lib: Add CRC-8 and CRC-16 checksums

These checksum will be handy for header checksums.

Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>

8 files changed, 358 insertions, 0 deletions

diff --git a/src/lib/CMakeLists.txt b/src/lib/CMakeLists.txt
index 34135ffa..74c3ac15 100644
--- a/src/lib/CMakeLists.txt
+++ b/src/lib/CMakeLists.txt
@@ -17,6 +17,8 @@ protobuf_generate_c(IPCP_PROTO_SRCS IPCP_PROTO_HDRS
 set(SOURCE_FILES_COMMON
   bitmap.c
   btree.c
+  crc8.c
+  crc16.c
   crc32.c
   crc64.c
   crypt.c
diff --git a/src/lib/crc16.c b/src/lib/crc16.c
new file mode 100644
index 00000000..55af8647
--- /dev/null
+++ b/src/lib/crc16.c
@@ -0,0 +1,64 @@
+/*
+ * Ouroboros - Copyright (C) 2016 - 2026
+ *
+ * 16-bit Cyclic Redundancy Check (CCITT-FALSE variant)
+ *
+ *    Dimitri Staessens <dimitri@ouroboros.rocks>
+ *    Sander Vrijders   <sander@ouroboros.rocks>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * version 2.1 as published by the Free Software Foundation.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., http://www.fsf.org/about/contact/.
+ */
+
+/*
+ * CRC-16/CCITT-FALSE (reveng catalog, alias CRC-16/IBM-3740):
+ *   poly   = 0x1021
+ *   init   = 0xffff
+ *   refin  = false
+ *   refout = false
+ *   xorout = 0x0000
+ *   check  = crc16_ccitt_false("123456789") == 0x29b1
+ */
+
+#include "config.h"
+
+#include <ouroboros/crc16.h>
+
+/* Bit-by-bit MSB-first CRC.  Header-check use case rarely exceeds a
+ * few hundred bytes; a 256-entry uint16_t table costs 512 B of
+ * .rodata and is easy to add later if profiling demands it.
+ */
+void crc16_ccitt_false(uint16_t *   crc,
+                       const void * buf,
+                       size_t       len)
+{
+        const uint8_t * p;
+        uint16_t        c;
+        size_t          n;
+        int             i;
+
+        p = (const uint8_t *) buf;
+        c = *crc ^ 0xffff;
+
+        for (n = 0; n < len; n++) {
+                c ^= ((uint16_t) p[n]) << 8;
+                for (i = 0; i < 8; i++) {
+                        if (c & 0x8000)
+                                c = (uint16_t) ((c << 1) ^ 0x1021);
+                        else
+                                c = (uint16_t) (c << 1);
+                }
+        }
+
+        *crc = c;
+}
diff --git a/src/lib/crc8.c b/src/lib/crc8.c
new file mode 100644
index 00000000..e8b9685a
--- /dev/null
+++ b/src/lib/crc8.c
@@ -0,0 +1,64 @@
+/*
+ * Ouroboros - Copyright (C) 2016 - 2026
+ *
+ * 8-bit Cyclic Redundancy Check (AUTOSAR variant)
+ *
+ *    Dimitri Staessens <dimitri@ouroboros.rocks>
+ *    Sander Vrijders   <sander@ouroboros.rocks>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * version 2.1 as published by the Free Software Foundation.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., http://www.fsf.org/about/contact/.
+ */
+
+/*
+ * CRC-8/AUTOSAR (reveng catalog):
+ *   poly   = 0x2f
+ *   init   = 0xff
+ *   refin  = false
+ *   refout = false
+ *   xorout = 0xff
+ *   check  = crc8_autosar("123456789") == 0xdf
+ */
+
+#include "config.h"
+
+#include <ouroboros/crc8.h>
+
+/* Bit-by-bit MSB-first CRC.  The expected use case is header check
+ * sequences of a handful of bytes; a 256-byte lookup table would not
+ * pay for the extra .rodata footprint at typical input sizes.
+ */
+void crc8_autosar(uint8_t *    crc,
+                  const void * buf,
+                  size_t       len)
+{
+        const uint8_t * p;
+        uint8_t         c;
+        size_t          n;
+        int             i;
+
+        p = (const uint8_t *) buf;
+        c = *crc ^ 0xff;
+
+        for (n = 0; n < len; n++) {
+                c ^= p[n];
+                for (i = 0; i < 8; i++) {
+                        if (c & 0x80)
+                                c = (uint8_t) ((c << 1) ^ 0x2f);
+                        else
+                                c = (uint8_t) (c << 1);
+                }
+        }
+
+        *crc = c ^ 0xff;
+}
diff --git a/src/lib/hash.c b/src/lib/hash.c
index f32001d9..7ffa5bc1 100644
--- a/src/lib/hash.c
+++ b/src/lib/hash.c
@@ -39,6 +39,8 @@
 #include <ouroboros/md5.h>
 #include <ouroboros/sha3.h>
 #endif
+#include <ouroboros/crc8.h>
+#include <ouroboros/crc16.h>
 #include <ouroboros/crc64.h>
 #include <string.h>
 #include <assert.h>
@@ -70,6 +72,10 @@ int hash_len_tbl [] = {
 
