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RSA Verify
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1. Added function wolfSSH_RsaVerify() which verifies the provided
   RSA signature with the provided key.
2. Call wolfSSH_RsaVerify() after all calls to wc_RsaSSL_Sign().
3. Changed a comparison between an unsigned and 0 to == from <=.
4. Fixed a spot where we still tried to sign a digest when the call
   to wc_DigestFinal() failed.
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@ejohnstown
ejohnstown committed Dec 21, 2023
1 parent 7f52e23 commit b97b6c7
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Showing 3 changed files with 82 additions and 15 deletions.
4 changes: 4 additions & 0 deletions src/agent.c
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Original file line number Diff line number Diff line change
Expand Up @@ -701,6 +701,10 @@ static int SignHashRsa(WOLFSSH_AGENT_KEY_RSA* rawKey, enum wc_HashType hashType,
WLOG(WS_LOG_DEBUG, "Bad RSA Sign");
ret = WS_RSA_E;
}
else {
ret = wolfSSH_RsaVerify(sig, *sigSz,
encSig, encSigSz, &key, heap, "SignHashRsa");
}
}

wc_FreeRsaKey(&key);
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89 changes: 74 additions & 15 deletions src/internal.c
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Original file line number Diff line number Diff line change
Expand Up @@ -9422,6 +9422,47 @@ static INLINE byte SigTypeForId(byte id)
}


#ifndef WOLFSSH_NO_RSA
/*
* wolfSSH_RsaVerify
* sig - signature to verify
* sigSz - signature to verify size
* digest - encoded digest for verification
* digestSz - encoded digest size
* key - key used to sign and verify signature
* heap - allocation heap
* loc - calling function for logging
*/
int wolfSSH_RsaVerify(byte *sig, word32 sigSz,
const byte* digest, word32 digestSz,
RsaKey* key, void* heap, const char* loc)
{
byte* checkSig;
int ret = WS_SUCCESS;

checkSig = (byte*)WMALLOC(sigSz, heap, DYNTYPE_TEMP);
if (checkSig == NULL) {
ret = WS_MEMORY_E;
}
else {
int checkSz;

checkSz = wc_RsaSSL_VerifyInline(sig, sigSz, &checkSig, key);
if (checkSz < 0
|| (word32)checkSz != digestSz
|| WMEMCMP(digest, checkSig, digestSz) != 0) {
WLOG(WS_LOG_DEBUG, "%s: %s", loc, "Bad RSA Sign Verify");
ret = WS_RSA_E;
}
ForceZero(checkSig, sigSz);
WFREE(checkSig, heap, DYNTYPE_TEMP);
}

return ret;
}
#endif /* WOLFSSH_NO_RSA */


/* SendKexDhReply()
* It is also the funciton used for MSGID_KEXECDH_REPLY. The parameters
* are analogous between the two messages. Where MSGID_KEXDH_REPLY has
Expand Down Expand Up @@ -9932,7 +9973,7 @@ int SendKexDhReply(WOLFSSH* ssh)
encSigSz = wc_EncodeSignature(encSig, digest,
wc_HashGetDigestSize(sigHashId),
wc_HashGetOID(sigHashId));
if (encSigSz <= 0) {
if (encSigSz == 0) {
WLOG(WS_LOG_DEBUG, "SendKexDhReply: Bad Encode Sig");
ret = WS_CRYPTO_FAILED;
}
Expand All @@ -9946,6 +9987,12 @@ int SendKexDhReply(WOLFSSH* ssh)
WLOG(WS_LOG_DEBUG, "SendKexDhReply: Bad RSA Sign");
ret = WS_RSA_E;
}
else {
ret = wolfSSH_RsaVerify(sig_ptr, sigSz,
encSig, encSigSz,
&sigKeyBlock_ptr->sk.rsa.key,
heap, "SendKexDhReply");
}
}
#ifdef WOLFSSH_SMALL_STACK
WFREE(encSig, heap, DYNTYPE_TEMP);
Expand Down Expand Up @@ -11175,6 +11222,11 @@ static int BuildUserAuthRequestRsa(WOLFSSH* ssh,
WLOG(WS_LOG_DEBUG, "SUAR: Bad RSA Sign");
ret = WS_RSA_E;
}
else {
ret = wolfSSH_RsaVerify(output + begin, keySig->sigSz,
encDigest, encDigestSz, &keySig->ks.rsa.key,
ssh->ctx->heap, "SUAR");
}
}
}

