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coap_block.c: Fix returning 2.03 for ETag match
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Tag server returned data with a digest computed ETag option value so
requests with an ETag option can return 2.03 if there is a match.

The size of bytes hash that is computed for the ETag can be overwritten by
localy defining COAP_ETAG_MAX_BYTES to be a value between 1 and 8 bytes
inclusive.  It is set to 4 by default.
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@mrdeep1
mrdeep1 committed Dec 2, 2024
1 parent 3457c2e commit 5f4c2ab
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Showing 4 changed files with 126 additions and 53 deletions.
1 change: 0 additions & 1 deletion include/coap3/coap_net_internal.h
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Original file line number Diff line number Diff line change
Expand Up @@ -163,7 +163,6 @@ struct coap_context_t {
uint32_t csm_timeout_ms; /**< Timeout for waiting for a CSM from
the remote side. */
uint32_t csm_max_message_size; /**< Value for CSM Max-Message-Size */
uint64_t etag; /**< Next ETag to use */

#if COAP_SERVER_SUPPORT
coap_cache_entry_t *cache; /**< CoAP cache-entry cache */
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2 changes: 1 addition & 1 deletion man/coap_block.txt.in
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Original file line number Diff line number Diff line change
Expand Up @@ -290,7 +290,7 @@ according to
Model]").

The application request handler for the resource is only called once instead of
potentially multiple times.
potentially multiple times, unless if COAP_BLOCK_STLESS_BLOCK2 is set.

*NOTE:* This function must only be called once per _pdu_.

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9 changes: 8 additions & 1 deletion man/coap_pdu_setup.txt.in
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Original file line number Diff line number Diff line change
Expand Up @@ -535,6 +535,13 @@ The *coap_add_data*() function adds in the specified payload _data_ of length
_length_ to the PDU _pdu_. Adding the payload data must be done after any
token or options are added. This function must only be called once per _pdu_.

*NOTE:* *coap_add_data*() cannot add data that will exceed the available space
within a single CoAP PDU.
It is recommended that *coap_add_data_large_request*(3) or
*coap_add_data_large_response*(3) (depending on whether _pdu_ is a request or response)
is used instead if there is a possibility of the PDU space being insufficient.
See *coap_block*(3).

*Function: coap_add_data_blocked_response()*

The *coap_add_data_blocked_response*() function adds in the appropriate part
Expand All @@ -552,7 +559,7 @@ received a part of the data and request the next block (with the appropriate
Block options) from the server. Returning the next requested block is handled
by this function.

*NOTE:* This function has been superseded by *coap_add_data_large_response*().
*NOTE:* This function has been superseded by *coap_add_data_large_response*(3).
See *coap_block*(3).

RETURN VALUES
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167 changes: 117 additions & 50 deletions src/coap_block.c
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,14 @@
#define min(a,b) ((a) < (b) ? (a) : (b))
#endif

/* Can be 1 - 8 bytes long */
#ifndef COAP_ETAG_MAX_BYTES
#define COAP_ETAG_MAX_BYTES 4
#endif
#if COAP_ETAG_MAX_BYTES < 1 || COAP_ETAG_MAX_BYTES > 8
#error COAP_ETAG_MAX_BYTES byte size invalid
#endif

#if COAP_Q_BLOCK_SUPPORT
int
coap_q_block_is_supported(void) {
Expand Down Expand Up @@ -273,10 +281,14 @@ coap_add_data_blocked_response(const coap_pdu_t *request,
size_t length,
const uint8_t *data
) {
coap_key_t etag;
unsigned char buf[4];
coap_block_t block2;
int block2_requested = 0;
#if COAP_SERVER_SUPPORT
uint64_t etag = 0;
coap_digest_t digest;
coap_digest_ctx_t *dctx = NULL;
#endif /* COAP_SERVER_SUPPORT */

memset(&block2, 0, sizeof(block2));
/*
Expand All @@ -297,10 +309,29 @@ coap_add_data_blocked_response(const coap_pdu_t *request,
}
response->code = COAP_RESPONSE_CODE(205);

