From 35e886f23fde338387c8e2a3a74c9251f7735c3b Mon Sep 17 00:00:00 2001
From: Jonathan McDowell <noodles@earth.li>
Date: Fri, 15 Sep 2023 18:25:51 +0530
Subject: [PATCH] Switch charfuncs to returning number of read/written
 characters

The charfuncs prototypes were returning 0 for success ("I wrote all the
characters you asked me to") or 1 for failure. When we get to verifying
signatures over data we may not know how much to read, so change them to
returning 0 on error/no more data and otherwise the count of the amount
of data read/written.
---
 armor.c          | 20 ++++++++++----------
 armor.h          |  4 ++--
 cgi/hashquery.c  |  4 ++--
 charfuncs.c      | 32 ++++++++++++++++++--------------
 charfuncs.h      | 12 ++++++------
 keydb/keydb_pg.c | 15 +++++++++++----
 marshal.c        | 28 ++++++++++++++--------------
 marshal.h        | 20 ++++++++++----------
 parsekey.c       | 37 +++++++++++++++++++------------------
 parsekey.h       |  4 ++--
 sendsync.c       |  6 ++----
 11 files changed, 96 insertions(+), 86 deletions(-)

diff --git a/armor.c b/armor.c
index 1341950..f218b55 100644
--- a/armor.c
+++ b/armor.c
@@ -96,7 +96,7 @@ struct armor_context {
 	/** A running CRC24 of the data we've seen. */
 	long crc24;
 	/** The function to output a character. */
-	int (*putchar_func)(void *ctx, size_t count, void *c);
+	size_t (*putchar_func)(void *ctx, size_t count, void *c);
 	/** Context for putchar_func. */
 	void *ctx;
 };
@@ -203,7 +203,7 @@ static int armor_putchar_int(void *ctx, unsigned char c)
 }
 
 
-static int armor_putchar(void *ctx, size_t count, void *c)
+static size_t armor_putchar(void *ctx, size_t count, void *c)
 {
 	int i;
 
@@ -211,8 +211,8 @@ static int armor_putchar(void *ctx, size_t count, void *c)
 	for (i = 0; i < count; i++) {
 		armor_putchar_int(ctx, ((char *) c)[i]);
 	}
-	
-	return 0;
+
+	return count;
 }
 
 /**
@@ -228,7 +228,7 @@ struct dearmor_context {
 	/** A running CRC24 of the data we've seen. */
 	long crc24;
 	/** The function to get the next character. */
-	int (*getchar_func)(void *ctx, size_t count, void *c);
+	size_t (*getchar_func)(void *ctx, size_t count, void *c);
 	/** Context for getchar_func. */
 	void *ctx;
 };
@@ -309,7 +309,7 @@ static int dearmor_getchar(void *ctx, unsigned char *c)
 	return (tmpc == 64);
 }
 
-static int dearmor_getchar_c(void *ctx, size_t count, void *c)
+static size_t dearmor_getchar_c(void *ctx, size_t count, void *c)
 {
 	int i, rc = 0;
 
@@ -317,10 +317,10 @@ static int dearmor_getchar_c(void *ctx, size_t count, void *c)
 		rc = dearmor_getchar(ctx, &((unsigned char *) c)[i]);
 	}
 
-	return rc;
+	return (rc == 0) ? i : 0;
 }
 
-int armor_openpgp_stream(int (*putchar_func)(void *ctx, size_t count,
+int armor_openpgp_stream(size_t (*putchar_func)(void *ctx, size_t count,
 						void *c),
 				void *ctx,
 				struct openpgp_packet_list *packets)
@@ -348,7 +348,7 @@ int armor_openpgp_stream(int (*putchar_func)(void *ctx, size_t count,
 	return 0;
 }
 
