SHA-1 implementation

src/lib/sha1.rs

@@ -0,0 +1,284 @@
+/*
+ * A SHA-1 implementation derived from Paul E. Jones's reference
+ * implementation, which is written for clarity, not speed. At some
+ * point this will want to be rewritten.
+ */
+
+import std._vec;
+import std._str;
+
+export sha1;
+export mk_sha1;
+
+state type sha1 = state obj {
+                        // Provide message input as bytes
+                        fn input(&vec[u8]);
+
+                        // Provide message input as string
+                        fn input_str(&str);
+
+                        // Read the digest as a vector of 20 bytes. After
+                        // calling this no further input may provided
+                        // until reset is called
+                        fn result() -> vec[u8];
+
+                        // Reset the sha1 state for reuse. This is called
+                        // automatically during construction
+                        fn reset();
+};
+
+// Some unexported constants
+const uint digest_buf_len = 5;
+const uint msg_block_len = 64;
+
+// Builds a sha1 object
+fn mk_sha1() -> sha1 {
+
+    state type sha1state = rec(vec[mutable u32] h,
+                               mutable u32 len_low,
+                               mutable u32 len_high,
+                               vec[mutable u8] msg_block,
+                               mutable uint msg_block_idx,
+                               mutable bool computed);
+
+    impure fn add_input(&sha1state st, &vec[u8] msg) {
+        // FIXME: Should be typestate precondition
+        check (!st.computed);
+
+        for (u8 element in msg) {
+            st.msg_block.(st.msg_block_idx) = element;
+            st.msg_block_idx += 1u;
+
+            st.len_low += 8u32;
+            if (st.len_low == 0u32) {
+                st.len_high += 1u32;
+                if (st.len_high == 0u32) {
+                    // FIXME: Need better failure mode
+                    fail;
+                }
+            }
+
+            if (st.msg_block_idx == msg_block_len) {
+                process_msg_block(st);
+            }
+        }
+    }
+
+    impure fn process_msg_block(&sha1state st) {
+
+        // FIXME: Make precondition
+        check (_vec.len[mutable u32](st.h) == digest_buf_len);
+
+        // Constants
+        auto k = vec(0x5A827999u32,
+                     0x6ED9EBA1u32,
+                     0x8F1BBCDCu32,
+                     0xCA62C1D6u32);
+
+        let int t; // Loop counter
+        let vec[mutable u32] w = _vec.init_elt[mutable u32](0u32, 80u);
+
+        // Initialize the first 16 words of the vector w
+        t = 0;
+        while (t < 16) {
+            w.(t) = (st.msg_block.(t * 4) as u32) << 24u32;
+            w.(t) = w.(t) | ((st.msg_block.(t * 4 + 1) as u32) << 16u32);
+            w.(t) = w.(t) | ((st.msg_block.(t * 4 + 2) as u32) << 8u32);
+            w.(t) = w.(t) | (st.msg_block.(t * 4 + 3) as u32);
+            t += 1;
+        }
+
+        // Initialize the rest of vector w
+        while (t < 80) {
+            auto val = w.(t-3) ^ w.(t-8) ^ w.(t-14) ^ w.(t-16);
+            w.(t) = circular_shift(1u32, val);
+            t += 1;
+        }
+
+        auto a = st.h.(0);
+        auto b = st.h.(1);
+        auto c = st.h.(2);
+        auto d = st.h.(3);
+        auto e = st.h.(4);
+
+        let u32 temp;
+
+        t = 0;
+        while (t < 20) {
+            temp = circular_shift(5u32, a)
+                + ((b & c) | ((~b) & d)) + e + w.(t) + k.(0);
+            e = d;
+            d = c;
+            c = circular_shift(30u32, b);
+            b = a;
+            a = temp;
+            t += 1;
+        }
+
+        while (t < 40) {
+            temp = circular_shift(5u32, a)
+                + (b ^ c ^ d) + e + w.(t) + k.(1);
+            e = d;
+            d = c;
+            c = circular_shift(30u32, b);
+            b = a;
+            a = temp;
+            t += 1;
+        }
+
+        while (t < 60) {
+            temp = circular_shift(5u32, a)
+                + ((b & c) | (b & d) | (c & d)) + e + w.(t) + k.(2);
+            e = d;
+            d = c;
+            c = circular_shift(30u32, b);
+            b = a;
+            a = temp;
+            t += 1;
+        }
+
+        while (t < 80) {
+            temp = circular_shift(5u32, a)
+                + (b ^ c ^ d) + e + w.(t) + k.(3);
+            e = d;
+            d = c;
+            c = circular_shift(30u32, b);
+            b = a;
+            a = temp;
+            t += 1;
+        }
+
+        st.h.(0) = st.h.(0) + a;