 uint16_t hash_len(enum hash_algo algo)
 {
+        if (algo == HASH_CRC8)
+                return CRC8_HASH_LEN;
+        if (algo == HASH_CRC16)
+                return CRC16_HASH_LEN;
         if (algo == HASH_CRC64)
                 return CRC64_HASH_LEN;
 #ifdef HAVE_LIBGCRYPT
@@ -84,6 +90,20 @@ void mem_hash(enum hash_algo  algo,
               const uint8_t * buf,
               size_t          len)
 {
+        if (algo == HASH_CRC8) {
+                uint8_t crc = 0;
+
+                crc8_autosar(&crc, buf, len);
+                *(uint8_t *) dst = crc;
+                return;
+        }
+        if (algo == HASH_CRC16) {
+                uint16_t crc = 0;
+
+                crc16_ccitt_false(&crc, buf, len);
+                *(uint16_t *) dst = htobe16(crc);
+                return;
+        }
         if (algo == HASH_CRC64) {
                 uint64_t crc = 0;
 
diff --git a/src/lib/tests/CMakeLists.txt b/src/lib/tests/CMakeLists.txt
index 417ec4b0..afe64884 100644
--- a/src/lib/tests/CMakeLists.txt
+++ b/src/lib/tests/CMakeLists.txt
@@ -10,6 +10,8 @@ create_test_sourcelist(${PARENT_DIR}_tests test_suite.c
   auth_test_slh_dsa.c
   bitmap_test.c
   btree_test.c
+  crc8_test.c
+  crc16_test.c
   crc32_test.c
   crc64_test.c
   crypt_test.c
diff --git a/src/lib/tests/crc16_test.c b/src/lib/tests/crc16_test.c
new file mode 100644
index 00000000..03a5b504
--- /dev/null
+++ b/src/lib/tests/crc16_test.c
@@ -0,0 +1,67 @@
+/*
+ * Ouroboros - Copyright (C) 2016 - 2026
+ *
+ * Test of the CRC-16/CCITT-FALSE function
+ *
+ *    Dimitri Staessens <dimitri@ouroboros.rocks>
+ *    Sander Vrijders   <sander@ouroboros.rocks>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., http://www.fsf.org/about/contact/.
+ */
+
+#include "config.h"
+
+#include <ouroboros/crc16.h>
+
+#include <test/test.h>
+
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+
+/* reveng-catalog smoke vectors. */
+static int test_crc16_ccitt_false_basic(void)
+{
+        uint16_t crc;
+
+        TEST_START();
+
+        crc = 0;
+        crc16_ccitt_false(&crc, "", 0);
+        if (crc != 0xffff)
+                goto fail;
+
+        crc = 0;
+        crc16_ccitt_false(&crc, "123456789", 9);
+        if (crc != 0x29b1)
+                goto fail;
+
+        TEST_SUCCESS();
+        return TEST_RC_SUCCESS;
+ fail:
+        TEST_FAIL();
+        return TEST_RC_FAIL;
+}
+
+int crc16_test(int     argc,
+               char ** argv)
+{
+        int ret = 0;
+
+        (void) argc;
+        (void) argv;
+
+        ret |= test_crc16_ccitt_false_basic();
+        return ret;
+}
diff --git a/src/lib/tests/crc8_test.c b/src/lib/tests/crc8_test.c
new file mode 100644
index 00000000..f7bb33b8
--- /dev/null
+++ b/src/lib/tests/crc8_test.c
@@ -0,0 +1,67 @@
+/*
+ * Ouroboros - Copyright (C) 2016 - 2026
+ *
+ * Test of the CRC-8/AUTOSAR function
+ *
+ *    Dimitri Staessens <dimitri@ouroboros.rocks>