-int dearmor_openpgp_stream(int (*getchar_func)(void *ctx, size_t count,
+int dearmor_openpgp_stream(size_t (*getchar_func)(void *ctx, size_t count,
 						void *c),
 				void *ctx,
 				struct openpgp_packet_list **packets)
@@ -363,7 +363,7 @@ int dearmor_openpgp_stream(int (*getchar_func)(void *ctx, size_t count,
 	 * with :s in them, then a blank line, then the data.
 	 */
 	state = 1;
-	while (state != 4 && !getchar_func(ctx, 1, &curchar)) {
+	while (state != 4 && getchar_func(ctx, 1, &curchar) == 1) {
 		switch (state) {
 			case 0:
 				if (curchar == '\n') {
diff --git a/armor.h b/armor.h
index bb660a1..7245589 100644
--- a/armor.h
+++ b/armor.h
@@ -31,7 +31,7 @@
  * This function ASCII armors a list of OpenPGP packets and outputs it
  * using putchar_func.
  */
-int armor_openpgp_stream(int (*putchar_func)(void *ctx, size_t count,
+int armor_openpgp_stream(size_t (*putchar_func)(void *ctx, size_t count,
 						void *c),
 				void *ctx,
 				struct openpgp_packet_list *packets);
@@ -46,7 +46,7 @@ int armor_openpgp_stream(int (*putchar_func)(void *ctx, size_t count,
  * armored OpenPGP stream and outputs the data as a linked list of
  * packets.
  */
-int dearmor_openpgp_stream(int (*getchar_func)(void *ctx, size_t count,
+int dearmor_openpgp_stream(size_t (*getchar_func)(void *ctx, size_t count,
 					void *c),
 				void *ctx,
 				struct openpgp_packet_list **packets);
diff --git a/cgi/hashquery.c b/cgi/hashquery.c
index 84efe97..7b8c6c4 100644
--- a/cgi/hashquery.c
+++ b/cgi/hashquery.c
@@ -74,7 +74,7 @@ int main(__unused int argc, __unused char *argv[])
 	}
 
 	hashes = (uint8_t **) unmarshal_array(buffer_fetchchar, &cgipostbuf,
-			(void * (*)(int (*)(void *, size_t,  void *), void *))
+			(void * (*)(size_t (*)(void *, size_t,  void *), void *))
 				unmarshal_skshash, &count);
 
 	free(cgipostbuf.buffer);
@@ -115,7 +115,7 @@ int main(__unused int argc, __unused char *argv[])
 
 	puts("Content-Type: pgp/keys\n");
 	marshal_array(stdout_putchar, NULL,
-			(void (*)(int (*)(void *, size_t,  void *),
+			(void (*)(size_t (*)(void *, size_t,  void *),
 					void *, const void *))
 				marshal_publickey, (void **) keys, found);
 	printf("\n");
diff --git a/charfuncs.c b/charfuncs.c
index 3aee0b0..59c8ca3 100644
--- a/charfuncs.c
+++ b/charfuncs.c
@@ -29,20 +29,20 @@
  *	@count: The number of characters to get from the buffer.
  *	@c: Where to put the characters retrieved.
  */
-int buffer_fetchchar(void *ctx, size_t count, void *c)
+size_t buffer_fetchchar(void *ctx, size_t count, void *c)
 {
 	struct buffer_ctx *buf = NULL;
 	
 	buf = (struct buffer_ctx *) ctx;
 
 	if (buf->offset + count > buf->size) {
-		return 1;
+		count = buf->size - buf->offset;
 	}
-	
+
 	memcpy(c, &buf->buffer[buf->offset], count);
 	buf->offset += count;
 
-	return 0;
+	return count;
 }
 
 /*
@@ -55,7 +55,7 @@ int buffer_fetchchar(void *ctx, size_t count, void *c)
  *	fill it then we double the size of the current buffer and then add the
  *	rest.
  */
-int buffer_putchar(void *ctx, size_t count, void *c)
+size_t buffer_putchar(void *ctx, size_t count, void *c)
 {
 	struct buffer_ctx *buf = NULL;
 	size_t newsize = 0;
@@ -73,37 +73,41 @@ int buffer_putchar(void *ctx, size_t count, void *c)
 	memcpy(&buf->buffer[buf->offset], c, count);
 	buf->offset += count;
 	
-	return 1;
+	return count;
 }
 
 /*
  * Fetches a char from a file.
  */
-int file_fetchchar(void *fd, size_t count, void *c)
+size_t file_fetchchar(void *fd, size_t count, void *c)
 {
-	return !(read( *(int *) fd, c, count));
+	ssize_t ret = read( *(int *) fd, c, count);
+
+	return (ret > 0) ? ret : 0;
 }
 
