Re: [Openvpn-devel] [PATCH] EVP_DigestSignFinal siglen parameter correction

[Arne Schwabe]

Am 12.03.21 um 16:06 schrieb Juliusz Sosinowicz:
> In the EVP_DigestSignFinal API, "before the call the siglen parameter should 
> contain the length of the sig buffer".
> 
> Signed-off-by: Juliusz Sosinowicz 
> ---
>  src/openvpn/crypto_openssl.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/src/openvpn/crypto_openssl.c b/src/openvpn/crypto_openssl.c
> index 49698e4b3..4486d246d 100644
> --- a/src/openvpn/crypto_openssl.c
> +++ b/src/openvpn/crypto_openssl.c
> @@ -1195,7 +1195,7 @@ tls1_P_hash(const EVP_MD *md, const unsigned char *sec,
>  EVP_MD_CTX ctx, ctx_tmp, ctx_init;
>  EVP_PKEY *mac_key;
>  unsigned char A1[EVP_MAX_MD_SIZE];
> -size_t A1_len;
> +size_t A1_len = EVP_MAX_MD_SIZE;
>  int ret = false;
>  
>  chunk = EVP_MD_size(md);
> @@ -1249,6 +1249,7 @@ tls1_P_hash(const EVP_MD *md, const unsigned char *sec,
>  
>  if (olen > chunk)
>  {
> +j = olen;
>  if (!EVP_DigestSignFinal(, out, ))
>  {
>  goto err;
> @@ -1263,6 +1264,7 @@ tls1_P_hash(const EVP_MD *md, const unsigned char *sec,
>  }
>  else
>  {
> +A1_len = EVP_MAX_MD_SIZE;
>  /* last one */
>  if (!EVP_DigestSignFinal(, A1, _len))
>  {
> 

Acked-By: Arne Schwabe 

The uninitialised parameter should not work and the OpenSSL
documentation says that it should contain the size of the buffer but the
internal code of OpenVPN seems to ignore that and somehow it still
works. But I cannot blame wolfSSL being lax about the OpenSSL API :)


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Re: [Openvpn-devel] [PATCH] EVP_DigestSignFinal siglen parameter correction

[Arne Schwabe]

Am 12.03.21 um 16:06 schrieb Juliusz Sosinowicz:
> In the EVP_DigestSignFinal API, "before the call the siglen parameter should 
> contain the length of the sig buffer".

This is probably correct but I need to take a closer look as this
function is directly taken from OpenSSL's internal function and only has
minimal adaptations. Note also that we plan to remove this compatibility
path as soon as we drop OpenSSL 1.0.2 support.

Arne


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[Openvpn-devel] [PATCH] EVP_DigestSignFinal siglen parameter correction

[Juliusz Sosinowicz]

In the EVP_DigestSignFinal API, "before the call the siglen parameter should 
contain the length of the sig buffer".

Signed-off-by: Juliusz Sosinowicz 
---
 src/openvpn/crypto_openssl.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/openvpn/crypto_openssl.c b/src/openvpn/crypto_openssl.c
index 49698e4b3..4486d246d 100644
--- a/src/openvpn/crypto_openssl.c
+++ b/src/openvpn/crypto_openssl.c
@@ -1195,7 +1195,7 @@ tls1_P_hash(const EVP_MD *md, const unsigned char *sec,
 EVP_MD_CTX ctx, ctx_tmp, ctx_init;
 EVP_PKEY *mac_key;
 unsigned char A1[EVP_MAX_MD_SIZE];
-size_t A1_len;
+size_t A1_len = EVP_MAX_MD_SIZE;
 int ret = false;
 
 chunk = EVP_MD_size(md);
@@ -1249,6 +1249,7 @@ tls1_P_hash(const EVP_MD *md, const unsigned char *sec,
 
 if (olen > chunk)
 {
+j = olen;
 if (!EVP_DigestSignFinal(, out, ))
 {
 goto err;
@@ -1263,6 +1264,7 @@ tls1_P_hash(const EVP_MD *md, const unsigned char *sec,
 }
 else
 {
+A1_len = EVP_MAX_MD_SIZE;
 /* last one */
 if (!EVP_DigestSignFinal(, A1, _len))
 {
-- 
2.25.1



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