+ *    Sander Vrijders   <sander@ouroboros.rocks>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., http://www.fsf.org/about/contact/.
+ */
+
+#include "config.h"
+
+#include <ouroboros/crc8.h>
+
+#include <test/test.h>
+
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+
+/* reveng-catalog smoke vectors. */
+static int test_crc8_autosar_basic(void)
+{
+        uint8_t crc;
+
+        TEST_START();
+
+        crc = 0;
+        crc8_autosar(&crc, "", 0);
+        if (crc != 0x00)
+                goto fail;
+
+        crc = 0;
+        crc8_autosar(&crc, "123456789", 9);
+        if (crc != 0xdf)
+                goto fail;
+
+        TEST_SUCCESS();
+        return TEST_RC_SUCCESS;
+ fail:
+        TEST_FAIL();
+        return TEST_RC_FAIL;
+}
+
+int crc8_test(int     argc,
+              char ** argv)
+{
+        int ret = 0;
+
+        (void) argc;
+        (void) argv;
+
+        ret |= test_crc8_autosar_basic();
+        return ret;
+}
diff --git a/src/lib/tests/hash_test.c b/src/lib/tests/hash_test.c
index 19343b17..451d3c25 100644
--- a/src/lib/tests/hash_test.c
+++ b/src/lib/tests/hash_test.c
@@ -39,6 +39,74 @@ struct vec_entry {
         char * out;
 };
 
+static int test_crc8(void)
+{
+        int ret = 0;
+
+        struct vec_entry vec [] = {
+                { "",          "00" },
+                { "123456789", "df" },
+                { NULL,        NULL }
+        };
+
+        struct vec_entry * cur = vec;
+
+        TEST_START();
+
+        while (cur->in != NULL) {
+                uint8_t crc;
+                char    res[3];
+
+                str_hash(HASH_CRC8, &crc, cur->in);
+
+                sprintf(res, "%02x", crc);
+                if (strcmp(res, cur->out) != 0) {
+                        printf("Hash failed %s != %s.\n", res, cur->out);
+                        ret |= -1;
+                }
+
+                ++cur;
+        }
+
+        TEST_END(ret);
+
+        return ret;
+}
+
+static int test_crc16(void)
+{
+        int ret = 0;
+
+        struct vec_entry vec [] = {
+                { "",          "ffff" },
+                { "123456789", "29b1" },
+                { NULL,        NULL   }
+        };
+
+        struct vec_entry * cur = vec;
+
+        TEST_START();
+
+        while (cur->in != NULL) {
+                uint8_t crc[2];
+                char    res[5];
+
+                str_hash(HASH_CRC16, crc, cur->in);
+
+                sprintf(res, "%02x%02x", crc[0], crc[1]);
+                if (strcmp(res, cur->out) != 0) {
+                        printf("Hash failed %s != %s.\n", res, cur->out);
+                        ret |= -1;
+                }
+
+                ++cur;
+        }
+
+        TEST_END(ret);
+
+        return ret;
+}
+
 static int test_crc32(void)
 {
         int ret = 0;
@@ -228,6 +296,10 @@ int hash_test(int     argc,
         (void) argc;
         (void) argv;
 
+        ret |= test_crc8();
+
+        ret |= test_crc16();
+
         ret |= test_crc32();
 
         ret |= test_crc64();