 /*
  * Puts a char to a file.
  */
-int file_putchar(void *fd, size_t count, void *c)
+size_t file_putchar(void *fd, size_t count, void *c)
 {
-	return !(write( *(int *) fd, c, count));
+	size_t ret = write( *(int *) fd, c, count);
+
+	return (ret > 0) ? ret : 0;
 }
 
 /*
  * Gets a char from stdin.
  */
-int stdin_getchar(__unused void *ctx, size_t count, void *c)
+size_t stdin_getchar(__unused void *ctx, size_t count, void *c)
 {
-	return (fread(c, 1, count, stdin) != count);
+	return fread(c, 1, count, stdin);
 }
 
 /*
  * Puts a char to stdout.
  */
-int stdout_putchar(__unused void *ctx, size_t count, void *c)
+size_t stdout_putchar(__unused void *ctx, size_t count, void *c)
 {
-	return (fwrite(c, 1, count, stdout) != count);
+	return fwrite(c, 1, count, stdout);
 }
diff --git a/charfuncs.h b/charfuncs.h
index 5dadf66..4d8997b 100644
--- a/charfuncs.h
+++ b/charfuncs.h
@@ -40,7 +40,7 @@ struct buffer_ctx {
  * @param count The number of characters to get from the buffer.
  * @param c Where to put the characters retrieved.
  */
-int buffer_fetchchar(void *ctx, size_t count, void *c);
+size_t buffer_fetchchar(void *ctx, size_t count, void *c);
 
 /**
  * @brief Puts a char to a buffer.
@@ -52,26 +52,26 @@ int buffer_fetchchar(void *ctx, size_t count, void *c);
  * fill it then we double the size of the current buffer and then add the
  * rest.
  */
-int buffer_putchar(void *ctx, size_t count, void *c);
+size_t buffer_putchar(void *ctx, size_t count, void *c);
 
 /**
  * @brief Fetches a char from a file.
  */
-int file_fetchchar(void *fd, size_t count, void *c);
+size_t file_fetchchar(void *fd, size_t count, void *c);
 
 /**
  * @brief Puts a char to a file.
  */
-int file_putchar(void *fd, size_t count, void *c);
+size_t file_putchar(void *fd, size_t count, void *c);
 
 /**
  * @brief Gets a char from stdin.
  */
-int stdin_getchar(void *ctx, size_t count, void *c);
+size_t stdin_getchar(void *ctx, size_t count, void *c);
 
 /**
  * @brief Puts a char to stdout.
  */
-int stdout_putchar(void *ctx, size_t count, void *c);
+size_t stdout_putchar(void *ctx, size_t count, void *c);
 
 #endif /* __CHARFUNCS_H__ */
diff --git a/keydb/keydb_pg.c b/keydb/keydb_pg.c
index c8392f7..85c16cc 100644
--- a/keydb/keydb_pg.c
+++ b/keydb/keydb_pg.c
@@ -47,21 +47,28 @@ struct pg_fc_ctx {
 /**
  *	keydb_fetchchar - Fetches a char from a file.
  */
-static int keydb_fetchchar(void *_ctx, size_t count, void *c)
+static size_t keydb_fetchchar(void *_ctx, size_t count, void *c)
 {
+	int ret;
+
 	struct pg_fc_ctx *ctx = (struct pg_fc_ctx *) _ctx;
 
-	return (!lo_read(ctx->dbconn, ctx->fd, (char *) c, count));
+	ret = lo_read(ctx->dbconn, ctx->fd, (char *) c, count);
+
+	return (ret > 0) ? ret : 0;
 }
 
 /**
  *	keydb_putchar - Puts a char to a file.
  */
-static int keydb_putchar(void *_ctx, size_t count, void *c)
+static size_t keydb_putchar(void *_ctx, size_t count, void *c)
 {
 	struct pg_fc_ctx *ctx = (struct pg_fc_ctx *) _ctx;
+	int ret;
+
+	ret = lo_write(ctx->dbconn, ctx->fd, (char *) c, count);
 
-	return !(lo_write(ctx->dbconn, ctx->fd, (char *) c, count));
+	return (ret > 0) ? ret : 0;
 }
 
 /**
diff --git a/marshal.c b/marshal.c
index 9eb3ccb..5f26cff 100644
--- a/marshal.c
+++ b/marshal.c
@@ -27,7 +27,7 @@
 #include "mem.h"
 #include "parsekey.h"
 
