Implemented public SHA1 interface

A number of XEPs require SHA1. Publishing its interface helps user to
reduce number of dependencies.

src/crypto.c

@@ -0,0 +1,184 @@
+/* crypto.c
+ * strophe XMPP client library -- public interface for digests, encodings
+ *
+ * Copyright (C) 2016 Dmitry Podgorny <pasis.ua@gmail.com>
+ *
+ *  This software is provided AS-IS with no warranty, either express
+ *  or implied.
+ *
+ *  This program is dual licensed under the MIT and GPLv3 licenses.
+ */
+
+/** @file
+ *  Public interface for digests and encodings used in XEPs.
+ */
+
+/** @defgroup Digests Message digests
+ */
+
+#include <assert.h>
+#include <string.h>     /* memset, memcpy */
+
+#include "common.h"     /* xmpp_alloc */
+#include "ostypes.h"    /* uint8_t, size_t */
+#include "sha1.h"
+#include "snprintf.h"   /* xmpp_snprintf */
+#include "strophe.h"    /* xmpp_ctx_t, xmpp_free */
+
+struct _xmpp_sha1_t {
+    xmpp_ctx_t *xmpp_ctx;
+    SHA1_CTX ctx;
+    uint8_t digest[SHA1_DIGEST_SIZE];
+};
+
+static char *digest_to_string(const uint8_t *digest, char *s, size_t len)
+{
+    int i;
+
+    if (len < SHA1_DIGEST_SIZE * 2 + 1)
+        return NULL;
+
+    for (i = 0; i < SHA1_DIGEST_SIZE; ++i)
+        xmpp_snprintf(s + i * 2, 3, "%02x", digest[i]);
+
+    return s;
+}
+
+static char *digest_to_string_alloc(xmpp_ctx_t *ctx, const uint8_t *digest)
+{
+    char *s;
+    size_t slen;
+
+    slen = SHA1_DIGEST_SIZE * 2 + 1;
+    s = xmpp_alloc(ctx, slen);
+    if (s) {
+        s = digest_to_string(digest, s, slen);
+        assert(s != NULL);
+    }
+    return s;
+}
+
+/** Compute SHA1 message digest
+ *  Returns an allocated string which represents SHA1 message digest in
+ *  hexadecimal notation. The string must be freed with xmpp_free().
+ *
+ *  @param ctx a Strophe context object
+ *  @param data buffer for digest computation
+ *  @param len size of the data buffer
+ *
+ *  @return an allocated string or NULL on allocation error
+ *
+ *  @ingroup Digests
+ */
+char *xmpp_sha1(xmpp_ctx_t *ctx, const unsigned char *data, size_t len)
+{
+    uint8_t digest[SHA1_DIGEST_SIZE];
+
+    crypto_SHA1((const uint8_t *)data, len, digest);
+    return digest_to_string_alloc(ctx, digest);
+}
+
+/** Create new SHA1 object
+ *
+ *  @param ctx a Strophe context onject
+ *
+ *  @return new SHA1 object
+ *
+ *  @ingroup Digests
+ */
+xmpp_sha1_t *xmpp_sha1_new(xmpp_ctx_t *ctx)
+{
+    xmpp_sha1_t *sha1;
+
+    sha1 = xmpp_alloc(ctx, sizeof(*sha1));
+    if (sha1) {
+        memset(sha1, 0, sizeof(*sha1));
+        crypto_SHA1_Init(&sha1->ctx);
+        sha1->xmpp_ctx = ctx;
+    }
+    return sha1;
+}
+
+/** Destroy SHA1 object
+ *
+ *  @param sha1 a SHA1 object
+ *
+ *  @ingroup Digests
+ */
+void xmpp_sha1_free(xmpp_sha1_t *sha1)
+{
+    xmpp_free(sha1->xmpp_ctx, sha1);
+}
+
+/** Update SHA1 context with the next portion of data
+ *  Can be called repeatedly.
+ *
+ *  @param sha1 a SHA1 object
+ *  @param data pointer to a buffer to be hashed
+ *  @param len size of the data buffer
+ *
+ *  @ingroup Digests
+ */
+void xmpp_sha1_update(xmpp_sha1_t *sha1, const unsigned char *data, size_t len)
+{
+    crypto_SHA1_Update(&sha1->ctx, data, len);
+}
+
+/** Finish SHA1 computation
+ *  Don't call xmpp_sha1_update() after this function. Retrieve resulting
+ *  message digest with xmpp_sha1_to_string() or xmpp_sha1_to_digest().
+ *
+ *  @param sha1 a SHA1 object
+ *
+ *  @ingroup Digests
+ */
+void xmpp_sha1_final(xmpp_sha1_t *sha1)
+{
+    crypto_SHA1_Final(&sha1->ctx, sha1->digest);
+}
+
+/** Return message digest rendered as a string
+ *  Stores the string to a user's buffer and returns the buffer. Call this
+ *  function after xmpp_sha1_final().
+ *
+ *  @param sha1 a SHA1 object
+ *  @param s output string
+ *  @param slen size reserved for the string including '\0'
+ *
+ *  @return pointer s or NULL if resulting string is bigger than slen bytes
+ *
+ *  @ingroup Digests
+ */
+char *xmpp_sha1_to_string(xmpp_sha1_t *sha1, char *s, size_t slen)
+{
+    return digest_to_string(sha1->digest, s, slen);
+}
+
+/** Return message digest rendered as a string
+ *  Returns an allocated string. Free the string using the Strophe context
+ *  which is passed to xmpp_sha1_new(). Call this function after
+ *  xmpp_sha1_final().
+ *
+ *  @param sha1 a SHA1 object
+ *
+ *  @return an allocated string
+ *
+ *  @ingroup Digests
+ */
+char *xmpp_sha1_to_string_alloc(xmpp_sha1_t *sha1)
+{
+    return digest_to_string_alloc(sha1->xmpp_ctx, sha1->digest);
+}
+
+/** Stores message digest to a user's buffer
+ *
+ *  @param sha1 a SHA1 object
+ *  @param digest output buffer of XMPP_SHA1_DIGEST_SIZE bytes
+ *
+ *  @ingroup Digests
+ */
+void xmpp_sha1_to_digest(xmpp_sha1_t *sha1, unsigned char *digest)
+{
+    assert(SHA1_DIGEST_SIZE == XMPP_SHA1_DIGEST_SIZE);
+    memcpy(digest, sha1->digest, SHA1_DIGEST_SIZE);
+}