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fwtpm: size RSASSA DigestInfo buffers for SHA-512, check Sign digest … #655

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Merged
dgarske merged 2 commits into from
Oct 28, 2026
Merged

fwtpm: size RSASSA DigestInfo buffers for SHA-512, check Sign digest … #655

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c5a6553
fwtpm: size RSASSA DigestInfo buffers for SHA-512, check Sign digest …
embhorn Oct 27, 2026
2ec9d79
Fix from review
embhorn Oct 27, 2026
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6 changes: 1 addition & 5 deletions examples/pcr/policy_sign.c
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Original file line number Diff line number Diff line change
Expand Up @@ -67,10 +67,6 @@ static void usage(void)
printf("./examples/pcr/policy_sign -pcr=16 -pcr=15 -pcrdigest=ba8ac02be16d9d33080d98611d70bb869aa8ac3fc684ab732b91f75f164b36bc\n");
}

#ifndef WC_MAX_ENCODED_DIG_ASN_SZ
#define WC_MAX_ENCODED_DIG_ASN_SZ 9 /* enum(bit or octet) + length(4) */
#endif

/* Function to sign policy with external key */
static int PolicySign(TPM_ALG_ID alg, const char* keyFile, const char* password,
TPM_ALG_ID hashAlg, byte* hash, word32 hashSz, byte* sig, word32* sigSz,
Expand Down Expand Up @@ -142,7 +138,7 @@ static int PolicySign(TPM_ALG_ID alg, const char* keyFile, const char* password,
#if !defined(NO_RSA) && !defined(NO_ASN)
rc = wc_InitRsaKey(&key.rsa, NULL);
if (rc == 0) {
byte encHash[WC_MAX_DIGEST_SIZE + WC_MAX_ENCODED_DIG_ASN_SZ];
byte encHash[WOLFTPM_MAX_DER_DIGEST_SZ];
word32 idx = 0;
#ifdef HAVE_PKCS8
/* skip PKCS8 header */
Expand Down
6 changes: 6 additions & 0 deletions src/fwtpm/fwtpm_command.c
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Original file line number Diff line number Diff line change
Expand Up @@ -9518,6 +9518,12 @@ static TPM_RC FwCmd_Sign(FWTPM_CTX* ctx, TPM2_Packet* cmd,
/* Use key's scheme if command scheme is NULL */
FwResolveSignScheme(obj, &sigScheme, &sigHashAlg);
}
/* Part 3 Sec.20.2.1: digest size MUST match the scheme hashAlg digest
* size (matches FwCmd_SignDigest). */
if (rc == 0 && sigHashAlg != TPM_ALG_NULL &&
digest.size != (UINT16)TPM2_GetHashDigestSize(sigHashAlg)) {
rc = TPM_RC_SIZE;
}

/* Parse validation ticket (TPMT_TK_HASHCHECK) */
if (rc == 0) {
Expand Down
6 changes: 2 additions & 4 deletions src/fwtpm/fwtpm_crypto.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3905,8 +3905,7 @@ TPM_RC FwSignDigestAndAppend(FWTPM_CTX* ctx, FWTPM_Object* obj,
}
else {
/* RSASSA PKCS#1 v1.5: wrap in ASN.1 DigestInfo */
byte encHash[WC_MAX_DIGEST_SIZE +
MAX_ENCODED_DIG_ASN_SZ];
byte encHash[WOLFTPM_MAX_DER_DIGEST_SZ];
int encSz;
int oid = wc_HashGetOID(
(enum wc_HashType)wcHashType);
Expand Down Expand Up @@ -4064,8 +4063,7 @@ TPM_RC FwVerifySignatureCore(FWTPM_Object* obj,
}
else {
FWTPM_DECLARE_BUF(decSig, FWTPM_MAX_PUB_BUF);
byte expDI[WC_MAX_DIGEST_SIZE +
MAX_ENCODED_DIG_ASN_SZ];
byte expDI[WOLFTPM_MAX_DER_DIGEST_SZ];
int wcHash = FwGetRsaHashOid(
sig->signature.rsassa.hash);
int oid = wc_HashGetOID(
Expand Down
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