diff --git a/src/libnm-std-aux/nm-std-utils.c b/src/libnm-std-aux/nm-std-utils.c index 8bc109f2e2..6c909dfab3 100644 --- a/src/libnm-std-aux/nm-std-utils.c +++ b/src/libnm-std-aux/nm-std-utils.c @@ -4,10 +4,14 @@ #include "nm-std-utils.h" -#include #include +#include +#include #include #include +#include +#include +#include /*****************************************************************************/ @@ -95,6 +99,114 @@ out_huge: /*****************************************************************************/ +bool +nm_utils_set_effective_user(const char *user, char *errbuf, size_t errbuf_len) +{ + struct passwd *pwentry; + int errsv; + char error[1024]; + + errno = 0; + pwentry = getpwnam(user); + if (!pwentry) { + errsv = errno; + if (errsv == 0) { + snprintf(errbuf, errbuf_len, "user not found"); + } else { + snprintf(errbuf, + errbuf_len, + "error getting user entry: %d (%s)\n", + errsv, + strerror_r(errsv, error, sizeof(error))); + } + return false; + } + + if (setgid(pwentry->pw_gid) != 0) { + errsv = errno; + snprintf(errbuf, + errbuf_len, + "failed to change group to %u: %d (%s)\n", + pwentry->pw_gid, + errsv, + strerror_r(errsv, error, sizeof(error))); + return false; + } + + if (initgroups(user, pwentry->pw_gid) != 0) { + errsv = errno; + snprintf(errbuf, + errbuf_len, + "failed to reset supplementary group list to %u: %d (%s)\n", + pwentry->pw_gid, + errsv, + strerror_r(errsv, error, sizeof(error))); + return false; + } + + if (setuid(pwentry->pw_uid) != 0) { + errsv = errno; + snprintf(errbuf, + errbuf_len, + "failed to change user to %u: %d (%s)\n", + pwentry->pw_uid, + errsv, + strerror_r(errsv, error, sizeof(error))); + return false; + } + + return true; +} + +/*****************************************************************************/ + +bool +nm_utils_read_file_to_stdout(const char *filename, char *errbuf, size_t errbuf_len) +{ + nm_auto_close int fd = -1; + char buffer[4096]; + char error[1024]; + ssize_t bytes_read; + int errsv; + + fd = open(filename, O_RDONLY); + if (fd == -1) { + errsv = errno; + snprintf(errbuf, + errbuf_len, + "error opening the file: %d (%s)", + errsv, + strerror_r(errsv, error, sizeof(error))); + return false; + } + + while ((bytes_read = read(fd, buffer, sizeof(buffer))) > 0) { + if (fwrite(buffer, 1, bytes_read, stdout) != (size_t) bytes_read) { + errsv = errno; + snprintf(errbuf, + errbuf_len, + "error writing to stdout: %d (%s)", + errsv, + strerror_r(errsv, error, sizeof(error))); + return false; + } + } + + if (bytes_read < 0) { + errsv = errno; + snprintf(errbuf, + errbuf_len, + "error reading the file: %d (%s)", + errsv, + strerror_r(errsv, error, sizeof(error))); + return false; + } + + return true; +} + +/*****************************************************************************/ + /** * _nm_strerror_r: * @errsv: the errno passed to strerror_r() diff --git a/src/libnm-std-aux/nm-std-utils.h b/src/libnm-std-aux/nm-std-utils.h index 015444c93d..04c61c30f5 100644 --- a/src/libnm-std-aux/nm-std-utils.h +++ b/src/libnm-std-aux/nm-std-utils.h @@ -37,4 +37,8 @@ size_t nm_utils_get_next_realloc_size(bool true_realloc, size_t requested); const char *_nm_strerror_r(int errsv, char *buf, size_t buf_size); +bool nm_utils_set_effective_user(const char *user, char *errbuf, size_t errbuf_size); + +bool nm_utils_read_file_to_stdout(const char *filename, char *errbuf, size_t errbuf_len); + #endif /* __NM_STD_UTILS_H__ */ diff --git a/src/nm-helpers/README.md b/src/nm-helpers/README.md index ccaa5bf5cd..ab0ea02444 100644 --- a/src/nm-helpers/README.md +++ b/src/nm-helpers/README.md @@ -7,12 +7,13 @@ components. nm-daemon-helper ---------------- -A internal helper application that is spawned by NetworkManager -to perform certain actions. +A internal helper application that is spawned by NetworkManager to +perform certain actions which can't be done in the daemon. -Currently all it does is doing a reverse DNS lookup, which -cannot be done by NetworkManager because the operation requires -to reconfigure the libc resolver (which is a process-wide operation). +Currently it's used to do a reverse DNS lookup after reconfiguring the +libc resolver (which is a process-wide operation), and to read files +on behalf of unprivileged users (which requires a seteuid that affects +all the threads of the process). This is not directly useful to the user. diff --git a/src/nm-helpers/nm-daemon-helper.c b/src/nm-helpers/nm-daemon-helper.c index 32be93a4ef..759993a451 100644 --- a/src/nm-helpers/nm-daemon-helper.c +++ b/src/nm-helpers/nm-daemon-helper.c @@ -137,6 +137,37 @@ cmd_resolve_address(void) return RETURN_ERROR; } +static int +cmd_read_file_as_user(void) +{ + nm_auto_free char *user = NULL; + nm_auto_free char *filename = NULL; + char error[1024]; + + user = read_arg(); + if (!user) + return RETURN_INVALID_ARGS; + + filename = read_arg(); + if (!filename) + return RETURN_INVALID_ARGS; + + if (more_args()) + return RETURN_INVALID_ARGS; + + if (!nm_utils_set_effective_user(user, error, sizeof(error))) { + fprintf(stderr, "Failed to set effective user '%s': %s", user, error); + return RETURN_ERROR; + } + + if (!nm_utils_read_file_to_stdout(filename, error, sizeof(error))) { + fprintf(stderr, "Failed to read file '%s' as user '%s': %s", filename, user, error); + return RETURN_ERROR; + } + + return RETURN_SUCCESS; +} + int main(int argc, char **argv) { @@ -150,6 +181,8 @@ main(int argc, char **argv) return cmd_version(); if (nm_streq(cmd, "resolve-address")) return cmd_resolve_address(); + if (nm_streq(cmd, "read-file-as-user")) + return cmd_read_file_as_user(); return RETURN_INVALID_CMD; }