/* add etag for the resource */
memset(etag, 0, sizeof(etag));
coap_hash(data, length, etag);
coap_insert_option(response, COAP_OPTION_ETAG, sizeof(etag), etag);
#if COAP_SERVER_SUPPORT
/* add ETag for the resource data */
if (length) {
dctx = coap_digest_setup();
if (!dctx)
goto error;
if (!coap_digest_update(dctx, data, length))
goto error;
if (!coap_digest_final(dctx, &digest))
goto error;
dctx = NULL;
memcpy(&etag, digest.key, sizeof(etag));
#if COAP_ETAG_MAX_BYTES != 8
etag = etag >> 8*(8 - COAP_ETAG_MAX_BYTES);
#endif
if (!etag)
etag = 1;
coap_update_option(response,
COAP_OPTION_ETAG,
coap_encode_var_safe8(buf, sizeof(buf), etag),
buf);
}
#endif /* COAP_SERVER_SUPPORT */

coap_insert_option(response, COAP_OPTION_CONTENT_FORMAT,
coap_encode_var_safe(buf, sizeof(buf),
Expand Down Expand Up @@ -366,6 +397,9 @@ coap_add_data_blocked_response(const coap_pdu_t *request,
return;

error:
#if COAP_SERVER_SUPPORT
coap_digest_free(dctx);
#endif /* COAP_SERVER_SUPPORT */
coap_add_data(response,
strlen(coap_response_phrase(response->code)),
(const unsigned char *)coap_response_phrase(response->code));
Expand Down Expand Up @@ -664,6 +698,10 @@ coap_add_data_large_internal(coap_session_t *session,
uint16_t alt_option;
#endif /* COAP_Q_BLOCK_SUPPORT */

#if !COAP_SERVER_SUPPORT
(void)etag;
#endif /* COAP_SERVER_SUPPORT */

assert(pdu);
if (pdu->data) {
coap_log_warn("coap_add_data_large: PDU already contains data\n");
Expand Down Expand Up @@ -697,6 +735,61 @@ coap_add_data_large_internal(coap_session_t *session,
}
#endif /* UINT_MAX > MAX_BLK_LEN */

#if COAP_SERVER_SUPPORT
if (COAP_PDU_IS_RESPONSE(pdu) && length) {
coap_opt_t *etag_opt = coap_check_option(pdu, COAP_OPTION_ETAG, &opt_iter);

if (etag_opt) {
/* Have to use ETag as supplied in the response PDU */
etag = coap_decode_var_bytes8(coap_opt_value(etag_opt),
coap_opt_length(etag_opt));
} else {
if (!etag) {
/* calculate ETag for the response */
coap_digest_t digest;
coap_digest_ctx_t *dctx = coap_digest_setup();

if (dctx) {
if (coap_digest_update(dctx, data, length)) {
if (coap_digest_final(dctx, &digest)) {
memcpy(&etag, digest.key, sizeof(etag));
#if COAP_ETAG_MAX_BYTES != 8
etag = etag >> 8*(8 - COAP_ETAG_MAX_BYTES);
#endif
dctx = NULL;
}
}
coap_digest_free(dctx);
}
if (!etag)
etag = 1;
}
coap_update_option(pdu,
COAP_OPTION_ETAG,
coap_encode_var_safe8(buf, sizeof(buf), etag),
buf);
}
if (request) {
etag_opt = coap_check_option(request, COAP_OPTION_ETAG, &opt_iter);
if (etag_opt) {
/* There may be multiple ETag - need to check each one */
coap_option_iterator_init(request, &opt_iter, COAP_OPT_ALL);
while ((etag_opt = coap_option_next(&opt_iter))) {
if (opt_iter.number == COAP_OPTION_ETAG) {
uint64_t etag_r = coap_decode_var_bytes8(coap_opt_value(etag_opt),
coap_opt_length(etag_opt));

if (etag == etag_r) {
pdu->code = COAP_RESPONSE_CODE(203);
return 1;
}
}
}
}
}
}
#endif /* COAP_SERVER_SUPPORT */

