Add SHA1x hash support

[onak.git] / sha1x.c

diff --git a/sha1x.c b/sha1x.c
new file mode 100644 (file)
index 0000000..1242440
--- /dev/null
+++ b/sha1x.c
@@ -0,0 +1,144 @@
+/*
+ * sha1x.c - Double width SHA-1 as per PGP 5.5
+ *
+ * Copyright 2013 Jonathan McDowell <noodles@earth.li>
+ *
+ * This is based on the description / code from PGP 5.5, where it is called
+ * "SHA Double". I have seen reference to SHA1X elsewhere, which is a more
+ * concise name, so I have used that here.
+ *
+ * I can't imagine there is a good reason to use this code other than for
+ * verifying signatures on ancient PGP keys.
+ *
+ * Placed into the public domain.
+ */
+
+#include "config.h"
+
+#include <stdbool.h>
+#include <stdint.h>
+#include <string.h>
+
+#ifdef HAVE_NETTLE
+#include <nettle/sha.h>
+#else
+#include "sha1.h"
+#endif
+#include "sha1x.h"
+
+#define BUFSIZE 64
+
+void sha1x_init(struct sha1x_ctx *ctx)
+{
+       unsigned char zeros[3];
+
+       zeros[0] = zeros[1] = zeros[2] = 0;
+       sha1_init(&ctx->a);
+       sha1_init(&ctx->b);
+       sha1_init(&ctx->c);
+       sha1_init(&ctx->d);
+
+       sha1_update(&ctx->b, 1, zeros);
+       sha1_update(&ctx->c, 2, zeros);
+       sha1_update(&ctx->d, 3, zeros);
+
+       /* We start at 0, so even */
+       ctx->odd = false;
+}
+
+void sha1x_update(struct sha1x_ctx *ctx, unsigned length, const uint8_t *data)
+{
+       uint8_t evenbuf[BUFSIZE], *evenp;
+       uint8_t oddbuf[BUFSIZE], *oddp;
+       bool newodd;
+
+       oddp = oddbuf;
+       evenp = evenbuf;
+
+       /* Track whether our first byte next time round is even or odd */
+       newodd = ctx->odd ^ (length & 1);
+
+       /* If our first byte is odd this time, add it to the odd buffer */
+       if (ctx->odd && length != 0) {
+               *oddp++ = *data++;
+               length--;
+       }
+       ctx->odd = newodd;
+
+       while (length != 0) {
+               while (length != 0 && oddp < oddbuf + BUFSIZE) {
+                       *evenp++ = *data++;
+                       length--;
+                       if (length == 0) {
+                               break;
+                       }
+                       *oddp++ = *data++;
+                       length--;
+               }
+               sha1_update(&ctx->a, evenp - evenbuf, evenbuf);
+               sha1_update(&ctx->b, evenp - evenbuf, evenbuf);
+               sha1_update(&ctx->c, oddp - oddbuf, oddbuf);
+               sha1_update(&ctx->d, oddp - oddbuf, oddbuf);
+
+               oddp = oddbuf;
+               evenp = evenbuf;
+       }
+}
+
+void sha1x_digest(struct sha1x_ctx *ctx, unsigned length, uint8_t *digest)
+{
+       uint8_t sha1final[8][SHA1_DIGEST_SIZE];
+       uint8_t zeros[7];
+       struct sha1_ctx e, f, g, h;
+       int i;
+
+       sha1_digest(&ctx->a, SHA1_DIGEST_SIZE, sha1final[0]);
+       sha1_digest(&ctx->b, SHA1_DIGEST_SIZE, sha1final[1]);
+       sha1_digest(&ctx->c, SHA1_DIGEST_SIZE, sha1final[2]);
+       sha1_digest(&ctx->d, SHA1_DIGEST_SIZE, sha1final[3]);
+
+       /* XOR sha1-c into sha1-a & sha1-d into sha1-b */
+       for (i = 0; i < SHA1_DIGEST_SIZE; i++) {
+               sha1final[0][i] ^= sha1final[2][i];
+               sha1final[1][i] ^= sha1final[3][i];
+       }
+
+       sha1_init(&e);
+       sha1_init(&f);
+       sha1_init(&g);
+       sha1_init(&h);
+
+       memset(zeros, 0, sizeof(zeros));
+       sha1_update(&e, 4, zeros);
+       sha1_update(&f, 5, zeros);
+       sha1_update(&g, 6, zeros);
+       sha1_update(&h, 7, zeros);
+
+       sha1_update(&e, SHA1_DIGEST_SIZE, sha1final[0]);
+       sha1_update(&f, SHA1_DIGEST_SIZE, sha1final[0]);
+       sha1_update(&g, SHA1_DIGEST_SIZE, sha1final[1]);
+       sha1_update(&h, SHA1_DIGEST_SIZE, sha1final[1]);
+
+       sha1_digest(&e, SHA1_DIGEST_SIZE, sha1final[4]);
+       sha1_digest(&f, SHA1_DIGEST_SIZE, sha1final[5]);
+       sha1_digest(&g, SHA1_DIGEST_SIZE, sha1final[6]);
+       sha1_digest(&h, SHA1_DIGEST_SIZE, sha1final[7]);
+
+       /* XOR sha1-g into sha1-e & sha1-h into sha1-f */
+       for (i = 0; i < SHA1_DIGEST_SIZE; i++) {
+               sha1final[4][i] ^= sha1final[6][i];
+               sha1final[5][i] ^= sha1final[7][i];
+       }
+
+       if (length > SHA1X_DIGEST_SIZE) {
+               length = SHA1X_DIGEST_SIZE;
+       }
+
+       for (i = 0; i < length; i++) {
+               if (i < SHA1_DIGEST_SIZE) {
+                       digest[i] = sha1final[4][i];
+               } else {
+                       digest[i] = sha1final[6][i - SHA1_DIGEST_SIZE];
+               }
+       }
+}