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agent: exchange whole messages when signing #1308

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18 changes: 12 additions & 6 deletions apps/wolfssh/wolfssh.c
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Original file line number Diff line number Diff line change
Expand Up @@ -877,6 +877,8 @@ static int wolfSSH_AGENT_DefaultActions(WS_AgentCbAction action, void* vCtx)
ret = WS_AGENT_SETUP_E;
err = errno;
fprintf(stderr, "connect() = %d", err);
close(ctx->fd);
ctx->fd = -1;
}
}

Expand All @@ -886,12 +888,15 @@ static int wolfSSH_AGENT_DefaultActions(WS_AgentCbAction action, void* vCtx)
else if (action == WOLFSSH_AGENT_LOCAL_CLEANUP) {
int err;

err = close(ctx->fd);
if (err != 0) {
err = errno;
fprintf(stderr, "close() = %d", err);
if (ret == 0)
ret = WS_AGENT_SETUP_E;
if (ctx->fd >= 0) {
err = close(ctx->fd);
ctx->fd = -1;
if (err != 0) {
err = errno;
fprintf(stderr, "close() = %d", err);
if (ret == 0)
ret = WS_AGENT_SETUP_E;
}
}
}
else
Expand Down Expand Up @@ -1246,6 +1251,7 @@ static THREAD_RETURN WOLFSSH_THREAD wolfSSH_Client(void* args)
#ifdef WOLFSSH_AGENT
if (useAgent) {
WMEMSET(&agentCbCtx, 0, sizeof(agentCbCtx));
agentCbCtx.fd = -1;
agentCbCtx.state = AGENT_STATE_INIT;
wolfSSH_set_agent_cb_ctx(ssh, &agentCbCtx);
}
Expand Down
18 changes: 12 additions & 6 deletions examples/client/client.c
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Original file line number Diff line number Diff line change
Expand Up @@ -701,6 +701,8 @@ static int wolfSSH_AGENT_DefaultActions(WS_AgentCbAction action, void* vCtx)
ret = WS_AGENT_SETUP_E;
err = errno;
fprintf(stderr, "connect() = %d", err);
close(ctx->fd);
ctx->fd = -1;
}
}

Expand All @@ -710,12 +712,15 @@ static int wolfSSH_AGENT_DefaultActions(WS_AgentCbAction action, void* vCtx)
else if (action == WOLFSSH_AGENT_LOCAL_CLEANUP) {
int err;

err = close(ctx->fd);
if (err != 0) {
err = errno;
fprintf(stderr, "close() = %d", err);
if (ret == 0)
ret = WS_AGENT_SETUP_E;
if (ctx->fd >= 0) {
err = close(ctx->fd);
ctx->fd = -1;
if (err != 0) {
err = errno;
fprintf(stderr, "close() = %d", err);
if (ret == 0)
ret = WS_AGENT_SETUP_E;
}
}
}
else
Expand Down Expand Up @@ -1017,6 +1022,7 @@ THREAD_RETURN WOLFSSH_THREAD client_test(void* args)
#ifdef WOLFSSH_AGENT
if (useAgent) {
WMEMSET(&agentCbCtx, 0, sizeof(agentCbCtx));
agentCbCtx.fd = -1;
agentCbCtx.state = AGENT_STATE_INIT;
wolfSSH_set_agent_cb_ctx(ssh, &agentCbCtx);
}
Expand Down
117 changes: 46 additions & 71 deletions src/agent.c
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Original file line number Diff line number Diff line change
Expand Up @@ -66,12 +66,6 @@
#endif


/* Read buffer size for a reply from an agent. Covers a signature and its
* message header for any key up to RSA-8192. */
#ifndef WOLFSSH_AGENT_MAX_RSP_SZ
#define WOLFSSH_AGENT_MAX_RSP_SZ 2048
#endif

/* Largest agent message this build will handle. The peer declares the
* length, so it is bounded before it drives an allocation. */
#ifndef WOLFSSH_AGENT_MAX_MSG_SZ
Expand Down Expand Up @@ -2289,9 +2283,10 @@ int wolfSSH_AGENT_SignRequest(WOLFSSH* ssh,
word32 flags)
{
int ret = WS_SUCCESS;
byte* rxBuf = NULL;
int rxSz;
byte* rsp = NULL;
word32 rspSz = 0;
word32 idx = 0;
byte setUp = 0;
WOLFSSH_AGENT_CTX* agent = NULL;

