diff options
Diffstat (limited to 'src/or/rendcommon.c')
| -rw-r--r-- | src/or/rendcommon.c | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/src/or/rendcommon.c b/src/or/rendcommon.c index 22599e9830..a9fdf84c04 100644 --- a/src/or/rendcommon.c +++ b/src/or/rendcommon.c @@ -936,3 +936,113 @@ rend_data_client_create(const char *onion_address, const char *desc_id, return NULL; } +/* Length of the 'extended' auth cookie used to encode auth type before + * base64 encoding. */ +#define REND_DESC_COOKIE_LEN_EXT (REND_DESC_COOKIE_LEN + 1) +/* Length of the zero-padded auth cookie when base64 encoded. These two + * padding bytes always (A=) are stripped off of the returned cookie. */ +#define REND_DESC_COOKIE_LEN_EXT_BASE64 (REND_DESC_COOKIE_LEN_BASE64 + 2) + +/** Encode a client authorization descriptor cookie. + * The result of this function is suitable for use in the HidServAuth + * option. The trailing padding characters are removed, and the + * auth type is encoded into the cookie. + * + * Returns a new base64-encoded cookie. This function cannot fail. + * The caller is responsible for freeing the returned value. + */ +char * +rend_auth_encode_cookie(const uint8_t *cookie_in, rend_auth_type_t auth_type) +{ + uint8_t extended_cookie[REND_DESC_COOKIE_LEN_EXT]; + char *cookie_out = tor_malloc_zero(REND_DESC_COOKIE_LEN_EXT_BASE64 + 1); + int re; + + tor_assert(cookie_in); + + memcpy(extended_cookie, cookie_in, REND_DESC_COOKIE_LEN); + extended_cookie[REND_DESC_COOKIE_LEN] = ((int)auth_type - 1) << 4; + re = base64_encode(cookie_out, REND_DESC_COOKIE_LEN_EXT_BASE64 + 1, + (const char *) extended_cookie, REND_DESC_COOKIE_LEN_EXT, + 0); + tor_assert(re == REND_DESC_COOKIE_LEN_EXT_BASE64); + + /* Remove the trailing 'A='. Auth type is encoded in the high bits + * of the last byte, so the last base64 character will always be zero + * (A). This is subtly different behavior from base64_encode_nopad. */ + cookie_out[REND_DESC_COOKIE_LEN_BASE64] = '\0'; + memwipe(extended_cookie, 0, sizeof(extended_cookie)); + return cookie_out; +} + +/** Decode a base64-encoded client authorization descriptor cookie. + * The descriptor_cookie can be truncated to REND_DESC_COOKIE_LEN_BASE64 + * characters (as given to clients), or may include the two padding + * characters (as stored by the service). + * + * The result is stored in REND_DESC_COOKIE_LEN bytes of cookie_out. + * The rend_auth_type_t decoded from the cookie is stored in the + * optional auth_type_out parameter. + * + * Return 0 on success, or -1 on error. The caller is responsible for + * freeing the returned err_msg. + */ +int +rend_auth_decode_cookie(const char *cookie_in, uint8_t *cookie_out, + rend_auth_type_t *auth_type_out, char **err_msg_out) +{ + uint8_t descriptor_cookie_decoded[REND_DESC_COOKIE_LEN_EXT + 1] = { 0 }; + char descriptor_cookie_base64ext[REND_DESC_COOKIE_LEN_EXT_BASE64 + 1]; + const char *descriptor_cookie = cookie_in; + char *err_msg = NULL; + int auth_type_val = 0; + int res = -1; + int decoded_len; + + size_t len = strlen(descriptor_cookie); + if (len == REND_DESC_COOKIE_LEN_BASE64) { + /* Add a trailing zero byte to make base64-decoding happy. */ + tor_snprintf(descriptor_cookie_base64ext, + sizeof(descriptor_cookie_base64ext), + "%sA=", descriptor_cookie); + descriptor_cookie = descriptor_cookie_base64ext; + } else if (len != REND_DESC_COOKIE_LEN_EXT_BASE64) { + tor_asprintf(&err_msg, "Authorization cookie has wrong length: %s", + escaped(cookie_in)); + goto err; + } + + decoded_len = base64_decode((char *) descriptor_cookie_decoded, + sizeof(descriptor_cookie_decoded), + descriptor_cookie, + REND_DESC_COOKIE_LEN_EXT_BASE64); + if (decoded_len != REND_DESC_COOKIE_LEN && + decoded_len != REND_DESC_COOKIE_LEN_EXT) { + tor_asprintf(&err_msg, "Authorization cookie has invalid characters: %s", + escaped(cookie_in)); + goto err; + } + + if (auth_type_out) { + auth_type_val = (descriptor_cookie_decoded[REND_DESC_COOKIE_LEN] >> 4) + 1; + if (auth_type_val < 1 || auth_type_val > 2) { + tor_asprintf(&err_msg, "Authorization cookie type is unknown: %s", + escaped(cookie_in)); + goto err; + } + *auth_type_out = auth_type_val == 1 ? REND_BASIC_AUTH : REND_STEALTH_AUTH; + } + + memcpy(cookie_out, descriptor_cookie_decoded, REND_DESC_COOKIE_LEN); + res = 0; + err: + if (err_msg_out) { + *err_msg_out = err_msg; + } else { + tor_free(err_msg); + } + memwipe(descriptor_cookie_decoded, 0, sizeof(descriptor_cookie_decoded)); + memwipe(descriptor_cookie_base64ext, 0, sizeof(descriptor_cookie_base64ext)); + return res; +} + |