Genesis commit

1 files changed, 265 insertions, 0 deletions

diff --git a/main.c b/main.c
new file mode 100644
index 0000000..d6168ab
--- /dev/null
+++ b/main.c
@@ -0,0 +1,265 @@
+/* References: https://datatracker.ietf.org/doc/html/rfc4226#section-5 */
+
+#include <err.h>
+#include <getopt.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+#include <time.h>
+
+#include <openssl/hmac.h>
+#include <uriparser/Uri.h>
+#include <uriparser/UriBase.h>
+
+#include "b32.h"
+
+#define DIE(...) err(EXIT_FAILURE, __VA_ARGS__)
+#define DIEX(...) errx(EXIT_FAILURE, __VA_ARGS__)
+#define STREQ(x, y) (strcmp(x, y) == 0)
+#define PRINT_CODE(w, x) printf("%0*d\n", (int)w, x)
+
+#define TOTP_DEFAULT (struct totp_config){ .len = 6, .p = 30 }
+
+typedef unsigned char uchar;
+
+struct totp_config {
+	const char *enc_sec;
+	long len, p;
+};
+
+extern char *__progname;
+
+static const char *bad_scheme = "Invalid scheme ‘%.*s’; expected ‘otpauth’";
+static const char *bad_param = "Invalid ‘%s’ parameter provided";
+static const char *empty_param = "Empty ‘%s’ parameter provided";
+static const char *usage_s =
+	"Usage: %s [-d digits] [-p period] [secret ...]\n"
+	"       %s [-u] [uri ...]\n";
+
+static void      usage(void);
+static bool      strtol_safe(long *, const char *);
+static bool      totp(struct totp_config, uint32_t *);
+static uint32_t  pow32(uint32_t, uint32_t);
+static bool      uri_parse(struct totp_config *, const char *);
+
+void
+usage(void)
+{
+	fprintf(stderr, usage_s, __progname, __progname);
+	exit(EXIT_FAILURE);
+}
+
+int
+main(int argc, char *argv[])
+{
+	int opt, rv;
+	bool uflag = false;
+	long n;
+	char *buf;
+	size_t bufsiz;
+	ssize_t nr;
+	uint32_t code;
+	struct totp_config conf = TOTP_DEFAULT;
+	struct option longopts[] = {
+		{"digits", required_argument, 0, 'd'},
+		{"period", required_argument, 0, 'p'},
+		{"uri",    no_argument,       0, 'u'},
+		{ NULL,    0,                 0,  0 },
+	};
+
+	while ((opt = getopt_long(argc, argv, "d:p:u", longopts, NULL)) != -1) {
+		switch (opt) {
+		case 'd':
+		case 'p':
+			if (!strtol_safe(&n, optarg))
+				DIEX(bad_param, opt == 'd' ? "digits" : "period");
+			if (opt == 'd')
+				conf.len = n;
+			else
+				conf.p = n;
+			break;
+		case 'u':
+			uflag = true;
+			break;
+		default:
+			usage();
+		}
+	}
+
+	argc -= optind;
+	argv += optind;
+
+	rv = EXIT_SUCCESS;
+
+	for (int i = 0; i < argc; i++) {
+		conf.enc_sec = argv[i];
+		if (uflag) {
+			conf = TOTP_DEFAULT;
+			if (!uri_parse(&conf, argv[i])) {
+				rv = EXIT_FAILURE;
+				continue;
+			}
+		} else
+			conf.enc_sec = argv[i];
+		if (totp(conf, &code))
+			PRINT_CODE(conf.len, code);
+	}
+
+	if (argc == 0) {
+		buf = NULL;
+		bufsiz = 0;
+
+		while ((nr = getline(&buf, &bufsiz, stdin)) > 0) {
+			if (buf[--nr] == '\n')
+				buf[nr] = '\0';
+			if (uflag) {
+				conf = TOTP_DEFAULT;
+				if (!uri_parse(&conf, buf)) {
+					rv = EXIT_FAILURE;
+					continue;
+				}
+			} else
+				conf.enc_sec = buf;
+			if (totp(conf, &code))
+				PRINT_CODE(conf.len, code);
+		}
+	}
+
+	return rv;
+}
+
+bool
+uri_parse(struct totp_config *conf, const char *uri_raw)
