core: add support of TOTP generation/validation (Time-based One-Time Password)

4 files changed, 357 insertions, 0 deletions

diff --git a/src/core/wee-secure.c b/src/core/wee-secure.c
index c4382d3f9..b9abe62c9 100644
--- a/src/core/wee-secure.c
+++ b/src/core/wee-secure.c
@@ -25,6 +25,9 @@
 
 #include <stdlib.h>
 #include <stdio.h>
+#include <stdint.h>
+#include <time.h>
+#include <math.h>
 #include <gcrypt.h>
 
 #include "weechat.h"
@@ -495,6 +498,195 @@ secure_decrypt_data_not_decrypted (const char *passphrase)
 }
 
 /*
+ * Generates a Time-based One-Time Password (TOTP), as described
+ * in the RFC 6238.
+ *
+ * Returns:
+ *   1: OK
+ *   0: error
+ */
+
+int
+secure_totp_generate_internal (const char *secret, int length_secret,
+                               uint64_t moving_factor, int digits,
+                               char *result)
+{
+    gcry_md_hd_t hd_md;
+    uint64_t moving_factor_swapped;
+    unsigned char *ptr_hash;
+    char hash[20];
+    int offset, length;
+    unsigned long bin_code;
+
+    if (gcry_md_open (&hd_md, GCRY_MD_SHA1, GCRY_MD_FLAG_HMAC) != 0)
+        return 0;
+
+    if (gcry_md_setkey (hd_md, secret, length_secret) != 0)
+    {
+        gcry_md_close (hd_md);
+        return 0;
+    }
+
+    moving_factor_swapped = (moving_factor >> 56)
+        | ((moving_factor << 40) & 0x00FF000000000000)
+        | ((moving_factor << 24) & 0x0000FF0000000000)
+        | ((moving_factor << 8) & 0x000000FF00000000)
+        | ((moving_factor >> 8) & 0x00000000FF000000)
+        | ((moving_factor >> 24) & 0x0000000000FF0000)
+        | ((moving_factor >> 40) & 0x000000000000FF00)
+        | (moving_factor << 56);
+
+    gcry_md_write (hd_md,
+                   &moving_factor_swapped, sizeof (moving_factor_swapped));
+
+    ptr_hash = gcry_md_read (hd_md, GCRY_MD_SHA1);
+    if (!ptr_hash)
+    {
+        gcry_md_close (hd_md);
+        return 0;
+    }
+
+    memcpy (hash, ptr_hash, sizeof (hash));
+
+    gcry_md_close (hd_md);
+
+    offset = hash[19] & 0xf;
+    bin_code = (hash[offset] & 0x7f) << 24
+        | (hash[offset+1] & 0xff) << 16
+        | (hash[offset+2] & 0xff) <<  8
+        | (hash[offset+3] & 0xff);
+
+    bin_code %= (unsigned long)(pow (10, digits));
+
+    length = snprintf (result, digits + 1, "%.*lu", digits, bin_code);
+    if (length != digits)
+        return 0;
+
+    return 1;
+}
+
+/*
+ * Generates a Time-based One-Time Password (TOTP), as described
+ * in the RFC 6238.
+ *
+ * Returns the password as string, NULL if error.
+ *
+ * Note: result must be freed after use.
+ */
+
+char *
+secure_totp_generate (const char *secret_base32, time_t totp_time, int digits)
+{
+    char *result, *secret;
+    int length_secret, rc;
+    uint64_t moving_factor;
+
+    secret = NULL;