-void marshal_publickey(int (*putchar_func)(void *ctx, size_t count,
+void marshal_publickey(size_t (*putchar_func)(void *ctx, size_t count,
 				void *c),
 				void *ctx,
 				const struct openpgp_publickey *key)
@@ -52,7 +52,7 @@ void marshal_publickey(int (*putchar_func)(void *ctx, size_t count,
 	free_packet_list(packets);
 }
 
-void marshal_skshash(int (*putchar_func)(void *ctx, size_t count,
+void marshal_skshash(size_t (*putchar_func)(void *ctx, size_t count,
 				void *c),
 				void *ctx,
 				const struct skshash *hash)
@@ -65,14 +65,14 @@ void marshal_skshash(int (*putchar_func)(void *ctx, size_t count,
 	putchar_func(ctx, sizeof(hash->hash), (void *) hash->hash);
 }
 
-struct skshash *unmarshal_skshash(int (*getchar_func)(void *ctx, size_t count,
+struct skshash *unmarshal_skshash(size_t (*getchar_func)(void *ctx, size_t count,
 				void *c),
 				void *ctx)
 {
 	uint32_t len;
 	struct skshash *hash;
 
-	if (getchar_func(ctx, sizeof(len), &len)) {
+	if (getchar_func(ctx, sizeof(len), &len) != sizeof(len)) {
 		return NULL;
 	}
 	len = ntohl(len);
@@ -80,7 +80,7 @@ struct skshash *unmarshal_skshash(int (*getchar_func)(void *ctx, size_t count,
 		return NULL;
 	}
 	hash = calloc(sizeof(struct skshash), 1);
-	if (getchar_func(ctx, len, hash->hash)) {
+	if (getchar_func(ctx, len, hash->hash) != len) {
 		free(hash);
 		return NULL;
 	}
@@ -88,7 +88,7 @@ struct skshash *unmarshal_skshash(int (*getchar_func)(void *ctx, size_t count,
 	return hash;
 }
 
-void marshal_string(int (*putchar_func)(void *ctx, size_t count,
+void marshal_string(size_t (*putchar_func)(void *ctx, size_t count,
 				void *c),
 				void *ctx,
 				const char *string)
@@ -102,19 +102,19 @@ void marshal_string(int (*putchar_func)(void *ctx, size_t count,
 	putchar_func(ctx, len, &string);
 }
 
-char *unmarshal_string(int (*getchar_func)(void *ctx, size_t count,
+char *unmarshal_string(size_t (*getchar_func)(void *ctx, size_t count,
 				void *c),
 				void *ctx)
 {
 	uint32_t len;
 	char *string;
 
-	if (getchar_func(ctx, sizeof(len), &len)) {
+	if (getchar_func(ctx, sizeof(len), &len) != sizeof(len)) {
 		return NULL;
 	}
 	len = ntohl(len);
 	string = malloc(len + 1);
-	if (getchar_func(ctx, len, string)) {
+	if (getchar_func(ctx, len, string) != len) {
 		free(string);
 		return NULL;
 	}
@@ -123,10 +123,10 @@ char *unmarshal_string(int (*getchar_func)(void *ctx, size_t count,
 	return string;
 }
 
-void marshal_array(int (*putchar_func)(void *ctx, size_t count,
+void marshal_array(size_t (*putchar_func)(void *ctx, size_t count,
 				void *c),
 				void *ctx,
-				void (*marshal_func)(int
+				void (*marshal_func)(size_t
 					(*putchar_func)(void *ctx,
 						size_t count, void *c),
 					void *ctx, const void *item),
@@ -145,10 +145,10 @@ void marshal_array(int (*putchar_func)(void *ctx, size_t count,
 	}
 }
 
-void **unmarshal_array(int (*getchar_func)(void *ctx, size_t count,
+void **unmarshal_array(size_t (*getchar_func)(void *ctx, size_t count,
 				void *c),
 				void *ctx,
-				void *(*unmarshal_func)(int
+				void *(*unmarshal_func)(size_t
 					(*getchar_func)(void *ctx,
 						size_t count, void *c),
 					void *ctx),
@@ -158,7 +158,7 @@ void **unmarshal_array(int (*getchar_func)(void *ctx, size_t count,
 	void **array;
 	int i;
 
