctx->hHash, (PUCHAR)data, datalen, 0);
 
     return BCRYPT_SUCCESS(ret) ? 0 : -1;
 }
@@ -586,19 +586,70 @@ _libssh2_wincng_hash(const unsigned char *data, ULONG datalen,
  * Windows CNG backend: HMAC functions
  */
 
-int
-_libssh2_wincng_hmac_final(_libssh2_wincng_hash_ctx *ctx,
-                           unsigned char *hash)
+int _libssh2_hmac_ctx_init(libssh2_hmac_ctx *ctx)
 {
-    int ret;
-
-    ret = BCryptFinishHash(ctx->hHash, hash, ctx->cbHash, 0);
-
-    return BCRYPT_SUCCESS(ret) ? 0 : -1;
+    memset(ctx, 0, sizeof(*ctx));
+    return 1;
 }
 
-void
-_libssh2_wincng_hmac_cleanup(_libssh2_wincng_hash_ctx *ctx)
+#if LIBSSH2_MD5
+int _libssh2_hmac_md5_init(libssh2_hmac_ctx *ctx,
+                           void *key, size_t keylen)
+{
+    int ret = _libssh2_wincng_hash_init(ctx, _libssh2_wincng.hAlgHmacMD5,
+                                        MD5_DIGEST_LENGTH,
+                                        key, (ULONG) keylen);
+
+    return ret == 0 ? 1 : 0;
+}
+#endif
+
+int _libssh2_hmac_sha1_init(libssh2_hmac_ctx *ctx,
+                            void *key, size_t keylen)
+{
+    int ret = _libssh2_wincng_hash_init(ctx, _libssh2_wincng.hAlgHmacSHA1,
+                                        SHA_DIGEST_LENGTH,
+                                        key, (ULONG) keylen);
+
+    return ret == 0 ? 1 : 0;
+}
+
+int _libssh2_hmac_sha256_init(libssh2_hmac_ctx *ctx,
+                              void *key, size_t keylen)
+{
+    int ret = _libssh2_wincng_hash_init(ctx, _libssh2_wincng.hAlgHmacSHA256,
+                                        SHA256_DIGEST_LENGTH,
+                                        key, (ULONG) keylen);
+
+    return ret == 0 ? 1 : 0;
+}
+
+int _libssh2_hmac_sha512_init(libssh2_hmac_ctx *ctx,
+                              void *key, size_t keylen)
+{
+    int ret = _libssh2_wincng_hash_init(ctx, _libssh2_wincng.hAlgHmacSHA512,
+                                        SHA512_DIGEST_LENGTH,
+                                        key, (ULONG) keylen);
+
+    return ret == 0 ? 1 : 0;
+}
+
+int _libssh2_hmac_update(libssh2_hmac_ctx *ctx,
+                         const void *data, size_t datalen)
+{
+    int ret = _libssh2_wincng_hash_update(ctx, data, (ULONG) datalen);
+
+    return ret == 0 ? 1 : 0;
+}
+
+int _libssh2_hmac_final(libssh2_hmac_ctx *ctx, void *data)
+{
+    int ret = BCryptFinishHash(ctx->hHash, data, ctx->cbHash, 0);
+
+    return BCRYPT_SUCCESS(ret) ? 1 : 0;
+}
+
+void _libssh2_hmac_cleanup(libssh2_hmac_ctx *ctx)
 {
     BCryptDestroyHash(ctx->hHash);
     ctx->hHash = NULL;
diff --git a/src/wincng.h b/src/wincng.h
index d88f6085..68407e31 100644
--- a/src/wincng.h
+++ b/src/wincng.h
@@ -158,8 +158,7 @@ typedef struct __libssh2_wincng_hash_ctx {
     (_libssh2_wincng_hash_init(ctx, _libssh2_wincng.hAlgHashSHA1, \
                                SHA_DIGEST_LENGTH, NULL, 0) == 0)
 #define libssh2_sha1_update(ctx, data, datalen) \
-    _libssh2_wincng_hash_update(&ctx, \
-                                (const unsigned char *) data, (ULONG) datalen)
+    _libssh2_wincng_hash_update(&ctx, data, (ULONG) datalen)
 #define libssh2_sha1_final(ctx, hash) \
     _libssh2_wincng_hash_final(&ctx, hash)
 #define libssh2_sha1(data, datalen, hash) \
@@ -171,8 +170,7 @@ typedef struct __libssh2_wincng_hash_ctx {
     (_libssh2_wincng_hash_init(ctx, _libssh2_wincng.hAlgHashSHA256, \
                                SHA256_DIGEST_LENGTH, NULL, 0) == 0)
 #define libssh2_sha256_update(ctx, data, datalen) \
-    _libssh2_wincng_hash_update(&ctx, \
-                                (const unsigned char *) data, (ULONG) datalen)
+    _libssh2_wincng_hash_update(&ctx, data, (ULONG) datalen)
 #define libssh2_sha256_final(ctx, hash) \
     _libssh2_wincng_hash_final(&ctx, hash)
 #define libssh2_sha256(data, datalen, hash) \
@@ -184,8 +182,7 @@ typedef struct __libssh2_wincng_hash_ctx {
     (_libssh2_wincng_hash_init(ctx, _libssh2_wincng.hAlgHashSHA384, \
                                SHA384_DIGEST_LENGTH, NULL, 0) == 0)
 #define libssh2_sha384_update(ctx, data, datalen) \
-    _libssh2_wincng_hash_update(&ctx, \
-                                (const unsigned char *) data, (ULONG) datalen)
+    _libssh2_wincng_hash_update(&ctx, data, (ULONG) datalen)
 #define libssh2_sha384_final(ctx, hash) \
     _libssh2_wincng_hash_final(&ctx, hash)
 #define libssh2_sha384(data, datalen, hash) \
@@ -197,8 +194,7 @@ typedef struct __libssh2_wincng_hash_ctx {
     (_libssh2_wincng_hash_init(ctx, _libssh2_wincng.hAlgHashSHA512, \
                                SHA512_DIGEST_LENGTH, NULL, 0) == 0)
 #define libssh2_sha512_update(ctx, data, datalen) \
-    _libssh2_wincng_hash_update(&ctx, \
-                                (const unsigned char *) data, (ULONG) datalen)
+    _libssh2_wincng_hash_update(&ctx, data, (ULONG) datalen)
 #define libssh2_sha512_final(ctx, hash) \
     _libssh2_wincng_hash_final(&ctx, hash)
 #define libssh2_sha512(data, datalen, hash) \
@@ -211,8 +207,7 @@ typedef struct __libssh2_wincng_hash_ctx {
     (_libssh2_wincng_hash_init(ctx, _libssh2_wincng.hAlgHashMD5, \
                                MD5_DIGEST_LENGTH, NULL, 0) == 0)
 #define libssh2_md5_update(ctx, data, datalen) \
-    _libssh2_wincng_hash_update(&ctx, \
-                                (const unsigned char *) data, (ULONG) datalen)
+    _libssh2_wincng_hash_update(&ctx, data, (ULONG) datalen)
 #define libssh2_md5_final(ctx, hash) \
     _libssh2_wincng_hash_final(&ctx, hash)
 #define libssh2_md5(data, datalen, hash) \
@@ -225,30 +220,6 @@ typedef struct __libssh2_wincng_hash_ctx {
  */
 
