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echoserver: wipe and bound the key load buffer #1340

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a2d4f7e
echoserver: wipe key load buffers in all builds
ejohnstown Oct 21, 2026
8524957
echoserver: bound the key list parse and copies
ejohnstown Oct 21, 2026
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187 changes: 93 additions & 94 deletions examples/echoserver/echoserver.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2638,6 +2638,7 @@ static int LoadMlDsaHostKeys(WOLFSSH_CTX* ctx, const char* keyList)
{
byte* mldsaBuf;
int loaded = 0;
int ret = 0;

mldsaBuf = (byte*)WMALLOC(MLDSA_MAX_BOTH_KEY_DER_SIZE, NULL, 0);
if (mldsaBuf == NULL) {
Expand All @@ -2650,14 +2651,14 @@ static int LoadMlDsaHostKeys(WOLFSSH_CTX* ctx, const char* keyList)
int mldsaSz = load_key_mldsa44(mldsaBuf, MLDSA_MAX_BOTH_KEY_DER_SIZE);
if (mldsaSz <= 0) {
fprintf(stderr, "Couldn't load ML-DSA-44 key file.\n");
WFREE(mldsaBuf, NULL, 0);
return -1;
ret = -1;
goto cleanup;
}
if (wolfSSH_CTX_UsePrivateKey_buffer(ctx, mldsaBuf, (word32)mldsaSz,
WOLFSSH_FORMAT_ASN1) < 0) {
fprintf(stderr, "Couldn't use ML-DSA-44 key buffer.\n");
WFREE(mldsaBuf, NULL, 0);
return -1;
ret = -1;
goto cleanup;
}
loaded++;
}
Expand All @@ -2668,14 +2669,14 @@ static int LoadMlDsaHostKeys(WOLFSSH_CTX* ctx, const char* keyList)
int mldsaSz = load_key_mldsa65(mldsaBuf, MLDSA_MAX_BOTH_KEY_DER_SIZE);
if (mldsaSz <= 0) {
fprintf(stderr, "Couldn't load ML-DSA-65 key file.\n");
WFREE(mldsaBuf, NULL, 0);
return -1;
ret = -1;
goto cleanup;
}
if (wolfSSH_CTX_UsePrivateKey_buffer(ctx, mldsaBuf, (word32)mldsaSz,
WOLFSSH_FORMAT_ASN1) < 0) {
fprintf(stderr, "Couldn't use ML-DSA-65 key buffer.\n");
WFREE(mldsaBuf, NULL, 0);
return -1;
ret = -1;
goto cleanup;
}
loaded++;
}
Expand All @@ -2686,26 +2687,29 @@ static int LoadMlDsaHostKeys(WOLFSSH_CTX* ctx, const char* keyList)
int mldsaSz = load_key_mldsa87(mldsaBuf, MLDSA_MAX_BOTH_KEY_DER_SIZE);
if (mldsaSz <= 0) {
fprintf(stderr, "Couldn't load ML-DSA-87 key file.\n");
WFREE(mldsaBuf, NULL, 0);
return -1;
ret = -1;
goto cleanup;
}
if (wolfSSH_CTX_UsePrivateKey_buffer(ctx, mldsaBuf, (word32)mldsaSz,
WOLFSSH_FORMAT_ASN1) < 0) {
fprintf(stderr, "Couldn't use ML-DSA-87 key buffer.\n");
WFREE(mldsaBuf, NULL, 0);
return -1;
ret = -1;
goto cleanup;
}
loaded++;
}
#endif /* WOLFSSH_NO_MLDSA87 */

WFREE(mldsaBuf, NULL, 0);
if (loaded == 0) {
fprintf(stderr, "ML-DSA key list '%s' matched no supported level.\n",
keyList);
return -1;
ret = -1;
}
return 0;

cleanup:
wc_ForceZero(mldsaBuf, MLDSA_MAX_BOTH_KEY_DER_SIZE);
WFREE(mldsaBuf, NULL, 0);
return ret;
}
#endif /* WOLFSSH_NO_MLDSA */

Expand Down Expand Up @@ -2967,6 +2971,17 @@ static int LoadPasswordBuffer(byte* buf, word32 bufSz, PwMapList* list)
}


/* Finds c in [str, end). Returns NULL when it is not there. */
static char* FindDelimiter(char* str, const char* end, char c)
{
for (; str < end; str++) {
if (*str == c)
return str;
}
return NULL;
}


static int LoadPublicKeyBuffer(byte* buf, word32 bufSz, PwMapList* list)
{
char* str = (char*)buf;
Expand All @@ -2981,33 +2996,31 @@ static int LoadPublicKeyBuffer(byte* buf, word32 bufSz, PwMapList* list)

