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Fix potential OOB-read in delta diff #719

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Merged
dgarske merged 3 commits into from
Mar 11, 2026
Merged

Fix potential OOB-read in delta diff #719

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6b64e84
Fix potential OOB-read in delta diff
danielinux Mar 10, 2026
249e078
Added missing parenthesis around macro
danielinux Mar 10, 2026
e99fc24
Addressed copilot's comments
danielinux Mar 11, 2026
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14 changes: 10 additions & 4 deletions src/delta.c
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Original file line number Diff line number Diff line change
Expand Up @@ -293,6 +293,7 @@ int wb_diff(WB_DIFF_CTX *ctx, uint8_t *patch, uint32_t len)
break;
if ((memcmp(pa, (ctx->src_b + ctx->off_b), BLOCK_HDR_SIZE) == 0)) {
uintptr_t b_start;
uint8_t *pa_limit = ctx->src_a + ctx->size_a;
/* Identical areas of BLOCK_HDR_SIZE bytes match between the images.
* initialize match_len; blk_start is the relative offset within
* the src image.
Expand All @@ -302,11 +303,13 @@ int wb_diff(WB_DIFF_CTX *ctx, uint8_t *patch, uint32_t len)
b_start = ctx->off_b;
pa+= BLOCK_HDR_SIZE;
ctx->off_b += BLOCK_HDR_SIZE;
while (*pa == *(ctx->src_b + ctx->off_b)) {
while ((pa < pa_limit) &&
(ctx->off_b < ctx->size_b) &&
(*pa == *(ctx->src_b + ctx->off_b))) {
/* Extend matching block if possible, as long as the
* identical sequence continues.
*/
if ((uint32_t)(pa + 1 - ctx->src_a) >= ctx->size_a) {
if ((pa + 1) >= pa_limit) {
/* Stop matching if the source image size limit is hit. */
break;
}
Expand Down Expand Up @@ -335,6 +338,7 @@ int wb_diff(WB_DIFF_CTX *ctx, uint8_t *patch, uint32_t len)
if (!found) {
/* Try matching an earlier section in the resulting image */
uintptr_t pb_end = page_start * wolfboot_sector_size;
uint8_t *pb_limit = ctx->src_b + pb_end;
pb = ctx->src_b;
while (((uintptr_t)(pb - ctx->src_b) < pb_end) && (p_off < len)) {
/* Check image boundary */
Expand All @@ -360,15 +364,17 @@ int wb_diff(WB_DIFF_CTX *ctx, uint8_t *patch, uint32_t len)
blk_start = pb - ctx->src_b;
pb+= BLOCK_HDR_SIZE;
ctx->off_b += BLOCK_HDR_SIZE;
while (*pb == *(ctx->src_b + ctx->off_b)) {
while ((pb < pb_limit) &&
(ctx->off_b < ctx->size_b) &&
(*pb == *(ctx->src_b + ctx->off_b))) {
/* Extend match as long as the areas have the
* same content. Block skipping in this case is
* not a problem since the distance between the patched
* area and the area to patch is always larger than one
* block size.
*/
pb++;
if ((uint32_t)(pb - ctx->src_b) >= pb_end) {
if (pb >= pb_limit) {
pb--;
break;
}
Expand Down
2 changes: 1 addition & 1 deletion src/libwolfboot.c
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Original file line number Diff line number Diff line change
Expand Up @@ -112,7 +112,7 @@ int wolfBoot_initialize_encryption(void)
/* MAGIC (4B) + PART_FLAG (1B) + ENCRYPT_KEY_SIZE + ENCRYPT_NONCE_SIZE */
#else
#define ENCRYPT_TMP_SECRET_OFFSET (WOLFBOOT_PARTITION_SIZE - (TRAILER_SKIP))
#define SECTOR_FLAGS_SIZE WOLFBOOT_SECTOR_SIZE - (4 + 1)
#define SECTOR_FLAGS_SIZE (WOLFBOOT_SECTOR_SIZE - (4 + 1))
/* MAGIC (4B) + PART_FLAG (1B) */
#endif /* EXT_FLASH && EXT_ENCRYPTED */

Expand Down
96 changes: 77 additions & 19 deletions tools/unit-tests/unit-delta.c
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@
#include <stdint.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>

#include "delta.h"
#define WC_RSA_BLINDING
Expand All @@ -35,7 +36,6 @@
#define DIFF_SIZE 8192



START_TEST(test_wb_patch_init_invalid)
{
WB_PATCH_CTX ctx;
Expand Down Expand Up @@ -142,11 +142,67 @@ START_TEST(test_wb_diff_init_invalid)
}
END_TEST

static void initialize_buffers(uint8_t *src_a, uint8_t *src_b)
START_TEST(test_wb_diff_match_extends_to_src_b_end)
{
WB_DIFF_CTX diff_ctx;
uint8_t src_a[BLOCK_HDR_SIZE + 2] = {0};
uint8_t src_b[BLOCK_HDR_SIZE + 1] = {0};
uint8_t patch[DELTA_BLOCK_SIZE] = {0};
int ret;

memset(src_a, 0x41, sizeof(src_a));
memset(src_b, 0x41, sizeof(src_b));

ret = wb_diff_init(&diff_ctx, src_a, sizeof(src_a), src_b, sizeof(src_b));
ck_assert_int_eq(ret, 0);

ret = wb_diff(&diff_ctx, patch, sizeof(patch));
ck_assert_int_gt(ret, 0);
}
END_TEST

