crypto: use glib as fallback for hash algorithm

GLib >= 2.16 provides GChecksum API which is good enough
for md5, sha1, sha256 and sha512. Use this as a final
fallback if neither nettle or gcrypt are available. This
lets us remove the stub hash impl, and so callers can
be sure those 4 algs are always available at compile
time. They may still be disabled at runtime, so a check
for qcrypto_hash_supports() is still best practice to
report good error messages.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

crypto/Makefile.objs

@@ -2,6 +2,7 @@ crypto-obj-y = init.o
 crypto-obj-y += hash.o
 crypto-obj-$(CONFIG_NETTLE) += hash-nettle.o
 crypto-obj-$(if $(CONFIG_NETTLE),n,$(CONFIG_GCRYPT)) += hash-gcrypt.o
+crypto-obj-$(if $(CONFIG_NETTLE),n,$(if $(CONFIG_GCRYPT),n,y)) += hash-glib.o
 crypto-obj-y += aes.o
 crypto-obj-y += desrfb.o
 crypto-obj-y += cipher.o
@@ -30,4 +31,3 @@ crypto-obj-y += block-luks.o
 crypto-aes-obj-y = aes.o
 
 stub-obj-y += pbkdf-stub.o
-stub-obj-y += hash-stub.o

crypto/hash-stub.c → crypto/hash-glib.c

@@ -22,20 +22,77 @@
 #include "qapi/error.h"
 #include "crypto/hash.h"
 
-gboolean qcrypto_hash_supports(QCryptoHashAlgorithm alg G_GNUC_UNUSED)
+
+static int qcrypto_hash_alg_map[QCRYPTO_HASH_ALG__MAX] = {
+    [QCRYPTO_HASH_ALG_MD5] = G_CHECKSUM_MD5,
+    [QCRYPTO_HASH_ALG_SHA1] = G_CHECKSUM_SHA1,
+    [QCRYPTO_HASH_ALG_SHA224] = -1,
+    [QCRYPTO_HASH_ALG_SHA256] = G_CHECKSUM_SHA256,
+    [QCRYPTO_HASH_ALG_SHA384] = -1,
+#if GLIB_CHECK_VERSION(2, 36, 0)
+    [QCRYPTO_HASH_ALG_SHA512] = G_CHECKSUM_SHA512,
+#else
+    [QCRYPTO_HASH_ALG_SHA512] = -1,
+#endif
+    [QCRYPTO_HASH_ALG_RIPEMD160] = -1,
+};
+
+gboolean qcrypto_hash_supports(QCryptoHashAlgorithm alg)
 {
+    if (alg < G_N_ELEMENTS(qcrypto_hash_alg_map) &&
+        qcrypto_hash_alg_map[alg] != -1) {
+        return true;
+    }
     return false;
 }
 
+
 int qcrypto_hash_bytesv(QCryptoHashAlgorithm alg,
-                        const struct iovec *iov G_GNUC_UNUSED,
-                        size_t niov G_GNUC_UNUSED,
-                        uint8_t **result G_GNUC_UNUSED,
-                        size_t *resultlen G_GNUC_UNUSED,
+                        const struct iovec *iov,
+                        size_t niov,
+                        uint8_t **result,
+                        size_t *resultlen,
                         Error **errp)
 {
-    error_setg(errp,
-               "Hash algorithm %d not supported without GNUTLS",
-               alg);
+    int i, ret;
+    GChecksum *cs;
+
+    if (alg >= G_N_ELEMENTS(qcrypto_hash_alg_map) ||
+        qcrypto_hash_alg_map[alg] == -1) {
+        error_setg(errp,
+                   "Unknown hash algorithm %d",
+                   alg);
+        return -1;
+    }
+
+    cs = g_checksum_new(qcrypto_hash_alg_map[alg]);
+
+    for (i = 0; i < niov; i++) {
+        g_checksum_update(cs, iov[i].iov_base, iov[i].iov_len);
+    }
+
+    ret = g_checksum_type_get_length(qcrypto_hash_alg_map[alg]);
+    if (ret < 0) {
+        error_setg(errp, "%s",
+                   "Unable to get hash length");
+        goto error;
+    }
+    if (*resultlen == 0) {
+        *resultlen = ret;
+        *result = g_new0(uint8_t, *resultlen);
+    } else if (*resultlen != ret) {
+        error_setg(errp,
+                   "Result buffer size %zu is smaller than hash %d",
+                   *resultlen, ret);
+        goto error;
+    }
+
+    g_checksum_get_digest(cs, *result, resultlen);
+
+    g_checksum_free(cs);
+    return 0;
+
+ error:
+    g_checksum_free(cs);
     return -1;
 }