c: Implement the passgeny module.

This is the C implementation of the passgeny library.

c/passgeny/inc/passgeny.h

@@ -0,0 +1,56 @@
+#ifndef PASSGENY_H_INCLUDED
+#define PASSGENY_H_INCLUDED
+
+#include <stdint.h>
+#include <stdbool.h>
+
+typedef struct passgeny passgeny_t;
+
+struct passgeny
+{
+    uint8_t     pg_master_hash[32];                 /* SHA256 of the master password */
+    char       *pg_pattern;                         /* Password pattern */
+    double      pg_last_bits_total;                 /* Total bits that were available for generating the last password */
+    double      pg_last_bits_used;                  /* Bits consumed when calculating the last password */
+};
+
+/*
+ * Initialize a new passgeny instance
+ *
+ * Note: The master password is hashed and remembered. The raw password is never
+ * stored in memory.
+ */
+bool passgeny_init(passgeny_t *passgeny, const char *master_password);
+
+/*
+ * Destroy a passgeny instance
+ */
+void passgeny_fini(passgeny_t *passgeny);
+
+/*
+ * Set the current pattern
+ */
+void passgeny_set_pattern(passgeny_t *passgeny, const char *pattern);
+
+/*
+ * Generate a new passgeny password using `domain`, `username` and optional
+ * tokens.
+ *
+ * The password is stored in the `out` string, where `out_sz` represents the
+ * maximum size of the string including '\0'
+ */
+bool passgeny_generate(
+        passgeny_t *passgeny,
+        char *out,
+        size_t out_sz,
+        const char *domain,
+        const char *username,
+        const char * const toknes[],
+        int ntokens);
+
+/*
+ * Dump some statistics
+ */
+void passgeny_dump_verbose(const passgeny_t *passgeny);
+
+#endif /* PASSGENY_H_INCLUDED */

c/passgeny/meson.build

@@ -0,0 +1,10 @@
+
+passgeny_inc = include_directories('inc')
+
+passgeny_lib = static_library(
+        'passgeny',
+        ['src/passgeny.c'],
+        include_directories : passgeny_inc,
+        dependencies: [ dependency('libcrypto'), dependency('libargon2'), phogen_dep, bhash_dep])
+
+passgeny_dep = declare_dependency(link_with : passgeny_lib, include_directories : passgeny_inc)

