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ed448: remove unreachable privKeySet operand in wc_ed448_check_key

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Premise:  ed448.c:1517 `if ((ret == 0) && key->privKeySet) { ... }` -- the
          sibling arm of the if/else this condition belongs to.
Claim:    ed448.c:1524 `else if ((ret == 0) && (!key->privKeySet))` -- the
          `!key->privKeySet` operand; and, as a direct consequence, the nested
          `if (ret == 0)` that opened the arm's body.
Proof:    entering the else arm means the sibling condition was false, i.e.
          (ret != 0) || (!privKeySet). && short-circuits, so the else arm's own
          `key->privKeySet` read happens only after `ret == 0` evaluated true --
          and with ret == 0 the sibling's falsity forces !privKeySet. The
          operand is therefore invariantly true. privKeySet is a plain bitfield,
          not volatile, and no statement runs between the two conditions.
          The nested `if (ret == 0)` follows from the same short-circuit: the
          arm is entered only with ret == 0 and nothing precedes the nested test.
Scope:    wc_ed448_check_key contains no #if/#ifdef, so this holds in every
          configuration that compiles ed448.c.
Evidence: llvm-cov MC/DC records this condition's pair as uncovered
          (reports/ed448/GAPS.md row 1503:14:1503:46:1, pre-drift numbering).

Reviewed with `git diff -w`: apart from the two removed lines the change is
pure de-indentation.

ed448.c is inside the FIPS module boundary. Released FIPS flavours pin ed448.c
to a tag and are unaffected; fips-dev/fips-ready build from master and
recompute the in-core hash.

Compiler cross-check: gcc -O2 emits byte-identical code for this file before
and after this commit -- the optimiser had already folded the removed
condition, independently confirming it was dead.
This commit is contained in:
Daniele Lacamera
2026-08-03 12:33:14 +02:00
parent 611cebde8b
commit 7ecbd7385a
1 changed files with 24 additions and 26 deletions
Download Patch File Download Diff File Expand all files Collapse all files
wolfcrypt/src/ed448.c
+24 -26
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@@ -1521,41 +1521,39 @@ int wc_ed448_check_key(ed448_key* key)
}
}
/* No private key, check Y is valid. */
else if ((ret == 0) && (!key->privKeySet)) {
else if (ret == 0) {
/* Verify that xQ and yQ are integers in the interval [0, p - 1].
* Only have yQ so check that ordinate.
* p = 2^448-2^224-1 = 0xff..fe..ff
*/
if (ret == 0) {
int i;
ret = PUBLIC_KEY_E;
int i;
ret = PUBLIC_KEY_E;
/* Check top part before 0xFE. */
for (i = ED448_PUB_KEY_SIZE - 1; i > ED448_PUB_KEY_SIZE/2; i--) {
if (key->p[i] < 0xff) {
ret = 0;
break;
}
/* Check top part before 0xFE. */
for (i = ED448_PUB_KEY_SIZE - 1; i > ED448_PUB_KEY_SIZE/2; i--) {
if (key->p[i] < 0xff) {
ret = 0;
break;
}
if (ret == WC_NO_ERR_TRACE(PUBLIC_KEY_E)) {
/* Check against 0xFE. */
if (key->p[ED448_PUB_KEY_SIZE/2] < 0xfe) {
ret = 0;
}
else if (key->p[ED448_PUB_KEY_SIZE/2] == 0xfe) {
/* Check bottom part before last byte. */
for (i = ED448_PUB_KEY_SIZE/2 - 1; i > 0; i--) {
if (key->p[i] != 0xff) {
ret = 0;
break;
}
}
/* Check last byte. */
if ((ret == WC_NO_ERR_TRACE(PUBLIC_KEY_E)) &&
(key->p[0] < 0xff)) {
}
if (ret == WC_NO_ERR_TRACE(PUBLIC_KEY_E)) {
/* Check against 0xFE. */
if (key->p[ED448_PUB_KEY_SIZE/2] < 0xfe) {
ret = 0;
}
else if (key->p[ED448_PUB_KEY_SIZE/2] == 0xfe) {
/* Check bottom part before last byte. */
for (i = ED448_PUB_KEY_SIZE/2 - 1; i > 0; i--) {
if (key->p[i] != 0xff) {
ret = 0;
break;
}
}
/* Check last byte. */
if ((ret == WC_NO_ERR_TRACE(PUBLIC_KEY_E)) &&
(key->p[0] < 0xff)) {
ret = 0;
}
}
}