From 37db69e0b4923bff331820ee6969681937d8b065 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Sat, 3 Nov 2018 14:56:03 -0700 Subject: crypto: user - clean up report structure copying There have been a pretty ridiculous number of issues with initializing the report structures that are copied to userspace by NETLINK_CRYPTO. Commit 4473710df1f8 ("crypto: user - Prepare for CRYPTO_MAX_ALG_NAME expansion") replaced some strncpy()s with strlcpy()s, thereby introducing information leaks. Later two other people tried to replace other strncpy()s with strlcpy() too, which would have introduced even more information leaks: - https://lore.kernel.org/patchwork/patch/954991/ - https://patchwork.kernel.org/patch/10434351/ Commit cac5818c25d0 ("crypto: user - Implement a generic crypto statistics") also uses the buggy strlcpy() approach and therefore leaks uninitialized memory to userspace. A fix was proposed, but it was originally incomplete. Seeing as how apparently no one can get this right with the current approach, change all the reporting functions to: - Start by memsetting the report structure to 0. This guarantees it's always initialized, regardless of what happens later. - Initialize all strings using strscpy(). This is safe after the memset, ensures null termination of long strings, avoids unnecessary work, and avoids the -Wstringop-truncation warnings from gcc. - Use sizeof(var) instead of sizeof(type). This is more robust against copy+paste errors. For simplicity, also reuse the -EMSGSIZE return value from nla_put(). Signed-off-by: Eric Biggers Signed-off-by: Herbert Xu --- crypto/rng.c | 12 ++++-------- 1 file changed, 4 insertions(+), 8 deletions(-) (limited to 'crypto/rng.c') diff --git a/crypto/rng.c b/crypto/rng.c index 547f16ecbfb0..2406501b90b7 100644 --- a/crypto/rng.c +++ b/crypto/rng.c @@ -74,17 +74,13 @@ static int crypto_rng_report(struct sk_buff *skb, struct crypto_alg *alg) { struct crypto_report_rng rrng; - strncpy(rrng.type, "rng", sizeof(rrng.type)); + memset(&rrng, 0, sizeof(rrng)); - rrng.seedsize = seedsize(alg); + strscpy(rrng.type, "rng", sizeof(rrng.type)); - if (nla_put(skb, CRYPTOCFGA_REPORT_RNG, - sizeof(struct crypto_report_rng), &rrng)) - goto nla_put_failure; - return 0; + rrng.seedsize = seedsize(alg); -nla_put_failure: - return -EMSGSIZE; + return nla_put(skb, CRYPTOCFGA_REPORT_RNG, sizeof(rrng), &rrng); } #else static int crypto_rng_report(struct sk_buff *skb, struct crypto_alg *alg) -- cgit v1.2.3-70-g09d2