-	if (getchar_func(ctx, sizeof(len), &len)) {
+	if (getchar_func(ctx, sizeof(len), &len) != sizeof(len)) {
 		return NULL;
 	}
 	*size = ntohl(len);
diff --git a/marshal.h b/marshal.h
index 3edb612..8b487b4 100644
--- a/marshal.h
+++ b/marshal.h
@@ -32,7 +32,7 @@
  *	a 32 bit size of the forthcoming data in network byte order and
  *	then the flattened byte representation of the key.
  */
-void marshal_publickey(int (*putchar_func)(void *ctx, size_t count,
+void marshal_publickey(size_t (*putchar_func)(void *ctx, size_t count,
 				void *c),
 				void *ctx,
 				const struct openpgp_publickey *key);
@@ -45,7 +45,7 @@ void marshal_publickey(int (*putchar_func)(void *ctx, size_t count,
  *	Returns an OpenPGP structure which is the unmarshalled result of
  *	the input byte stream - ie the inverse of marshal_publickey.
  */
-struct openpgp_publickey *unmarshal_publickey(int (*getchar_func)(void *ctx,
+struct openpgp_publickey *unmarshal_publickey(size_t (*getchar_func)(void *ctx,
 				size_t count,
 				void *c),
 				void *ctx);
@@ -60,7 +60,7 @@ struct openpgp_publickey *unmarshal_publickey(int (*getchar_func)(void *ctx,
  *	a 32 bit size of the forthcoming data (16 bytes) in network byte order
  *	and then the byte representation of the hash.
  */
-void marshal_skshash(int (*putchar_func)(void *ctx, size_t count,
+void marshal_skshash(size_t (*putchar_func)(void *ctx, size_t count,
 				void *c),
 				void *ctx,
 				const struct skshash *hash);
@@ -73,7 +73,7 @@ void marshal_skshash(int (*putchar_func)(void *ctx, size_t count,
  *	Returns an SKS hash structure which is the unmarshalled result of
  *	the input byte stream - ie the inverse of marshal_skshash.
  */
-struct skshash *unmarshal_skshash(int (*getchar_func)(void *ctx, size_t count,
+struct skshash *unmarshal_skshash(size_t (*getchar_func)(void *ctx, size_t count,
 				void *c),
 				void *ctx);
 
@@ -86,7 +86,7 @@ struct skshash *unmarshal_skshash(int (*getchar_func)(void *ctx, size_t count,
  *	Takes a string and marshals it to a byte stream - writes a 32 bit size
  *	of the forthcoming data in network byte order and then the string.
  */
-void marshal_string(int (*putchar_func)(void *ctx, size_t count,
+void marshal_string(size_t (*putchar_func)(void *ctx, size_t count,
 				void *c),
 				void *ctx,
 				const char *string);
@@ -99,7 +99,7 @@ void marshal_string(int (*putchar_func)(void *ctx, size_t count,
  *	Returns a string which is the unmarshalled result of the input byte
  *	stream - ie the inverse of marshal_string.
  */
-char *unmarshal_string(int (*getchar_func)(void *ctx, size_t count,
+char *unmarshal_string(size_t (*getchar_func)(void *ctx, size_t count,
 				void *c),
 				void *ctx);
 
@@ -116,10 +116,10 @@ char *unmarshal_string(int (*getchar_func)(void *ctx, size_t count,
  *	calls marshal_func for each element in the array to provide the
  *	marshalled contents.
  */
-void marshal_array(int (*putchar_func)(void *ctx, size_t count,
+void marshal_array(size_t (*putchar_func)(void *ctx, size_t count,
 				void *c),
 				void *ctx,
-				void (*marshal_func)(int
+				void (*marshal_func)(size_t
 					(*putchar_func)(void *ctx,
 						size_t count, void *c),
 					void *ctx, const void *item),
@@ -137,10 +137,10 @@ void marshal_array(int (*putchar_func)(void *ctx, size_t count,
  *	as determined by the supplied unmarshal_func function. ie the reverse
  *	of marshal_array.
  */
-void **unmarshal_array(int (*getchar_func)(void *ctx, size_t count,
+void **unmarshal_array(size_t (*getchar_func)(void *ctx, size_t count,
 				void *c),
 				void *ctx,
-				void *(*unmarshal_func)(int
+				void *(*unmarshal_func)(size_t
 					(*getchar_func)(void *ctx,
 						size_t count, void *c),
 					void *ctx),
diff --git a/parsekey.c b/parsekey.c
index 49b91bf..ceff429 100644
--- a/parsekey.c
+++ b/parsekey.c
@@ -182,7 +182,7 @@ int debug_packet(struct openpgp_packet *packet)
  *	packet stream and reads the packets into a linked list of packets
  *	ready for parsing as a public key or whatever.
  */
-onak_status_t read_openpgp_stream(int (*getchar_func)(void *ctx, size_t count,
+onak_status_t read_openpgp_stream(size_t (*getchar_func)(void *ctx, size_t count,
 				void *c),
 				void *ctx,
 				struct openpgp_packet_list **packets,
@@ -204,7 +204,7 @@ onak_status_t read_openpgp_stream(int (*getchar_func)(void *ctx, size_t count,
 	}
 