Expand Down Expand Up @@ -11324,21 +11376,23 @@ static int BuildUserAuthRequestRsaCert(WOLFSSH* ssh,
if (ret == WS_SUCCESS)
ret = wc_HashFinal(&hash, hashId, digest);

c32toa(keySig->sigSz + 7 + LENGTH_SZ * 2, output + begin);
begin += LENGTH_SZ;
c32toa(7, output + begin);
begin += LENGTH_SZ;
WMEMCPY(output + begin, "ssh-rsa", 7);
begin += 7;
c32toa(keySig->sigSz, output + begin);
begin += LENGTH_SZ;
encDigestSz = wc_EncodeSignature(encDigest, digest, digestSz,
wc_HashGetOID(hashId));
if (encDigestSz <= 0) {
WLOG(WS_LOG_DEBUG, "SUAR: Bad Encode Sig");
ret = WS_CRYPTO_FAILED;
if (ret == WS_SUCCESS) {
c32toa(keySig->sigSz + 7 + LENGTH_SZ * 2, output + begin);
begin += LENGTH_SZ;
c32toa(7, output + begin);
begin += LENGTH_SZ;
WMEMCPY(output + begin, "ssh-rsa", 7);
begin += 7;
c32toa(keySig->sigSz, output + begin);
begin += LENGTH_SZ;
encDigestSz = wc_EncodeSignature(encDigest, digest, digestSz,
wc_HashGetOID(hashId));
if (encDigestSz <= 0) {
WLOG(WS_LOG_DEBUG, "SUAR: Bad Encode Sig");
ret = WS_CRYPTO_FAILED;
}
}
else {
if (ret == WS_SUCCESS) {
int sigSz;
WLOG(WS_LOG_INFO, "Signing hash with RSA.");
sigSz = wc_RsaSSL_Sign(encDigest, encDigestSz,
Expand All @@ -11348,6 +11402,11 @@ static int BuildUserAuthRequestRsaCert(WOLFSSH* ssh,
WLOG(WS_LOG_DEBUG, "SUAR: Bad RSA Sign");
ret = WS_RSA_E;
}
else {
ret = wolfSSH_RsaVerify(output + begin, keySig->sigSz,
encDigest, encDigestSz, &keySig->ks.rsa.key,
ssh->ctx->heap, "SUAR");
}
}

if (ret == WS_SUCCESS)
Expand Down
4 changes: 4 additions & 0 deletions wolfssh/internal.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,7 @@
#include <wolfssl/wolfcrypt/aes.h>
#include <wolfssl/wolfcrypt/dh.h>
#include <wolfssl/wolfcrypt/ecc.h>
#include <wolfssl/wolfcrypt/rsa.h>
#ifdef WOLFSSH_SCP
#include <wolfssh/wolfscp.h>
#endif
Expand Down Expand Up @@ -1195,6 +1196,9 @@ WOLFSSH_LOCAL int wsScpSendCallback(WOLFSSH*, int, const char*, char*, word32,


WOLFSSH_LOCAL int wolfSSH_CleanPath(WOLFSSH* ssh, char* in);
WOLFSSH_LOCAL int wolfSSH_RsaVerify(byte *sig, word32 sigSz,
const byte* digest, word32 digestSz,
RsaKey* key, void* heap, const char* loc);
WOLFSSH_LOCAL void DumpOctetString(const byte*, word32);
WOLFSSH_LOCAL int wolfSSH_oct2dec(WOLFSSH* ssh, byte* oct, word32 octSz);
WOLFSSH_LOCAL void AddAssign64(word32*, word32);
Expand Down

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