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agent: size the signature buffer from the identity #1179

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Merged
ejohnstown merged 1 commit into from
Aug 20, 2026
+466 −12
Merged

agent: size the signature buffer from the identity #1179

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59 changes: 55 additions & 4 deletions src/agent.c
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Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,12 @@
#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

/* payloadSz is an estimate, but it shall be greater-than/equal-to
* the actual value. */
static int PrepareMessage(WOLFSSH_AGENT_CTX* agent, word32 payloadSz)
Expand Down Expand Up @@ -826,10 +832,10 @@ static int PostSignRequest(WOLFSSH_AGENT_CTX* agent,
word32 flags)
{
WOLFSSH_AGENT_ID* id = NULL;
byte* sig = NULL;
int ret = WS_SUCCESS;
byte sig[256];
byte digest[WC_MAX_DIGEST_SIZE];
word32 sigSz = sizeof(sig);
word32 sigSz = 0;
word32 digestSz = sizeof(digest);
enum wc_HashType hashType;
int curveId = 0, signRsa = 0, signEcc = 0;
Expand Down Expand Up @@ -901,6 +907,36 @@ static int PostSignRequest(WOLFSSH_AGENT_CTX* agent,
ret = WS_CRYPTO_FAILED;
}

/* Size the signature buffer from the identity. */
if (ret == WS_SUCCESS) {
#if !defined(WOLFSSH_NO_RSA_SHA2_256) || \
!defined(WOLFSSH_NO_RSA_SHA2_512)
if (signRsa) {
/* The signature is as long as the modulus. The stored mpint
* carries a leading zero byte for the sign bit. */
sigSz = id->key.rsa.nSz;
if (sigSz > (RSA_MAX_SIZE / 8) + 1) {
WLOG(WS_LOG_AGENT, "Sign: RSA key too large.");
ret = WS_BUFFER_E;
}
}
#endif
#if !defined(WOLFSSH_NO_ECDSA_SHA2_NISTP256) || \
!defined(WOLFSSH_NO_ECDSA_SHA2_NISTP384) || \
!defined(WOLFSSH_NO_ECDSA_SHA2_NISTP521)
if (signEcc)
sigSz = ECDSA_ASN_SIG_SZ;
#endif
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if (ret == WS_SUCCESS && sigSz == 0)
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ret = WS_BUFFER_E;
}

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

if (ret == WS_SUCCESS) {
#if !defined(WOLFSSH_NO_RSA_SHA2_256) || \
!defined(WOLFSSH_NO_RSA_SHA2_512)
Expand All @@ -924,6 +960,9 @@ static int PostSignRequest(WOLFSSH_AGENT_CTX* agent,
ret = SendSignResponse(agent, sig, sigSz);
}

if (sig != NULL)
WFREE(sig, agent->heap, DYNTYPE_AGENT_BUFFER);

WLOG_LEAVE(ret);
return ret;
}
Expand Down Expand Up @@ -1814,7 +1853,7 @@ int wolfSSH_AGENT_SignRequest(WOLFSSH* ssh,
word32 flags)
{
int ret = WS_SUCCESS;
byte rxBuf[512];
byte* rxBuf = NULL;
int rxSz;
word32 idx = 0;
WOLFSSH_AGENT_CTX* agent = NULL;
Expand All @@ -1834,6 +1873,13 @@ int wolfSSH_AGENT_SignRequest(WOLFSSH* ssh,
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;
Expand Down Expand Up @@ -1868,7 +1914,7 @@ int wolfSSH_AGENT_SignRequest(WOLFSSH* ssh,

if (ret == WS_SUCCESS) {
rxSz = ssh->ctx->agentIoCb(WOLFSSH_AGENT_IO_READ,
rxBuf, sizeof(rxBuf), ssh->agentCbCtx);
rxBuf, WOLFSSH_AGENT_MAX_RSP_SZ, ssh->agentCbCtx);
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if (rxSz > 0) {
ret = DoMessage(ssh->agent, rxBuf, rxSz, &idx);
if (ret == WS_SUCCESS) {
Expand Down Expand Up @@ -1915,6 +1961,11 @@ int wolfSSH_AGENT_SignRequest(WOLFSSH* ssh,
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
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