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Add minimal KDC MS-RPCE (NDR) encoder/decoder
Add NDR marshalling functions for S4U_DELEGATION_INFO PAC buffers. [ghudson@mit.edu: added safety checks; made minor style changes; edited commit message]
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| /* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */ | ||
| /* kdc/ndr.c - NDR encoding and decoding functions */ | ||
| /* | ||
| * Copyright (C) 2021 by Red Hat, Inc. | ||
| * All rights reserved. | ||
| * | ||
| * Redistribution and use in source and binary forms, with or without | ||
| * modification, are permitted provided that the following conditions | ||
| * are met: | ||
| * | ||
| * * Redistributions of source code must retain the above copyright | ||
| * notice, this list of conditions and the following disclaimer. | ||
| * | ||
| * * Redistributions in binary form must reproduce the above copyright | ||
| * notice, this list of conditions and the following disclaimer in | ||
| * the documentation and/or other materials provided with the | ||
| * distribution. | ||
| * | ||
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | ||
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | ||
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS | ||
| * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE | ||
| * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, | ||
| * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES | ||
| * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR | ||
| * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | ||
| * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, | ||
| * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) | ||
| * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED | ||
| * OF THE POSSIBILITY OF SUCH DAMAGE. | ||
| */ | ||
|
|
||
| #include "k5-int.h" | ||
| #include "k5-input.h" | ||
| #include "k5-buf.h" | ||
| #include "k5-utf8.h" | ||
| #include "kdc_util.h" | ||
|
|
||
| struct encoded_wchars { | ||
| uint16_t bytes_len; | ||
| uint16_t num_wchars; | ||
| uint8_t *encoded; | ||
| }; | ||
|
|
||
| /* | ||
| * MS-DTYP 2.3.10: | ||
| * | ||
| * typedef struct _RPC_UNICODE_STRING { | ||
| * unsigned short Length; | ||
| * unsigned short MaximumLength; | ||
| * [size_is(MaximumLength/2), length_is(Length/2)] WCHAR* Buffer; | ||
| * } RPC_UNICODE_STRING, *PRPC_UNICODE_STRING; | ||
| * | ||
| * Note that Buffer is not a String - there's no termination. | ||
| * | ||
| * We don't actually decode Length and MaximumLength here - this is a | ||
| * conformant-varying array, which means that (per DCE-1.1-RPC 14.3.7.2) where | ||
| * those actually appear in the serialized data is variable depending on | ||
| * whether the string is at top level of the struct or not. (This also | ||
| * affects where the pointer identifier appears.) | ||
| * | ||
| * See MS-RPCE 4.7 for what an RPC_UNICODE_STRING looks like when not at | ||
| * top-level. | ||
| */ | ||
| static krb5_error_code | ||
| dec_wchar_pointer(struct k5input *in, char **out) | ||
| { | ||
| const uint8_t *bytes; | ||
| uint32_t actual_count; | ||
|
|
||
| /* Maximum count. */ | ||
| (void)k5_input_get_uint32_le(in); | ||
| /* Offset - all zeroes, "should" not be checked. */ | ||
| (void)k5_input_get_uint32_le(in); | ||
|
|
||
| actual_count = k5_input_get_uint32_le(in); | ||
| if (actual_count > UINT32_MAX / 2) | ||
| return ERANGE; | ||
|
|
||
| bytes = k5_input_get_bytes(in, actual_count * 2); | ||
| if (bytes == NULL || k5_utf16le_to_utf8(bytes, actual_count * 2, out) != 0) | ||
| return EINVAL; | ||
|
|
||
| /* Always align on 4. */ | ||
| if (actual_count % 2 == 1) | ||
| (void)k5_input_get_uint16_le(in); | ||
|
|
||
| return 0; | ||
| } | ||
|
|
||
| static krb5_error_code | ||
| enc_wchar_pointer(const char *utf8, struct encoded_wchars *encoded_out) | ||
| { | ||
| krb5_error_code ret; | ||
| struct k5buf b; | ||
| size_t utf16len, num_wchars; | ||
| uint8_t *utf16; | ||
|
|
||
| k5_buf_init_dynamic(&b); | ||
|
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| ret = k5_utf8_to_utf16le(utf8, &utf16, &utf16len); | ||
| if (ret) | ||
| return ret; | ||
|
|
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| num_wchars = utf16len / 2; | ||
|
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| k5_buf_add_uint32_le(&b, num_wchars + 1); | ||
| k5_buf_add_uint32_le(&b, 0); | ||
