From 3eb0ae9b58683cc59468e3f5b2e28163a722e11b Mon Sep 17 00:00:00 2001
From: Samuel Fadel <samuel@nihil.ws>
Date: Sun, 9 Apr 2023 10:41:31 +0200
Subject: Proper argument parsing.

Also started charset restriction implementation.

* lpass.c: Argument parsing & stub charset restriction.
---
 lpass.c | 103 ++++++++++++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 87 insertions(+), 16 deletions(-)

diff --git a/lpass.c b/lpass.c
index 2193359..44f88a2 100644
--- a/lpass.c
+++ b/lpass.c
@@ -1,13 +1,16 @@
-#include <openssl/bn.h>
-#include <openssl/evp.h>
-
 #include <stdint.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 
+#include <getopt.h>
+#include <openssl/bn.h>
+#include <openssl/evp.h>
+
 #define MAX_BUF 1024
 #define ENTROPY_ITERATIONS 100000
 #define ENTROPY_KEY_LENGTH 32
+#define DEFAULT_LENGTH 16
 
 #define CHAR_SUBSET_LOWER "abcdefghijklmnopqrstuvwxyz"
 #define CHAR_SUBSET_UPPER "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
@@ -19,6 +22,13 @@ const char *CHAR_SET = (CHAR_SUBSET_LOWER
                         CHAR_SUBSET_DIGITS
                         CHAR_SUBSET_SYMBOLS);
 
+enum CharSet {
+    CHAR_SET_LOWER   = 1 << 0,
+    CHAR_SET_UPPER   = 1 << 1,
+    CHAR_SET_DIGITS  = 1 << 2,
+    CHAR_SET_SYMBOLS = 1 << 3,
+};
+
 static BIGNUM *
 calc_entropy(const char *site,
              const char *login,
@@ -30,7 +40,7 @@ calc_entropy(const char *site,
     memset(salt, 0, sizeof(salt));
     int saltlen = snprintf(salt, MAX_BUF, "%s%s%lx", site, login, counter);
     if (saltlen > MAX_BUF) {
-        return 0;
+        return NULL;
     }
 
     unsigned char key[ENTROPY_KEY_LENGTH];
@@ -42,7 +52,7 @@ calc_entropy(const char *site,
                                    ENTROPY_KEY_LENGTH,
                                    key);
     if (status == 0) {
-        return 0;
+        return NULL;
     }
 
     /* NULL as last arg to allocate a new BIGNUM */
@@ -132,26 +142,87 @@ render_pass(BIGNUM *entropy, char *out, int length)
     insert_str_pseudo_randomly(out, entropy, str_to_add);
 }
 
+static void
+err(const char *msg)
+{
+    fprintf(stderr, "lpass: %s\n", msg);
+    exit(EXIT_FAILURE);
+}
+
+static void
+usage()
+{
+    fputs("usage: lpass SITE LOGIN [OPTIONS]\n", stderr);
+    fputs("\nlpass is a C implementation of LessPass, a stateless password manager.\n", stderr);
+    fputs("\nPositional arguments:\n", stderr);
+    fputs("  SITE    The domain name or URL used in password generation.\n", stderr);
+    fputs("  LOGIN   The username/login used in that domain or URL.\n", stderr);
+    fputs("\nOptions:\n", stderr);
+    fputs("  -L LENGTH, --length LENGTH\n", stderr);
+    fputs("                      password length (default: 16)\n", stderr);
+    fputs("  --no-symbols        no symbols in password\n", stderr);
+    fputs("\nThe environment variable LESSPASS_MASTER_PASSWORD must be set with the master\n", stderr);
+    fputs("password for producing the desired password.\n", stderr);
+}
+
 int
 main(int argc, char *argv[])
 {
-    if (argc != 5) {
-        return 1;
+    const char *master_pass = getenv("LESSPASS_MASTER_PASSWORD");
+    if (master_pass == NULL) {
+        err("environment variable LESSPASS_MASTER_PASSWORD is not set");
     }
 
-    const char *master_pass = argv[1];
-    int passlen = strlen(master_pass);
-    const char *site = argv[2];
-    const char *login = argv[3];
-    int length = 0;
-    if (sscanf(argv[4], "%d", &length) == 0) {
-        return 1;
+    int c;
+    int length = DEFAULT_LENGTH;
+    uint8_t charsets = 0;
+    for (;;) {
+        int option_index = 0;
+        static struct option long_options[] = {
+            {"length",     required_argument, 0, 'L'},
+            {"no-symbols", no_argument,       0,  0 },
+            {0,            0,                 0,  0 }
+        };
+
+        c = getopt_long(argc, argv, "L:", long_options, &option_index);
+        if (c == -1) {
+            break;
+        }
+
+        switch (c) {
+        case 0:
+            if (option_index == 1) {
+                /* TODO: no-symbols */
+            }
+            break;
+        case 'L':
+            if (!optarg || sscanf(optarg, "%d", &length) == 0 || length < 1) {
+                usage();
+                exit(EXIT_FAILURE);
+            }
+            break;
+        default:
+            usage();
+            exit(EXIT_FAILURE);
+        }
+    }
+
+    /*
+     * We are still looking for 2 positional arguments, abort if they
+     * are not there.
+     */
+    if (optind > argc - 2) {
+        usage();
+        exit(EXIT_FAILURE);
     }
 
+    const char *site = argv[optind++];
+    const char *login = argv[optind++];
+    int passlen = strlen(master_pass);
     uint64_t counter = 1;
     BIGNUM *entropy = calc_entropy(site, login, counter, master_pass, passlen);
     if (entropy == NULL) {
-        return 1;
+        err("Failed to calculate entropy");
     }
 
     char generated_pass[length + 1];
@@ -159,5 +230,5 @@ main(int argc, char *argv[])
     render_pass(entropy, generated_pass, length);
     printf("%s\n", generated_pass);
     BN_free(entropy);
-    return 0;
+    return EXIT_SUCCESS;
 }
-- 
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