/* Each line of passwd.txt is in the format
* ssh-rsa AAAB3BASE64ENCODEDPUBLICKEYBLOB username\n
* This function modifies the passed-in buffer. */
* This function modifies the passed-in buffer, which need not be
* NUL-terminated. */
if (list == NULL)
return -1;

if (buf == NULL || bufSz == 0)
return 0;

while (str < end && *str != 0) {
/* Skip the public key type. This example will always be ssh-rsa. */
delimiter = WSTRCHR(str, ' ');
/* Skip the OpenSSH public-key type; the decoded blob carries the
* algorithm. */
delimiter = FindDelimiter(str, end, ' ');
if (delimiter == NULL) {
return -1;
}
if (str >= end)
break;
str = delimiter + 1;
delimiter = WSTRCHR(str, ' ');
delimiter = FindDelimiter(str, end, ' ');
if (delimiter == NULL) {
return -1;
}
publicKey64 = (byte*)str;
*delimiter = 0;
publicKey64Sz = (word32)(delimiter - str);
if (str >= end)
break;
str = delimiter + 1;
delimiter = WSTRCHR(str, '\n');
delimiter = FindDelimiter(str, end, '\n');
if (delimiter == NULL) {
return -1;
}
Expand Down Expand Up @@ -3648,6 +3661,31 @@ static int SetDefaultSftpPath(WOLFSSH* ssh, const char* defaultSftpPath,
#endif


/* Wipes the key load buffer, which held host private keys, and frees it
* when it came from the heap. */
static void KeyLoadBufFree(byte* buf)
{
wc_ForceZero(buf, EXAMPLE_KEYLOAD_BUFFER_SZ);
#ifdef WOLFSSH_SMALL_STACK
WFREE(buf, NULL, 0);
#endif
}


/* Copies str and its terminator into the key load buffer and sets *sz to
* the length of str. Returns 0, or -1 when it does not fit. */
static int CopyToKeyLoadBuf(byte* buf, const char* str, word32* sz)
{
word32 len = (word32)WSTRLEN(str);

if (len >= EXAMPLE_KEYLOAD_BUFFER_SZ)
return -1;
WMEMCPY(buf, str, len + 1);
*sz = len;
return 0;
}


static void ShowUsage(void)
{
printf("echoserver %s linked with wolfSSL %s\n", LIBWOLFSSH_VERSION_STRING,
Expand Down Expand Up @@ -4253,10 +4291,7 @@ THREAD_RETURN WOLFSSH_THREAD echoserver_test(void* args)
if (tpmHostKeyPath != NULL) {
if (EchoserverInitTpmHostKey(ctx, tpmHostKeyPath,
ECHOSERVER_TPM_KEY_AUTH_DEFAULT) != 0) {
#ifdef WOLFSSH_SMALL_STACK
wc_ForceZero(keyLoadBuf, EXAMPLE_KEYLOAD_BUFFER_SZ);
WFREE(keyLoadBuf, NULL, 0);
#endif
KeyLoadBufFree(keyLoadBuf);
ES_ERROR("Couldn't load TPM host key from %s.\n",
tpmHostKeyPath);
}
Expand Down Expand Up @@ -4289,10 +4324,7 @@ THREAD_RETURN WOLFSSH_THREAD echoserver_test(void* args)
}
}
if (storeErr != NULL) {
#ifdef WOLFSSH_SMALL_STACK
wc_ForceZero(keyLoadBuf, EXAMPLE_KEYLOAD_BUFFER_SZ);
WFREE(keyLoadBuf, NULL, 0);
#endif
KeyLoadBufFree(keyLoadBuf);
#ifdef WOLFSSH_KEYBOARD_INTERACTIVE
if (kbAuthData.promptCount > 0) {
WFREE(kbAuthData.promptLengths, NULL, 0);
Expand All @@ -4313,18 +4345,12 @@ THREAD_RETURN WOLFSSH_THREAD echoserver_test(void* args)
#if !defined(WOLFSSH_NO_RSA) || !defined(WOLFSSH_NO_ECDSA)
bufSz = load_key(peerEcc, keyLoadBuf, bufSz);
if (bufSz == 0) {
#ifdef WOLFSSH_SMALL_STACK
wc_ForceZero(keyLoadBuf, EXAMPLE_KEYLOAD_BUFFER_SZ);
WFREE(keyLoadBuf, NULL, 0);
#endif
KeyLoadBufFree(keyLoadBuf);
ES_ERROR("Couldn't load first key file.\n");
}
if (wolfSSH_CTX_UsePrivateKey_buffer(ctx, keyLoadBuf, bufSz,
WOLFSSH_FORMAT_ASN1) < 0) {
#ifdef WOLFSSH_SMALL_STACK
wc_ForceZero(keyLoadBuf, EXAMPLE_KEYLOAD_BUFFER_SZ);
WFREE(keyLoadBuf, NULL, 0);
#endif
KeyLoadBufFree(keyLoadBuf);
ES_ERROR("Couldn't use first key buffer.\n");
}