| k5_buf_add_uint32_le(&b, num_wchars); | ||
| k5_buf_add_len(&b, utf16, utf16len); | ||
|
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| free(utf16); | ||
|
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| if (num_wchars % 2 == 1) | ||
| k5_buf_add_uint16_le(&b, 0); | ||
|
|
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| ret = k5_buf_status(&b); | ||
| if (ret) | ||
| return ret; | ||
|
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| encoded_out->bytes_len = b.len; | ||
| encoded_out->num_wchars = num_wchars; | ||
| encoded_out->encoded = b.data; | ||
| return 0; | ||
| } | ||
|
|
||
| /* | ||
| * Decode a delegation info structure, leaving room to add an additional | ||
| * service. | ||
| * | ||
| * MS-PAC 2.9: | ||
| * | ||
| * typedef struct _S4U_DELEGATION_INFO { | ||
| * RPC_UNICODE_STRING S4U2proxyTarget; | ||
| * ULONG TransitedListSize; | ||
| * [size_is(TransitedListSize)] PRPC_UNICODE_STRING S4UTransitedServices; | ||
| * } S4U_DELEGATION_INFO, *PS4U_DELEGATION_INFO; | ||
| */ | ||
| krb5_error_code | ||
| ndr_dec_delegation_info(krb5_data *data, struct pac_s4u_delegation_info **out) | ||
| { | ||
| krb5_error_code ret; | ||
| struct pac_s4u_delegation_info *di = NULL; | ||
| struct k5input in; | ||
| uint32_t i, object_buffer_length; | ||
| uint8_t version, endianness, common_header_length; | ||
|
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| *out = NULL; | ||
|
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| di = k5alloc(sizeof(*di), &ret); | ||
| if (di == NULL) | ||
| return ret; | ||
|
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| k5_input_init(&in, data->data, data->length); | ||
|
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| /* Common Type Header - MS-RPCE 2.2.6.1 */ | ||
| version = k5_input_get_byte(&in); | ||
| endianness = k5_input_get_byte(&in); | ||
| common_header_length = k5_input_get_uint16_le(&in); | ||
| (void)k5_input_get_uint32_le(&in); /* Filler - 0xcccccccc. */ | ||
| if (version != 1 || endianness != 0x10 || common_header_length != 8) { | ||
| ret = EINVAL; | ||
| goto error; | ||
| } | ||
|
|
||
| /* Private Header for Constructed Type - MS-RPCE 2.2.6.2 */ | ||
| object_buffer_length = k5_input_get_uint32_le(&in); | ||
| if (data->length < 16 || object_buffer_length != data->length - 16) { | ||
| ret = EINVAL; | ||
| goto error; | ||
| } | ||
|
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| (void)k5_input_get_uint32_le(&in); /* Filler - 0. */ | ||
|
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||
| /* This code doesn't handle re-used pointers, which could come into play in | ||
| * the unlikely case of a delegation loop. */ | ||
|
|
||
| /* Pointer. Microsoft always starts at 00 00 02 00 */ | ||
| (void)k5_input_get_uint32_le(&in); | ||
| /* Length of proxy target - 2 */ | ||
| (void)k5_input_get_uint16_le(&in); | ||
| /* Length of proxy target */ | ||
| (void)k5_input_get_uint16_le(&in); | ||
| /* Another pointer - 04 00 02 00. Microsoft increments by 4 (le). */ | ||
| (void)k5_input_get_uint32_le(&in); | ||
|
|
||
| /* Transited services length - header version. */ | ||
| (void)k5_input_get_uint32_le(&in); | ||
|
|
||
| /* More pointer: 08 00 02 00 */ | ||
| (void)k5_input_get_uint32_le(&in); | ||
|
|
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| ret = dec_wchar_pointer(&in, &di->proxy_target); | ||
| if (ret) | ||
| goto error; | ||
| di->transited_services_length = k5_input_get_uint32_le(&in); | ||
|
|
||
| /* Here, we have encoded 2 bytes of length, 2 bytes of (length + 2), and 4 | ||
| * bytes of pointer, for each element (deferred pointers). */ | ||
| if (di->transited_services_length > UINT32_MAX / 8) { | ||
| ret = ERANGE; | ||
| goto error; | ||
| } | ||
| (void)k5_input_get_bytes(&in, 8 * di->transited_services_length); | ||
|
|
||
| /* Since we're likely to add another entry, leave a blank at the end. */ | ||
| di->transited_services = k5calloc(di->transited_services_length + 1, | ||
| sizeof(char *), &ret); | ||
| if (di->transited_services == NULL) | ||
| goto error; | ||
|
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| for (i = 0; i < di->transited_services_length; i++) { | ||
| ret = dec_wchar_pointer(&in, &di->transited_services[i]); | ||
| if (ret) | ||
| goto error; | ||
| } | ||
|
|
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| ret = in.status; | ||
| if (ret) | ||
