On Sun, Aug 22, 2021 at 03:10:55AM +0300, Vitaly Chikunov wrote:
> After CRYPTO_secure_malloc_init OpenSSL will store private keys in
> secure heap. This facility is only available since OpenSSL_1_1_0-pre1.
>
> Signed-off-by: Vitaly Chikunov <vt@xxxxxxxxxxxx>
> ---
> src/evmctl.c | 148 +++++++++++++++++++++++++++++++++++++++++----------
> 1 file changed, 121 insertions(+), 27 deletions(-)
>
> diff --git a/src/evmctl.c b/src/evmctl.c
> index 5f7c2b8..cebe9ec 100644
> --- a/src/evmctl.c
> +++ b/src/evmctl.c
> @@ -59,6 +59,7 @@
> #include <assert.h>
>
> #include <openssl/asn1.h>
> +#include <openssl/crypto.h>
> #include <openssl/sha.h>
> #include <openssl/pem.h>
> #include <openssl/hmac.h>
> @@ -165,6 +166,24 @@ struct tpm_bank_info {
> static char *pcrfile[MAX_PCRFILE];
> static unsigned npcrfile;
>
> +#if OPENSSL_VERSION_NUMBER <= 0x10100000
> +#warning Your OpenSSL version is too old to have OPENSSL_secure_malloc, \
> + falling back to use plain OPENSSL_malloc.
> +#define OPENSSL_secure_malloc OPENSSL_malloc
> +#define OPENSSL_secure_free OPENSSL_free
> +/*
> + * Secure heap memory automatically cleared on free, but
> + * OPENSSL_secure_clear_free will be used in case of fallback
> + * to plain OPENSSL_malloc.
> + */
> +#define OPENSSL_secure_clear_free OPENSSL_clear_free
> +#define OPENSSL_clear_free(ptr, num) \
> + do { \
> + OPENSSL_cleanse(ptr, num); \
> + OPENSSL_free(ptr); \
> + } while (0)
> +#endif
> +
> static int bin2file(const char *file, const char *ext, const unsigned char *data, int len)
> {
> FILE *fp;
> @@ -188,7 +207,9 @@ static int bin2file(const char *file, const char *ext, const unsigned char *data
> return err;
> }
>
> -static unsigned char *file2bin(const char *file, const char *ext, int *size)
> +/* Return data in OpenSSL secure heap if 'secure' is true. */
> +static unsigned char *file2bin(const char *file, const char *ext, int *size,
> + int secure)
> {
> FILE *fp;
> size_t len;
> @@ -215,7 +236,10 @@ static unsigned char *file2bin(const char *file, const char *ext, int *size)
> }
> len = stats.st_size;
>
> - data = malloc(len);
> + if (secure)
> + data = OPENSSL_secure_malloc(len);
> + else
> + data = malloc(len);
> if (!data) {
> log_err("Failed to malloc %zu bytes: %s\n", len, name);
> fclose(fp);
> @@ -224,7 +248,10 @@ static unsigned char *file2bin(const char *file, const char *ext, int *size)
> if (fread(data, len, 1, fp) != 1) {
> log_err("Failed to fread %zu bytes: %s\n", len, name);
> fclose(fp);
> - free(data);
> + if (secure)
> + OPENSSL_secure_clear_free(data, len);
> + else
> + free(data);
> return NULL;
> }
> fclose(fp);
> @@ -872,7 +899,7 @@ static int verify_ima(const char *file)
> int len;
>
> if (sigfile) {
> - void *tmp = file2bin(file, "sig", &len);
> + void *tmp = file2bin(file, "sig", &len, 0);
>
> if (!tmp) {
> log_err("Failed reading: %s\n", file);
> @@ -1001,7 +1028,7 @@ static int cmd_import(struct command *cmd)
>
> if (!pkey)
> return 1;
> - pub = file2bin(inkey, NULL, &len);