Expand All @@ -4334,18 +4360,12 @@ THREAD_RETURN WOLFSSH_THREAD echoserver_test(void* args)

bufSz = load_key(peerEcc, keyLoadBuf, bufSz);
if (bufSz == 0) {
#ifdef WOLFSSH_SMALL_STACK
wc_ForceZero(keyLoadBuf, EXAMPLE_KEYLOAD_BUFFER_SZ);
WFREE(keyLoadBuf, NULL, 0);
#endif
KeyLoadBufFree(keyLoadBuf);
ES_ERROR("Couldn't load second key file.\n");
}
if (wolfSSH_CTX_UsePrivateKey_buffer(ctx, keyLoadBuf, bufSz,
WOLFSSH_FORMAT_ASN1) < 0) {
#ifdef WOLFSSH_SMALL_STACK
wc_ForceZero(keyLoadBuf, EXAMPLE_KEYLOAD_BUFFER_SZ);
WFREE(keyLoadBuf, NULL, 0);
#endif
KeyLoadBufFree(keyLoadBuf);
ES_ERROR("Couldn't use second key buffer.\n");
}
#endif
Expand All @@ -4355,18 +4375,12 @@ THREAD_RETURN WOLFSSH_THREAD echoserver_test(void* args)
bufSz = EXAMPLE_KEYLOAD_BUFFER_SZ;
bufSz = load_key_ed25519(keyLoadBuf, bufSz);
if (bufSz == 0) {
#ifdef WOLFSSH_SMALL_STACK
wc_ForceZero(keyLoadBuf, EXAMPLE_KEYLOAD_BUFFER_SZ);
WFREE(keyLoadBuf, NULL, 0);
#endif
KeyLoadBufFree(keyLoadBuf);
ES_ERROR("Couldn't load Ed25519 key file.\n");
}
if (wolfSSH_CTX_UsePrivateKey_buffer(ctx, keyLoadBuf, bufSz,
WOLFSSH_FORMAT_ASN1) < 0) {
#ifdef WOLFSSH_SMALL_STACK
wc_ForceZero(keyLoadBuf, EXAMPLE_KEYLOAD_BUFFER_SZ);
WFREE(keyLoadBuf, NULL, 0);
#endif
KeyLoadBufFree(keyLoadBuf);
ES_ERROR("Couldn't use Ed25519 key buffer.\n");
}
#endif /* WOLFSSH_NO_ED25519 */
Expand All @@ -4391,10 +4405,7 @@ THREAD_RETURN WOLFSSH_THREAD echoserver_test(void* args)
}

if (mldsaErr) {
#ifdef WOLFSSH_SMALL_STACK
wc_ForceZero(keyLoadBuf, EXAMPLE_KEYLOAD_BUFFER_SZ);
WFREE(keyLoadBuf, NULL, 0);
#endif
KeyLoadBufFree(keyLoadBuf);
ES_ERROR("Error loading ML-DSA host keys.\n");
}
else {
Expand All @@ -4410,21 +4421,15 @@ THREAD_RETURN WOLFSSH_THREAD echoserver_test(void* args)
mldsaMatched = 1;
if (LoadMlDsaCompositeHostKey(ctx, entry->fileName,
entry->label) != 0) {
#ifdef WOLFSSH_SMALL_STACK
wc_ForceZero(keyLoadBuf, EXAMPLE_KEYLOAD_BUFFER_SZ);
WFREE(keyLoadBuf, NULL, 0);
#endif
KeyLoadBufFree(keyLoadBuf);
ES_ERROR("Error loading %s host key.\n",
entry->label);
}
}
}

if (!mldsaMatched) {
#ifdef WOLFSSH_SMALL_STACK
wc_ForceZero(keyLoadBuf, EXAMPLE_KEYLOAD_BUFFER_SZ);
WFREE(keyLoadBuf, NULL, 0);
#endif
KeyLoadBufFree(keyLoadBuf);
ES_ERROR("ML-DSA key list '%s' matched no supported "
"level.\n", keyList);
}
Expand All @@ -4442,23 +4447,20 @@ THREAD_RETURN WOLFSSH_THREAD echoserver_test(void* args)

