lib: uicc_lwm2m: Add UICC LwM2M library

Add functionality to read LwM2M bootstrap data from UICC.

Signed-off-by: Stig Bjørlykke <stig.bjorlykke@nordicsemi.no>

CODEOWNERS

@@ -147,6 +147,7 @@ Kconfig*                                  @tejlmand
 /lib/pcm_stream_channel_modifier/         @nrfconnect/ncs-audio
 /lib/sample_rate_converter/               @andvib @gWacey
 /lib/tone/                                @nrfconnect/ncs-audio
+/lib/uicc_lwm2m/                          @stig-bjorlykke
 /modules/                                 @tejlmand
 /modules/hostap/                          @krish2718 @jukkar @rado17 @sachinthegreen @rlubos
 /modules/mcuboot/                         @de-nordic @nordicjm
@@ -189,6 +190,7 @@ Kconfig*                                  @tejlmand
 /samples/cellular/modem_trace_flash/      @eivindj-nordic
 /samples/cellular/slm_shell/              @MarkusLassila @tomi-font
 /samples/cellular/sms/                    @trantanen @tokangas
+/samples/cellular/uicc_lwm2m/             @stig-bjorlykke
 /samples/openthread/                      @rlubos @edmont @canisLupus1313 @maciejbaczmanski
 /samples/nrf_profiler/                    @pdunaj
 /samples/peripheral/radio_test/           @KAGA164 @maje-emb
@@ -329,6 +331,7 @@ Kconfig*                                  @tejlmand
 /tests/lib/pcm_stream_channel_modifier/   @nrfconnect/ncs-audio
 /tests/lib/sample_rate_converter/         @andvib @gWacey
 /tests/lib/tone/                          @nrfconnect/ncs-audio
+/tests/lib/uicc_lwm2m/                    @stig-bjorlykke
 /tests/modules/lib/zcbor/                 @oyvindronningstad
 /tests/modules/mcuboot/direct_xip/        @hakonfam
 /tests/modules/mcuboot/external_flash/    @hakonfam @sigvartmh

include/modem/uicc_lwm2m.h

@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2024 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+#ifndef UICC_LWM2M_H_
+#define UICC_LWM2M_H_
+
+#include <stdint.h>
+#include <stdbool.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @file uicc_lwm2m.h
+ *
+ * @defgroup uicc_lwm2m UICC LwM2M
+ *
+ * @{
+ *
+ * @brief Public APIs of the UICC LwM2M library.
+ */
+
+/** UICC record max size is 256 bytes. The buffer size needed for the AT response is
+ * (256 * 2) + 4 bytes for SW + 1 byte for NUL. Using 516 bytes is adequate to read
+ * a full UICC record.
+ */
+#define UICC_RECORD_BUFFER_MAX ((256 * 2) + 4 + 1)
+
+/**
+ * @brief Read UICC LwM2M bootstrap record.
+ *
+ * @param[inout] p_buffer Buffer to store UICC LwM2M bootstrap record. This buffer is also
+ *                        used internally by the function reading the AT response, so it must
+ *                        be twice the size of expected LwM2M content + 4 bytes for UICC SW.
+ * @param[in] buffer_size Total size of buffer.
+ *
+ * @return Length of UICC LwM2M bootstrap record, -errno on error.
+ */
+int uicc_lwm2m_bootstrap_read(uint8_t *p_buffer, int buffer_size);
+
+/** @} */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* UICC_LWM2M_H_ */

lib/CMakeLists.txt

@@ -49,3 +49,4 @@ add_subdirectory_ifdef(CONFIG_DATA_FIFO data_fifo)
 add_subdirectory_ifdef(CONFIG_FEM_AL_LIB fem_al)
 add_subdirectory_ifdef(CONFIG_SAMPLE_RATE_CONVERTER sample_rate_converter)
 add_subdirectory_ifdef(CONFIG_NCS_BOOT_BANNER boot_banner)
+add_subdirectory_ifdef(CONFIG_UICC_LWM2M uicc_lwm2m)

lib/Kconfig

@@ -50,5 +50,6 @@ rsource "data_fifo/Kconfig"
 rsource "fem_al/Kconfig"
 rsource "sample_rate_converter/Kconfig"
 rsource "boot_banner/Kconfig"
+rsource "uicc_lwm2m/Kconfig"
 
 endmenu

lib/uicc_lwm2m/CMakeLists.txt

@@ -0,0 +1,17 @@
+#
+# Copyright (c) 2024 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+
+zephyr_library()
+
+zephyr_include_directories(
+  ${ZEPHYR_NRFXLIB_MODULE_DIR}/nrf_modem/include/
+)
+
+zephyr_library_sources(
+    asn1_decode.c
+    pkcs15_decode.c
+    uicc_lwm2m.c
+)

lib/uicc_lwm2m/Kconfig

@@ -0,0 +1,11 @@
+#
+# Copyright (c) 2024 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+
+config UICC_LWM2M
+	bool "UICC LwM2M bootstrap support"
+	depends on NRF_MODEM_LIB
+	help
+	  "Enable UICC LwM2M bootstrap library"