c/passgeny/src/passgeny.c

@@ -0,0 +1,341 @@
+#include <ctype.h>
+#include <regex.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <openssl/sha.h>
+#include <argon2.h>
+
+#include "bhash.h"
+#include "phogen.h"
+
+#include "passgeny.h"
+
+/*
+ * =========================================================================
+ * Passgeny default parameters and constants
+ * =========================================================================
+ */
+
+/*
+ * The default pattern used for password generation
+ */
+#define PASSGENY_DEFAULT_PATTERN "^6p^6p^6ps2p100d"
+
+/*
+ * List of special characters (order is important)
+ */
+#define PASSGENY_SPECIAL "-./=_ "
+
+/*
+ * Argon2 parameters
+ */
+#define PASSGENY_ARGON2_SALT            "Passgeny v1"
+#define PASSGENY_ARGON2_MEMORY_COST     8192
+#define PASSGENY_ARGON2_TIME_COST       6
+#define PASSGENY_ARGON2_PARALLEL        4
+#define PASSGENY_ARGON2_HASH_LEN        128
+
+/* Ensure that pg_master_hash is big enough to hold a SHA256 hash */
+_Static_assert(
+        sizeof(((passgeny_t *)NULL)->pg_master_hash) == SHA256_DIGEST_LENGTH,
+        "pg_master_hash doesn't match SHA256_DIGEST_LENGTH");
+
+static bool passgeny_patmatch(
+        const char **pstr,
+        const char *pattern,
+        char *out,
+        size_t out_len);
+
+static void passgeny_gen_str(char *out, size_t out_sz, const char *pool, bhash_t *bh);
+
+/*
+ * =========================================================================
+ * Public API
+ * =========================================================================
+ */
+bool passgeny_init(passgeny_t *passgeny, const char *master_password)
+{
+    SHA256_CTX sha256;
+
+    memset(passgeny, 0, sizeof(*passgeny));
+
+    SHA256_Init(&sha256);
+    SHA256_Update(&sha256, master_password, strlen(master_password));
+    SHA256_Final(passgeny->pg_master_hash, &sha256);
+
+    passgeny->pg_pattern = strdup(PASSGENY_DEFAULT_PATTERN);
+
+    return true;
+}
+
+void passgeny_fini(passgeny_t *passgeny)
+{
+    /* Just nuke the master hash from memory */
+    explicit_bzero(passgeny->pg_master_hash, sizeof(passgeny->pg_master_hash));
+    free(passgeny->pg_pattern);
+}
+
+void passgeny_set_pattern(passgeny_t *passgeny, const char *pattern)
+{
+    free(passgeny->pg_pattern);
+    passgeny->pg_pattern = strdup(pattern);
+}
+
+bool passgeny_generate(
+        passgeny_t *passgeny,
+        char *out,
+        size_t out_sz,
+        const char *domain,
+        const char *username,
+        const char * const tokens[],
+        int ntokens)
+{
+    char ahash[PASSGENY_ARGON2_HASH_LEN];
+    char popt[32];
+    bhash_t bh;
+    int ti;
+    int rc;
+
+    const char *ppat = passgeny->pg_pattern;
+
+    /*
+     * Generate the Argon2 hash
+     */
+
+    /* Caculate the input length */
+    size_t in_len = 0;
+    in_len += strlen(domain) + 1;
+    in_len += strlen(username) + 1;
+    in_len += sizeof(passgeny->pg_master_hash);
+
+    for (ti = 0; ti < ntokens; ti++)
+    {
+        in_len += strlen(tokens[ti]);
+    }
+
+    char in[in_len];
+    char *pin = in;
+
+    strcpy(pin, domain);
+    pin += strlen(domain) + 1;
+
+    strcpy(pin, username);
+    pin += strlen(username) + 1;
+
+    for (ti = 0; ti < ntokens; ti++)
+    {
+        strcpy(pin, tokens[ti]);
+        pin += strlen(tokens[ti]) + 1;
+    }
+
+    memcpy(pin, passgeny->pg_master_hash, sizeof(passgeny->pg_master_hash));
+    pin += sizeof(passgeny->pg_master_hash);
+
+    rc = argon2id_hash_raw(
+            PASSGENY_ARGON2_TIME_COST,
+            PASSGENY_ARGON2_MEMORY_COST,
+            PASSGENY_ARGON2_PARALLEL,
+            in,
+            pin - in,
+            PASSGENY_ARGON2_SALT,
+            strlen(PASSGENY_ARGON2_SALT),
+            ahash,
+            sizeof(ahash));
+    if (rc != 0)
+    {
+        fprintf(stderr, "Error generating argon2 hash.");
+        return false;
+    }
+
+    bhash_init(&bh, ahash, sizeof(ahash));
+
+    /*
+     * Generate the password according to the currently set pattern
+     */
+    char cword[256];
+    char cflags = '\0';
+    while (*ppat != 0)
+    {
+        if (passgeny_patmatch(&ppat, "\\^", popt, sizeof(popt)))
+        {
+            cflags = '^';
+            continue;
+        }
+        else if (passgeny_patmatch(&ppat, "([0-9]*)p", popt, sizeof(popt)))
+        {
+            size_t clen = atoi(popt);
+            if (clen >= sizeof(cword))
+            {