+        st.h.(1) = st.h.(1) + b;
+        st.h.(2) = st.h.(2) + c;
+        st.h.(3) = st.h.(3) + d;
+        st.h.(4) = st.h.(4) + e;
+
+        st.msg_block_idx = 0u;
+    }
+
+    fn circular_shift(u32 bits, u32 word) -> u32 {
+        // FIXME: This is a workaround for a rustboot
+        // "unrecognized quads" codegen bug
+        auto bits_hack = bits;
+        ret (word << bits_hack) | (word >> (32u32 - bits));
+    }
+
+    impure fn mk_result(&sha1state st) -> vec[u8] {
+        if (!st.computed) {
+            pad_msg(st);
+            st.computed = true;
+        }
+
+        let vec[u8] res = vec();
+        for (u32 hpart in st.h) {
+            res += (hpart >> 24u32) & 0xFFu32 as u8;
+            res += (hpart >> 16u32) & 0xFFu32 as u8;
+            res += (hpart >> 8u32) & 0xFFu32 as u8;
+            res += hpart & 0xFFu32 as u8;
+        }
+        ret res;
+    }
+
+    /*
+     * According to the standard, the message must be padded to an even
+     * 512 bits.  The first padding bit must be a '1'.  The last 64 bits
+     * represent the length of the original message.  All bits in between
+     * should be 0.  This function will pad the message according to those
+     * rules by filling the message_block array accordingly.  It will also
+     * call ProcessMessageBlock() appropriately.  When it returns, it
+     * can be assumed that the message digest has been computed.
+     */
+    impure fn pad_msg(&sha1state st) {
+        // FIXME: Should be a precondition
+        check (_vec.len[mutable u8](st.msg_block) == msg_block_len);
+
+        /*
+         * Check to see if the current message block is too small to hold
+         * the initial padding bits and length.  If so, we will pad the
+         * block, process it, and then continue padding into a second block.
+         */
+        if (st.msg_block_idx > 55u) {
+            st.msg_block.(st.msg_block_idx) = 0x80u8;
+            st.msg_block_idx += 1u;
+
+            while (st.msg_block_idx < msg_block_len) {
+                st.msg_block.(st.msg_block_idx) = 0u8;
+                st.msg_block_idx += 1u;
+            }
+
+            process_msg_block(st);
+        } else {
+            st.msg_block.(st.msg_block_idx) = 0x80u8;
+            st.msg_block_idx += 1u;
+        }
+
+        while (st.msg_block_idx < 56u) {
+            st.msg_block.(st.msg_block_idx) = 0u8;
+            st.msg_block_idx += 1u;
+        }
+
+        // Store the message length as the last 8 octets
+        st.msg_block.(56) = (st.len_high >> 24u32) & 0xFFu32 as u8;
+        st.msg_block.(57) = (st.len_high >> 16u32) & 0xFFu32 as u8;
+        st.msg_block.(58) = (st.len_high >> 8u32) & 0xFFu32 as u8;
+        st.msg_block.(59) = st.len_high & 0xFFu32 as u8;
+        st.msg_block.(60) = (st.len_low >> 24u32) & 0xFFu32 as u8;
+        st.msg_block.(61) = (st.len_low >> 16u32) & 0xFFu32 as u8;
+        st.msg_block.(62) = (st.len_low >> 8u32) & 0xFFu32 as u8;
+        st.msg_block.(63) = st.len_low & 0xFFu32 as u8;
+
+        process_msg_block(st);
+    }
+
+    state obj sha1(sha1state st) {
+
+        fn reset() {
+            // FIXME: Should be typestate precondition
+            check (_vec.len[mutable u32](st.h) == digest_buf_len);
+
+            st.len_low = 0u32;
+            st.len_high = 0u32;
+            st.msg_block_idx = 0u;
+
+            st.h.(0) = 0x67452301u32;
+            st.h.(1) = 0xEFCDAB89u32;
+            st.h.(2) = 0x98BADCFEu32;
+            st.h.(3) = 0x10325476u32;
+            st.h.(4) = 0xC3D2E1F0u32;
+
+            st.computed = false;
+        }
+
+        fn input(&vec[u8] msg) {
+            add_input(st, msg);
+        }
+
+        fn input_str(&str msg) {
+            add_input(st, _str.bytes(msg));
+        }
+
+        fn result() -> vec[u8] {
+            ret mk_result(st);
+        }
+    }
+
+    auto st = rec(h = _vec.init_elt[mutable u32](0u32, digest_buf_len),
+                  mutable len_low = 0u32,
+                  mutable len_high = 0u32,
+                  msg_block = _vec.init_elt[mutable u8](0u8, msg_block_len),
+                  mutable msg_block_idx = 0u,
+                  mutable computed = false);
+    auto sh = sha1(st);
+    sh.reset();
+    ret sh;
+}
+
+// Local Variables:
+// mode: rust;
+// fill-column: 78;
+// indent-tabs-mode: nil
+// c-basic-offset: 4
+// buffer-file-coding-system: utf-8-unix
+// compile-command: "make -k -C .. 2>&1 | sed -e 's/\\/x\\//x:\\//g'";
+// End:

src/lib/std.rc

@@ -57,6 +57,7 @@ mod dbg;
 mod bitv;
 mod sort;
 mod path;
+mod sha1;
 
 // Local Variables:
 // mode: rust;