From 5f0124c4923dc44a6f2bf1666fafcecc0c90306b Mon Sep 17 00:00:00 2001
From: Paul Duncan <pabs@pablotron.org>
Date: Fri, 1 Sep 2023 23:40:28 -0400
Subject: main.c: add shake128-xof and shake256-xof commands

---
 main.c | 124 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 109 insertions(+), 15 deletions(-)

diff --git a/main.c b/main.c
index 62fc21b..febf001 100644
--- a/main.c
+++ b/main.c
@@ -1,39 +1,122 @@
+#include <stdbool.h>
+#include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
 #include "sha3.h"
 
+static void run_shake128_xof(const uint8_t *msg, const size_t msg_len, const size_t out_len) {
+  // init xof
+  sha3_xof_t xof;
+  shake128_xof_init(&xof);
+
+  // absorb
+  if (!shake128_xof_absorb(&xof, msg, msg_len)) {
+    fprintf(stderr, "Error: shake128_xof_absorb() failed\n");
+    exit(-1);
+  }
+
+  // finalize
+  if (!shake128_xof_absorb_done(&xof)) {
+    fprintf(stderr, "Error: shake128_xof_absorb_done() failed\n");
+    exit(-1);
+  }
+
+  // squeeze
+  uint8_t buf[64];
+  for (size_t i = 0; i < out_len; i += sizeof(buf)) {
+    const size_t len = (out_len - i < sizeof(buf)) ? out_len - i : sizeof(buf);
+
+    if (!shake128_xof_squeeze(&xof, buf, len)) {
+      fprintf(stderr, "Error: shake128_xof_absorb_done() failed\n");
+      exit(-1);
+    }
+
+    // print result
+    for (size_t j = 0; j < len; j++) {
+      printf("%02x", buf[j]);
+    }
+  }
+
+  fputs("\n", stdout);
+}
+
+static void run_shake256_xof(const uint8_t * const msg, const size_t msg_len, const size_t out_len) {
+  // init xof
+  sha3_xof_t xof;
+  shake256_xof_init(&xof);
+
+  // absorb
+  if (!shake256_xof_absorb(&xof, msg, msg_len)) {
+    fprintf(stderr, "Error: shake256_xof_absorb() failed\n");
+    exit(-1);
+  }
+
+  // finalize
+  if (!shake256_xof_absorb_done(&xof)) {
+    fprintf(stderr, "Error: shake256_xof_absorb_done() failed\n");
+    exit(-1);
+  }
+
+  // squeeze
+  uint8_t buf[64];
+  for (size_t i = 0; i < out_len; i += sizeof(buf)) {
+    const size_t len = (out_len - i < sizeof(buf)) ? out_len - i : sizeof(buf);
+
+    if (!shake256_xof_squeeze(&xof, buf, len)) {
+      fprintf(stderr, "Error: shake256_xof_absorb_done() failed\n");
+      exit(-1);
+    }
+
+    // print result
+    for (size_t j = 0; j < len; j++) {
+      printf("%02x", buf[j]);
+    }
+  }
+
+  fputs("\n", stdout);
+}
+
 // available functions
 static const struct {
   const char *name;
   const size_t size;
-  void (*func)(const uint8_t *, size_t, uint8_t *);
+  void (*hash_func)(const uint8_t *, size_t, uint8_t *);
+  void (*xof_func)(const uint8_t *, size_t, size_t);
 } fns[] = {{
   .name = "sha3-224",
   .size = 28,
-  .func = sha3_224,
+  .hash_func = sha3_224,
 }, {
   .name = "sha3-256",
   .size = 32,
-  .func = sha3_256,
+  .hash_func = sha3_256,
 }, {
   .name = "sha3-384",
   .size = 48,
-  .func = sha3_384,
+  .hash_func = sha3_384,
 }, {
   .name = "sha3-512",
   .size = 64,
-  .func = sha3_512,
+  .hash_func = sha3_512,
 }, {
   .name = "shake128",
   .size = 16,
-  .func = shake128,
+  .hash_func = shake128,
 }, {
   .name = "shake256",
   .size = 32,
-  .func = shake256,
+  .hash_func = shake256,
+}, {
+  .name = "shake128-xof",
+  .size = 16,
+  .xof_func = run_shake128_xof,
+}, {
+  .name = "shake256-xof",
+  .size = 32,
+  .xof_func = run_shake256_xof,
 }};
 
-#define USAGE "Usage: %s <algo> <data>\n" \
+#define USAGE "Usage: %s <algo> <data> [xof-size]\n" \
               "\n" \
               "Algorithms:\n" \
               "- sha3-224\n" \
@@ -42,6 +125,8 @@ static const struct {
               "- sha3-512\n" \
               "- shake128\n" \
               "- shake256\n" \
+              "- shake128-xof (XOF)\n" \
+              "- shake256-xof (XOF)\n" \
               "\n" \
               "Example:\n" \
               "  %s sha3-256 \"asdf\"\n" \
@@ -54,20 +139,29 @@ int main(int argc, char *argv[]) {
     return -1;
   }
 
+  const uint8_t * const msg = (uint8_t*) argv[2];
+  const size_t len = strlen(argv[2]);
+
   for (size_t i = 0; i < sizeof(fns)/sizeof(fns[0]); i++) {
     if (strncmp(argv[1], fns[i].name, strlen(fns[i].name) + 1)) {
       continue;
     }
 
-    // hash into buf
-    uint8_t buf[64];
-    fns[i].func((uint8_t*) argv[2], strlen(argv[2]), buf);
+    if (fns[i].xof_func) {
+      // get output size
+      const size_t out_size = (argc == 4) ? (size_t) atoi(argv[3]) : fns[i].size;
+      fns[i].xof_func(msg, len, out_size);
+    } else {
+      // hash into buf
+      uint8_t buf[64];
+      fns[i].hash_func(msg, len, buf);
 
-    // print result
-    for (size_t j = 0; j < fns[i].size; j++) {
-      printf("%02x", buf[j]);
+      // print result
+      for (size_t j = 0; j < fns[i].size; j++) {
+        printf("%02x", buf[j]);
+      }
+      fputs("\n", stdout);
     }
-    fputs("\n", stdout);
 
     // exit with success
     return 0;
-- 
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