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correct ASN.1 cert parsing #408

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Merged
dgarske merged 1 commit into from
Mar 27, 2025
Merged

correct ASN.1 cert parsing #408

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45 changes: 24 additions & 21 deletions src/tpm2_asn.c
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Original file line number Diff line number Diff line change
Expand Up @@ -157,7 +157,7 @@ int TPM2_ASN_DecodeX509Cert(uint8_t* input, int inputSz,
}

/* Store certificate location */
if (rc == 0) {
if (rc >= 0) {
x509->certBegin = idx;
x509->cert = &input[idx];

Expand All @@ -166,76 +166,78 @@ int TPM2_ASN_DecodeX509Cert(uint8_t* input, int inputSz,
&idx, &cert_len, inputSz);
}

if (rc == 0) {
if (rc >= 0) {
x509->certSz = cert_len + (idx - x509->certBegin);

/* Decode version */
rc = TPM2_ASN_GetHeader(input, TPM2_ASN_CONTEXT_SPECIFIC | TPM2_ASN_CONSTRUCTED,
&idx, &len, inputSz);
}

if (rc == 0) {
if (rc >= 0) {
/* check version == 1 */
if (input[idx] != TPM2_ASN_INTEGER || input[idx] != 1) {
if (input[idx] != TPM2_ASN_INTEGER && input[idx] != 1) {
rc = TPM_RC_VALUE;
}
}

if (rc == 0) {
if (rc >= 0) {
idx += len; /* skip version */

/* Skip serial number */
rc = TPM2_ASN_GetHeader(input, TPM2_ASN_INTEGER, &idx, &len, inputSz);
}

if (rc == 0) {
if (rc >= 0) {
idx += len; /* skip serial */

/* Skip algorithm identifier */
rc = TPM2_ASN_GetHeader(input, TPM2_ASN_SEQUENCE | TPM2_ASN_CONSTRUCTED,
&idx, &len, inputSz);
}

if (rc == 0) {
if (rc >= 0) {
idx += len; /* skip signature oid */

/* Skip issuer */
rc = TPM2_ASN_GetHeader(input, TPM2_ASN_SEQUENCE | TPM2_ASN_CONSTRUCTED,
&idx, &len, inputSz);
}

if (rc == 0) {
if (rc >= 0) {
idx += len; /* skip issuer */

/* Skip validity */
rc = TPM2_ASN_GetHeader(input, TPM2_ASN_SEQUENCE | TPM2_ASN_CONSTRUCTED,
&idx, &len, inputSz);
}

if (rc == 0) {
if (rc >= 0) {
idx += len; /* skip validity */

/* Skip subject */
rc = TPM2_ASN_GetHeader(input, TPM2_ASN_SEQUENCE | TPM2_ASN_CONSTRUCTED,
&idx, &len, inputSz);
}

if (rc == 0) {
if (rc >= 0) {
idx += len; /* skip subject */

/* Skip subject public key info */
/* subject public key info */
rc = TPM2_ASN_GetHeader(input, TPM2_ASN_SEQUENCE | TPM2_ASN_CONSTRUCTED,
&idx, &len, inputSz);
}

if (rc == 0) {
idx += len; /* skip subject public key info */

if (rc >= 0) {
/* cert - subject public key alg oid */
rc = TPM2_ASN_GetHeader(input, TPM2_ASN_SEQUENCE | TPM2_ASN_CONSTRUCTED,
&idx, &len, inputSz);
}
if (rc >= 0) {
idx += len; /* skip alg oid */
/* Get public key */
rc = TPM2_ASN_GetHeader(input, TPM2_ASN_BIT_STRING, &idx, &pubkey_len, inputSz);
}

if (rc == 0) {
if (rc >= 0) {
/* skip leading zero for bit string */
if (input[idx] == 0x00) {
idx++;
Expand All @@ -250,25 +252,26 @@ int TPM2_ASN_DecodeX509Cert(uint8_t* input, int inputSz,
&idx, &len, inputSz);
}

if (rc == 0) {
if (rc >= 0) {
/* signature oid */
rc = TPM2_ASN_GetHeader(input, TPM2_ASN_OBJECT_ID, &idx, &len, inputSz);
}

if (rc == 0) {
if (rc >= 0) {
idx += len; /* skip oid */

/* Skip signature algorithm parameters */
rc = TPM2_ASN_GetHeader(input, TPM2_ASN_TAG_NULL, &idx, &len, inputSz);
}

if (rc == 0) {
if (rc >= 0) {
idx += len; /* skip tag */

/* Get signature */
rc = TPM2_ASN_GetHeader(input, TPM2_ASN_BIT_STRING, &idx, &sig_len, inputSz);
}

if (rc == 0) {
if (rc >= 0) {
/* skip leading zero for bit string */
if (input[idx] == 0x00) {
idx++;
Expand Down