lib/uicc_lwm2m/asn1_decode.c

@@ -0,0 +1,83 @@
+/*
+ * Copyright (c) 2024 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+#include <zephyr/sys/util.h>
+
+#include "asn1_decode.h"
+
+bool asn1_dec_head(asn1_ctx_t *ctx, uint8_t *tag, size_t *len)
+{
+	uint32_t hlen = 2; /* Minimum two bytes for header */
+
+	if (ctx->error || ((ctx->offset + hlen) > ctx->length)) {
+		/* Error detected or out of data (happens at end of sequence) */
+		return false;
+	}
+
+	*tag = ctx->asnbuf[ctx->offset++];
+	*len = ctx->asnbuf[ctx->offset++];
+
+	if ((*tag & 0x1F) == 0x1F) {
+		/* Extended tag number is unsupported */
+		ctx->error = true;
+		return false;
+	}
+
+	if (*len & 0x80) {
+		int n = *len & 0x7F;
+
+		hlen += n;
+		if (n > 3 || (ctx->offset + hlen) > ctx->length) {
+			/* Unsupported header length or out of data (header is past buffer) */
+			ctx->error = true;
+			return false;
+		}
+
+		*len = 0;
+		for (int i = 0; i < n; i++) {
+			*len = (*len << 8) + ctx->asnbuf[ctx->offset++];
+		}
+	}
+
+	if ((ctx->offset + *len) > ctx->length) {
+		/* Out of data (value is past buffer) */
+		ctx->error = true;
+		return false;
+	}
+
+	return true;
+}
+
+void asn1_dec_octet_string(asn1_ctx_t *ctx, size_t len, uint8_t *value, size_t max_len)
+{
+	if (bin2hex(&ctx->asnbuf[ctx->offset], len, value, max_len) == 0) {
+		/* OCTET STRING too long for buffer */
+		ctx->error = true;
+		return;
+	}
+
+	ctx->offset += len;
+}
+
+void asn1_dec_sequence(asn1_ctx_t *ctx, size_t len, void *data, asn1_sequence_func_t sequence_func)
+{
+	/* Create a subset from the buffer */
+	asn1_ctx_t seq_ctx = {
+		.asnbuf = &ctx->asnbuf[ctx->offset],
+		.length = len
+	};
+
+	sequence_func(&seq_ctx, data);
+	ctx->offset += len;
+
+	/* Copy error from subset */
+	ctx->error = seq_ctx.error;
+}
+
+void asn1_dec_skip(asn1_ctx_t *ctx, size_t len)
+{
+	ctx->offset += len;
+}

lib/uicc_lwm2m/asn1_decode.h

@@ -0,0 +1,89 @@
+/*
+ * Copyright (c) 2024 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+/* A minimalistic ASN.1 BER/DER decoder (X.690).
+ *
+ * Supported types:
+ *   OCTET STRING
+ *   SEQUENCE / SEQUENCE OF
+ */
+
+#ifndef ASN1_DECODE_H_
+#define ASN1_DECODE_H_
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/** Commonly used ASN.1 tags. */
+#define UP4  0x04
+#define UP6  0x06
+#define UC16 0x30
+#define AP15 0x4F
+#define AP16 0x50
+#define CC1  0xA1
+#define CC7  0xA7
+
+/** ASN.1 context values */
+typedef struct {
+	const uint8_t *asnbuf;	/**< ASN.1 BER/DER encoded buffer */
+	size_t length;		/**< Length of the data buffer */
+	uint32_t offset;	/**< Current offset into asnbuf */
+	bool error;		/**< Error detected in ASN.1 syntax */
+} asn1_ctx_t;
+
+/** Function called to handle elements in a SEQUENCE */
+typedef void (*asn1_sequence_func_t)(asn1_ctx_t *ctx, void *data);
+
+/**
+ * @brief Decode ASN.1 header.
+ *
+ * @param[in]  ctx ASN.1 context values.
+ * @param[out] tag ASN.1 TAG.
+ * @param[out] len Length of ASN.1 value.
+ *
+ * @return true when valid ASN.1 and a value exists
+ */
+bool asn1_dec_head(asn1_ctx_t *ctx, uint8_t *tag, size_t *len);
+
+/**
+ * @brief Decode ASN.1 OCTET STRING.
+ *
+ * @param[in]  ctx     ASN.1 context values.
+ * @param[in]  len     Length of octet string to decode.
+ * @param[out] value   Decoded octet string.
+ * @param[in]  max_len Maximum length of octet string to decode.
+ */
+void asn1_dec_octet_string(asn1_ctx_t *ctx, size_t len, uint8_t *value, size_t max_len);
+
+/**
+ * @brief Decode ASN.1 SEQUENCE.
+ *
+ * @param[in]    ctx           ASN.1 context values.
+ * @param[in]    len           Length of sequence to decode.
+ * @param[inout] data          Pointer to application specific values.
+ * @param[in]    sequence_func Function to be called to handle sequence elements.
+ */
+void asn1_dec_sequence(asn1_ctx_t *ctx, size_t len, void *data, asn1_sequence_func_t sequence_func);
+
+/**
+ * @brief Skip a subset of ASN.1 content.
+ *        This is used to skip parts of the content which is not of interest.
+ *
+ * @param[in] ctx ASN.1 context values.
+ * @param[in] len Length of data to skip.
+ */
+void asn1_dec_skip(asn1_ctx_t *ctx, size_t len);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ASN1_DECODE_H_ */