+{
+	int n;
+	bool reject;
+	size_t len;
+	UriUriA uri;
+	UriQueryListA *qs;
+	const char *epos;
+
+	if ((n = uriParseSingleUriA(&uri, uri_raw, &epos)) != URI_SUCCESS) {
+		len = epos - uri_raw;
+		warnx("Failed to parse URI ‘%s’\n"
+		      "%*c Error detected here",
+		      uri_raw, (int)(len + 24 + strlen(__progname)), '^');
+		return false;
+	}
+
+	len = uri.scheme.afterLast - uri.scheme.first;
+	reject = len != strlen("otpauth");
+	reject = reject || strncasecmp(uri.scheme.first, "otpauth", len) != 0;
+
+	if (reject) {
+		warnx(bad_scheme, (int)len, uri.scheme.first);
+		return false;
+	}
+	if (uriDissectQueryMallocA(&qs, NULL, uri.query.first,
+	                           uri.query.afterLast) != URI_SUCCESS) {
+		warnx("Failed to parse query string");
+		return false;
+	}
+
+	for (UriQueryListA *p = qs; p != NULL; p = p->next) {
+		if (STREQ(p->key, "secret")) {
+			if (p->value == NULL) {
+				warnx("Secret key has no value");
+				return false;
+			}
+			conf->enc_sec = p->value;
+		} else if (STREQ(p->key, "digits")) {
+			if (p->value == NULL) {
+				warnx(empty_param, "digits");
+				return false;
+			}
+			if (!strtol_safe(&conf->len, p->value)) {
+				warnx(bad_param, "digits");
+				return false;
+			}
+		} else if (STREQ(p->key, "period")) {
+			if (p->value == NULL) {
+				warnx(empty_param, "period");
+				return false;
+			}
+			if (!strtol_safe(&conf->p, p->value)) {
+				warnx(bad_param, "period");
+				return false;
+			}
+		}
+	}
+
+	uriFreeQueryListA(qs);
+	uriFreeUriMembersA(&uri);
+
+	return true;
+}
+
+bool
+totp(struct totp_config conf, uint32_t *code)
+{
+	int off;
+	char *key;
+	uchar *mac;
+	time_t epoch;
+	size_t keylen;
+	uint8_t buf[sizeof(time_t)];  /* Enough for a 64bit num */
+	uint32_t binc;
+	
+	/* TODO: conf.enc_sec needs to be ‘=’ padded to a multiple of 8 */
+
+	/* When decoding base32, you need ceil(conf.enc_sec / 1.6) bytes */
+	keylen = strlen(conf.enc_sec) / 1.6 + 1;
+	key = calloc(keylen, sizeof(char));
+	b32toa(key, conf.enc_sec, strlen(conf.enc_sec));
+
+	if (time(&epoch) == (time_t)-1)
+		DIE("time");
+
+	epoch /= conf.p;
+
+	buf[0] = (epoch >> 56) & 0xFF;
+	buf[1] = (epoch >> 48) & 0xFF;
+	buf[2] = (epoch >> 40) & 0xFF;
+	buf[3] = (epoch >> 32) & 0xFF;
+	buf[4] = (epoch >> 24) & 0xFF;
+	buf[5] = (epoch >> 16) & 0xFF;
+	buf[6] = (epoch >>  8) & 0xFF;
+	buf[7] = (epoch >>  0) & 0xFF;
+	
+	mac = HMAC(EVP_sha1(), key, keylen, buf, sizeof(buf), NULL, NULL);
+	if (mac == NULL)
+		return false;
+
+        /* SHA1 hashes are 20 bytes long */
+	off = mac[19] & 0x0F;
+	binc = (mac[off + 0] & 0x7F) << 24
+             | (mac[off + 1] & 0xFF) << 16
+             | (mac[off + 2] & 0xFF) <<  8
+             | (mac[off + 3] & 0xFF) <<  0;
+
+	*code = binc % pow32(10, conf.len);
+	return true;
+}
+
+bool
+strtol_safe(long *n, const char *s)
+{
+	char *e;
+	*n = strtol(s, &e, 10);
+	return *n > 0 && *s != '\0' && *e == '\0';
+}
+
+/* This could overflow if you did some autistic shit */
+uint32_t
+pow32(uint32_t x, uint32_t y)
+{
+	int n = x;
+	if (y == 0)
+		return 1;
+	while (--y != 0)
+		x *= n;
+	return x;
+}