Wipe (some) secrets from memory after use

[tinc] / src / gcrypt / rsa.c

diff --git a/src/gcrypt/rsa.c b/src/gcrypt/rsa.c
index 1162ddf..83f177b 100644 (file)
--- a/src/gcrypt/rsa.c
+++ b/src/gcrypt/rsa.c
@@ -130,7 +130,7 @@ rsa_t *rsa_set_hex_public_key(const char *n, const char *e) {
 
        if(err) {
                logger(DEBUG_ALWAYS, LOG_ERR, "Error while reading RSA public key: %s", gcry_strerror(errno));
-               free(rsa);
+               rsa_free(rsa);
                return false;
        }
 
@@ -152,8 +152,8 @@ rsa_t *rsa_set_hex_private_key(const char *n, const char *e, const char *d) {
 
        if(err) {
                logger(DEBUG_ALWAYS, LOG_ERR, "Error while reading RSA public key: %s", gcry_strerror(errno));
-               free(rsa);
-               return false;
+               rsa_free(rsa);
+               return NULL;
        }
 
        return rsa;
@@ -177,7 +177,7 @@ rsa_t *rsa_read_pem_public_key(FILE *fp) {
                        || !ber_read_mpi(&derp, &derlen, &rsa->e)
                        || derlen) {
                logger(DEBUG_ALWAYS, LOG_ERR, "Error while decoding RSA public key");
-               free(rsa);
+               rsa_free(rsa);
                return NULL;
        }
 
@@ -207,10 +207,11 @@ rsa_t *rsa_read_pem_private_key(FILE *fp) {
                        || !ber_read_mpi(&derp, &derlen, NULL) // u
                        || derlen) {
                logger(DEBUG_ALWAYS, LOG_ERR, "Error while decoding RSA private key");
-               free(rsa);
-               return NULL;
+               rsa_free(rsa);
+               rsa = NULL;
        }
 
+       memzero(derbuf, sizeof(derbuf));
        return rsa;
 }
 
@@ -218,19 +219,27 @@ size_t rsa_size(const rsa_t *rsa) {
        return (gcry_mpi_get_nbits(rsa->n) + 7) / 8;
 }
 
+static bool check(gcry_error_t err) {
+       if(err) {
+               logger(DEBUG_ALWAYS, LOG_ERR, "gcrypt error %s/%s", gcry_strsource(err), gcry_strerror(err));
+       }
+
+       return !err;
+}
+
 /* Well, libgcrypt has functions to handle RSA keys, but they suck.
  * So we just use libgcrypt's mpi functions, and do the math ourselves.
  */
 
-// TODO: get rid of this macro, properly clean up gcry_ structures after use
-#define check(foo) { gcry_error_t err = (foo); if(err) {logger(DEBUG_ALWAYS, LOG_ERR, "gcrypt error %s/%s at %s:%d", gcry_strsource(err), gcry_strerror(err), __FILE__, __LINE__); return false; }}
+static bool rsa_powm(const gcry_mpi_t ed, const gcry_mpi_t n, const void *in, size_t len, void *out) {
+       gcry_mpi_t inmpi = NULL;
 
-bool rsa_public_encrypt(rsa_t *rsa, const void *in, size_t len, void *out) {
-       gcry_mpi_t inmpi;
-       check(gcry_mpi_scan(&inmpi, GCRYMPI_FMT_USG, in, len, NULL));
+       if(!check(gcry_mpi_scan(&inmpi, GCRYMPI_FMT_USG, in, len, NULL))) {
+               return false;
+       }
 
-       gcry_mpi_t outmpi = gcry_mpi_new(len * 8);
-       gcry_mpi_powm(outmpi, inmpi, rsa->e, rsa->n);
+       gcry_mpi_t outmpi = gcry_mpi_snew(len * 8);
+       gcry_mpi_powm(outmpi, inmpi, ed, n);
 
        size_t out_bytes = (gcry_mpi_get_nbits(outmpi) + 7) / 8;
        size_t pad = len - MIN(out_bytes, len);
@@ -240,28 +249,20 @@ bool rsa_public_encrypt(rsa_t *rsa, const void *in, size_t len, void *out) {
                *pout++ = 0;
        }
 
-       check(gcry_mpi_print(GCRYMPI_FMT_USG, pout, len, NULL, outmpi));
-
-       return true;
-}
+       bool ok = check(gcry_mpi_print(GCRYMPI_FMT_USG, pout, len, NULL, outmpi));
 
-bool rsa_private_decrypt(rsa_t *rsa, const void *in, size_t len, void *out) {
-       gcry_mpi_t inmpi;
-       check(gcry_mpi_scan(&inmpi, GCRYMPI_FMT_USG, in, len, NULL));
-
-       gcry_mpi_t outmpi = gcry_mpi_new(len * 8);
-       gcry_mpi_powm(outmpi, inmpi, rsa->d, rsa->n);
-
-       size_t pad = len - (gcry_mpi_get_nbits(outmpi) + 7) / 8;
-       unsigned char *pout = out;
+       gcry_mpi_release(outmpi);
+       gcry_mpi_release(inmpi);
 
-       for(; pad; --pad) {
-               *pout++ = 0;
-       }
+       return ok;
+}
 
-       check(gcry_mpi_print(GCRYMPI_FMT_USG, pout, len, NULL, outmpi));
+bool rsa_public_encrypt(rsa_t *rsa, const void *in, size_t len, void *out) {
+       return rsa_powm(rsa->e, rsa->n, in, len, out);
+}
 
-       return true;
+bool rsa_private_decrypt(rsa_t *rsa, const void *in, size_t len, void *out) {
+       return rsa_powm(rsa->d, rsa->n, in, len, out);
 }
 
 void rsa_free(rsa_t *rsa) {