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acdc8eed8

Martin Lewis

2020-06-29

SUCCESS Duration: 151s

Subject

udhcp: add option scanner

Binary

No binary (build failed)

Architecture & Compiler Flags

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

—

Build Log

(log yok)

Commit Diff GitHub →

networking/udhcp/common.c +54 -42 networking/udhcp/common.h +8 -0

networking/udhcp/common.c+54 -42

@@ -15,7 +15,7 @@ const uint8_t MAC_BCAST_ADDR[6] ALIGN2 = {
	};

	#if ENABLE_UDHCPC \|\| ENABLE_UDHCPD
-	/* Supported options are easily added here.
+	/* Supported options are easily added here, they need to be sorted.
	* See RFC2132 for more options.
	* OPTION_REQ: these options are requested by udhcpc (unless -o).
	*/
@@ -222,79 +222,91 @@ unsigned FAST_FUNC udhcp_option_idx(const char name, const char option_strings
	}
	}

-	/* Get an option with bounds checking (warning, result is not aligned) */
-	uint8_t* FAST_FUNC udhcp_get_option(struct dhcp_packet *packet, int code)
+	/* Initialize state to be used between subsequent udhcp_scan_options calls */
+	void FAST_FUNC init_scan_state(struct dhcp_packet packet, struct dhcp_scan_state scan_state)
+	{
+	scan_state->overload = 0;
+	scan_state->rem = sizeof(packet->options);
+	scan_state->optionptr = packet->options;
+	}
+
+	/* Iterate over packet's options, each call returning the next option.
+	* scan_state needs to be initialized with init_scan_state beforehand.
+	* Warning, result is not aligned. */
+	uint8_t* FAST_FUNC udhcp_scan_options(struct dhcp_packet packet, struct dhcp_scan_state scan_state)
	{
-	uint8_t *optionptr;
	int len;
-	int rem;
-	int overload = 0;
	enum {
	FILE_FIELD101 = FILE_FIELD * 0x101,
	SNAME_FIELD101 = SNAME_FIELD * 0x101,
	};

	/* option bytes: [code][len][data1][data2]..[dataLEN] */
-	optionptr = packet->options;
-	rem = sizeof(packet->options);
	while (1) {
-	if (rem <= 0) {
+	if (scan_state->rem <= 0) {
	complain:
	bb_simple_error_msg("bad packet, malformed option field");
	return NULL;
	}

	/* DHCP_PADDING and DHCP_END have no [len] byte */
-	if (optionptr[OPT_CODE] == DHCP_PADDING) {
-	rem--;
-	optionptr++;
+	if (scan_state->optionptr[OPT_CODE] == DHCP_PADDING) {
+	scan_state->rem--;
+	scan_state->optionptr++;
	continue;
	}
-	if (optionptr[OPT_CODE] == DHCP_END) {
-	if ((overload & FILE_FIELD101) == FILE_FIELD) {
+	if (scan_state->optionptr[OPT_CODE] == DHCP_END) {
+	if ((scan_state->overload & FILE_FIELD101) == FILE_FIELD) {
	/* can use packet->file, and didn't look at it yet */
-	overload \|= FILE_FIELD101; /* "we looked at it" */
-	optionptr = packet->file;
-	rem = sizeof(packet->file);
+	scan_state->overload \|= FILE_FIELD101; /* "we looked at it" */
+	scan_state->optionptr = packet->file;
+	scan_state->rem = sizeof(packet->file);
	continue;
	}
-	if ((overload & SNAME_FIELD101) == SNAME_FIELD) {
+	if ((scan_state->overload & SNAME_FIELD101) == SNAME_FIELD) {
	/* can use packet->sname, and didn't look at it yet */
-	overload \|= SNAME_FIELD101; /* "we looked at it" */
-	optionptr = packet->sname;
-	rem = sizeof(packet->sname);
+	scan_state->overload \|= SNAME_FIELD101; /* "we looked at it" */
+	scan_state->optionptr = packet->sname;
+	scan_state->rem = sizeof(packet->sname);
	continue;
	}
	break;
	}

-	if (rem <= OPT_LEN)
+	if (scan_state->rem <= OPT_LEN)
	goto complain; /* complain and return NULL */
-	len = 2 + optionptr[OPT_LEN];
-	rem -= len;
-	if (rem < 0)
+	len = 2 + scan_state->optionptr[OPT_LEN];
+	scan_state->rem -= len;
+	/* So far no valid option with length 0 known. */
+	if (scan_state->rem < 0 \|\| scan_state->optionptr[OPT_LEN] == 0)
	goto complain; /* complain and return NULL */

-	if (optionptr[OPT_CODE] == code) {
-	if (optionptr[OPT_LEN] == 0) {
-	/* So far no valid option with length 0 known.
-	* Having this check means that searching
-	* for DHCP_MESSAGE_TYPE need not worry
-	* that returned pointer might be unsafe
-	* to dereference.
-	*/
-	goto complain; /* complain and return NULL */
-	}
-	log_option("option found", optionptr);
-	return optionptr + OPT_DATA;
+	if (scan_state->optionptr[OPT_CODE] == DHCP_OPTION_OVERLOAD) {
+	if (len >= 3)
+	scan_state->overload \|= scan_state->optionptr[OPT_DATA];
+	} else {
+	uint8_t *return_ptr = scan_state->optionptr;
+	scan_state->optionptr += len;
+	return return_ptr;
	}
+	scan_state->optionptr += len;
+	}

-	if (optionptr[OPT_CODE] == DHCP_OPTION_OVERLOAD) {
-	if (len >= 3)
-	overload \|= optionptr[OPT_DATA];
-	/* fall through */
+	return NULL;
+	}
+
+	/* Get an option with bounds checking (warning, result is not aligned) */
+	uint8_t* FAST_FUNC udhcp_get_option(struct dhcp_packet *packet, int code)
+	{
+	uint8_t *optptr;
+	struct dhcp_scan_state scan_state;
+
+	init_scan_state(packet, &scan_state);
+	while ((optptr = udhcp_scan_options(packet, &scan_state)) != NULL) {
+	if (optptr[OPT_CODE] == code) {
+	log_option("option found", optptr);
+	return optptr + OPT_DATA;
	}
-	optionptr += len;
	}

	/* log3 because udhcpc uses it a lot - very noisy */

networking/udhcp/common.h+8 -0

@@ -107,6 +107,12 @@ enum {
	OPTION_LIST = 0x20,
	};

+	struct dhcp_scan_state {
+	int overload;
+	int rem;
+	uint8_t *optionptr;
+	};
+
	/* DHCP option codes (partial list). See RFC 2132 and
	* http://www.iana.org/assignments/bootp-dhcp-parameters/
	* Commented out options are handled by common option machinery,
@@ -206,6 +212,8 @@ extern const uint8_t dhcp_option_lengths[] ALIGN1;

	unsigned FAST_FUNC udhcp_option_idx(const char name, const char option_strings);

+	void init_scan_state(struct dhcp_packet packet, struct dhcp_scan_state scan_state) FAST_FUNC;
+	uint8_t udhcp_scan_options(struct dhcp_packet packet, struct dhcp_scan_state *scan_state) FAST_FUNC;
	uint8_t udhcp_get_option(struct dhcp_packet packet, int code) FAST_FUNC;
	/* Same as above + ensures that option length is 4 bytes
	* (returns NULL if size is different)