CVE-2013-2546 (C, published 2013-03-15T20:55Z)
Description: value: The report API in the crypto user configuration API in the Linux kernel through 3.8.2 uses an incorrect C library function for copying strings, which allows local users to obtain sensitive information from kernel stack memory by leveraging the CAP_NET_ADMIN capability.
Severity: LOW (CVSS v3 base score: )
Weakness: CWE-310 \u2014 Cryptographic Issues
Weaknesses in this category are related to the design and implementation of data confidentiality and integrity. Frequently these deal with the use of encoding techniques, encryption libraries, and hashing algorithms. The weaknesses in this category could lead to a degradation of the quality data if they are not addressed.
Repository: https://github.com/torvalds/linux
Files changed:
crypto/ablkcipher.c
crypto/aead.c
crypto/ahash.c
crypto/blkcipher.c
crypto/crypto_user.c
crypto/pcompress.c
crypto/rng.c
crypto/shash.c
Commit message: crypto: user - fix info leaks in report API

Three errors resulting in kernel memory disclosure:

1/ The structures used for the netlink based crypto algorithm report API
are located on the stack. As snprintf() does not fill the remainder of
the buffer with null bytes, those stack bytes will be disclosed to users
of the API. Switch to strncpy() to fix this.

2/ crypto_report_one() does not initialize all field of struct
crypto_user_alg. Fix this to fix the heap info leak.

3/ For the module name we should copy only as many bytes as
module_name() returns -- not as much as the destination buffer could
hold. But the current code does not and therefore copies random data
from behind the end of the module name, as the module name is always
shorter than CRYPTO_MAX_ALG_NAME.

Also switch to use strncpy() to copy the algorithm's name and
driver_name. They are strings, after all.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>


Vulnerable code:
	snprintf(rblkcipher.type, CRYPTO_MAX_ALG_NAME, "%s", "ablkcipher");
	snprintf(rblkcipher.geniv, CRYPTO_MAX_ALG_NAME, "%s",
		 alg->cra_ablkcipher.geniv ?: "<default>");
	snprintf(rblkcipher.type, CRYPTO_MAX_ALG_NAME, "%s", "givcipher");
	snprintf(rblkcipher.geniv, CRYPTO_MAX_ALG_NAME, "%s",
		 alg->cra_ablkcipher.geniv ?: "<built-in>");
	snprintf(raead.type, CRYPTO_MAX_ALG_NAME, "%s", "aead");
	snprintf(raead.geniv, CRYPTO_MAX_ALG_NAME, "%s",
		 aead->geniv ?: "<built-in>");
	snprintf(raead.type, CRYPTO_MAX_ALG_NAME, "%s", "nivaead");
	snprintf(raead.geniv, CRYPTO_MAX_ALG_NAME, "%s", aead->geniv);
	snprintf(rhash.type, CRYPTO_MAX_ALG_NAME, "%s", "ahash");
	snprintf(rblkcipher.type, CRYPTO_MAX_ALG_NAME, "%s", "blkcipher");
	snprintf(rblkcipher.geniv, CRYPTO_MAX_ALG_NAME, "%s",
		 alg->cra_blkcipher.geniv ?: "<default>");
	snprintf(rcipher.type, CRYPTO_MAX_ALG_NAME, "%s", "cipher");
	snprintf(rcomp.type, CRYPTO_MAX_ALG_NAME, "%s", "compression");

	memcpy(&ualg->cru_name, &alg->cra_name, sizeof(ualg->cru_name));
	memcpy(&ualg->cru_driver_name, &alg->cra_driver_name,
	       sizeof(ualg->cru_driver_name));
	memcpy(&ualg->cru_module_name, module_name(alg->cra_module),
	       CRYPTO_MAX_ALG_NAME);

		snprintf(rl.type, CRYPTO_MAX_ALG_NAME, "%s", "larval");

	snprintf(rpcomp.type, CRYPTO_MAX_ALG_NAME, "%s", "pcomp");

	snprintf(rrng.type, CRYPTO_MAX_ALG_NAME, "%s", "rng");
	snprintf(rhash.type, CRYPTO_MAX_ALG_NAME, "%s", "shash");

Fixed code:
	strncpy(rblkcipher.type, "ablkcipher", sizeof(rblkcipher.type));
	strncpy(rblkcipher.geniv, alg->cra_ablkcipher.geniv ?: "<default>",
		sizeof(rblkcipher.geniv));
	strncpy(rblkcipher.type, "givcipher", sizeof(rblkcipher.type));
	strncpy(rblkcipher.geniv, alg->cra_ablkcipher.geniv ?: "<built-in>",
		sizeof(rblkcipher.geniv));
	strncpy(raead.type, "aead", sizeof(raead.type));
	strncpy(raead.geniv, aead->geniv ?: "<built-in>", sizeof(raead.geniv));
	strncpy(raead.type, "nivaead", sizeof(raead.type));
	strncpy(raead.geniv, aead->geniv, sizeof(raead.geniv));
	strncpy(rhash.type, "ahash", sizeof(rhash.type));
	strncpy(rblkcipher.type, "blkcipher", sizeof(rblkcipher.type));
	strncpy(rblkcipher.geniv, alg->cra_blkcipher.geniv ?: "<default>",
		sizeof(rblkcipher.geniv));
	strncpy(rcipher.type, "cipher", sizeof(rcipher.type));
	strncpy(rcomp.type, "compression", sizeof(rcomp.type));
	strncpy(ualg->cru_name, alg->cra_name, sizeof(ualg->cru_name));
	strncpy(ualg->cru_driver_name, alg->cra_driver_name,
		sizeof(ualg->cru_driver_name));
	strncpy(ualg->cru_module_name, module_name(alg->cra_module),
		sizeof(ualg->cru_module_name));

	ualg->cru_type = 0;
	ualg->cru_mask = 0;
		strncpy(rl.type, "larval", sizeof(rl.type));
	strncpy(rpcomp.type, "pcomp", sizeof(rpcomp.type));
	strncpy(rrng.type, "rng", sizeof(rrng.type));
	strncpy(rhash.type, "shash", sizeof(rhash.type));