| goto error; | ||
|
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| *out = di; | ||
| return 0; | ||
|
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||
| error: | ||
| ndr_free_delegation_info(di); | ||
| return ret; | ||
| } | ||
|
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||
| /* Empirically, Microsoft starts pointers at 00 00 02 00, and if treated little | ||
| * endian, they increase by 4. */ | ||
| static inline void | ||
| write_ptr(struct k5buf *buf, uint32_t *pointer) | ||
| { | ||
| if (*pointer == 0) | ||
| *pointer = 0x00020000; | ||
| k5_buf_add_uint32_le(buf, *pointer); | ||
| *pointer += 4; | ||
| } | ||
|
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||
| krb5_error_code | ||
| ndr_enc_delegation_info(struct pac_s4u_delegation_info *in, krb5_data *out) | ||
| { | ||
| krb5_error_code ret; | ||
| size_t i; | ||
| struct k5buf b; | ||
| struct encoded_wchars pt_encoded = { 0 }, *tss_encoded = NULL; | ||
| uint32_t pointer = 0; | ||
|
|
||
| /* Encode ahead of time since we need the lengths. */ | ||
| ret = enc_wchar_pointer(in->proxy_target, &pt_encoded); | ||
| if (ret) | ||
| goto cleanup; | ||
|
|
||
| tss_encoded = k5calloc(in->transited_services_length, sizeof(*tss_encoded), | ||
| &ret); | ||
| if (tss_encoded == NULL) | ||
| goto cleanup; | ||
|
|
||
| k5_buf_init_dynamic(&b); | ||
|
|
||
| /* Common Type Header - MS-RPCE 2.2.6.1 */ | ||
| k5_buf_add_len(&b, "\x01\x10\x08\x00", 4); | ||
| k5_buf_add_uint32_le(&b, 0xcccccccc); | ||
|
|
||
| /* Private Header for Constructed Type - MS-RPCE 2.2.6.2 */ | ||
| k5_buf_add_uint32_le(&b, 0); /* Skip over where payload length goes. */ | ||
| k5_buf_add_uint32_le(&b, 0); /* Filler - all zeroes. */ | ||
|
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| write_ptr(&b, &pointer); | ||
| k5_buf_add_uint16_le(&b, 2 * pt_encoded.num_wchars); | ||
| k5_buf_add_uint16_le(&b, 2 * (pt_encoded.num_wchars + 1)); | ||
| write_ptr(&b, &pointer); | ||
|
|
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| k5_buf_add_uint32_le(&b, in->transited_services_length); | ||
| write_ptr(&b, &pointer); | ||
|
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| k5_buf_add_len(&b, pt_encoded.encoded, pt_encoded.bytes_len); | ||
|
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| k5_buf_add_uint32_le(&b, in->transited_services_length); | ||
|
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| /* Deferred pointers. */ | ||
| for (i = 0; i < in->transited_services_length; i++) { | ||
| ret = enc_wchar_pointer(in->transited_services[i], &tss_encoded[i]); | ||
| if (ret) | ||
| goto cleanup; | ||
|
|
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| k5_buf_add_uint16_le(&b, 2 * tss_encoded[i].num_wchars); | ||
| k5_buf_add_uint16_le(&b, 2 * (tss_encoded[i].num_wchars + 1)); | ||
| write_ptr(&b, &pointer); | ||
| } | ||
|
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| for (i = 0; i < in->transited_services_length; i++) | ||
| k5_buf_add_len(&b, tss_encoded[i].encoded, tss_encoded[i].bytes_len); | ||
|
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| /* Now, pad to 8 bytes. RPC_UNICODE_STRING is aligned on 4 bytes. */ | ||
| if (b.len % 8 != 0) | ||
| k5_buf_add_uint32_le(&b, 0); | ||
|
|
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| /* Record the payload length where we skipped over it previously. */ | ||
| if (b.data != NULL) | ||
| store_32_le(b.len - 0x10, ((uint8_t *)b.data) + 8); | ||
|
|
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| ret = k5_buf_status(&b); | ||
| if (ret) | ||
| goto cleanup; | ||
|
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| *out = make_data(b.data, b.len); | ||
| b.data = NULL; | ||
|
|
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| cleanup: | ||
| free(b.data); | ||
| free(pt_encoded.encoded); | ||
| for (i = 0; tss_encoded != NULL && i < in->transited_services_length; i++) | ||
| free(tss_encoded[i].encoded); | ||
| free(tss_encoded); | ||
| return ret; | ||
| } | ||
|
|
||
| void | ||
| ndr_free_delegation_info(struct pac_s4u_delegation_info *di) | ||
| { | ||
| uint32_t i; | ||
|
|
||
| if (di == NULL) | ||
| return; | ||
| free(di->proxy_target); | ||
| for (i = 0; i < di->transited_services_length; i++) | ||
| free(di->transited_services[i]); | ||
| free(di->transited_services); | ||
| free(di); | ||
| } |
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