From d1b01f0a04e54c55183fd5cee4b713e28e4e2cd7 Mon Sep 17 00:00:00 2001 From: Jakub Hrozek Date: Mon, 28 May 2018 21:41:49 +0200 Subject: [PATCH] SSH: Do not exit abruptly if SSHD closes its end of the pipe before reading all the SSH keys MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Resolves: https://pagure.io/SSSD/sssd/issue/3747 Before writing the keys to sshd, ignore SIGPIPE so that if the pipe towards the authorizedkeys helper is closed, the sss_ssh_authorizedkeys helper is not terminated with SIGPIPE, but instead proceeds and then the write(2) calls would non-terminally fail with EPIPE. Reviewed-by: Fabiano Fidêncio (cherry picked from commit cb138d7d060611e891d341db08477e41f9a3d17d) --- src/sss_client/ssh/sss_ssh_authorizedkeys.c | 35 ++++++++++++++++++++++++++++- 1 file changed, 34 insertions(+), 1 deletion(-) diff --git a/src/sss_client/ssh/sss_ssh_authorizedkeys.c b/src/sss_client/ssh/sss_ssh_authorizedkeys.c index 782a9f44379bff5346c896b3e03570720632c0be..b0280fbf8b0ed0501d792973241b826fc4a7a04d 100644 --- a/src/sss_client/ssh/sss_ssh_authorizedkeys.c +++ b/src/sss_client/ssh/sss_ssh_authorizedkeys.c @@ -21,6 +21,7 @@ #include #include #include +#include #include "util/util.h" #include "util/crypto/sss_crypto.h" @@ -99,8 +100,16 @@ int main(int argc, const char **argv) goto fini; } + /* if sshd closes its end of the pipe, we don't want sss_ssh_authorizedkeys + * to exit abruptly, but to finish gracefully instead because the valid + * key can be present in the data already written + */ + signal(SIGPIPE, SIG_IGN); + /* print results */ for (i = 0; i < ent->num_pubkeys; i++) { + char *repr_break = NULL; + ret = sss_ssh_format_pubkey(mem_ctx, &ent->pubkeys[i], &repr); if (ret != EOK) { DEBUG(SSSDBG_OP_FAILURE, @@ -109,7 +118,31 @@ int main(int argc, const char **argv) continue; } - printf("%s\n", repr); + /* OpenSSH expects a linebreak after each key */ + repr_break = talloc_asprintf(mem_ctx, "%s\n", repr); + talloc_zfree(repr); + if (repr_break == NULL) { + ret = ENOMEM; + goto fini; + } + + ret = sss_atomic_write_s(STDOUT_FILENO, repr_break, strlen(repr_break)); + /* Avoid spiking memory with too many large keys */ + talloc_zfree(repr_break); + if (ret < 0) { + ret = errno; + if (ret == EPIPE) { + DEBUG(SSSDBG_MINOR_FAILURE, + "SSHD closed the pipe before all keys could be written\n"); + /* Return 0 so that openssh doesn't abort pubkey auth */ + ret = 0; + goto fini; + } + DEBUG(SSSDBG_CRIT_FAILURE, + "sss_atomic_write_s() failed (%d): %s\n", + ret, strerror(ret)); + goto fini; + } } ret = EXIT_SUCCESS; -- 2.14.4