CVE-2021-3711

In order to decrypt SM2 encrypted data an application is expected to call the API function EVP_PKEY_decrypt(). Typically an application will call this function twice. The first time, on entry, the "out" parameter can be NULL and, on exit, the "outlen" parameter is populated with the buffer size required to hold the decrypted plaintext. The application can then allocate a sufficiently sized buffer and call EVP_PKEY_decrypt() again, but this time passing a non-NULL value for the "out" parameter. A bug in the implementation of the SM2 decryption code means that the calculation of the buffer size required to hold the plaintext returned by the first call to EVP_PKEY_decrypt() can be smaller than the actual size required by the second call. This can lead to a buffer overflow when EVP_PKEY_decrypt() is called by the application a second time with a buffer that is too small. A malicious attacker who is able present SM2 content for decryption to an application could cause attacker chosen data to overflow the buffer by up to a maximum of 62 bytes altering the contents of other data held after the buffer, possibly changing application behaviour or causing the application to crash. The location of the buffer is application dependent but is typically heap allocated. Fixed in OpenSSL 1.1.1l (Affected 1.1.1-1.1.1k).

In order to decrypt SM2 encrypted data an application is expected to call the API function EVP_PKEY_decrypt(). Typically an application will call this function twice. The first time, on entry, the "out" parameter can be NULL and, on exit, the "outlen" parameter is populated with the buffer size required to hold the decrypted plaintext. The application can then allocate a sufficiently sized buffer and call EVP_PKEY_decrypt() again, but this time passing a non-NULL value for the "out" parameter. A bug in the implementation of the SM2 decryption code means that the calculation of the buffer size required to hold the plaintext returned by the first call to EVP_PKEY_decrypt() can be smaller than the actual size required by the second call. This can lead to a buffer overflow when EVP_PKEY_decrypt() is called by the application a second time with a buffer that is too small. A malicious attacker who is able present SM2 content for decryption to an application could cause attacker chosen data to overflow the buffer by up to a maximum of 62 bytes altering the contents of other data held after the buffer, possibly changing application behaviour or causing the application to crash. The location of the buffer is application dependent but is typically heap allocated. Fixed in OpenSSL 1.1.1l (Affected 1.1.1-1.1.1k).

In order to decrypt SM2 encrypted data an application is expected to call the API function `EVP_PKEY_decrypt()`. Typically an application will call this function twice. The first time, on entry, the "out" parameter can be NULL and, on exit, the "outlen" parameter is populated with the buffer size required to hold the decrypted plaintext. The application can then allocate a sufficiently sized buffer and call `EVP_PKEY_decrypt()` again, but this time passing a non-NULL value for the "out" parameter. A bug in the implementation of the SM2 decryption code means that the calculation of the buffer size required to hold the plaintext returned by the first call to `EVP_PKEY_decrypt()` can be smaller than the actual size required by the second call. This can lead to a buffer overflow when `EVP_PKEY_decrypt()` is called by the application a second time with a buffer that is too small. A malicious attacker who is able present SM2 content for decryption to an application could cause attacker chosen data to overflow the buffer by up to a maximum of 62 bytes altering the contents of other data held after the buffer, possibly changing application behaviour or causing the application to crash. The location of the buffer is application dependent but is typically heap allocated.

In order to decrypt SM2 encrypted data an application is expected to call the API function EVP_PKEY_decrypt(). Typically an application will call this function twice. The first time, on entry, the "out" parameter can be NULL and, on exit, the "outlen" parameter is populated with the buffer size required to hold the decrypted plaintext. The application can then allocate a sufficiently sized buffer and call EVP_PKEY_decrypt() again, but this time passing a non-NULL value for the "out" parameter. A bug in the implementation of the SM2 decryption code means that the calculation of the buffer size required to hold the plaintext returned by the first call to EVP_PKEY_decrypt() can be smaller than the actual size required by the second call. This can lead to a buffer overflow when EVP_PKEY_decrypt() is called by the application a second time with a buffer that is too small. A malicious attacker who is able present SM2 content for decryption to an application could cause attacker chosen data to overflow the buffer by up to a maximum of 62 bytes altering the contents of other data held after the buffer, possibly changing application behaviour or causing the application to crash. The location of the buffer is application dependent but is typically heap allocated. Fixed in OpenSSL 1.1.1l (Affected 1.1.1-1.1.1k).

Para descifrar los datos cifrados de SM2 se espera que una aplicación llame a la función de la API EVP_PKEY_decrypt(). Normalmente, una aplicación llamará a esta función dos veces. La primera vez, al entrar, el parámetro "out" puede ser NULL y, al salir, el parámetro "outlen" se rellena con el tamaño del búfer necesario para contener el texto plano descifrado. La aplicación puede entonces asignar un búfer de tamaño suficiente y llamar de nuevo a EVP_PKEY_decrypt(), pero esta vez pasando un valor no NULL para el parámetro "out". Un bug en la implementación del código de descifrado SM2 significa que el cálculo del tamaño del búfer necesario para mantener el texto plano devuelto por la primera llamada a EVP_PKEY_decrypt() puede ser menor que el tamaño real requerido por la segunda llamada. Esto puede conllevar a un desbordamiento del búfer cuando la aplicación llama a EVP_PKEY_decrypt() por segunda vez con un búfer demasiado pequeño. Un atacante malicioso que sea capaz de presentar el contenido de SM2 para su descifrado a una aplicación podría causar que los datos elegidos por el atacante desborden el búfer hasta un máximo de 62 bytes alterando el contenido de otros datos mantenidos después del búfer, posiblemente cambiando el comportamiento de la aplicación o causando el bloqueo de la misma. La ubicación del búfer depende de la aplicación, pero normalmente se asigna a la pila. Corregido en OpenSSL versión 1.1.1l (Afectada 1.1.1-1.1.1k).