> + pub = file2bin(inkey, NULL, &len, 0);
> if (!pub) {
> EVP_PKEY_free(pkey);
> return 1;
> @@ -1040,9 +1067,9 @@ static int setxattr_ima(const char *file, char *sig_file)
> int len, err;
>
> if (sig_file)
> - sig = file2bin(sig_file, NULL, &len);
> + sig = file2bin(sig_file, NULL, &len, 0);
> else
> - sig = file2bin(file, "sig", &len);
> + sig = file2bin(file, "sig", &len, 0);
> if (!sig)
> return 0;
>
> @@ -1082,9 +1109,9 @@ static int calc_evm_hmac(const char *file, const char *keyfile, unsigned char *h
> unsigned int mdlen;
> char **xattrname;
> unsigned char xattr_value[1024];
> - unsigned char *key;
> + unsigned char *key; /* @secure heap */
> int keylen;
> - unsigned char evmkey[MAX_KEY_SIZE];
> + unsigned char *evmkey; /* @secure heap */
> char list[1024];
> ssize_t list_size;
> struct h_misc_64 hmac_misc;
> @@ -1096,21 +1123,30 @@ static int calc_evm_hmac(const char *file, const char *keyfile, unsigned char *h
> pctx = HMAC_CTX_new();
> #endif
>
> - key = file2bin(keyfile, NULL, &keylen);
> + key = file2bin(keyfile, NULL, &keylen, 1);
> if (!key) {
> log_err("Failed to read a key: %s\n", keyfile);
> return -1;
> }
>
> - if (keylen > sizeof(evmkey)) {
> + evmkey = OPENSSL_secure_malloc(MAX_KEY_SIZE);
> + if (!evmkey) {
> + log_err("Failed to allocate %d bytes\n", MAX_KEY_SIZE);
> + goto out;
> + }
> +
> + if (keylen > MAX_KEY_SIZE) {
> log_err("key is too long: %d\n", keylen);
> goto out;
> }
>
> /* EVM key is 128 bytes */
> memcpy(evmkey, key, keylen);
> - if (keylen < sizeof(evmkey))
> - memset(evmkey + keylen, 0, sizeof(evmkey) - keylen);
> + if (keylen < MAX_KEY_SIZE)
> + memset(evmkey + keylen, 0, MAX_KEY_SIZE - keylen);
> +
> + /* Shorten lifetime of key data. */
> + OPENSSL_cleanse(key, keylen);
>
> if (lstat(file, &st)) {
> log_err("Failed to stat: %s\n", file);
> @@ -1147,12 +1183,15 @@ static int calc_evm_hmac(const char *file, const char *keyfile, unsigned char *h
> goto out;
> }
>
> - err = !HMAC_Init_ex(pctx, evmkey, sizeof(evmkey), md, NULL);
> + err = !HMAC_Init_ex(pctx, evmkey, MAX_KEY_SIZE, md, NULL);
> if (err) {
> log_err("HMAC_Init() failed\n");
> goto out;
> }
>
> + /* Shorten lifetime of evmkey data. */
> + OPENSSL_cleanse(evmkey, MAX_KEY_SIZE);
> +
> for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
> err = lgetxattr(file, *xattrname, xattr_value, sizeof(xattr_value));
> if (err < 0) {
> @@ -1222,7 +1261,9 @@ out_ctx_cleanup:
> HMAC_CTX_free(pctx);
> #endif
> out:
> - free(key);
> + if (evmkey)
> + OPENSSL_secure_clear_free(evmkey, MAX_KEY_SIZE);
> + OPENSSL_secure_clear_free(key, keylen);
Minor thing: considering you already OPENSSL_cleanse() both evmkey and
key, is it necessary to call OPENSSL_secure_clear_free() instead of only
OPENSSL_secure_free()?
But like I said, that's a minor thing :)
Reviewed-by: Bruno Meneguele <bmeneg@xxxxxxxxxx>
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bmeneg
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