/* create temp buffer and load in file */
if (userBufSz == 0) {
#ifdef WOLFSSH_SMALL_STACK
wc_ForceZero(keyLoadBuf, EXAMPLE_KEYLOAD_BUFFER_SZ);
WFREE(keyLoadBuf, NULL, 0);
#endif
KeyLoadBufFree(keyLoadBuf);
ES_ERROR("Couldn't find size of file %s.\n", userPubKey);
}

userBuf = (byte*)WMALLOC(userBufSz, NULL, 0);
if (userBuf == NULL) {
#ifdef WOLFSSH_SMALL_STACK
wc_ForceZero(keyLoadBuf, EXAMPLE_KEYLOAD_BUFFER_SZ);
WFREE(keyLoadBuf, NULL, 0);
#endif
KeyLoadBufFree(keyLoadBuf);
ES_ERROR("WMALLOC failed\n");
}
load_file(userPubKey, userBuf, &userBufSz);
LoadPublicKeyBuffer(userBuf, userBufSz, &pwMapList);
if (LoadPublicKeyBuffer(userBuf, userBufSz, &pwMapList) != 0) {
fprintf(stderr, "Couldn't load every key in %s.\n",
userPubKey);
}
WFREE(userBuf, NULL, 0);
}
#endif
Expand All @@ -4468,18 +4470,16 @@ THREAD_RETURN WOLFSSH_THREAD echoserver_test(void* args)
if (caCert) {
/* PEM or DER is detected from the file's content. */
if (wolfSSH_CTX_AddRootCert_file(ctx, caCert) != WS_SUCCESS) {
#ifdef WOLFSSH_SMALL_STACK
wc_ForceZero(keyLoadBuf, EXAMPLE_KEYLOAD_BUFFER_SZ);
WFREE(keyLoadBuf, NULL, 0);
#endif
KeyLoadBufFree(keyLoadBuf);
ES_ERROR("Couldn't add root cert\n");
}
}
#endif

bufSz = (word32)WSTRLEN(samplePasswordBuffer);
WMEMCPY(keyLoadBuf, samplePasswordBuffer, bufSz);
keyLoadBuf[bufSz] = 0;
if (CopyToKeyLoadBuf(keyLoadBuf, samplePasswordBuffer, &bufSz) != 0) {
KeyLoadBufFree(keyLoadBuf);
ES_ERROR("Sample password list doesn't fit.\n");
}
LoadPasswordBuffer(keyLoadBuf, bufSz, &pwMapList);

#if defined(WOLFSSH_NO_RSA) && defined(WOLFSSH_NO_ECDSA)
Expand All @@ -4505,23 +4505,22 @@ THREAD_RETURN WOLFSSH_THREAD echoserver_test(void* args)
}
#endif
if (bufName != NULL) {
bufSz = (word32)WSTRLEN(bufName);
WMEMCPY(keyLoadBuf, bufName, bufSz);
keyLoadBuf[bufSz] = 0;
if (CopyToKeyLoadBuf(keyLoadBuf, bufName, &bufSz) != 0) {
KeyLoadBufFree(keyLoadBuf);
ES_ERROR("Sample public key list doesn't fit.\n");
}
LoadPublicKeyBuffer(keyLoadBuf, bufSz, &pwMapList);
}

#ifdef WOLFSSH_ALLOW_USERAUTH_NONE
bufSz = (word32)WSTRLEN(sampleNoneBuffer);
WMEMCPY(keyLoadBuf, sampleNoneBuffer, bufSz);
keyLoadBuf[bufSz] = 0;
if (CopyToKeyLoadBuf(keyLoadBuf, sampleNoneBuffer, &bufSz) != 0) {
KeyLoadBufFree(keyLoadBuf);
ES_ERROR("Sample none list doesn't fit.\n");
}
LoadNoneBuffer(keyLoadBuf, bufSz, &pwMapList);
#endif /* WOLFSSH_ALLOW_USERAUTH_NONE */

#ifdef WOLFSSH_SMALL_STACK
wc_ForceZero(keyLoadBuf, EXAMPLE_KEYLOAD_BUFFER_SZ);
WFREE(keyLoadBuf, NULL, 0);
#endif
KeyLoadBufFree(keyLoadBuf);
}
#ifdef WOLFSSL_NUCLEUS
{
Expand Down
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