fix: zeroize DSA private key buffers#270
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Pull request overview
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Fixes a security issue where DSA private key material could remain in freed heap memory by explicitly zeroizing temporary DER/PEM buffers before freeing them in the DSA key generation path.
Changes:
- Zeroize the PEM-encoded DSA private key buffer (
pem) beforeXFREE - Zeroize the DER-encoded DSA private key buffer (
outBuf) beforeXFREE
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Bug
In
wolfCLU_DsaParamSetup(src/dsa/clu_dsa.c), thegenKeypath serializes a freshly generated DSA key including the secret exponent x. The DER buffer (outBuf, populated bywc_DsaKeyToDer) and the PEM buffer (pem,DSA_PRIVATEKEY_TYPE) are freed at the end of the block viaXFREEwithout being zeroized first. The private key material persists in freed heap.Fix
Call
wolfCLU_ForceZero(buf, sz)on both buffers beforeXFREE, matching wolfCLU's existing pattern for private-key buffers elsewhere (clu_parse.c, clu_pkcs8.c, clu_genkey.c). Only the genKey block is touched; the sibling param block (lines 210-279) serializes only public params (p,q,g viaDSA_PARAM_TYPE) and needs no change.Build verification
Compiled the patched translation unit clean under the project build flags against a full-featured wolfSSL install (DSA enabled).
objdump -dr src/dsa/clu_dsa.oshows two relocations towolfCLU_ForceZero, confirming the zeroize calls are live.Reported by static analysis (Fenrir finding 665).