 #define libssh2_hmac_ctx _libssh2_wincng_hash_ctx
-#define libssh2_hmac_ctx_init(ctx)
-#define libssh2_hmac_sha1_init(ctx, key, keylen) \
-    _libssh2_wincng_hash_init(ctx, _libssh2_wincng.hAlgHmacSHA1, \
-                              SHA_DIGEST_LENGTH, key, (ULONG) keylen)
-#if LIBSSH2_MD5
-#define libssh2_hmac_md5_init(ctx, key, keylen) \
-    _libssh2_wincng_hash_init(ctx, _libssh2_wincng.hAlgHmacMD5, \
-                              MD5_DIGEST_LENGTH, key, (ULONG) keylen)
-#endif
-#define libssh2_hmac_ripemd160_init(ctx, key, keylen)
-    /* not implemented */
-#define libssh2_hmac_sha256_init(ctx, key, keylen) \
-    _libssh2_wincng_hash_init(ctx, _libssh2_wincng.hAlgHmacSHA256, \
-                              SHA256_DIGEST_LENGTH, key, (ULONG) keylen)
-#define libssh2_hmac_sha512_init(ctx, key, keylen) \
-    _libssh2_wincng_hash_init(ctx, _libssh2_wincng.hAlgHmacSHA512, \
-                              SHA512_DIGEST_LENGTH, key, (ULONG) keylen)
-#define libssh2_hmac_update(ctx, data, datalen) \
-    _libssh2_wincng_hash_update(&ctx, \
-                                (const unsigned char *) data, (ULONG) datalen)
-#define libssh2_hmac_final(ctx, hash) \
-    _libssh2_wincng_hmac_final(&ctx, hash)
-#define libssh2_hmac_cleanup(ctx) \
-    _libssh2_wincng_hmac_cleanup(ctx)
 
 
 /*******************************************************************/
@@ -466,7 +437,7 @@ _libssh2_wincng_hash_init(_libssh2_wincng_hash_ctx *ctx,
                           unsigned char *key, ULONG keylen);
 int
 _libssh2_wincng_hash_update(_libssh2_wincng_hash_ctx *ctx,
-                            const unsigned char *data, ULONG datalen);
+                            const void *data, ULONG datalen);
 int
 _libssh2_wincng_hash_final(_libssh2_wincng_hash_ctx *ctx,
                            unsigned char *hash);
@@ -475,12 +446,6 @@ _libssh2_wincng_hash(const unsigned char *data, ULONG datalen,
                      BCRYPT_ALG_HANDLE hAlg,
                      unsigned char *hash, ULONG hashlen);
 
-int
-_libssh2_wincng_hmac_final(_libssh2_wincng_hash_ctx *ctx,
-                           unsigned char *hash);
-void
-_libssh2_wincng_hmac_cleanup(_libssh2_wincng_hash_ctx *ctx);
-
 void
 _libssh2_wincng_rsa_free(libssh2_rsa_ctx *rsa);