/* Determine the block size to use, adding in sensible options if needed */
if (COAP_PDU_IS_REQUEST(pdu)) {
coap_lg_xmit_t *q;
Expand Down Expand Up @@ -820,30 +913,14 @@ coap_add_data_large_internal(coap_session_t *session,
size_t rem;

if (length >= block.num * chunk) {
if (session->block_mode & COAP_BLOCK_STLESS_BLOCK2 && session->type != COAP_SESSION_TYPE_CLIENT) {
#if COAP_SERVER_SUPPORT
if (session->block_mode & COAP_BLOCK_STLESS_BLOCK2 && session->type != COAP_SESSION_TYPE_CLIENT) {
/* We are running server stateless */
coap_update_option(pdu,
COAP_OPTION_SIZE2,
coap_encode_var_safe(buf, sizeof(buf),
(unsigned int)length),
buf);
if (etag == 0) {
coap_digest_t digest;
coap_digest_ctx_t *dctx = coap_digest_setup();

if (!dctx)
goto fail;
if (!coap_digest_update(dctx, data, length))
goto fail;
if (!coap_digest_final(dctx, &digest))
goto fail;
memcpy(&etag, digest.key, sizeof(etag));
}
coap_update_option(pdu,
COAP_OPTION_ETAG,
coap_encode_var_safe8(buf, sizeof(buf), etag),
buf);
if (request) {
if (!coap_get_block_b(session, request, option, &block))
block.num = 0;
Expand All @@ -858,8 +935,8 @@ coap_add_data_large_internal(coap_session_t *session,
coap_encode_var_safe(buf, sizeof(buf),
(block.num << 4) | (block.m << 3) | block.aszx),
buf);
#endif /* COAP_SERVER_SUPPORT */
}
#endif /* COAP_SERVER_SUPPORT */
rem = chunk;
if (chunk > length - block.num * chunk)
rem = length - block.num * chunk;
Expand Down Expand Up @@ -969,15 +1046,6 @@ coap_add_data_large_internal(coap_session_t *session,
coap_encode_var_safe(buf, sizeof(buf),
(unsigned int)length),
buf);
if (etag == 0) {
if (++session->context->etag == 0)
++session->context->etag;
etag = session->context->etag;
}
coap_update_option(pdu,
COAP_OPTION_ETAG,
coap_encode_var_safe8(buf, sizeof(buf), etag),
buf);
}

if (!setup_block_b(session, pdu, &block, block.num,
Expand Down Expand Up @@ -1051,12 +1119,6 @@ coap_add_data_large_internal(coap_session_t *session,
LL_PREPEND(session->lg_xmit,lg_xmit);
} else {
/* No need to use blocks */
if (etag) {
coap_update_option(pdu,
COAP_OPTION_ETAG,
coap_encode_var_safe8(buf, sizeof(buf), etag),
buf);
}
if (have_block_defined) {
coap_update_option(pdu,
option,
Expand Down Expand Up @@ -2474,18 +2536,23 @@ coap_handle_request_send_block(coap_session_t *session,

etag_opt = coap_check_option(pdu, COAP_OPTION_ETAG, &opt_iter);
if (etag_opt) {
uint64_t etag = coap_decode_var_bytes8(coap_opt_value(etag_opt),
coap_opt_length(etag_opt));
if (etag != lg_xmit->b.b2.etag) {
/* There may be multiple ETag - need to check each one */
coap_option_iterator_init(pdu, &opt_iter, COAP_OPT_ALL);
while ((etag_opt = coap_option_next(&opt_iter))) {
if (opt_iter.number == COAP_OPTION_ETAG) {
uint64_t etag = coap_decode_var_bytes8(coap_opt_value(etag_opt),
coap_opt_length(etag_opt));
if (etag == lg_xmit->b.b2.etag) {
break;
}
}
}
if (!etag_opt) {
/* Not a match - pass up to a higher level */
return 0;
}
out_pdu->code = COAP_RESPONSE_CODE(203);
coap_ticks(&lg_xmit->last_sent);
goto skip_app_handler;
} else {
out_pdu->code = lg_xmit->pdu.code;
}
out_pdu->code = lg_xmit->pdu.code;
coap_ticks(&lg_xmit->last_obs);
lg_xmit->last_all_sent = 0;

Expand Down Expand Up @@ -2683,10 +2750,10 @@ coap_handle_request_send_block(coap_session_t *session,
}
}

if (!etag_opt && !coap_add_block_b_data(out_pdu,
lg_xmit->length,
lg_xmit->data,
&block)) {
if (!coap_add_block_b_data(out_pdu,
lg_xmit->length,
lg_xmit->data,
&block)) {
goto internal_issue;
}
if (i + 1 < request_cnt) {
Expand Down

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