WLOG_ENTER();
Expand All @@ -2305,102 +2300,82 @@ int wolfSSH_AGENT_SignRequest(WOLFSSH* ssh,
}

if (ret == WS_SUCCESS) {
if (sigSz == NULL)
if (sig == NULL || sigSz == NULL
|| (digest == NULL && digestSz != 0)
|| (keyBlob == NULL && keyBlobSz != 0))
ret = WS_BAD_ARGUMENT;
}

if (ret == WS_SUCCESS) {
rxBuf = (byte*)WMALLOC(WOLFSSH_AGENT_MAX_RSP_SZ,
ssh->agent->heap, DYNTYPE_AGENT_BUFFER);
if (rxBuf == NULL)
ret = WS_MEMORY_E;
}

if (ret == WS_SUCCESS) {
agent = ssh->agent;
agent->requestFailure = 0;
agent->requestSuccess = 0;
agent->msg = NULL;
agent->msgSz = 0;
agent->lastMsgId = 0;
if (ssh->ctx->agentCb)
ret = ssh->ctx->agentCb(WOLFSSH_AGENT_LOCAL_SETUP, ssh->agentCbCtx);
if (ssh->ctx->agentCb) {
/* The callback answers in WS_AgentCbError, where failure is
* positive. */
if (ssh->ctx->agentCb(WOLFSSH_AGENT_LOCAL_SETUP, ssh->agentCbCtx)
!= WS_AGENT_SUCCESS) {
ret = WS_AGENT_CXN_FAIL;
}
else
setUp = 1;
}
}

if (ret == WS_SUCCESS)
ret = SendSignRequest(agent, digest, digestSz,
keyBlob, keyBlobSz, flags);

if (ret == WS_SUCCESS) {
int wrote;

wrote = ssh->ctx->agentIoCb(WOLFSSH_AGENT_IO_WRITE,
agent->msg, agent->msgSz, ssh->agentCbCtx);
if (wrote != (int)agent->msgSz) {
WLOG(WS_LOG_AGENT, "agent write incomplete");
ret = WS_AGENT_CXN_FAIL;
}
}
if (ret == WS_SUCCESS)
ret = AgentWriteAll(ssh, agent->msg, agent->msgSz, NULL);

if (agent != NULL && agent->msg != NULL) {
WFREE(ssh->agent->msg, ssh->agent->heap, DYNTYPE_AGENT_BUFFER);
ssh->agent->msg = NULL;
ssh->agent->msgSz = 0;
WFREE(agent->msg, agent->heap, DYNTYPE_AGENT_BUFFER);
agent->msg = NULL;
agent->msgSz = 0;
}

if (ret == WS_SUCCESS)
ret = AgentReadMessage(ssh, &rsp, &rspSz);

if (ret == WS_SUCCESS)
ret = DoMessage(agent, rsp, rspSz, &idx);

if (ret == WS_SUCCESS) {
rxSz = ssh->ctx->agentIoCb(WOLFSSH_AGENT_IO_READ,
rxBuf, WOLFSSH_AGENT_MAX_RSP_SZ, ssh->agentCbCtx);
if (rxSz > 0) {
ret = DoMessage(ssh->agent, rxBuf, rxSz, &idx);
if (ret == WS_SUCCESS) {
if (ssh->agent->lastMsgId != MSGID_AGENT_SIGN_RESPONSE) {
WLOG(WS_LOG_AGENT,
"agent response was not a signature message");
ret = WS_AGENT_NO_KEY_E;
}
else {
if (ssh->agent->requestFailure ||
ssh->agent->msg == NULL ||
ssh->agent->msgSz == 0) {
ssh->agent->requestFailure = 0;
ret = WS_AGENT_NO_KEY_E;
}
else {
word32 maxSigSz = *sigSz;

if (ssh->agent->msgSz > maxSigSz) {
WLOG(WS_LOG_AGENT,
"agent signature too large for caller buffer");
ret = WS_BUFFER_E;
}
else {
WMEMCPY(sig, ssh->agent->msg, ssh->agent->msgSz);
*sigSz = ssh->agent->msgSz;
}
}
}
}
if (agent->lastMsgId != MSGID_AGENT_SIGN_RESPONSE) {
WLOG(WS_LOG_AGENT, "agent response was not a signature message");
ret = WS_AGENT_NO_KEY_E;
}
else if (agent->requestFailure || agent->msg == NULL ||
agent->msgSz == 0) {
agent->requestFailure = 0;
ret = WS_AGENT_NO_KEY_E;
}
else if (agent->msgSz > *sigSz) {
WLOG(WS_LOG_AGENT, "agent signature too large for caller buffer");
ret = WS_BUFFER_E;
}
else {
WMEMCPY(sig, agent->msg, agent->msgSz);
*sigSz = agent->msgSz;
}
else ret = WS_AGENT_NO_KEY_E;
}

if (ret != WS_SUCCESS && sigSz != NULL)
*sigSz = 0;

if (agent != NULL) {
/* The reply was parsed in place out of rxBuf. */
agent->msg = NULL;
agent->msgSz = 0;
AgentBufferReset(agent->rxBuf);
}

if (ssh != NULL && ssh->ctx != NULL && ssh->ctx->agentCb != NULL) {
if (setUp)
ssh->ctx->agentCb(WOLFSSH_AGENT_LOCAL_CLEANUP, ssh->agentCbCtx);
}

/* The agent's message was parsed in place out of this buffer, so it is
* freed after the last use of agent->msg. */
if (rxBuf != NULL)
WFREE(rxBuf, ssh->agent->heap, DYNTYPE_AGENT_BUFFER);