+                fprintf(stderr, "Invalid phogen length: %zd\n", clen);
+                return false;
+            }
+            else if (clen == 0)
+            {
+                clen = 1;
+            }
+
+            phogen_encode(cword, clen + 1, &bh);
+        }
+        else if (passgeny_patmatch(&ppat, "([0-9]*)s", popt, sizeof(popt)))
+        {
+            size_t clen = atoi(popt);
+            if (clen >= sizeof(cword))
+            {
+                fprintf(stderr, "Invalid special string length: %zd\n", clen);
+                return false;
+            }
+            else if (clen == 0)
+            {
+                clen = 1;
+            }
+
+            passgeny_gen_str(cword, clen + 1, PASSGENY_SPECIAL, &bh);
+        }
+        else if (passgeny_patmatch(&ppat, "([0-9]*)d", popt, sizeof(popt)))
+        {
+            int id = atoi(popt);
+            if (id > INT_MAX)
+            {
+                fprintf(stderr, "Invalid decimal length: %d\n", id);
+                return false;
+            }
+            else if (id == 0)
+            {
+                id = 10;
+            }
+
+            snprintf(cword, sizeof(cword), "%d", bhash_mod32(&bh, id));
+        }
+        else if (passgeny_patmatch(&ppat, "([0-9]*)x", popt, sizeof(popt)))
+        {
+            size_t clen = atoi(popt);
+            if (clen >= sizeof(cword))
+            {
+                fprintf(stderr, "Invalid hex string length: %zd\n", clen);
+                return false;
+            }
+            else if (clen == 0)
+            {
+                clen = 1;
+            }
+
+            passgeny_gen_str(cword, clen + 1, "0123456789abcdef", &bh);
+        }
+        else
+        {
+            printf("Error parsing pattern at: %s\n", ppat);
+            return false;
+        }
+
+        if (cflags == '^')
+        {
+            cword[0] = toupper(cword[0]);
+        }
+
+        /* Reset flags */
+        cflags = '\0';
+
+        /* Store cword to out */
+        size_t clen = strlen(cword);
+        if (clen >= out_sz)
+        {
+            fprintf(stderr, "passgeny: Output string buffer is too short.\n");
+            return false;
+        }
+
+        memcpy(out, cword, clen);
+        out += clen;
+        out_sz -= clen;
+    }
+
+    *out = '\0';
+
+    passgeny->pg_last_bits_total = bhash_bits_avail(&bh);
+    passgeny->pg_last_bits_used = bhash_bits_used(&bh);
+
+    return true;
+}
+
+void passgeny_dump_verbose(const passgeny_t *pg)
+{
+    fprintf(stderr, "Total hash size is %2.0f bits.\n", pg->pg_last_bits_total);
+    fprintf(stderr, "Used bits when generating the password: %0.2f.\n", pg->pg_last_bits_used);
+}
+
+/*
+ * =========================================================================
+ * Private functions
+ * =========================================================================
+ */
+
+/*
+ * Perform a pattern match on string `pstr`.
+ *
+ * If there's no match, this function returns false.
+ *
+ * If there's a match, pstr will be moved forward (past the pattern) and `opt`
+ * will be filled with the first group match in regex.
+ *
+ * The value stored in `opt` will be truncated if its too long.
+ */
+static bool passgeny_patmatch(
+        const char **pstr,
+        const char *pattern,
+        char *opt,
+        size_t opt_sz)
+{
+    regmatch_t rm[2];
+    regex_t re;
+
+    bool retval = false;
+
+    if (regcomp(&re, pattern, REG_EXTENDED) != 0)
+    {
+        return false;
+    }
+
+    if (regexec(&re, *pstr, sizeof(rm) / sizeof(rm[0]), rm, 0) == REG_NOMATCH)
+    {
+        goto exit;
+    }
+
+    /* All matches must start at the beginning of the string */
+    if (rm[0].rm_so != 0) goto exit;
+
+    if (opt != NULL && rm[1].rm_so >= 0 && rm[1].rm_eo >= 0)
+    {
+        size_t ropt_sz = rm[1].rm_eo - rm[1].rm_so + 1;
+        if (ropt_sz > opt_sz) ropt_sz = opt_sz;
+
+        memcpy(opt, *pstr + rm[1].rm_so, ropt_sz - 1);
+        opt[ropt_sz - 1] = '\0';
+    }
+
+    *pstr += rm[0].rm_eo;
+    retval = true;
+
+exit:
+    regfree(&re);
+    return retval;
+}
+
+/*
+ * Generate a string by using the bhash and a pool of characters
+ */
+static void passgeny_gen_str(char *out, size_t out_sz, const char *pool, bhash_t *bh)
+{
+    int ii;
+    size_t psz;
+
+    if (out_sz == 0) return;
+
+    psz = strlen(pool);
+
+    for (ii = 0; ii < (out_sz - 1); ii++)
+    {
+        out[ii] = pool[bhash_mod32(bh, psz)];
+    }
+    out[ii] = '\0';
+}