 	while (rc == ONAK_E_OK && (maxnum == 0 || keys < maxnum) &&
-			!getchar_func(ctx, 1, &curchar)) {
+			(getchar_func(ctx, 1, &curchar) == 1)) {
 		if (curchar & 0x80) {
 			/*
 			 * New packet. Allocate memory for it.
@@ -231,14 +231,14 @@ onak_status_t read_openpgp_stream(int (*getchar_func)(void *ctx, size_t count,
 			 */
 			if (curpacket->packet->newformat) {
 				curpacket->packet->tag = (curchar & 0x3F);
-				if (getchar_func(ctx, 1, &curchar)) {
+				if (getchar_func(ctx, 1, &curchar) == 0) {
 					rc = ONAK_E_INVALID_PKT;
 					break;
 				}
 				curpacket->packet->length = curchar;
 				if (curpacket->packet->length > 191 &&
 					curpacket->packet->length < 224) {
-					rc = getchar_func(ctx, 1, &curchar);
+					rc = getchar_func(ctx, 1, &curchar) ? ONAK_E_OK : ONAK_E_IO_ERROR;
 					curpacket->packet->length -= 192;
 					curpacket->packet->length <<= 8;
 					curpacket->packet->length += curchar;
@@ -250,28 +250,28 @@ onak_status_t read_openpgp_stream(int (*getchar_func)(void *ctx, size_t count,
 					rc = ONAK_E_UNSUPPORTED_FEATURE;
 				} else if (curpacket->packet->length == 255) {
 					/*
-					 * 5 byte length; ie 255 followed by 3
+					 * 5 byte length; ie 255 followed by 4
 					 * bytes of MSB length.
 					 */
-					if (getchar_func(ctx, 1, &curchar)) {
+					if (getchar_func(ctx, 1, &curchar) != 1) {
 						rc = ONAK_E_INVALID_PKT;
 						break;
 					}
 					curpacket->packet->length = curchar;
 					curpacket->packet->length <<= 8;
-					if (getchar_func(ctx, 1, &curchar)) {
+					if (getchar_func(ctx, 1, &curchar) != 1) {
 						rc = ONAK_E_INVALID_PKT;
 						break;
 					}
 					curpacket->packet->length += curchar;
 					curpacket->packet->length <<= 8;
-					if (getchar_func(ctx, 1, &curchar)) {
+					if (getchar_func(ctx, 1, &curchar) != 1) {
 						rc = ONAK_E_INVALID_PKT;
 						break;
 					}
 					curpacket->packet->length += curchar;
 					curpacket->packet->length <<= 8;
-					if (getchar_func(ctx, 1, &curchar)) {
+					if (getchar_func(ctx, 1, &curchar) != 1) {
 						rc = ONAK_E_INVALID_PKT;
 						break;
 					}
@@ -281,45 +281,45 @@ onak_status_t read_openpgp_stream(int (*getchar_func)(void *ctx, size_t count,
 				curpacket->packet->tag = (curchar & 0x3C) >> 2;
 				switch (curchar & 3) {
 				case 0:
-					if (getchar_func(ctx, 1, &curchar)) {
+					if (getchar_func(ctx, 1, &curchar) != 1) {
 						rc = ONAK_E_INVALID_PKT;
 						break;
 					}
 					curpacket->packet->length = curchar;
 					break;
 				case 1:
-					if (getchar_func(ctx, 1, &curchar)) {
+					if (getchar_func(ctx, 1, &curchar) != 1) {
 						rc = ONAK_E_INVALID_PKT;
 						break;
 					}
 					curpacket->packet->length = curchar;
 					curpacket->packet->length <<= 8;
-					if (getchar_func(ctx, 1, &curchar)) {
+					if (getchar_func(ctx, 1, &curchar) != 1) {
 						rc = ONAK_E_INVALID_PKT;
 						break;
 					}
 					curpacket->packet->length += curchar;
 					break;