WLOG_LEAVE(ret);
return ret;
Expand Down
84 changes: 70 additions & 14 deletions src/internal.c
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Original file line number Diff line number Diff line change
Expand Up @@ -20959,7 +20959,21 @@ static int PrepareUserAuthRequestEcc(WOLFSSH* ssh, word32* payloadSz,

if (ret == WS_SUCCESS) {
if (authData->sf.publicKey.hasSignature) {
int sigSz = wc_ecc_sig_size(&keySig->ks.ecc.key);
int sigSz;

#ifdef WOLFSSH_AGENT
if (ssh->agentEnabled) {
/* The agent answers with r and s as mpints, each at most a
* pad byte over the curve size. */
sigSz = wc_ecc_size(&keySig->ks.ecc.key);
if (sigSz > 0)
sigSz = 2 * (sigSz + 1);
else
sigSz = WS_ECC_E;
}
else
#endif
sigSz = wc_ecc_sig_size(&keySig->ks.ecc.key);

if (sigSz >= 0) {
*payloadSz += (LENGTH_SZ * 5) + (word32)sigSz +
Expand All @@ -20976,8 +20990,9 @@ static int PrepareUserAuthRequestEcc(WOLFSSH* ssh, word32* payloadSz,
}


/* outputSz bounds the variable-length r/s mpint encoding; the fixed-size
* builders (RSA, Ed25519, ML-DSA) fit PreparePacket()'s estimate unbounded. */
/* outputSz bounds the variable-length r/s mpint encoding and the agent's
* blob; the fixed-size builders (RSA, Ed25519, ML-DSA) fit PreparePacket()'s
* estimate unbounded. */
static int BuildUserAuthRequestEcc(WOLFSSH* ssh,
byte* output, word32 outputSz, word32* idx,
const WS_UserAuthData* authData,
Expand Down Expand Up @@ -21046,23 +21061,64 @@ static int BuildUserAuthRequestEcc(WOLFSSH* ssh,

#ifdef WOLFSSH_AGENT
if (ssh->agentEnabled) {
if (ret == WS_SUCCESS)
/* The room PrepareUserAuthRequestEcc() reserved for the agent's
* signature blob: the algorithm name and the r and s mpints. */
word32 agentSigSz = (LENGTH_SZ * 4) + keySig->sigSz +
authData->sf.publicKey.publicKeyTypeSz;
const byte* agentSigName = NULL;
word32 agentSigNameSz = 0;
word32 nameIdx = 0;
byte effSigId = keySig->sigId;

#ifdef WOLFSSH_OSSH_CERTS
/* An OpenSSH certificate is dispatched by its cert id, but the
* agent signs under the curve's own name. */
switch (keySig->sigId) {
#ifndef WOLFSSH_NO_ECDSA_SHA2_NISTP256
case ID_OSSH_CERT_ECDSA_SHA2_NISTP256:
effSigId = ID_ECDSA_SHA2_NISTP256;
break;
#endif
#ifndef WOLFSSH_NO_ECDSA_SHA2_NISTP384
case ID_OSSH_CERT_ECDSA_SHA2_NISTP384:
effSigId = ID_ECDSA_SHA2_NISTP384;
break;
#endif
#ifndef WOLFSSH_NO_ECDSA_SHA2_NISTP521
case ID_OSSH_CERT_ECDSA_SHA2_NISTP521:
effSigId = ID_ECDSA_SHA2_NISTP521;
break;
#endif
default:
break;
}
#endif

if (ret == WS_SUCCESS && (outputSz <= begin ||
outputSz - begin < LENGTH_SZ + agentSigSz)) {
WLOG(WS_LOG_DEBUG, "SUAR: ECDSA agent sig doesn't fit output");
ret = WS_BUFFER_E;
}
if (ret == WS_SUCCESS) {
WLOG(WS_LOG_INFO, "Signing with ECDSA through the agent.");
ret = wolfSSH_AGENT_SignRequest(ssh, checkData, checkDataSz,
sig_ptr, &sigSz,
output + begin + LENGTH_SZ, &agentSigSz,
authData->sf.publicKey.publicKey,
authData->sf.publicKey.publicKeySz, 0);
}
/* An agent may answer under another algorithm or curve. */
if (ret == WS_SUCCESS) {
/* begin indexes into output, whose capacity is outputSz. */
if (outputSz <= begin || outputSz - begin < LENGTH_SZ + sigSz) {
WLOG(WS_LOG_DEBUG, "SUAR: ECDSA agent sig doesn't fit output");
ret = WS_BUFFER_E;
}
ret = GetStringRef(&agentSigNameSz, &agentSigName,
output + begin + LENGTH_SZ, agentSigSz, &nameIdx);
}
if (ret == WS_SUCCESS && NameToId((const char*)agentSigName,
agentSigNameSz) != effSigId) {
WLOG(WS_LOG_DEBUG, "SUAR: agent signed with another algorithm");
ret = WS_INVALID_ALGO_ID;
}
if (ret == WS_SUCCESS) {
c32toa(sigSz, output + begin);
begin += LENGTH_SZ;
XMEMCPY(output + begin, sig_ptr, sigSz);
begin += sigSz;
c32toa(agentSigSz, output + begin);
begin += LENGTH_SZ + agentSigSz;
}
}
else
Expand Down
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