START_TEST(test_wb_diff_self_match_extends_to_src_b_end)
{
WB_DIFF_CTX diff_ctx;
uint8_t *src_a;
uint8_t *src_b;
uint8_t patch[DELTA_BLOCK_SIZE] = {0};
int sector_size_ret;
size_t sector_size;
int ret;

sector_size_ret = wb_diff_get_sector_size();
ck_assert_int_gt(sector_size_ret, BLOCK_HDR_SIZE);
sector_size = (size_t)sector_size_ret;

src_a = calloc(1, sector_size + BLOCK_HDR_SIZE);
src_b = calloc(1, sector_size + BLOCK_HDR_SIZE + 1);
ck_assert_ptr_nonnull(src_a);
ck_assert_ptr_nonnull(src_b);

ret = wb_diff_init(&diff_ctx, src_a, sector_size + BLOCK_HDR_SIZE,
src_b, sector_size + BLOCK_HDR_SIZE + 1);
ck_assert_int_eq(ret, 0);

memset(src_a + sector_size, 0x11, BLOCK_HDR_SIZE);
memset(src_b, 0x22, BLOCK_HDR_SIZE + 1);
memset(src_b + sector_size, 0x22, BLOCK_HDR_SIZE + 1);
diff_ctx.off_b = sector_size;

ret = wb_diff(&diff_ctx, patch, sizeof(patch));
ck_assert_int_gt(ret, 0);

free(src_a);
free(src_b);
}
END_TEST

static void initialize_buffers(uint8_t *src_a, uint8_t *src_b, size_t size)
{
uint32_t pseudo_rand = 0;
uint8_t tmp[128];
for (int i = 0; i < SRC_SIZE; ++i) {
size_t i;

for (i = 0; i < size; ++i) {
src_a[i] = pseudo_rand % 256;
src_b[i] = pseudo_rand % 256;
if ((i % 100) == 42) {
Expand All @@ -158,24 +214,24 @@ static void initialize_buffers(uint8_t *src_a, uint8_t *src_b)
}

/* Introduce differences */
src_b[100] = src_a[100] + 1;
src_b[200] = src_a[200] + 2;
if (size > 100) {
src_b[100] = src_a[100] + 1;
}
if (size > 200) {
src_b[200] = src_a[200] + 2;
}

/* 10-bytes difference across two blocks */
for (int i = 1020; i < 1040; ++i) {
for (int i = 1020; i < 1040 && (size_t)i < size; ++i) {
src_b[i] = src_a[i] + 3;
}


/* Copy a sequence from A to B, behind */
src_a[510] = ESC;
memcpy(src_b + 4090, src_a + 500, 20);


/* Copy a sequence from B to itself, ahead */
src_b[1022] = ESC;
memcpy(tmp, src_b + 1020, 30);
memcpy(src_b + 7163, tmp, 30);
if (size > 510) {
src_a[510] = ESC;
}
if (size > 1022) {
src_b[1022] = ESC;
}

}

Expand All @@ -192,7 +248,7 @@ START_TEST(test_wb_patch_and_diff)
uint32_t p_written = 0;


initialize_buffers(src_a, src_b);
initialize_buffers(src_a, src_b, SRC_SIZE);

ret = wb_diff_init(&diff_ctx, src_a, SRC_SIZE, src_b, SRC_SIZE);
ck_assert_int_eq(ret, 0);
Expand Down Expand Up @@ -224,7 +280,7 @@ START_TEST(test_wb_patch_and_diff)
ck_assert_int_eq(i, SRC_SIZE); // The patched length should match the buffer size

/* Verify that the patched destination matches src_b */
for (int i = 0; i < SRC_SIZE; ++i) {
for (i = 0; i < SRC_SIZE; ++i) {
ck_assert_uint_eq(patched_dst[i], src_b[i]);
}
}
Expand All @@ -247,6 +303,8 @@ Suite *patch_diff_suite(void)
tcase_add_test(tc_wolfboot_delta, test_wb_patch_resume_bounds_invalid);
tcase_add_test(tc_wolfboot_delta, test_wb_patch_resume_large_len);
tcase_add_test(tc_wolfboot_delta, test_wb_patch_trailing_escape_invalid);
tcase_add_test(tc_wolfboot_delta, test_wb_diff_match_extends_to_src_b_end);
tcase_add_test(tc_wolfboot_delta, test_wb_diff_self_match_extends_to_src_b_end);
tcase_add_test(tc_wolfboot_delta, test_wb_patch_and_diff);
suite_add_tcase(s, tc_wolfboot_delta);

Expand Down
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