 				case 2:
-					if (getchar_func(ctx, 1, &curchar)) {
+					if (getchar_func(ctx, 1, &curchar) != 1) {
 						rc = ONAK_E_INVALID_PKT;
 						break;
 					}
 					curpacket->packet->length = 
 						((unsigned) curchar << 24);
-					if (getchar_func(ctx, 1, &curchar)) {
+					if (getchar_func(ctx, 1, &curchar) != 1) {
 						rc = ONAK_E_INVALID_PKT;
 						break;
 					}
 					curpacket->packet->length +=
 						(curchar << 16);
-					if (getchar_func(ctx, 1, &curchar)) {
+					if (getchar_func(ctx, 1, &curchar) != 1) {
 						rc = ONAK_E_INVALID_PKT;
 						break;
 					}
 					curpacket->packet->length +=
 						(curchar << 8);
-					if (getchar_func(ctx, 1, &curchar)) {
+					if (getchar_func(ctx, 1, &curchar) != 1) {
 						rc = ONAK_E_INVALID_PKT;
 						break;
 					}
@@ -346,7 +346,8 @@ onak_status_t read_openpgp_stream(int (*getchar_func)(void *ctx, size_t count,
 				} else {
 					rc = getchar_func(ctx,
 						curpacket->packet->length,
-						curpacket->packet->data);
+						curpacket->packet->data) ?
+						ONAK_E_OK : ONAK_E_IO_ERROR;
 				}
 			}
 		} else {
@@ -422,7 +423,7 @@ onak_status_t read_openpgp_stream(int (*getchar_func)(void *ctx, size_t count,
  *	This function uses putchar_func to write characters to an OpenPGP
  *	packet stream from a linked list of packets.
  */
-onak_status_t write_openpgp_stream(int (*putchar_func)(void *ctx, size_t count,
+onak_status_t write_openpgp_stream(size_t (*putchar_func)(void *ctx, size_t count,
 						void *c),
 				void *ctx,
 				struct openpgp_packet_list *packets)
diff --git a/parsekey.h b/parsekey.h
index c237aa9..edf44c2 100644
--- a/parsekey.h
+++ b/parsekey.h
@@ -59,7 +59,7 @@ int debug_packet(struct openpgp_packet *packet);
  *	then only the public key component of the last key will be returned,
  *	none of the other packets of the key will be read.
  */
-onak_status_t read_openpgp_stream(int (*getchar_func)(void *ctx, size_t count,
+onak_status_t read_openpgp_stream(size_t (*getchar_func)(void *ctx, size_t count,
 				void *c),
 				void *ctx,
 				struct openpgp_packet_list **packets,
@@ -74,7 +74,7 @@ onak_status_t read_openpgp_stream(int (*getchar_func)(void *ctx, size_t count,
  *	This function uses putchar_func to write characters to an OpenPGP
  *	packet stream from a linked list of packets.
  */
-onak_status_t write_openpgp_stream(int (*putchar_func)(void *ctx, size_t count,
+onak_status_t write_openpgp_stream(size_t (*putchar_func)(void *ctx, size_t count,
 						void *c),
 				void *ctx,
 				struct openpgp_packet_list *packets);
diff --git a/sendsync.c b/sendsync.c
index e81da7d..429b8f7 100644
--- a/sendsync.c
+++ b/sendsync.c
@@ -29,11 +29,9 @@
 #include "parsekey.h"
 #include "sendsync.h"
 
-int fd_putchar(void *ctx, size_t count, void *c)
+size_t fd_putchar(void *ctx, size_t count, void *c)
 {
-	fwrite(c, sizeof(char), count, ctx);
-
-	return 0;
+	return fwrite(c, sizeof(char), count, ctx);
 }
 
 /**
-- 
2.39.5