+    result = NULL;
+
+    if (!secret_base32 || !secret_base32[0]
+        || (digits < SECURE_TOTP_MIN_DIGITS)
+        || (digits > SECURE_TOTP_MAX_DIGITS))
+    {
+        goto error;
+    }
+
+    secret = malloc ((strlen (secret_base32) * 4) + 16 + 1);
+    if (!secret)
+        goto error;
+
+    length_secret = string_decode_base32 (secret_base32, secret);
+    if (length_secret < 0)
+        goto error;
+
+    result = malloc (digits + 1);
+    if (!result)
+        goto error;
+
+    if (totp_time == 0)
+        totp_time = time (NULL);
+
+    moving_factor = totp_time / 30;
+
+    rc = secure_totp_generate_internal (secret, length_secret,
+                                        moving_factor, digits, result);
+    if (!rc)
+        goto error;
+
+    free (secret);
+
+    return result;
+
+error:
+    if (secret)
+        free (secret);
+    if (result)
+        free (result);
+    return NULL;
+}
+
+/*
+ * Validates a Time-based One-Time Password (TOTP).
+ *
+ * Returns:
+ *   1: OTP is OK
+ *   0: OTP is invalid
+ */
+
+int
+secure_totp_validate (const char *secret_base32, time_t totp_time, int window,
+                      const char *otp)
+{
+    char *secret, str_otp[16];
+    int length_secret, digits, rc, otp_ok;
+    uint64_t i, moving_factor;
+
+    secret = NULL;
+
+    if (!secret_base32 || !secret_base32[0] || (window < 0) || !otp || !otp[0])
+        goto error;
+
+    digits = strlen (otp);
+    if ((digits < SECURE_TOTP_MIN_DIGITS) || (digits > SECURE_TOTP_MAX_DIGITS))
+        goto error;
+
+    secret = malloc (strlen (secret_base32) + 1);
+    if (!secret)
+        goto error;
+
+    length_secret = string_decode_base32 (secret_base32, secret);
+    if (length_secret < 0)
+        goto error;
+
+    if (totp_time == 0)
+        totp_time = time (NULL);
+
+    moving_factor = totp_time / 30;
+
+    otp_ok = 0;
+
+    for (i = moving_factor - window; i <= moving_factor + window; i++)
+    {
+        rc = secure_totp_generate_internal (secret, length_secret,
+                                            i, digits, str_otp);
+        if (rc && (strcmp (str_otp, otp) == 0))
+        {
+            otp_ok = 1;
+            break;
+        }
+    }
+
+    free (secret);
+
+    return otp_ok;
+
+error:
+    if (secret)
+        free (secret);
+    return 0;
+}
+
+/*
  * Initializes secured data.
  *
  * Returns:
diff --git a/src/core/wee-secure.h b/src/core/wee-secure.h
index 4a2e9dc9d..f20a249fd 100644
--- a/src/core/wee-secure.h
+++ b/src/core/wee-secure.h
@@ -24,6 +24,8 @@
 #define SECURE_SALT_DEFAULT         "WeeChat!"
 #define SECURE_DATA_PASSPHRASE_FLAG "__passphrase__"
 #define SECURE_SALT_SIZE            8
+#define SECURE_TOTP_MIN_DIGITS      4
+#define SECURE_TOTP_MAX_DIGITS      10
 
 enum t_secure_config_hash_algo
 {
@@ -59,6 +61,10 @@ extern int secure_decrypt_data (const char *buffer, int length_buffer,
                                 const char *passphrase, char **decrypted,
                                 int *length_decrypted);
 extern int secure_decrypt_data_not_decrypted (const char *passphrase);
+extern char *secure_totp_generate (const char *secret, time_t totp_time,
+                                   int digits);
+extern int secure_totp_validate (const char *secret, time_t totp_time,
+                                 int window, const char *otp);
 extern int secure_init ();
 extern void secure_end ();
 
diff --git a/src/core/wee-string.c b/src/core/wee-string.c
index 9c525ff6c..8ff1de3de 100644
--- a/src/core/wee-string.c
+++ b/src/core/wee-string.c
@@ -2776,6 +2776,163 @@ string_decode_base16 (const char *from, char *to)
 }
 
 /*
+ * Encodes a string in base32.
+ *
+ * Argument "length" is number of bytes in "from" to convert (commonly
+ * strlen(from)).
+ *
+ * This function is inspired by:
+ *   https://github.com/google/google-authenticator-libpam/blob/master/src/base32.c
+ *
+ * Original copyright:
+ *
+ *   Copyright 2010 Google Inc.
+ *   Author: Markus Gutschke
+ *
+ *   Licensed under the Apache License, Version 2.0 (the "License");
+ *   you may not use this file except in compliance with the License.
+ *   You may obtain a copy of the License at
+ *
+ *        http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *   Unless required by applicable law or agreed to in writing, software
+ *   distributed under the License is distributed on an "AS IS" BASIS,
+ *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *   See the License for the specific language governing permissions and
+ *   limitations under the License.
+ *
+ * Returns length of string in "*to" (it does not count final \0).
+ */
+
+int
+string_encode_base32 (const char *from, int length, char *to)
+{
+    unsigned char base32_table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
+    int count, value, next, bits_left, pad, index;
+    int length_padding[8] = { 0, 0, 6, 0, 4, 3, 0, 2 };
+
+    if (!from || !to)
+        return -1;
+
+    count = 0;
+
+    if (length > 0)
+    {
+        value = from[0];
+        next = 1;
+        bits_left = 8;
+        while ((bits_left > 0) || (next < length))
+        {
+            if (bits_left < 5)
+            {
+                if (next < length)
+                {
+                    value <<= 8;
+                    value |= from[next++] & 0xFF;
+                    bits_left += 8;
+                }
+                else
+                {
+                    pad = 5 - bits_left;
+                    value <<= pad;
+                    bits_left += pad;
+                }
+            }
+            index = 0x1F & (value >> (bits_left - 5));
+            bits_left -= 5;
+            to[count++] = base32_table[index];
+        }
+    }
+    pad = length_padding[count % 8];
+    while (pad > 0)
+    {
+        to[count++] = '=';
+        pad--;
+    }
+    to[count] = '\0';
+
+    return count;
+}
+
+/*
+ * Decodes a base32 string.
+ *
+ * This function is inspired by:
+ *   https://github.com/google/google-authenticator-libpam/blob/master/src/base32.c
+ *
+ * Original copyright:
+ *
+ *   Copyright 2010 Google Inc.
+ *   Author: Markus Gutschke
+ *
+ *   Licensed under the Apache License, Version 2.0 (the "License");
+ *   you may not use this file except in compliance with the License.
+ *   You may obtain a copy of the License at
+ *
+ *        http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *   Unless required by applicable law or agreed to in writing, software
+ *   distributed under the License is distributed on an "AS IS" BASIS,
+ *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *   See the License for the specific language governing permissions and
+ *   limitations under the License.
+ *
+ *
+ * Returns length of string in "*to" (it does not count final \0).
+ */
+
+int
+string_decode_base32 (const char *from, char *to)
+{
+    const char *ptr_from;
+    int value, bits_left, count;
+    unsigned char c;
+
+    if (!from || !to)
+        return -1;
+
+    ptr_from = from;
+    value = 0;
+    bits_left = 0;
+    count = 0;
+
+    while (ptr_from[0])
+    {
+        c = (unsigned char)ptr_from[0];
+        value <<= 5;
+        if (((c >= 'A') && (c <= 'Z')) || ((c >= 'a') && (c <= 'z')))
+        {
+            c = (c & 0x1F) - 1;
+        }
+        else if ((c >= '2') && (c <= '7'))
+        {
+            c -= '2' - 26;
+        }
+        else if (c == '=')
+        {
+            /* padding */
+            break;
+        }
+        else
+        {
+            /* invalid base32 char */
+            return -1;
+        }
+        value |= c;
+        bits_left += 5;
+        if (bits_left >= 8)
+        {
+            to[count++] = value >> (bits_left - 8);
+            bits_left -= 8;
+        }
+        ptr_from++;
+    }
+    to[count] = '\0';
+
+    return count;
+}
+
+/*
  * Converts 3 bytes of 8 bits in 4 bytes of 6 bits.
  */
 
diff --git a/src/core/wee-string.h b/src/core/wee-string.h
index 605aa1598..7e33352c8 100644
--- a/src/core/wee-string.h
+++ b/src/core/wee-string.h
@@ -107,6 +107,8 @@ extern int string_fprintf (FILE *file, const char *data, ...);
 extern char *string_format_size (unsigned long long size);
 extern void string_encode_base16 (const char *from, int length, char *to);
 extern int string_decode_base16 (const char *from, char *to);
+extern int string_encode_base32 (const char *from, int length, char *to);
+extern int string_decode_base32 (const char *from, char *to);
 extern void string_encode_base64 (const char *from, int length, char *to);
 extern int string_decode_base64 (const char *from, char *to);
 extern char *string_hex_dump (const char *data, int data_size,